Current Trends in Synthesis

#### **Chapter 1**

## Recent Advances in the Synthesis of Graphene and Its Derivative Materials

*Aafreen, Priyanka Verma and Haris Saeed*

#### **Abstract**

Graphene (G) is a 2D material of sp2 hybridized carbon atoms, discovered by Geim and Novoselov in 2004. The material presents a wide range of peculiar electronics and thermal, optical, mechanical, structural, and surface properties, which have attracted considerable interest from researchers and technologists. The conevntional techniques for graphenization have presented some drawbacks including low yield, costliness, high chances of contamination, and their time-consuming nature. These limitations have led to proliferation of research, which has led to the discovery of more advanced techniques for G synthesis over the years. At the moment, trending approaches to G production include chemical vapor disposition (CVD), epitaxial growth on silicon carbide (SiC), G oxide reduction, chemical synthesis, electrochemical synthesis, and laser-induced graphenization. There is a growing demand to produce G in large quantities and good quality. Nonetheless, because the conventional techniques have presented significant difficulties and imperfections in large-scale G production, various investigations have been conducted to identify new techniques for manufacturing cost-effective, large-scale, and high-quality G with novel applications such as energy storage, sensors, drug delivery, and biomedical devices. Each technique can be used for certain applications and has its own advantages. This chapter deals with the two approaches (top-down and bottom-up) for the synthesis of G and their procedure, limitations, and applications.

**Keywords:** biosensors, carbon nanotubes, exfoliation, graphene, graphene oxide, graphene synthesis

#### **1. Introduction**

In 1960, researchers Ubbelohde and Lewis successfully isolated a monolayer of graphite and determined that graphite is composed of layers, consisting of interconnected hexagonal carbon atom rings [1]. However, as stated by Mouras et al. in 1987, the term "graphene" was initially coined to refer to a solitary sheet of graphite during that time. Graphite serves as the foundational element in graphitic materials such as graphite itself, fullerene, and carbon nanotubes [2]. Although G was discovered to be in existance by Benjamin Collins Brodie in 1859 [3], since its first discovery in 1962 [4] which was observed in an electron microscope, Wallace has spent many years

studying it theoretically [5, 6]. However, the properties of the graphenic material were only attained in 2004 when Novoselov and Geim successfully isolated and studied a single-atom-thick crystallite (G) from bulk graphite and transferred them onto thin silicon dioxide on a silicon wafer using the well-known scotch tape technique. Notably, the pioneering method of producing the first G involved micromechanical cleavage of graphite [7]. Konstantin Novoselov and Andre Geim shared the 2010 Nobel Prize in Physics for their ground-breaking work on this two-dimensional material as a result of this feat [8, 9]. The popular nanomaterial G is currently taking the place of silicon in a variety of scientific disciplines. This is because of their nanoscale mechanical, chemical, thermal, and physical characteristics, and due to its potential, G is attracting sponsors and significant donations [10].

The exploration of various commercial applications for these materials is currently underway with a particular emphasis on a range of fields, which include sensors, energy generation, and energy storage devices, which represent some of the fastest growing domains of technology [11–13]. Additionally, the realm of 2D-layered materials exhibits an extensive array of crystalline structures, corresponding to a diverse spectrum of physical properties [1, 14].

The atoms of these bulk layered materials are weakly connected by inter-layer van der Waals forces, but they are strongly bound to one another within the same plane [14]. The creation of 2D-layered nanoscale materials from these bound sheets through chemical or physical interactions opens up interesting possibilities for novel devices that are distinct from those made from conventional bulk materials [15, 16]. Plus, due to the wide range of shapes and sizes that a single graphitic layer can take, G is sometimes referred to as the "mother" of all graphitic-based nanostructures. It can be folded into one-dimensional (1D) carbon nanotubes (CNTs), wrapped into a zero-dimensional (0D) "buckyball" structure, or layered into multiple-layer 3D G sheets [17–22].

#### **2. Graphene synthesis**

There are numerous ways by which G is produced. The conventional techniques include (1) mechanical exfoliation, (2) chemical vapor deposition, and (3) epitaxial growth. At the moment, the trending G production techniques are electrochemical exfoliation, laser-induced graphenization, hydrothermal synthesis, and microwaveassisted synthesis. This chapter provides a summary of conventional and trending techniques that are used for the synthesis of G. Nonotheless, G needs to be produced at a price that is comparable to or lower than that of existing materials in order to be successfully applied in industry. The development of G synthesis processes with the qualities of high product yield, high product quality, cost-effectiveness, and scalable production is, however, difficult. As a result, these properties are the main subject of the discussion in the subsequent sections but G's full production and characterization mechanisms have been documented elsewhere in the literature [22].

G must be produced at rates that are compatible with existing materials in order to be utilized by various industries [23, 24]. The development of the production processes that deliver high yields and high-quality products while being cost-effective, reliable, and scalable remains to be a big challenge [25]. As a result, these attributes are the main focus of the following discussion on techniques of G synthesis [26]. Depending on the desired outcome and purity, different methods have been developed to create layers and thin films of G. The schematic representation of the bottomup (construction) and top-down (destruction) mechanism is depicted in **Figure 1**.

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

**Figure 1.** *Synthesis of G from top-down and bottom-up approaches.*

Thus, a bottom-up process is the one in which the initial raw materials are found in a smaller entity and are then transferred to a larger entity or sustrate. Chemical vapor deposition (CVD) is an example of a bottom-up strategy for synthesizing G. Because it is more likely to result in fewer flaws, a more homogeneous chemical composition, and better short- and long-range ordering of G, the bottom-up strategy is preferable to the top-down approach. On the other hand, a top-down strategy begins with large or small-scale structures and reduces the size using a variety of techniques. Furthermore, it is believed that the planes or layers (the building blocks) necessary to create the desired nanostructure are taken out of the substrate during the synthesis process. For better control of G synthesis, the top-down method is typically used. The graphite exfoliation in the top-down techniques can be achieved by both mechanically and chemically in the top-down approach [27, 28].

The conventional top-down and bottom-up techniques used for G synthesis are displayed in **Figure 2**.

#### *Chemistry of Graphene – Synthesis, Reactivity, Applications and Toxicities*

#### **Figure 2.** *Conventional G synthesis approaches.*

### **2.1 Top-down approaches**

The top-down approach is defined as a tactic that concentrates on the attack of powdered raw graphite. Eventually, the attack will split its layers and create G sheets. Chemical synthesis and mechanical or chemical exfoliation are some of the commonly used top-down approaches for G synthesis [29] and are discussed below.

#### *2.1.1 Mechanical exfoliation*

Multiple single-atomic layers of G make up the structure of graphite. Weak van der Waals forces accumulate and hold everything together. The interlayer spacing between each layer is 3.3 Å (0.33 nm), and the interbond energy is 2 eV/nm2 (eVnm−2). Mechanical exfoliation is the rarest and earliest recognized technique for extracting G flakes from a graphitic substrat. This is a top-down approach in nanotechnology in which longitudinal or transverse stress is applied to the graphite surface using a cheap adhesive tape (scotch tape) or AFM (atomic force microscopy) tip. Mechanically cleaving graphitic materials such as highly oriented pyrolytic graphite (HOPG), single-crystal graphite, or natural graphite, can produce singlelayer graphene (SLG) to few-layer graphene (FLG) by slicing down the layers [30, 31]. A single G layer may be separated from graphite using this technique by applying an external strain of approximately 300 nN/μm<sup>2</sup> [32]. A variety of methods such as scotch tape, use of an electric field [33], and ultrasonication [34] or even by transfer printing techniques [35, 36] can be used to exfoliate G from graphite. To increase the yield of SLG and FLG flakes, the HOPG has occasionally been bonded to the substrate using a common adhesives like epoxy resin [34, 37]. A recent study has demonstrated how gold films can be used to transfer print macroscopic G designs from patterned HOPG [38]. It is undoubtedly the least expensive way to make high-quality G. G is exfoliated from a graphite crystal by adhesive tape in this micromechanical process. Multiple-layer graphene that is still on the tape after being removed from the graphite is separated into numerous flakes of few-layer G through repeated peeling. In order to detach the tape, it is then bonded to the acetone substrate, and the last peeling is

#### *Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

done with an unused tape. The resulting flakes have varied sizes and thickness, with diameters of a single-layer G based on wafer ranging from nanometers to many tens of micrometers. Due to interference effects, single-layer G on SiO2/Si can still be seen under a light microscope despite having an absorption rate of 2% [39]. Optical microscopy, Raman spectroscopy, and AFM are typically used to characterize G flakes produced by mechanical exfoliation techniques.

Despite the absence of sustainable flakes, it is actually difficult to produce high quantity of G with this exfoliation technique. Although this process has very little difficulty, it requires a lot of labor to locate the G flakes on the substrate surface. The prepared G has nearly no defects and a very high quality, which is suited for the manufacture of FET (field effect transistor) devices. However, for large-scale, defect-free, high-purity G for mass manufacturing in the field of nanotechnology, the mechanical exfoliation method still needs to be improved.

#### *2.1.2 Chemical exfoliation*

One of the finest methods for producing G is chemical synthesis. The first chemical production of G oxide occurred in 1860 using the Brodie method [40]. This was followed by the development of the Hummers [41] and Staudenmaier [42] processes. G is modified from graphite and a graphite intercalation compound using a chemical processs that produces colloidal suspension. Chemical exfoliation involves two steps; it increases the interlayer separation by first reducing the van der Waals forces between the graphite layers by creating G intercalated compounds (GICs) [43, 44]. Then, fast heating or sonication are used to exfoliate single to few layers of G. Ultrasonification is used to produce single-layer G oxide (SGO) [2, 42, 45–48], while density gradient ultracentrifugation is used to create different layer thicknesses [49, 50]. By using the Hummers process, which involves oxidizing graphite using potent oxidizing agents like KMnO4 and NaNO3 in H2SO4/H3PO4, it is simple to produce G oxide (GO) [42, 51]. SLG was produced via ultrasonication in a DMF/ water (9:1) combination. Interlayer spacing therefore increases from 3.7 to 9.5 A. High density of functional groups make oxidation necessary, and reduction is required to get G-like characteristics. Chemical reduction with hydrazine monohydrate is used to scatter single-layer G sheets [2, 47].

Elsewhere, G has been produced using polycyclic aromatic hydrocarbons (PAHs) [51–53] by utilizing a precursor to the dendrict that has undergone cyclodehydrogenation and planarization [54] to create tiny G domains. According to these authors, small domains of G can be produced by using this approach, but larger flakes are produced by the precursor of poly-dispersed hyper-branched polyphenylene. The first one was synthesized via oxidative cyclodehydrogenation with FeCl3. Orthodichlorobenzene [55], perfluorinated aromatic solvents [56], and even low-boiling solvents like chloroform and isopropanol [57, 58] are employed to disperse G. G on SiO2/Si substrates exhibits electrostatic interaction between HOPG and the Si substrate [59]. HOPG has also been subjected to pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser exfoliation in order to create FG [60, 61]. Good-quality G, also known as reduced G oxide (rGO), is produced via reduction of graphite oxide (GO). Fabrication of energy storage materials [62], polymer composites [63], transparent conductive electrodes [64], and several types of paper [40], among others, have already employed the chemical technique to produce G.

#### *2.1.3 Oxidative exfoliation reduction*

The majority of GO is created through the reduction of reduced G oxide (rGO) or from G sheets after oxidative graphite exfoliation. Staudenmaier, Brodie, Hummers, and Hofmann are the most common methods for producing GO [27].

#### *2.1.3.1 Brodie's method*

The first person to use KClO3 in severely fuming HNO3 to produce a novel compound containing carbon, oxygen, and hydrogen was Benjamin Collins Brodie, at the University of Oxford, London. The quality of flake G has improved as a result of this innovative approach. The batch was washed to remove any salts that had formed throughout the process, dehydrated at 100°C, and then put back into the oxidizing atmosphere. A substance with a "light yellow color" that did not change with additional oxidation treatment was produced after three successive attempts of that method. He provided the final molecular composition of the oxidized graphite as C11H4O5, in accordance with the elemental analysis of his product. In addition, he discovered that the chemical precipitated in acidic surroundings but dispersed in basic or pure water, after which he came up with the name "graphic acid" for the newly synthesized substance. The shift in the material's C:H:O composition to 80.13:0.58:19.29 was brought about by the reduction in carbonic acid and carbonic oxide after heating at 220°C. However, despite the fact that this method can oxidize graphite, its application is constrained by the lengthy response time and dangerous toxic gas emissions [41, 65].

#### *2.1.3.2 Staudenmaier's method*

Staudenmaier from Freising university, München, Germany, used enormous quantities of sulfuric acid and an excess of oxidizing chemicals to enhance Brodie's method. Numerous aliquots of concentrated sulfuric acid (H2SO4) were added, and throughout the procedure, potassium chlorate solution was added to the reaction mixture in order to improve Brodie's KClO3-fuming HNO3 formulation's ability to oxidize. These modifications made it possible to produce a highly oxidized GO product in a single reaction vessel, greatly simplifying the GO synthesis process. Although Staudenmaeir's approach was improved, Brodie's method's shortcomings remained, making the oxidation process time-consuming and dangerous. When potassium chlorate is introduced, it can last for more than a week, and when chlorine dioxide is removed from the inert gas, deadly gas explosions can occur continuously [43, 65].

#### *2.1.3.3 Hofmann's method*

To improve the work of both Brodie and Staudenmaier, Hofmann et al. used concentrated sulfuric acid and concentrated nitric acid and KClO3 to synthesize GO in place of fuming nitric acid because fuming HNO3 is exceedingly deadly and dangerous. In addition to acting as an in situ source of dioxygen in acid solutions, KClO3 demonstrated a significant degree of oxidation capacity as the principal oxidant. So far, numerous research teams have used this technique to effectively manufacture GO [65].

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

#### *2.1.3.4 Hummer's and modified Hummer's method*

So, a different method for producing GO was developed by chemists Hummers and Offeman at the Mellon Institution of Industrial Research around 60 years after Staudenmaier's approach. A concentrated sulfuric acid, sodium nitrate, and potassium permanganate solution was prepared and held at temperatures under 45°C to oxidize graphite. First, 100 g of graphite powder and 50 g of sodium nitrate were added to 2.3 L of sulfuric acid to chill it to 0°C in an ice bath. After then, the suspension received 300 g of potassium permanganate gradually. The suspension's internal temperature was raised to 35° when the ice bath was removed, and it was maintained there for 30 min. The combination turned brownish-gray and pasty, and barely any gas had emerged after 20 minutes. After 30 minutes, 4.6 L of water was gradually added to the paste, causing it to fizz vigorously and increase in temperature to 98°C. When this reaction was allowed to continue for 15 minutes at this temperature, the diluted sample turned brown. In order to convert the leftover permanganate and manganese dioxide into colorless soluble manganese sulfate, 3% H2O2 was added after the operation. To remove the soluble salt of mellitic acid, the diluted solution was filtered and constantly washed with warm water. Centrifugation was used initially to obtain the dry form of GO and then dehydration at 40°C over phosphorous pentoxide under vacuum.

#### *2.1.3.5 Recent advances in G and G oxide synthesis*

**Figure 3** illustrates the response patterns of these low-temperature operation G production approaches; normally conducted at lowest possible reaction temperatures to keep production costs down. However, most of these methods except Hummers method result in the production of toxic gases such as nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4) [29] raising public health and environmental safety concerns. The Hummers technique is presently extensively employed for the synthesis of GO due to its notable efficiency and safety. Additionally, it does not produce dangerous gases like ClO2 (chlorine dioxide) or acidic fog as it uses sodium nitrate (NaNO3)


**Figure 3.** *Various routes of G oxidation.* and potassium permanganate (KMnO4) rather than nitric acid (HNO3) and potassium perchlorate (KClO4). Overtime, improvements to the Hummers method have led to a more environment-friendly method of producing GO.

However, the G research "gold-rush" started in 2004, and GO also became a prominent material. Numerous articles on its preparation, reduction, and structure have been written. In 2010, Marcano et al. revealed an improved method for making GO. They reduced the amount of NaNO3 and raised the amount of KMnO4 in this new procedure. They also introduced H3PO4 to the reaction container in the place of the original acid. This improved method prevents a significant exotherm and produces no toxic gas. GO produced using this approach has a higher yield and degree of oxidation than GO produced using Hummers' process. They also found that the new method affects the graphite's basal plane less than Hummers' approach [42, 65].

The addition of graphite intercalation components in the oxidation process of graphite leads to a notable enhancement in the separation between graphite layers. Consequently, this enhancement may facilitate the formation of well-dispersed single-, bi-, and few-layer G oxide (GO) structures in suitable solvents. Tetrahydrofuran (THF), water, and N-methyl-2 pyrrolidone (NMP) are some of the fluids in which GO can disperse due to oxygen-containing functional groups including carboxylic, hydroxyl, and carbonyl groups. Electrochemical, thermal, and chemical reduction is then employed to eliminate the functional groups and reconstruct the honeycomb lattice of GO as its sp2 bonding is broken. In the chemical reduction techniques, hydrazine (N2H4) is typically used to lower the oxygen content of GO. However, N2H4 use is restricted due to its high cost and dangerous nature. As a result, a safer alternative to the dangerous N2H4 used in GO reduction was developed. Among the reducing agents used were proteins, microorganisms, plant extracts, amino acids, metal-alkaline, metal-acid, reagents (nitrogen, sulfur, oxygen), hydrohalic acid, aluminum hydrides, borohydrides, and hormones.

Nonetheless, even though numerous GO reduction techniques are mentioned in the literature [66] including electrochemical reducation, plasma therapy, sonochemical, photocatalytic, laser, photothermal, and microwave technology, the electrochemical GO reduction has gained more prominence because of its economic viability, quick reduction, and simplicity of implementation. More importantly, it uses safer reductants than chemical reduction does.

In general, a reasonable cost and good yield are associated with the production of GO through the oxidative exfoliation of graphite and subsequent reduction to rGO. However, it is found that the product from this approach has a small surface area, lower solubility, and weaker electrical conductivity because of van der Waals attraction, and it is liable to irreversible sheet restacking [67, 68].

Furthermore, it is still not possible to fully reduce GO to produce pure G [69]. Nonetheless, although it has some imperfections and different sizes from pure G, the resulting rGO is pretty comparable to it. Greater rGO quality is produced via high deoxygenation, which is caused by a high C:O ratio.

#### *2.1.4 Liquid phase exfoliation*

Liquid phase exfoliation or LPE has traditionally involved two basic methods for exfoliating graphite: (1) cavitation in sonication, and (2) shear forces in high-shear mixers [68]. Recently, it has been discovered that a microfluidizer may effectively exfoliate graphite in appropriate aqueous solutions at high shear rates [70]. LPE is an easy-to-use high-shear mixing or sonication instrument that is widely accessible. *Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

**Figure 4.** *Liquid exfoliation.*

Additionally, LPE does not need a vacuum or high-temperature systems to operate because its working conditions are mild. However, the low amount of G and the significant energy consumption during the fabrication process has limited the widespread use of sonication-assisted LPE as shown in **Figure 4**. The microfluidizer or high-shear mixing is a developing LPE technique, which successfully exfoliates graphite using fluid dynamics powered by a high-shear mixer [71, 72].

#### *2.1.4.1 Sonication*

At high concentrations, sonication is an effective exfoliation method that has the potential to produce monolayer- or few-layer G. By creating cavitation bubbles, sonication is frequently used to effect physical or chemical changes in a variety of systems [73]. Compressions and rarefactions impose high and low pressure, pushing and pulling molecules, as ultrasonic waves move across the medium. With each cycle of rarefaction, microbubbles get larger until they reach an unstable state and burst, producing enormous shockwaves [74].

Sonication is classified into two types, bath sonication (BS) and tip sonication (TS), which have been used together or separately to generate monolayer- or fewlayer G sheets by exfoliating G [75]. Sonication-assisted LPE typically consists of three phases [76]: (1) production of graphite dispersion in a particular solvent; (2) exfoliation of graphite dispersion using sonication; and (3) G purification. The cavitation-induced pressure pulsations are responsible for the formation and collapse of microbubbles in liquids during sonication. The cavitation action produces highspeed microjets and shockwaves, which create normal and shear stresses on graphite [77], which are important in the exfoliation of graphite to produce G [75]. The exfoliation impact is generally affected by the sonication power, the liquid medium, and the centrifugation rate utilized to disperse the G nanosheets [78]. The appropriate liquid media are chosen to establish an environment that allows for stable G dispersions during sonication, and centrifugation is used in removing big and unevenly distributed graphite particles or aggregates.

#### *2.1.4.2 High-shear mixing*

Until recently, the exfoliation of graphite by high-shear mixing has not been well researched; in particular, few investigations have focused on high-shear mixing in

aqueous systems utilizing ionic- or non-ionic surfactants. Nonetheless, it has been demonstrated that G may be exfoliated from graphite using shear force in a suitable liquid [79]. Furthermore, strong shear pressures applied by high-shear mixers are considered to be scalable techniques of graphite exfoliation [80]. Shear exfoliation is analogous to sonication exfoliation in that aqueous liquids may be utilized to aid graphite exfoliation and generate stable G dispersions, hence removing the need for use of toxic organic liquids. It is critical to develop industrially scalable ways for producing high-quality G using novel exfoliation processes such as sonication. Coleman and co-workers achieved substantial success in G production by shear exfoliation in 2014 [80], which fueled the great growth of the shear exfoliation process. They proved that high-shear mixing of graphite in suitable solvents might produce highconcentrated G nanosheet dispersions. The resulting G flakes had not been oxidized and had no basal-plane flaws. Notably, when the local shear rate surpassed 104 s−1, graphite was exfoliated in both laminar and turbulent zones. When comparing shear exfoliation to sonication, shear exfoliation is more efficient, and when a liquid volume of 10 m3 is reached, their scaling rule allowed for a rate of up to 100 gh−1. Recently, the modified Hummers' approach was used to generate G oxide using high-shear mixing [81]. **Table 1** displays the concentration of G dispersion produced by high-shear mixing with various solvents, with 10 mgmL−1 being the greatest concentration.

#### *2.1.4.3 Microfluidization*

High pressure is applied to the fluid during the high-pressure homogenization process known as microfluidization, which drives the fluid through a microchannel with a diameter of d < 100 μm [83, 84]. It produces mild exfoliation conditions, which can assist to reduce the creation of flaws. In general, microfluidization is used in nanoemulsification [85], the food sector [86], cell disintegration [87], carbon nanotube dispersion [85], and fluidizing active medicinal components [88]. Recently, G quantum dots [89] and G-based conductive inks were produced using a microfluidizer. The fundamental advantage of mircrofluidization over sonication and high-shear mixing is that a high shear rate (less than 10<sup>6</sup> cm − <sup>1</sup> ) exists throughout the fluid area.


#### **Table 1.**

*G concentrations obtained via high-shear mixing in different solvents.*

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

#### *2.1.5 Unzipping carbon nanotubes (CNTs)*

In this process, cylindrical carbon nanotubes (CNT) are sliced into flat G sheets with one, two, or a few layers in either the axial or longitudinal orientation. Starting materials can be single-wall carbon nanotubes (SWCNT) or multi-wall carbon nanotubes (MWCNT) [90] The unzipping of CNT can be accomplished using a number of techniques, including plasma etching [91], chemical unzipping [92], intercalation and exfoliation [93], and metal catalyzed cutting [94]. The generation of nanoribbons is caused by the longitudinal unzipping of CNT.

In chemical unzipping, H2SO4 treatment and oxidation with KMnO4 results in longitudinal cutting of CNTs. After that, chemical reduction of the oxidized G will take place utilizing NH4OH and hydrazine monohydrate (N2H4H2O) solution [92]. Because the precursor is destroyed during oxidation and G loses some of its electrical properties due to the presence of oxygen defect sites, this approach is regarded as being of low significance [95]. When MWCNT is intercalated in oxalic acid, as a chemical medium, before the chemical unzipping, G yield is increased. The suitable size of oxalic acid, which intercalates nicely between the interlayers of the MWCNT [96], resulting in an increase in G yield is 0.34 nm. Polymer films like poly-methyl methacrylate are utilized in plasma etching. This technique involves embedding CNT into the film, followed by the separation of the film and CNT combination in a KOH solution. After that, CNT is exposed to plasma made of argon, and the CNT's longitudinal C∙C link is dismantled to provide G with clean edges [91]. Another way to unzip CNT is through intercalation and exfoliation, where CNTs are exposed to a reaction between lithium and ammonia. The separation of the G layers occurs as a result of a significant amount of stress being applied between the CNT layers during this procedure [93]. Researchers looked at other metal nanoparticles like nickel, cobalt, and copper and discovered that these nanoparticles broke the C∙C bonds and hydrogen bonds in MWCNT [97], but the techniques employed expensive and dangerous chemicals. Using an electric field from a tungsten electrode, MWCNT can be unzipped [98] producing highly pure, defect-free G nanoribbons. Therefore, due to its accuracy, viability, and environmental friendliness, the electric field approach is preferred.

#### *2.1.6 Ball milling*

An innovative technique for producing high-quality G by dissolving layered graphite into G is ball-milling method, which is said to have begun some 150 years ago, when it was used to produce talc powder, communicate ore size, and for a number of other purposes, but now, the method has recently been suggested for the producing nanoparticles at room temperature [99–101]. It is an easy and highly successful solid-state approach for reducing a variety of materials to fine powders, synthesizing nanocomposites, and foxides, making it a potential method for producing G in large quantities at a reasonable cost [102]. Large graphite sheets undergo shear stresses during milling, whereas normal force is used to crush graphite flakes into nano-sized materials and expose cracks in the basal plane. Both wet and dry conditions can be used to perform the milling procedure [103]. Lv et al. employed Na2SO4 salt to make G nanosheets with ripple-like corrugations in hundreds of square nanometer range [103, 104]. Elsewhere, ball milling was carried out in a planetary ball-mill machine with graphite, dry ice, and stainless-steel balls as shown in **Figure 5** [105]. It is found that the type of media utilized affects the size and quality of the materials produced. By using wet ball milling to exfoliate graphite into G flakes in a

**Figure 5.** *Ball milling method.*

liquid media, Zhao et al. provided a fresh perspective on the ball milling process. The measured thickness was found to be between 0.8 and 1.8 nm, which is equivalent to discrete monolayer and few-layer G (up to three layers). Because of this, there has been a lot of recent research activities in ball milling [106]. Additionally, Caicedo et al. reported on the oxidation of graphite using the ball-milling process in order to exfoliate G from graphite using KClO4 and filtered water. It was shown that, as the milling time was increased, the degree of oxidation also did. Furthermore, the effects of oxidation were investigated using different ball milling time intervals (6, 12, 18, 24, and 30 h) in this manner, and the results were compared to those of the samples that were obtained form the Hummers methods. Thus, after 18 h of milling, the sample displayed improved dispersion and a darker hue as a result of the elimination of functional groups including carboxyl, hydroxyl, and epoxy [99, 107]. Here, the sample obtained after 16 h of milling was the best sample in terms of the level of oxidation, length, and energy utilization parameters assessed. The advantage of the ball milling approach is its ability to produce high-quality and low-cost G. It is a useful technique for exfoliating and functionalizing G. However, the prolonged processing times have resulted in a significant decrease in synthesis of G [99].

#### **2.2 Bottom-up approaches**

In the bottom-up techniques of synthesis, G sheets are generated directly from organic precursors such as methane and other hydrocarbon sources as illustrated in **Figure 2**. These methods transform molecular source materials into G-based substances [108]. Various examples of these approaches include chemical vapor deposition (CVD) [109], epitaxial growth [110], substrate-free gas-phase synthesis (SFGP) [111], template routes [112], and comprehensive organic synthesis [113]. While bottom-up strategies yield G products characterized by large surface areas and minimal defects, they often entail elevated production expenses.

#### *2.2.1 Chemical vapor disposition*

Methane (CH4), acetylene (C2H2), ethylene (C2H4), and hexane (C6H14) are a few of the hydrocarbon gases that are broken down during CVD in order to develop G sheets on metallic catalysts (such as Cu and Ni films) at high temperatures (650– 1000°C) [27]. The carbon precursor separates into free carbon and hydrogen atoms when it comes into contact with a metal catalyst's heated surface. Once the carbon

#### *Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

atom attains the carbon solubility threshold, it undergoes diffusion throughout the surface and the bulk of the metal catalyst, ultimately resulting in the formation of a G layer on the metal substrate. Substrates such as glass, quartz, silicon, silicon oxide, boron nitride, and sapphire have been utilized for G production in an effort to optimize CVD techniques described in the work of Chen et al. [114].

Chemical vapor deposition (CVD) enables the production of high-quality G characterized by, a densely interconnected structure, substantial surface area, and minimal structural defects. Nevertheless, it presents drawbacks such as elevated production expenses, modest output, the necessity for additional purification to eliminate catalyst remnants, and the challenge of transferring G to alternative substrates [115]. Furthermore, CVD alone falls short of meeting commercialization needs due to the demand for substantial improvements in manufacturing cost and yield. To surmount these challenges without compromising G quality, researchers have directed their efforts toward refining synthesis conditions, targeting lower temperatures and ambient pressure [116]. For example, by employing surface wave plasma-enhanced CVD (PECVD), Kalita et al. achieved G synthesis at 450°C. This innovation considerably enhanced the overall process by significantly reducing growth temperature and deposition time (5 min) [113, 117]. The conventional CVD setup can be adapted to accommodate PECVD. To be practical on a commercial scale, the development of CVD must continue in conjunction with other technologies like thermal-based and plasma-based CVD.

#### *2.2.2 Epitaxial growth on silicon carbide*

G can also be synthesized by thermally decomposing silicon carbide (SiC) hexagonal substrate at temperatures between 120o and 1600°C in an inert or vacuum environment, as shown in **Figure 6**. Because silicon (Si) melts at a high temperature (1100°C), too many C atoms remain behind and create a sp2 hybridized network, which promotes the formation of G [117]. The epitaxial growth of G on SiC is the term used to describe this process [118]. The G created using this process, however, is not homogeneous [119]. It has been documented that SiC and polytetrafluoroethylene (PTFE) undergo a unique exothermic reaction [120]. Due to the energy-intensiveness of the technique and constrained size of commercial SiC substrate, epitaxial development of G would be expensive under current synthesis conditions. Additionally, the

#### **Figure 6.**

*Epitaxial growth on SiC showing Si (yellow spheres) and C (gray spheres) atoms (under elevated temperatures, Si atoms evaporate (arrow), creating a carbon-rich surface that gives rise to the formation of G sheets).*

epitaxial development might result in polar faces like Si-face or C-face that degrade the quality of the finished G product as shown in **Figure 6** [113, 121]. This technique makes it simple to modify the amount of G layers that are dependent on the heating temperature [122].

The most noticeable benefit of G on the Si-face is that we can easily regulate the G thickness at the wafer size on the semi-insulating SiC substrate. By adjusting the growth temperature optimally, this control is accomplished. Images, captured by a high-resolution transmission electron microscope (HRTEM), of the G produced is monolayer, bilayer, trilayer, and eight-layer configurations at various temperatures. The number of G layers can be calculated directly from HRTEM images. Monolayer G is used to layer the buffer layer [123]. Like graphite, bilayer G is AB-stacked (Bernal-stacked) [124]. Further HRTEM observation revealed an ABC-stacking (rhombohedral stacking) of more than three layers [124]. This is a striking contrast to the Bernal bulk stacking graphite. An electric field-induced bandgap is present in the ABC-stacked trilayer G. The ABC-stacked trilayer G demonstrates a ferrimagnetic spin arrangement, an anomalous quantum Hall effect, and an electric field-driven bandgap [125–128]. By using HRTEM observation, the aforementioned atomic-scale growth mechanism was also studied.

#### *2.2.3 Pyrolysis*

Using the solvothermal approach, G can be formed chemically using the bottom-up method throughout the pyrolysis technique. For example, during the thermal reaction, the molar ratio of sodium and ethanol is determined 1:1 in the reaction vessel. This process involves heating a 1:1 molar reaction between 2 g sodium and 5 mL ethanol in a sealed reactor vessel at 220°C for 72 hours to produce the G precursor, also known as the solid solvo thermal product. The leftover precursor is then quickly pyrolyzed and washed with 100 mL deionized water. After that, the suspended solid is vacuumfiltered and dried for 24 hours at 100°C. This process yields 0.5 g of G per reaction, or 0.1 g of G every milliliter of ethanol [123]. Another example is the sonication-based pyrolization of sodium ethoxide. A PTFE (Polytetrafluoroethylene) melting pot was placed in an inert atmosphere and filled with 5 ml of ethanol and 2 g of sodium. To produce sodium ethoxide, the tank was firmly sealed and heated to 180°C for 24 hours. This was placed in an ignition dish and ignited in air and left to burn. Keep in mind that handling high pressure, sodium, or open flames requires the utmost caution. After being gathered, the carbonized product was broken up using a pestle, combined with deionized water, and sonated for a number of hours. After that, it was cleaned in deionized water using the method in [123]. The procedure might easily improve the detachment of G sheets. As a result, the produced G sheets have a thickness of 10 μm. To further investigate the graphitic properties, crystalline structure, band structure, and various layers of materials is executed by using Raman spectroscopy, selected area (electron) diffraction, and transmission electron microscopy [129].

#### *2.2.4 Substrate-free gas-phase method*

The substrate-free gas-phase (SFGP) approach is a relatively recent technique for producing G materials through gas-phase reactions by eliminating the need for substrates [130]. This process involves introducing liquid ethanol and Ar gas into microwave-generated plasma under atmospheric conditions. As ethanol droplets vaporize and dissociate within the plasma region over a time span of approximately

#### *Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

1 second, G is synthesized. Notably, this method reportedly yielded 2 mgmin−1 of G from an input of 164 mgmin−1 of ethanol [131]. Dato and Frenklach [132], on the other hand, explored the potential of different carbon precursors using this technique. Isopropyl alcohol and dimethyl ether were identified as possible precursors for generating G nanosheets.

#### *2.2.5 Total organic synthesis*

Total organic synthesis involves using polycyclic aromatic hydrocarbons (PAHs) with specific characteristics to create G. PAHs, often described as 2D G segments, composed entirely of sp2 carbons due to their structural resemblance, can be readily modified with aliphatic chains to tailor the solubility of the final product [133]. Crucial to this method is the selection of appropriate precursors that produce high yield quality G through a straight forward reaction pathway. The process results in 2D G nanoribbons (GNRs) up to 12 nm in length, as demonstrated by Yan et al. [134, 135]. However, the relatively narrow size distribution of PAHs might affect the quality of G due to reduced solubility and potential side reactions stemming from their higher molecular weight. Subsequent improvements by Yan et al. addressed these limitations [135].

#### *2.2.6 Template route*

The template route employs one-dimensional templates, such as metals, oxides, or polymers, to synthesize G derivatives with high throughput, quality, and well-defined structures [135]. Wei et al. initiated this approach [136]. Through physical vapor deposition (PVD), ZnS ribbons were created as templates for G formation using CH4 as the carbon source. Subsequent etching with HCl removed residual ZnS nanobelts. Another template-based strategy involves G synthesis through the self-assembly of G on a meso-structured silica template formed from a pyrrole moiety-containing surfactant [137].

#### **2.3 Trending techniques of synthesis of G**

#### *2.3.1 Microwave-assisted synthesis*

Graphite or GO that has undergone a modified version of Hummer's process is typically used to produce G nanosheets (GNS) [60, 138–140]. Chemical procedures are typically used to rGO in the presence of several hazardous reduction agents, including hydrazine and NaBH4. Thermal treatment, in contrast, uses no toxic reduction chemicals, making it a greener option. The environmentally friendly microwaveassisted method has gained increasing attention as a substitute for the traditional preparation of G in traditional heating systems (furnace or oil bath). In this method, GO [141, 142] or natural graphite [143] can be treated using the microwave-assisted solvothermal/hydrothermal methods in a microwave oven or microwave plasmaenhanced chemical vapor deposition (MPCVD) system.

In this method, nontoxic solvents are used to exfoliate GO within a short reaction period of 1 to 15 min at a relatively low temperature range of 180 to 300°C [138]. According to a study, an easy microwave-assisted solvothermal technique may produce a stable G suspension from a GO suspension in an alkaline medium (pH 10) or in polar solvents such as N,N-dimethylformamide, ethanol, 1-butanol, and water.

Additionally, the water-soluble polymer-grafted G sheets have been produced from GO by preparing them for 4 min at 450 W in a standard household microwave [138]. A residential microwave was used to create a three-dimensional (3D) nanostructure of a "G nano-cup" anchored on a few layers of G substrate [138]. Two stages were reported: the one-pot synthesis of G coated metal nanoparticles anchored on the G sheets and the subsequent etching of metals. This was done under the microwave irradiation in a home microwave oven [138]. More importantly, highly hydrogenated G could be created from GO by a one-step microwave irradiation process in hydrogen plasma, in which the deoxidation and concurrent hydrogenation were both accomplished. Giant G sheets could also be obtained by double microwave-assisted exfoliation of expandable graphite. High local temperatures and pressure are provided by microwave irradiation, and energy is sent directly into the inside of the GO. The polar link of oxygen-containing functional groups on the surface and edge of GO sheets interacts with radiation to produce heat [144]. Additionally, a key element in determining the regularity of deposits is the interaction between polar solvents and the surface oxides on GO sheets. Furthermore, the reduction degree of G sheets is further enhanced, and the functional groups on the surface of GO are successfully lowered.

There are several distinct advantages of utilizing microwave technology to create G. First of all, the microwave-assisted technique is quick and does not require a difficult synthesis process. Second, compared to more traditional methods, this technique is very cost-effective because it uses less chemicals. Third, compared to G made using the traditional heating approach, those produced using microwave-assisted technology may have an average size that is ten times larger. Finally, high-quality G with regulated structure and residual functional groups is produced using microwave-assisted technique [138]. Microwave sources enable localized high temperatures, rapid energy transfer, and efficient precursor disintegration. These attributes lead to homogenous nucleation environments, rapid crystallization, controlled particle size distribution, and precise morphology regulation [145, 146]. This technique facilitates the creation of G-based nanocomposites with adjustable sizes and shapes, enhancing applications like particle/crystal-on-sheet, nanorod/nanofiber-on-sheet, and nanosheet-on-sheet [147].

#### *2.3.2 Electrochemical exfoliation*

Electrochemical exfoliation of graphite has become a popular way to make G compounds in recent years. Graphite can be utilized as working electrodes in liquid electrolytes in a range of geometries, such as powders, foils, rods, flakes, or plates [148]. There are two types of exfoliation techniques: cathodic, which applies a negative bias to graphite electrodes, and anodic, which uses a positive bias. In cathodic exfoliation, positively charged electrolyte ions such Li+ would be drawn to graphite electrodes. In anodic exfoliation, negatively charged ions, such as SO4 −2, may be drawn to electrodes. The van der Waals forces have been hypothesized to be broken by electrochemical reactions, which causes graphite's structural expansion [149]. Additionally, during electrochemical exfoliation, chemical interactions with functionalizing agents can occur simultaneously in order to perform in situ chemical doping (functionalization) of G materials to create a variety of G-based composite materials [150, 151].

#### *2.3.3 Hydrothermal synthesis*

Hydrothermal treatment is a thermo-chemical conversion technique that results in efficient hydrolysis, pyrolysis, dehydration, polymerization, and aromatization

#### *Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

of organic precursors, as well as high oxygenated functional group content and condensed aromatic structures [152]. The hydrothermal treatment approach, which primarily involves the carbonization and reduction process, can convert biomass and GO to solid char and G, respectively [153]. During the hydrothermal treatment of biomass, small-molecules soluble byproducts such as aromatic compounds, polysaccharides, aldehydic, ketonic, and furan derivatives are also created, from which solid products are produced by further polymerization [154]. Based on pyrolysis, selfassembly, and dehydration, water-soluble and low-molecular weight fulvic acid (FA) can be transformed into G quantum dots. To our knowledge, however, no parallel investigations on water-insoluble, high-molecular-weight humic acid and the associated reaction mechanism have yet been published.

#### *2.3.4 Laser-induced graphenization*

Laser-induced graphitization (LIG) is an innovative technique that transforms carbon-rich sources into conductive carbon using lasers [155]. This approach holds promise for creating highly conductive graphenic materials suitable for energy storage devices, sensors, biomedical applications, and hydrogen evolution [156]. LIG has been applied to a variety of bio-based carbon sources, such as paper and wood, to achieve significant graphitization, potentially contributing to their use in various applications.

#### **3. Conclusion**

Due to its large surface area, thermal, electrical, and physical properties, the carbon material known as "graphene" has become important in the fields of micromanufacturing, nanomaterials, biomedical, and composite materials. However, due to its vast range of applications, G must be produced in large quantities, which has recently received a lot of attention from researchers and technologists. Therefore, improving the production process is essential for increasing the yield. Producing high-quality G is also necessary, but the most critical step is to use an easy, affordable, and environmentally friendly method. Future research should therefore focus on the yield measurement, biocompatibility as a result of the use of nontoxic chemicals, high energy, pressure, and poor transfer processes in chemical approaches, all of which have significantly contributed to high production costs, poor yield, and imperfections in the obtained G. The development of new techniques and environmentally friendly materials is crucial for the synthesis of G materials in electronics, nanomaterials, and biomaterials, all other factors being held constant. The size, shape, and optical properties of the resulting material are significantly influenced by the manufacturing processes and the carbon precursor sources used. G is suitable for use in electronics, energy storage, sensors, composites, drug delivery, and biomedical devices, because of its high transparency, thermal and electrical conductivity, and mechanical strength, in addition to its specific area. The improvements in G synthesis have opened up new opportunities for exploiting its extraordinary qualities and developing cutting-edge technology for a variety of industries. In summary, despite extensive study into producing G since its discovery, no method has been found to satisfactorily produce G on an industrial scale. This overview covered prospective uses for G as well as a comparative research and potential approaches.

### **Acknowledgements**

We would like to express our sincere gratitude to Dr. Arshad Jamal Ansari, Postdoctoral Scholar, at University of Southern California and institutions for his valuable suggestions and editing to the completion of this research endeavor.

### **Competing interests**

The authors declare no competing interests.

### **Author details**

Aafreen1†, Priyanka Verma1† and Haris Saeed2 \*

1 Faculty of Pharmacy, Shri Ram Murti Smarak College of Engineering and Technology, Bareilly, Uttar Pradesh, India

2 Keck School of Medicine, University of Southern California, Los Angeles, USA

\*Address all correspondence to: haris6229@gmail.com

† These authors are equally contributed.

© 2024 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

#### **References**

[1] Shinohara H, Tiwari A. Graphene: An Introduction to the Fundamentals and Industrial Applications. Beverly, Massachusetts, USA: John Wiley & Sons; 2015

[2] Allen MJ, Tung VC, Kaner RB. Honeycomb carbon: A review of graphene. Chemical Reviews. 2010;**110**(1):132-145

[3] Brodie BC. On the atomic weight of graphite. Philosophical Transactions of the Royal Society A. 1859;**149**:249-259

[4] Boehm HP, Clauss A, Fischer GO, Hofmann U. Das adsorptionsverhalten sehr dünner kohlenstoff‐folien. Zeitschrift für anorganische und allgemeine Chemie. 1962;**316**(3-4):119-127

[5] Wallace PR. The band theory of graphite. Physics Review. 1947;**71**:622-663

[6] Trivedi S, Lobo K, Ramakrishna Matte HSS. Synthesis, properties, and applications of graphene. In: Fundamentals and Sensing Applications of 2D Materials [Internet]. Sawston, United Kingdom: Elsevier; 2019. pp. 25-90

[7] Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, et al. Electric field effect in atomically thin carbon films. Science. 2004;**306**(5696):666-669

[8] Randviir EP, Brownson DAC, Banks CE. A decade of graphene research: Production, applications and outlook. Materials Today. 2014;**17**(9):426-432

[9] Shams SS, Zhang R, Zhu J. Graphene synthesis: A review. Materials Science-Poland. 2015;**33**(3):566-578

[10] Chen D, Feng H, Li J. Graphene oxide: Preparation, functionalization, and electrochemical applications. Chemical Reviews. 2012;**112**(11): 6027-6053

[11] Kumar R, Sahoo S, Joanni E, Singh RK, Yadav RM, Verma RK, et al. A review on synthesis of graphene, h-BN and MoS2 for energy storage applications: Recent progress and perspectives. Nano Research. 2019;**12**(11):2655-2694

[12] Mas-Ballesté R, Gómez-Navarro C, Gómez-Herrero J, Zamora F. 2D materials: To graphene and beyond. Nanoscale. 2011;**3**(1):20-30

[13] Singh RK, Kumar R, Singh DP. Graphene oxide: Strategies for synthesis, reduction and frontier applications. RSC Advances. 2016;**6**(69):64993-65011

[14] Dong R, Zhang T, Feng X. Interfaceassisted synthesis of 2D materials: Trend and challenges. Chemical Reviews. 2018;**118**(13):6189-6235

[15] Singh DP, Herrera CE, Singh B, Singh S, Singh RK, Kumar R. Graphene oxide: An efficient material and recent approach for biotechnological and biomedical applications. Materials Science and Engineering: C. 2018;**86**:173-197

[16] Farooqui UR, Ahmad AL, Hamid NA. Graphene oxide: A promising membrane material for fuel cells. Renewable and Sustainable Energy Reviews. 2018;**82**:714-733

[17] Yadav SK, Kumar R, Sundramoorthy AK, Singh RK, Koo CM. Simultaneous reduction and covalent grafting of polythiophene on graphene oxide sheets for excellent capacitance retention. RSC Advances. 2016;**6**(58):52945-52949

[18] Shuvo MAI, Khan MAR, Karim H, Morton P, Wilson T, Lin Y. Investigation of modified graphene for energy storage applications. ACS Applied Materials & Interfaces. 2013;**5**(16):7881-7885

[19] Tao LQ, Zhang KN, Tian H, Liu Y, Wang DY, Chen YQ, et al. Graphenepaper pressure sensor for detecting human motions. ACS Nano. 2017;**11**(9):8790-8795

[20] Rosli NN, Ibrahim MA, Ahmad Ludin N, Mat Teridi MA, Sopian K. A review of graphene based transparent conducting films for use in solar photovoltaic applications. Renewable and Sustainable Energy Reviews. 2019;**99**:83-99

[21] Ghawanmeh AA, Ali GAM, Algarni H, Sarkar SM, Chong KF. Graphene oxide-based hydrogels as a nanocarrier for anticancer drug delivery. Nano Research. 2019;**12**(5):973-990

[22] Zhang H. Introduction: 2D materials chemistry. Chemical Reviews. 2018;**118**(13):6089-6090

[23] Xia W, Dai L, Yu P, Tong X, Song W, Zhang G, et al. Recent progress in van der Waals heterojunctions. Nanoscale. 2017;**9**(13):4324-4365

[24] Ferrari AC, Bonaccorso F, Fal'ko V, Novoselov KS, Roche S, Bøggild P, et al. Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems. Nanoscale. 2015;**7**(11):4598-4810

[25] Singh A, Ahmed A, Sharma A, Arya S. Graphene and its derivatives: Synthesis and application in the electrochemical detection of analytes in sweat. Biosensors. 2022;**12**(10):910

[26] Yu H, Zhang B, Bulin C, Li R, Xing R. High-efficient synthesis of graphene oxide based on improved Hummers method. Scientific Reports. 2016;**6**(1):36143

[27] Singh V, Joung D, Zhai L, Das S, Khondaker SI, Seal S. Graphene based materials: Past, present and future. Progress in Materials Science. 2011;**56**(8):1178-1271

[28] Soldano C, Mahmood A, Dujardin E. Production, properties and potential of graphene. Carbon. 2010;**48**(8):2127-2150

[29] Gutiérrez-Cruz A, Ruiz-Hernández AR, Vega-Clemente JF, Luna-Gazcón DG, Campos-Delgado J. A review of top-down and bottom-up synthesis methods for the production of graphene, graphene oxide and reduced graphene oxide. Journal of Materials Science. 2022;**57**(31):14543-14578

[30] Lu X, Yu M, Huang H, Ruoff RS. Tailoring graphite with the goal of achieving single sheets. Nanotechnology. 1999;**10**(3):269-272

[31] Lang B. A LEED study of the deposition of carbon on platinum crystal surfaces. Surface Science. 1975;**53**(1):317-329

[32] Liang X, Chang ASP, Zhang Y, Harteneck BD, Choo H, Olynick DL, et al. Electrostatic force assisted exfoliation of prepatterned few-layer graphenes into device sites. Nano Letters. 2009;**9**(1):467-472

[33] Ci L, Song L, Jariwala D, Elías AL, Gao W, Terrones M, et al. Graphene shape control by multistage cutting and transfer. Advanced Materials. 2009;**21**(44):4487-4491

[34] Liang X, Fu Z, Chou SY. Graphene transistors fabricated via transfer-printing in device

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

active-areas on large wafer. Nano Letters. 2007;**7**(12):3840-3844

[35] Chen JH, Ishigami M, Jang C, Hines DR, Fuhrer MS, Williams ED. Printed graphene circuits. Advanced Materials. 2007;**19**:3623-3627. Available from: https://arxiv.org/abs/0809.1634 [Accessed: December 20, 2023]

[36] Huc V, Bendiab N, Rosman N, Ebbesen T, Delacour C, Bouchiat V. Large and flat graphene flakes produced by epoxy bonding and reverse exfoliation of highly oriented pyrolytic graphite. Nanotechnology. 2008;**19**(45):455601

[37] Song L, Ci L, Gao W, Ajayan P.M. Transfer printing of graphene using gold film. ACS Nano 2009; 3(6): 1353-1356

[38] Casiraghi C, Hartschuh A, Lidorikis E, Qian H, Harutyunyan H, Gokus T, et al. Rayleigh imaging of graphene and graphene layers. Nano Letters. 2007;**7**(9):2711-2717

[39] Stoller MD, Park S, Zhu Y, An J, Ruoff RS. Graphene-based ultracapacitors. Nano Letters. 2008;**8**(10):3498-3502

[40] Brodie BC. Sur le poids atomique du graphite. Annales de Chimie Physique. 1860;**59**:466-472

[41] Hummers WS, Offeman RE. Preparation of graphitic oxide. Journal of the American Chemical Society. 1958;**80**(6):1339-1339

[42] Staudenmaier L. Verfahren zur darstellung der graphitsäure. Berichte der deutschen chemischen Gesellschaft. 1898;**31**(2):1481-1487

[43] Wu YH, Yu T, Shen ZX. Twodimensional carbon nanostructures: Fundamental properties, synthesis, characterization, and potential

applications. Journal of Applied Physics. 2010;**108**(7):071301

[44] Marcano DC, Kosynkin DV, Berlin JM, Sinitskii A, Sun Z, Slesarev A, et al. Improved synthesis of graphene oxide. ACS Nano. 2010;**4**(8):4806-4814

[45] Park S, An J, Jung I, Piner RD, An SJ, Li X, et al. Colloidal suspensions of highly reduced graphene oxide in a wide variety of organic solvents. Nano Letters. 2009;**9**(4):1593-1597

[46] Park S, Suk JW, An J, Oh J, Lee S, Lee W, et al. The effect of concentration of graphene nanoplatelets on mechanical and electrical properties of reduced graphene oxide papers. Carbon. 2012;**50**(12):4573-4578

[47] Paredes JI, Villar-Rodil S, Martínez-Alonso A, Tascón JMD. Graphene oxide dispersions in organic solvents. Langmuir. 2008;**24**(19):10560-10564

[48] Green AA, Hersam MC. Emerging methods for producing monodisperse graphene dispersions. Journal of Physical Chemistry Letters. 2010;**1**(2):544-549

[49] Green AA, Hersam MC. Solution phase production of graphene with controlled thickness via density differentiation. Nano Letters. 2009;**9**(12):4031-4036

[50] Wu J, Pisula W, Müllen K. Graphenes as potential material for electronics. Chemical Reviews. 2007;**107**(3):718-747

[51] Cai J, Ruffieux P, Jaafar R, Bieri M, Braun T, Blankenburg S, et al. Atomically precise bottom-up fabrication of graphene nanoribbons. Nature. 2010;**466**(7305):470-473

[52] Yan X, Cui X, Li B, Li L shi. Large, Solution-processable graphene quantum dots as light absorbers for photovoltaics. Nano Letters 2010;10(5):1869-1873

[53] Zhi L, Müllen K. A bottom-up approach from molecular nanographenes to unconventional carbon materials. Journal of Materials Chemistry. 2008;**18**(13):1472

[54] Hernandez Y, Nicolosi V, Lotya M, Blighe FM, Sun Z, De S, et al. High-yield production of graphene by liquidphase exfoliation of graphite. Nature Nanotechnology. 2008;**3**(9):563-568

[55] Hamilton CE, Lomeda JR, Sun Z, Tour JM, Barron AR. High-yield organic dispersions of unfunctionalized graphene. Nano Letters. 2009;**9**(10):3460-3462

[56] O'Neill A, Khan U, Nirmalraj PN, Boland J, Coleman JN. Graphene dispersion and exfoliation in low boiling point solvents. Journal of Physical Chemistry C. 2011;**115**(13):5422-5428

[57] Hernandez Y, Lotya M, Rickard D, Bergin SD, Coleman JN. Measurement of multicomponent solubility parameters for graphene facilitates solvent discovery. Langmuir. 2010;**26**(5):3208-3213

[58] Zheng QF, Guo Y, Liang Y, Shen Q. Graphene nanoribbons from electrostatic-force-controlled electric unzipping of single- and multi-walled carbon nanotubes. ACS Applied Nano Materials. 2020;**3**(5):4708-4716

[59] Chae SJ, Güneş F, Kim KK, Kim ES, Han GH, Kim SM, et al. Synthesis of large‐area graphene layers on poly‐nickel substrate by chemical vapor deposition: Wrinkle formation. Advanced Materials. 2009;**21**(22):2328-2333

[60] Qian M, Zhou YS, Gao Y, Park JB, Feng T, Huang SM, et al. Formation of graphene sheets through laser

exfoliation of highly ordered pyrolytic graphite. Applied Physics Letters. 2011;**98**(17):173108

[61] Zhang Y, Zhou CG, Hua YX, Gao HL, Gao KZ, Cao Y. Synthesis of nafionreduced graphene oxide/polyaniline as novel positive electrode additives for high performance lead-acid batteries. Electrochimica Acta. 2023;**466**:143045

[62] Stankovich S, Dikin DA, Dommett GHB, Kohlhaas KM, Zimney EJ, Stach EA, et al. Graphenebased composite materials. Nature. 2006;**442**:282-286

[63] Wang X, Zhi L, Mullen K. Transparent, conductive graphene electrodes for dye-sensitized solar cells. Nano Letters. 2008;**8**(1):323-327

[64] Dikin DA, Stankovich S, Zimney EJ, Piner RD, Dommett GHB, Evmenenko G, et al. Preparation and characterization of graphene oxide paper. Nature. 2007;**448**:457-460

[65] Somanathan T, Prasad K, Ostrikov K, Saravanan A, Krishna V. Graphene oxide synthesis from agro waste. Nanomaterials. 2015;**5**(2):826-834

[66] Guo S, Garaj S, Bianco A, Ménard-Moyon C. Controlling covalent chemistry on graphene oxide. Nature Reviews Physics. 2022;**4**(4):247-262

[67] Khanra P, Kuila T, Kim NH, Bae SH, Sheng YD, Lee JH. Simultaneous biofunctionalization and reduction of graphene oxide by baker's yeast. Chemical Engineering Journal. 2012;**183**:526-533

[68] Chua CK, Pumera M. Chemical reduction of graphene oxide: A synthetic chemistry viewpoint. Chemical Society Reviews. 2014;**43**(1):291-312

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

[69] Kumar PV, Bardhan NM, Chen GY, Li Z, Belcher AM, Grossman JC. New insights into the thermal reduction of graphene oxide: Impact of oxygen clustering. Carbon. 2016;**100**:90-98

[70] Zheng X, Peng Y, Yang Y, Chen J, Tian H, Cui X, et al. Hydrothermal reduction of graphene oxide; effect on surface‐enhanced Raman scattering. Journal of Raman Specroscopy. 2017;**48**(1):97-103

[71] Coleman JN. Liquid exfoliation of defect-free graphene. Accounts of Chemical Research. 2013;**46**(1):14-22

[72] Pilli S, Bhunia P, Yan S, LeBlanc RJ, Tyagi RD, Surampalli RY. Ultrasonic pretreatment of sludge: A review. Ultrasonics Sonochemistry. 2011;**18**(1):1-18

[73] Flint EB, Suslick KS. The temperature of cavitation. Science. 1991;**253**(5026):1397-1399

[74] Lotya M, King PJ, Khan U, De S, Coleman JN. High-concentration, surfactant-stabilized graphene dispersions. ACS Nano. 2010;**4**(6):3155-3162

[75] Ciesielski A, Samorì P. Grapheneviasonication assisted liquidphase exfoliation. Chemical Society Reviews. 2014;**43**(1):381-398

[76] Han JT, Jang JI, Kim H, Hwang JY, Yoo HK, Woo JS, et al. Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation. Scientific Reports. 2014;**4**(1):5133

[77] Lin Z, Karthik P, Hada M, Nishikawa T, Hayashi Y. Simple technique of exfoliation and dispersion of multilayer graphene from natural graphite by ozone-assisted sonication. Nanomaterials. 2017;**7**(6):125

[78] Chen X, Dobson JF, Raston CL. Vortex fluidic exfoliation of graphite and boron nitride. Chemical Communications. 2012;**48**(31):3703

[79] Paton KR, Varrla E, Backes C, Smith RJ, Khan U, O'Neill A, et al. Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids. Nature Materials. 2014;**13**(6):624-630

[80] Chong KY, Chia CH, Chook SW, Zakaria S, Lucas D. Simplified production of graphene oxide assisted by high shear exfoliation of graphite with controlled oxidation. New Journal of Chemistry. 2018;**42**(6):4507-4512

[81] Wang YZ, Chen T, Gao XF, Liu HH, Zhang XX. Liquid phase exfoliation of graphite into fewlayer graphene by sonication and microfluidization. Materials Express. 2017;**7**(6):491-499

[82] Pavlova AS, Obraztsova EA, Belkin AV, Monat C, Rojo-Romeo P, Obraztsova ED. Liquid-phase exfoliation of flaky graphite. Journal of Nanophotonics. 2016;**10**(1):012525

[83] Paton KR, Anderson J, Pollard AJ, Sainsbury T. Production of few-layer graphene by microfluidization. Materials Research Express. 2017;**4**(2):025604

[84] Narsimhan G, Goel P. Drop coalescence during emulsion formation in a high-pressure homogenizer for tetradecane-in-water emulsion stabilized by sodium dodecyl sulfate. Journal of Colloid and Interface Science. 2001;**238**(2):420-432

[85] Jafari SM, He Y, Bhandari B. Production of sub-micron emulsions by ultrasound and microfluidization techniques. Journal of Food Engineering. 2007;**82**(4):478-488

[86] Burhan M, Chua KJE, Ng KC. Simulation and development of a multileg homogeniser concentrating assembly for concentrated photovoltaic (CPV) system with electrical rating analysis. Energy Conversion and Management. 2016;**116**:58-71

[87] Azoubel S, Magdassi S. The formation of carbon nanotube dispersions by high pressure homogenization and their rapid characterization by analytical centrifuge. Carbon. 2010;**48**(12):3346-3352

[88] Qian J, Yan J, Shen C, Xi F, Dong X, Liu J. Graphene quantum dots-assisted exfoliation of graphitic carbon nitride to prepare metal-free zerodimensional/two-dimensional composite photocatalysts. Journal of Materials Science. 2018;**53**(17):12103-12114

[89] Santhiran A, Iyngaran P, Abiman P, Kuganathan N. Graphene synthesis and its recent advances in applications—A review. C. 2021;**7**(4):76

[90] Baig Z, Mamat O, Mustapha M, Mumtaz A, Munir KS, Sarfraz M. Investigation of tip sonication effects on structural quality of graphene nanoplatelets (GNPs) for superior solvent dispersion. Ultrasonics Sonochemistry. 2018;**45**:133-149

[91] Jiao L, Zhang L, Wang X, Diankov G, Dai H, et al. Narrow graphene nanoribbons from carbon nanotubes. Nature. 2009;**458**(7240):877-880

[92] Kosynkin DV, Higginbotham AL, Sinitskii A, Lomeda R, Dimiev A, Price BK, et al. Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons. Nature. 2009;**458**(7240):845-846

[93] Abraham GCM, Macias RF, Delgado JC, Gonzalez ECG, Lopez FT, et al. Ex-MWNTs: Graphene sheets

and ribbons produced by lithium intercalation and exfoliation of carbon nanotubes. Nano Letters. 2009;**9**(4):1527-1533

[94] Thess A, Lee R, Nikolaev P, Dai H, Petit P, Robert JSG, et al. Crystalline ropes of metallic carbon nanotubes. Science. 1996;**273**(5274):483-487

[95] Liu J, Kim GH, Xue Y, Kim JY, Baek JB, Durstock M, et al. Graphene oxide nanoribbon as hole extraction layer to enhance efficiency and stability of polymer solar cells. Advanced Materials. 2014;**26**(5):786-790

[96] Mahmoud WE, Hazmi FS, Harbi GH. Wall by wall controllable unzipping of MWCNTs via intercalation with oxalic acid to produce multilayers graphene oxide ribbon. Chemical Engineering Journal. 2015;**281**:192-198

[97] Bhuyan MSA, Uddin MN, Islam MM, Bipasha FA, et al. Synthesis of graphene. International Nano Letters. 2016;**6**:65-83

[98] Sood AK, Chakraborty B. In: Rao CNR, Sood AK, editors. Understanding Graphene Via Raman Scattering. Hoboken, NJ, USA: John Wiley & Sons; 2012. pp. 49-90

[99] Mousavi BSM, Sadaf S, Walder L, Gallei M, et al. Poly(vinylferrocene) reduced graphene oxide as a high power/high capacity cathodic battery material. Advanced Energy Materials. 2016;**1600108**:1-13

[100] Hassanzadeh N, Sadrnezhaad SK, Chen GH. Ball mill assisted synthesis of Na3MnCO3PO4 nanoparticles anchored on reduced graphene oxide for sodium ion battery cathodes. Electrochimica Acta. 2016;**220**:683

[101] Lv YY, Yu LS, Jiang CM. Synthesis of graphene nanosheet powder with

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

layer number control via a soluble salt-assisted route. RSC Advances. 2014;**4**:13350-13354

[102] Kairi MI, Dayou S, Kairi NI. Toward high production of graphene flakes–a review on recent developments in their synthesis methods and scalability. Journal of Materials Chemistry A. 2018;**6**:15010-15026

[103] Jeon IY, Shin YR, Sohn GJ. Edgecarboxylated graphene nanosheets via ball milling. PNAS. 2012;**109**(15):5588-5593

[104] Zhao WF, Fang M, Wu FR. Preparation of graphene by exfoliation of graphite using wet ball milling. Journal of Materials Chemistry. 2010;**20**:5817-5819

[105] Dash P, Dash T, Rout TK, Biswal SK, et al. Preparation of graphene oxide by dry planetary ball milling process from natural graphite. RSC Advances. 2016;**6**:12657-12668

[106] Caicedo CFM, Lopez VE, Agarwal A, Drozd V, et al. Synthesis of graphene oxide from graphite by ball milling. Diamond and Related Materials. 2020;**109**:108064

[107] Lee XJ, Hiew BYZ, Lai KC, Lee YL, et al. Review on graphene and its derivatives: Synthesis methods and potential industrial implementation. Journal of the Taiwan Institute of Chemical Engineers. 2018;**18**:13

[108] Jacobberger RM, Machhi R, Wroblewski J, Taylor B, Gillian-Daniel AL, Arnold MS, et al. Simple graphene synthesis via chemical vapor deposition. Journal of Chemical Education. 2015;**92**:1903-1907

[109] Huang H, Chen S, Wee ATS, Chen W. Epitaxial growth of graphene on silicon carbide (SiC). In: Graphene. Sawston, United Kingdom: Woodhead Publishing; 2014. pp. 3-26

[110] Olatomiwa AL, Adam T, Gopinath SCB, Kolawole SY, Olayinka OH, et al. Graphene synthesis, fabrication, characterization based on bottom-up and top-down approaches: An overview. Journal of Semiconductors. 2022;**43**(6):1-15

[111] Albert D, Michael F. Substratefree microwave synthesis of graphene: Experimental conditions and hydrocarbon precursors. New Journal of Physics. 2010;**12**:125013

[112] Yang Y, Liu R, Wu J, Jiang X, Cao P, Hu X, et al. Bottom-up fabrication of graphene on silicon/silica substrate via a facile soft-hard template approach. Scientific Reports. 2015;**5**:13480

[113] Nair RR. Fine structure constant defines visual transparency of graphene. Science. 2008;**320**(5881):1308

[114] Brownson DA, Banks CE. The electrochemistry of CVD graphene: Progress and prospects. Physical Chemistry Chemical Physics. 2012;**14**(23):8264-8281

[115] Chen X, Wu B, Liu Y. Direct preparation of high quality graphene on dielectric substrates. Chemical Society Reviews. 2016;**45**(8):2057-2074

[116] Gupta B, Notarianni M, Mishra N, Shafiei M, Iacopi F, Motta N, et al. Evolution of epitaxial graphene layers on 3C SiC/Si (111) as a function of annealing temperature in UHV. Carbon. 2014;**68**:563-572

[117] Jang J, Son M, Chung S, Kim K, Cho C, Lee BH, et al. Low-temperature– grown continuous graphene films from benzene by chemical vapor deposition at ambient pressure. Scientific Reports. 2015;**5**:17955

[118] Wei D, Lu Y, Han C, Niu T, Chen W, Wee AT, et al. Critical crystal growth of graphene on dielectric substrates at low temperature for electronic devices. Angewandte Chemie (International Ed. in English). 2013;**52**(52):14121-14126

[119] Mishra N, Boeckl J, Motta N, Iacopi F, et al. Graphene growth on silicon carbide: A review (Phys. Status solidi a 9 2016). Physica Status Solidi A: Applications and Material Science. 2016;**213**:2269-2289

[120] Riedl C, Coletti C, Starke U. Structural and electronic properties of epitaxial graphene on SiC(0001): A review of growth, characterization, transfer doping and hydrogen intercalation. Journal of Physics D: Applied Physics. 2010;**43**(37):374009

[121] Manukyan KV, Rouvimov S, Wolf EE, Mukasyan AS, et al. Combustion synthesis of graphene materials. Carbon. 2013;**62**:302-311

[122] Norimatsu W, Kusunoki M. Epitaxial graphene on SiC{0001}: Advances and perspectives. Physical Chemistry Chemical Physics. 2014;**16**:3501-3511

[123] Zhang F, Jung J, Fiete GA, Niu Q, MacDonald AH, et al. Physical Review Letters. 2011;**106**:156801

[124] Lui CH, Li Z, Mak KF, Cappelluti E, Heinz TF. Nature Physics. 2011;**7**:944-947

[125] Bao W, Jing L, Velasco J, Lee Y, Liu G, Tran D, et al. Stacking-dependent band gap and quantum transport in trilayer graphene. Nature Physics. 2011;**7**:948-952

[126] Zhang L, Zhang Y, Camacho Y, Khodas M, Zaliznyak I, et al. The experimental observation of quantum hall effect of l=3 chiral quasiparticles

in trilayer graphene. Nature Physics. 2011;**7**:953.957

[127] Shioyama H, Sakakihara H, Iwashita N, Tatsumi K, Sawada Y. On the generation of fine metallic particles in graphite matrix. Journal of Materials Science Letters. 1994;**13**:1056

[128] Choi W, Lahiri I, Seelaboyina R, Kang YS, et al. Synthesis of graphene and its applications: A review. Critical Reviews in Solid State and Materials Sciences. 2010;**35**(1):52-71

[129] Jihn YL, Mubarak NM, Abdullah EC, Nizamuddin SK, Mohammad I. Recent trends in the synthesis of graphene and graphene oxide based nanomaterials for removal of heavy metals—A review. Journal of Industrial and Engineering Chemistry. 2018;**66**:29-44

[130] Choucair M, Thordarson P, Stride JA. Gram-scale production of graphene based on solvothermal synthesis and sonication. Nature Nanotech. 2008;**4**(1):30-33

[131] Dato A, Radmilovic V, Lee Z, Phillips J, Frenklach M, et al. Substrate-free gas-phase synthesis of graphene sheets. Nano Letters. 2008;**8**:2012-2016

[132] Dato A, Lee Z, Jeon KJ, Erni R, Radmilovic V, Richardson TJ, et al. Clean and highly ordered graphene synthesized in the gas phase. Chemical Communications. 2009;**40**:6095-6097

[133] Dato A, Frenklach M. Substratefree microwave synthesis of graphene: Experimental conditions and hydrocarbon precursors. New Journal of Physics. 2010;**12**(12):125013

[134] Choi W, Lee J. Graphene: Synthesis and Applications. Vol. 1. Boca Raton, FL, USA: CRC Press; 2011. pp. 1-394

*Recent Advances in the Synthesis of Graphene and Its Derivative Materials DOI: http://dx.doi.org/10.5772/intechopen.114280*

[135] Zheng Q, Kim J-K. Synthesis, Structure, and Properties of Graphene and Graphene Oxide, in Graphene for Transparent Conductors: Synthesis, Properties and Applications. Vol. 2. New York: Springer New York; 2015. pp. 29-94

[136] Yang X, Dou X, Rouhanipour A, Zhi L, Rader HJ, Müllen K, et al. Twodimensional graphene nanoribbons. Journal of the American Chemical Society. 2008;**130**(13):4216-4217

[137] Guo S, Dong S. Graphene nanosheet: Synthesis, molecular engineering, thin film, hybrids, and energy and analytical applications. Chemical Society Reviews. 2010;**40**:2644-2672

[138] Wang Y, Sun W, Li H. Microwaveassisted synthesis of graphene nanocomposites: Recent developments on lithium-ion batteries. Reports in Electrochemistry. 2015;**5**:1-19

[139] Murugan AV, Muraliganth T, Manthiram A. Rapid, facile microwavesolvothermal synthesis of graphene nanosheets and their polyaniline nanocomposites for energy strorage. Chemistry of Materials. 2009;**21**:5004-5006

[140] Wang Y, Liu G, An CH, et al. Bimetallic NiCo functional graphene: An efficient catalyst for hydrogen-storage properties of MgH2. Chemistry, an Asian Journal. 2014;**9**:2576-2583

[141] Chen W, Yan L, Bangal PR. Preparation of graphene by the rapid and mild thermal reduction of graphene oxide induced by microwaves. Carbon. 2010;**48**:1146-1152

[142] Hassan MAH, Abdelsayed V, Khder AERS, et al. Microwave synthesis of graphene sheets supporting metal nanocrystals in aqueous and organic

media. Journal of Materials Chemistry. 2009;**19**:3832-3837

[143] Wu ZS, Ren WC, Gao LB, Liu BL, Jiang CB, Cheng HM, et al. Synthesis of high-quality graphene with a predetermined number of layers. Carbon. 2008;**47**:493-499

[144] Motasemi F, Afzal MT. A review on the microwave-assisted pyrolysis technique. Renewable and Sustainable Energy Reviews. 2013;**28**:317-330

[145] Mutyala S, Fairbridge C, Pare JRJ, Belanger JMR, Ng S, Hawkins R, et al. Microwave applications to oil sands and petroleum: A review. Fuel Processing Technology. 2010;**91**:127-135

[146] Vazquez E, Giacalone F, Prato M. Non-conventional methods and media for the activation and manipulation of carbon nanoforms. Chemical Society Reviews. 2013;**43**:58-69

[147] Gallis KW, Landry CC. Rapid calcination of nanostructured silicate composites by microwave irradiation. Advanced Materials. 2001;**13**:23-26

[148] Nagarajan R, Alan HT. Synthesis, passivation, and stabilization of nanoparticles, nanorods, and nanowires by microwave irradiation. In: Nanoparticles: Synthesis, Stabilization, Passivation, and Functionalization. Vol. 996. Washington, DC, USA: ACS Publication; 2008. pp. 225-247

[149] Panda AB, Glaspell G, El-Shall MS. Microwave synthesis and optical properties of uniform nanorods and nanoplates of rare earth oxides. Journal of Physical Chemistry C. 2007;**111**:1861-1864

[150] Liu F, Wang C, Sui X, Riaz MA, Xu M, Wei L, et al. Synthesis of graphene materials by electrochemical exfoliation:

Recent progress and future potential. Carbon Energy. 2019;**1**(2):173-199

[151] Su CY, Lu AY, Xu Y, Chen FR, Khlobystov AN, Li LJ, et al. Highquality thin graphene films from fast electrochemical exfoliation. ACS Nano. 2011;**5**(3):2332-2339

[152] Abdelkader AM, Cooper AJ, Dryfe RAW, Kinloch IA, et al. How to get between the sheets: A review of recent works on the electrochemical exfoliation of graphene materials from bulk graphite. Nanoscale. 2015;**7**:6944-6956

[153] Huang G, Kang W, Geng Q, Xing B, Liu Q, Jia J, et al. One-step green hydrothermal synthesis of fewlayer graphene oxide from humic acid. Nanomaterials. 2018;**8**(4):215

[154] Shi W, Fan H, Ai S, Zhu L, et al. Preparation of fluorescent graphene quantum dots from humic acid for bioimaging application. New Journal of Chemistry. 2015;**1**(10):1-6

[155] Bai Y, Rakhi RB, Chen W, Alshareef HN, et al. Effect of pH-induced chemical modification of hydrothermally reduced graphene oxide on supercapacitor performance. Journal of Power Sources. 2013;**233**:313-319

[156] Edberg J, Brooke R, Hosseinaei O, Fall A, Wijeratne K, Sandberg M, et al. Laser-induced graphitization of a forestbased ink for use in flexible and printed electronics. npj Flexible Electronics. 2020;**4**(1):17

#### **Chapter 2**

## Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications

*Md. Nizam Uddin, Md. Aliahsan Bappy, Md Fozle Rab, Faycal Znidi and Mohamed Morsy*

#### **Abstract**

Materials based on 3D graphene, such as aerogels, hydrogels, sponges, and foams, are attracting substantial interest due to their superb electrical conductivity, remarkable mechanical properties, and expedited mass and electron transport. These substances preserve the inherent characteristics of 2D graphene sheets and introduce enhanced features like low density, substantial surface area, high porosity, and steadfast mechanical properties. The applications for 3D graphene-based materials are vast, ranging from flexible electronics, sensors, absorbents, and composites to catalysis, energy storage devices, agricultural uses, water purification, biomedical applications, and solar steam generation devices, among others. In this book chapter, we consolidate the latest advancements in the fabrication of 3D graphene-based materials, discussing their properties and the emerging uses in composites and energy storage apparatuses. The synthesis of 3D graphene-based materials on a larger scale poses substantial challenges, the discussion of which might spur innovation and novel approaches in this domain. We aim to provide a comprehensive overview of the contemporary progress in this field, emphasizing the synthesis, properties, and diverse applications of these advanced materials. Our research is anticipated to establish a groundwork for the widespread preparation, understanding of structure–property relationships, and utilization of 3D graphene-based architectures (3DGAs) across various fields, including but not limited to tissue engineering, electronics, supercapacitors, composites, and energy storage devices.

**Keywords:** 3D graphene, energy storage devices, composites, porous materials, graphene foam

#### **1. Introduction**

Carbon is a crucial building block of our universe and plays a significant role in both natural phenomena and technological advancements. In recent years, our understanding of carbon's versatility has grown significantly, especially in the field of sp2-hybridized carbon nanomaterials. Graphene, which is an example of a 2D sp2 hybridized carbon lattice that is only one atom thick, has remarkable physicochemical properties. Its derivatives have found application in various domains like lowdimensional physics, energy storage, electronic devices, catalysis, sensors, and medical equipment. However, a major challenge in harnessing graphene's potential at macroscopic scales is restacking when using 2D graphene sheets, which reduces efficiency and diminishes their unique properties. One solution to this challenge is the conversion of 2D graphene layers into interconnected, 3D frameworks that prevent restacking and retain 2D graphene's exceptional properties. This requires large-scale production and the conversion of individual graphene sheets into multifunctional 3D architectures. A critical step in manufacturing 3D graphene materials, specifically 3D reduced graphene oxide (3D-rGO), involves the reduction of graphene oxide (GO), which is achieved through different chemical methods designed to eliminate oxygencontaining functional groups on the GO plane. While early research focused primarily on synthesizing high-quality graphene sheets from GO, numerous strategies have since emerged, including thermal reduction in inert atmospheres, chemical reduction using various reducing agents, photocatalytic reduction, hydro/solvothermal techniques, laser/flashlight irradiation, electrochemical reduction, hydrogen-plasma/arcdischarge, microwave treatment, and combinations of these methods. Nonetheless, although significant progress has been made in the development of 3D graphene materials in recent years, there is a need for a comprehensive understanding of 3D architectures and their performance in various applications.

This study aims to bridge this gap by presenting advanced fabrication processes and design considerations for 3D graphene-based architectures (3DGAs). It will explore the relationship between 3D graphene properties, formation mechanisms, and key components, ultimately providing an encompassing overview of the 3D graphene family of materials. This will also highlight the significance of these materials in diverse applications and inspire new directions for their development, particularly focusing on simplifying the preparation and functionalization of 3D graphene materials. In the subsequent sections, we will describe the synthesis methods, properties, and potential applications of 3DGAs [1].

#### **2. Synthesis of 3D graphene structure**

Over the last decade, numerous techniques for synthesizing 3D graphene have emerged. These methods include electrospraying, supercritical drying, freeze drying, vacuum drying, chemical vapor deposition (CVD), hydrothermal processes, selfassembly, and various other approaches, which this review will explore and discuss the associated distinct advantages and disadvantages of each.

#### **2.1 Template-assisted method**

The templates-assisted method involves reducing GO and subsequently extracting the template from the structure. The template-assisted approach, outlined by Ding and Li [2] as well as by Qiu et al. [3], stands out due to its advantages in controlling the formation of 3D graphene structures, offering meticulously crafted morphologies compared to other fabrication methodologies. Within this technique, the chosen template, predominantly constructed from materials such as polystyrene (PS) or silicon dioxide (SiO2), holds crucial significance, with graphene sheets gathering around it through electrostatic forces. These forces originate from the interaction between negatively charged graphene sheets and the positively charged templates, culminating in the creation of an organized

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

#### **Figure 1.**

*Synthesis and water resistance characteristics of nano SiO2 modified graphene oxide composite [5].*

composite structure. Compared to self-assembly strategies, this technique ensures superior control over the final product's architecture and morphological attributes.

Several research studies have underscored the efficacy of template-assisted methods in developing 3D graphene-based materials. For instance, positively charged PS spheres were used as templates, coated with GO sheets, which were later reduced to obtain reduced graphene oxide (rGO) using hydrazine. The process was then finalized by calcination to eliminate the PS core, resulting in graphene hollow spheres [4]. This example highlights the extensive potential and adaptability of template-assisted techniques in creating diversified 3D graphene configurations. One remarkable study demonstrated a synthesis pathway for graphene-based hollow spheres, utilizing strong electrostatic interactions between polyethylenimine-functionalized SiO2 spheres and graphene sheets, forming GO-SiO2 spherical entities (**Figure 1**). Graphene-based hollow spheres were acquired after reducing and treating with hydrofluoric acid to eliminate the SiO2 template, showcasing the method's versatility [6]. Additionally, Huang and his team have studied developing nanoporous graphene foams (GFs), emphasizing the role of hydrophobic interactions between GO sheets and modified SiO2 spherical templates, resulting in nanoporous GF structures with customizable pore sizes [7]. This innovation marks a substantial progression in modifying the structural attributes of 3D graphene materials to accommodate specific needs and applications [8].

The template-assisted fabrication of 3DGAs unveils a multifaceted and regulated strategy to construct graphene-based configurations with optimal morphologies. Employing templates like PS and SiO2, coupled with specialized electrostatic interactions and reduction phases, allows scientists to innovate in creating 3D graphene materials with a spectrum of applications that range from catalysis, to sensing, and energy storage. The continuous evolution in this domain suggests that template-assisted techniques are important for fostering groundbreaking progressions in materials science and technology.

#### **2.2 Electrospraying**

Electrospinning and electrospraying are simple and versatile techniques that can produce graphene-based fibers, spherical structures, and bead-like materials. The resulting structures can have diameters ranging from a few micrometers to nanometers and have precise control over their shape [9, 10]. The process involves applying a strong electric field between a nozzle containing a graphene-based solution and a grounded metallic collector plate. When the electric field is strong enough, a droplet elongates and forms a continuous jet, ultimately depositing graphene-based fibers or spherical structures on the collector plate. One of the great benefits of electrospinning/ electrospraying is its ability to fine-tune the process parameters, allowing for the creation of materials with specific properties. Researchers have made numerous attempts to integrate graphene into fiber structures using both classic and core-shell electrospinning technologies. The core-shell approach has recently gained attention due to its ability to address challenges and enhance control over the resulting structures [11].

Poudeh and colleagues introduced a novel design for creating 3D graphene-based hollow and filled polymeric spheres through a one-step core-shell electrospraying technique (**Figure 2**) [12]. To achieve the desired spherical morphology, the study determined the optimal polymer concentration using Mark–Houwink–Sakurada equations [12]. Proper polymer concentration and solution viscosity are crucial for obtaining the desired spherical shape. In cases where hollowness is desired, the core material should contain a solvent with a higher vapor pressure than the shell solution. By using this innovative approach, researchers have overcome challenges such as crumbling and agglomeration of 2D graphene sheets and ensured better dispersion of graphene layers through the polymer chains. This technique has expanded the potential applications of fabricated structures across various fields, including drug delivery, energy storage, sensors, and nanocomposites. The final morphology of the produced materials is influenced by a combination of solution properties, such as viscosity and electrical conductivity, and process parameters including applied voltage and flow rate.

The interactions that occur between polymeric chains and graphene sheets throughout the sphere formation process are essential in determining the characteristics and capabilities of the subsequently formed materials. The core-shell electrospraying method unveils novel prospects for creating sophisticated graphene-centric structures characterized by customized properties, thus presenting a promising

**Figure 2.** *Preparation of 3D graphene-based spheres by tri-axial electrospraying technique [12].*

#### *Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

path for assorted materials science and technology applications. In essence, the electrospinning and electrospraying techniques grant meticulous control in synthesizing graphene-centric materials, enabling the development of structures with the preferred morphologies and attributes. The cutting-edge progress in core-shell electrospraying unveils pathways for creating versatile materials with multifunctional applications spanning various domains. Incorporating graphene into such structures is poised to fuel advancements in sectors like drug delivery, energy storage, sensing technologies, and nanocomposite materials, showcasing immense potential for breakthroughs in innovation.

#### **2.3 Supercritical drying method**

Traditional drying techniques, including air drying and vacuum drying, present substantial challenges when employed on graphene hydrogels due to their minimal solid content. The elevated capillary forces induced by solvent evaporation during these methods can disrupt and collapse the graphene network structure, inflicting irreversible damage. To resolve this problem and uphold the network's integrity, advanced drying approaches such as supercritical drying and freeze-drying have been introduced. Supercritical drying emerged as a leading method for synthesizing materials like SiO2 aerogels. This technique transforms the solvent into a supercritical fluid by meticulously modulating temperature and pressure conditions. At the supercritical state, the lack of a distinct liquid–gas interface effectively eradicates capillary pressure within the network, allowing for the gentle removal of the supercritical fluid through depressurization, yielding aerogels. This method has shown tremendous efficacy in retaining the pristine network structure of SiO2 aerogels with minimal contraction [13]. However, for graphene-based materials such as 3DGAs, certain constraints exist.

In contrast to SiO2 aerogels, which possess a network with robust Si-O covalent bonds, 3DGAs have graphene sheets bound by π-π interactions. These sheets are prone to slippage during supercritical drying, causing increased volume and density reduction compared to SiO2 aerogels. Consequently, supercritical drying is not ideal for fabricating large-scale, low-density 3DGAs. Additionally, the technique's requirement for high pressure and extended durations elevates production costs, making it less advantageous for preparing 3DGAs designated for low-density, large-scale utilization [14]. Therefore, alternative methods, like freeze-drying and air drying, might be more apt for specific graphene-based materials, considering the respective application intents and requisite attributes.

#### **2.4 Freeze drying method**

Lyophilization, or freeze drying, is a feasible alternative for mitigating capillary forces during the drying phase of materials like graphene-based hydrogels. This method entails multiple phases to maintain the structural wholeness of the hydrogel, initiated by substituting the solvent in the wet graphene hydrogel with water. The hydrogel is then exposed to freezing at sub-zero temperatures, and the encapsulated water transitions directly to gas via sublimation under vacuum, avoiding the liquid phase completely and thereby preserving the graphene framework. For freezedrying, specific considerations are essential. When utilized on SiO2 gels possessing diminutive pore sizes, often around tens of nanometers, the volumetric expansion of water during freezing might compromise the network structure, potentially decreasing the porosity to levels around 80% and halving the material's specific surface area

relative to outcomes from supercritical drying. In some instances, the stress induced by freezing might even induce fractures in the sample [15]. Nonetheless, graphene hydrogels, due to their expansive pore dimensions- ranging from several micrometers to tens of micrometers—are more compatible with freeze-drying compared to SiO2 hydrogels. 3DGAs fabricated via freeze drying exhibit diminished densities, possibly down to 0.16 mg/cm3 , and the method permits structural control by influencing ice crystal formation [16].

However, the process is not devoid of challenges; the water freezing can potentially distort and eject the microstructure of the graphene network, thereby reducing the specific surface area Moreover, freeze drying demands sub-zero temperatures, elevated vacuum levels, and prolonged drying durations, escalating energy usage and preparation expenditures. While lyophilization provides a substantial alternative for contending with capillary forces in the drying of graphene-based hydrogels. It is particularly favorable for graphene hydrogels due to their extensive pore dimensions and potential to produce low-density 3DGAs. However, it involves compromises like potential reductions in specific surface area and heightened energy and cost inputs, which must be weighed against the benefits depending on the intended applications.

#### **2.5 Vacuum drying method**

While effective for preserving the structural integrity of 3DGAs, supercritical and freeze drying come with certain drawbacks that hinder their suitability for large-scale production. The main challenges of specific drying methods arise from the requisition of low vacuum, low temperatures, or high-pressure states, which significantly amplify equipment, energy, and time costs. As highlighted earlier, supercritical drying entails modifying a solvent into a supercritical fluid under designated temperature and pressure states, followed by depressurization to yield aerogels. While it proficiently preserves the initial network structure of substances like silica aerogels, it encounters constraints when implemented on 3DGAs. The π–π interactions connecting the graphene sheets tend to displace, causing notable volume reduction in the supercritical drying phase, yielding structures with densities higher than what is optimal for applications necessitating low-density 3DGAs [17]. Furthermore, the time-intensive nature of supercritical drying, coupled with high-pressure conditions, escalates production expenditures. Freeze drying is another alternative, proffering benefits in maintaining the structural soundness of 3DGAs, especially those with expansive pore sizes. Still, it demands elevated vacuum levels, low temperatures, and prolonged durations, elevating energy usage and subsequent costs, especially when juxtaposed with other drying techniques.

In contrast, vacuum drying is a more economically and temporally efficient approach for 3DGAs synthesis, exempting the process from the need for specialized apparatus for temperature, high pressure, or solvent exchange and instead utilizing vacuum conditions for solvent removal. However, the process is challenged by the potential collapse of the delicate network structures of 3D graphene gels, intensifying the density of the final product. While such collapse can be perceived as a constraint, it can also be strategically utilized for the construction of dense 3D graphene network assemblies, marked by their enhanced volumetric/gravimetric energy density, making them ideal for advanced energy storage devices like highperformance batteries. Vacuum drying is a pragmatic and economical technique for developing 3D graphene network assemblies, especially when high volumetric/ gravimetric energy density is prioritized. The induced collapse of the 3D network can be optimized to develop materials with properties aligned with the needs of diverse applications, predominantly in advanced energy storage sectors.

#### **2.6 Air drying method**

Air drying serves as a simplistic and economical method conducted under atmospheric pressure conditions, presenting a practical solution for drying substances like SiO2 gels. This method is especially beneficial for the mass production of aerogels compared to intricate techniques such as supercritical drying and freeze-drying. Nonetheless, air drying has challenges; the Young–Laplace equation illustrates that, during the process, the interaction between liquid and air within the pores can create significant capillary pressure due to the minuscule pore size, typically in the tens of nanometers range. This pressure can result in the gradual shrinkage and cracking of the SiO2 gel skeleton. Various approaches are implemented to counteract these issues, including replacing the solvent in the wet gel with one of lower surface tension to minimize capillary forces and chemically treating the SiO2 gel skeleton to avoid further condensation of adjacent surface functional groups on the skeleton under capillary stresses. Introducing non-polar groups to the skeleton is vital in maintaining the structural integrity of SiO2 aerogels throughout the air-drying process [14].

Contrarily, 3DGAs are more adaptable to large-scale production via air drying due to their larger pore sizes, diminishing the capillary forces experienced during the process. Several research endeavors have effectively employed air drying to construct 3DGAs with impressive properties. For instance, durable and flexible 3DGAs have been fabricated by in situ polymerization of polyacrylamide, fortifying the graphene network and allowing it to endure capillary forces during air and vacuum drying while preserving low density. Other investigations have utilized diverse methods, such as GO liquid crystal-stabilized bubbles and ice crystals and air bubbles as templates, to manufacture 3DGAs with the air-drying method, resulting in strong and uniformly porous structures with excellent mechanical properties [18]. Recent research has evidenced the fruitful application of air drying in creating resilient 3DGAs, underscoring the role of aspects like graphene sheet sizes, interconnections between graphene sheets, and the overall graphene network structure in influencing the mechanical characteristics of these materials. Optimization of these elements is paramount for the creation of robust graphene networks with tailored properties suitable for diverse applications.

#### **2.7 Photoinduced reduction**

Photoinduced reduction is an innovative process that reduces graphene oxide without the use of chemicals. It delivers high efficiency and rapid processing. This approach harnesses photon energy and has shown remarkable progress as a technique for GO reduction. Researchers began using photon energy for the reduction of GO in solutions as early as 2008 [19]. They employed semiconductor photocatalysts like titanium dioxide (TiO2) under ultraviolet (UV) light irradiation. This approach paved the way for the development of graphene/semiconductor composites. Later, it was discovered that GO reduction could occur directly under UV light, yielding by-products such as CO, O2, H2O, and CO2 [20]. Additionally, xenon lamp-equipped photographic camera lights and laser lights were found to be capable of thermally deoxygenating GO. In the early days, photoreduction of GO in dilute solutions typically resulted in rGO suspension instead of the desired 3D rGO structures. However,

the photoreduction of GO films led to the formation of pore-rich 3D rGO materials characterized by high conductivity and expanded interlayer spacing. Photoinduced reduction of GO occurs through two distinct mechanisms: the photothermal effect and photochemical reduction. Photochemical reduction involves the use of UV light with a wavelength below 390 nm. Wavelengths longer than 390 nm induce the photothermal effect, which involves higher temperatures (approximately 200–230°C) and is highly effective for GO reduction. Laser lights can create intense localized heating by focusing the laser beam on a specific point, leading to rapid reduction [20].

In both mechanisms, strong excitation of the GO surface triggers particle ejection and the formation of plasma plumes. Energy transfer from the plume to the lattice results in the removal of oxygen groups from GO, leading to the formation of CO and CO2, as well as the evaporation of internal water. This process generates interlayer pressure, causing the rGO layers to expand and form a porous structure. The photoinduced reduction process is also applicable to chemically reduced GO films. Laser lights are widely employed for this purpose. Laser scribing allows for synchronous reduction while patterning GO films. By adjusting laser-processing variables such as intensity, shifting pitch, and scanning pitch, precise control over the degree of reduction in the resulting 3DGAs can be achieved. These 3D graphene patterns, generated through laser-induced reduction, hold significant potential in various biomedical applications, including tissue engineering and cell culture.

The reaction atmosphere plays a crucial role in laser-induced GO reduction, influencing the degree of reduction. The process is notably enhanced in an oxygenfree environment. When the GO precursor is subjected to laser reduction under liquid nitrogen, thermal expansion is suppressed, resulting in 3D rGO films with fewer defects and higher conductivity. Laser intensity can also be directly used to assemble 3D rGO in crystalline GO suspension. By adjusting the focus and intensity of the laser, researchers can create arbitrary homogeneous 3D structures on the inside surface. This approach is particularly favorable for precise 3D localization in electronics and photonics applications. This technique has evolved significantly since its inception, allowing for precise control over the reduction process and opening up a wide range of applications, from composite materials to biomedical scaffolds and electronics.

#### **2.8 Chemical reduction**

Chemical reduction is a widely used method to reduce GO to rGO using various chemical routes. Initially, hydrazine was used to reduce dilute GO suspensions, leading to rGO dispersions. Later, researchers focused on synthesizing 3D graphene hydrogels and aerogels using more concentrated GO colloidal solutions and milder reducing agents. The reduction temperature typically ranges from 60 to 100°C, with reagents and absorbed water removed through washing and lyophilization. Several reducing agents, including Na2S, HI, H3PO4/I2, gelatin, and sodium ascorbate, have been explored to simultaneously reduce and construct 3D GO structures. For instance, sodium ascorbate has been employed for the reduction of GO, resulting in the development of 3D graphene frameworks [21]. The formation of π-π interlinkages among sheets has been identified as a key factor governing the self-assembly of chemically reduced GO. Additionally, the functional groups attached to reducing agents play a crucial role in 3D rGO sheet construction. Covalent bonds form between GO sheets and reducing agents, leading to the substitution of oxygen-containing hydroxyl and epoxy groups and cross-linking of the GO sheets. Carboxylic groups present in reducing agents further promote the development of interlayer hydrogen bonds.

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

**Figure 3.** *Schematic of the fermentation process to prepare rGO foam [22].*

During the chemical reduction of GO, the evolution of CO and CO2 gases is common, contributing to the restacking of GO and rGO sheets and modulating the pore structure of 3D materials. Water bubbles can also be introduced through controlled heating, and the number of bubbles plays a critical role. Fewer bubbles may fail to suppress restacking, while an excess can affect the self-assembly of rGO sheets. Hydrazine is considered favorable for reducing GO into 3D structures due to its ability to generate an appropriate number of bubbles. Active metals such as Al, Cu, Al, Fe, and Co can also serve as reducing agents, enabling both reduction and the formation of 3DGAs assemblies on their surfaces. This process relies on redox reactions between metals and GO, occurring at room temperature and accelerating at 60°C. Interestingly, when a conductive substance is placed on the active metal substrate, no reduction in the development of 3D rGO assembly is observed. This unique property has been harnessed to create specialized graphene structures, such as microtubes and micropatterns, with applications in rechargeable Li-ion batteries and flexible rGO 3D thin film devices.

Moreover, vapors produced by reducing agents can also effectively reduce both dried GO films and sponges, leading to side-by-side alterations in 3D structures. For instance, when a dense GO film is used as a precursor, vapor-based reduction significantly alters its 3D configuration. Niu et al. performed the reduction of filtrated GO film by positioning it on the top of a hydrazine monohydrate solution at 90°C for 10 hours (**Figure 3**) [22]. By controlling the concentration of the hydrazine monohydrate solution, the open pore structure can be tuned.

Despite the progress in the chemical reduction of GO, there is still much to learn about the changes that occur during the reduction process. Minimizing the amount of non-carbon impurities in the final product remains a challenge, necessitating further research and optimization of reduction methods. Chemical reduction offers a versatile approach to obtaining 3D graphene structures, with various reducing agents and strategies available to tailor the properties and morphology of the resulting materials.

#### **2.9 Electrochemical reduction**

Electrochemical reduction is a prevalent technique for producing 3D graphene constructs, particularly in crafting electrodes for electrochemical devices directly. It permits the formation of resilient 3D graphene frameworks straight on electrode surfaces, optimizing the efficacy of several electrochemical setups. The procedure of electrochemical reduction requires settling GO on a cathode from a GO mixture. Contrasting typical solid graphite strata, the graphene strata in 3D formations are aligned in a fortifying manner, establishing a stable and integrated 3D graphene grid. This method is frequently termed as the immediate expansion of rGO sheets from the electrode interface. The developed 3D graphene lattice presents numerous perks such as superior porosity and escalated electrochemical efficacy.

A crucial consideration in developing 3D rGO substances electrochemically is the selection of the electrode material. Several substances like stainless steel lattice, platinum (Pt) leaf, nickel (Ni) froth, and gold (Au) fiber are feasible as electrode foundations. Utilizing graphene paper as the foundation for the electrode resulted in a closely bonded structure of highly porous rGO layers onto the substrate. Consequently, this yielded a carbon electrode with outstanding versatility for flexible device applications. Employing Ni foam as the electrode base results in the interior vacuities being occupied by rGO, forging a systematic porous framework with diverse pore dimensions. Moreover, hierarchical 3D structures can be synthesized by employing previously acquired 3D rGO substances as electrode foundations [23]. The electrochemical technique is also viable for reducing pre-shaped GO films on electrodes. This method provides superior regulation over the alignment of GO sheets in the casting phase and assures proficient reduction via the electrochemical mechanism. The electrochemical reduction of GO facilitates the production of high-caliber electrodes with customized 3D configurations, enriching their utilization in energy conservation apparatuses, detectors, and other varied electrochemical setups. Electrochemical reduction is a multifaceted and efficient strategy for developing 3D graphene formations, especially significant for the advancement of electrodes in electrochemical appliances. The 3D graphene frameworks that result possess enhanced electrochemical traits, rendering them instrumental in an extensive array of applications.

#### **2.10 Thermal expansion of GO bulk**

Expanding GO bulk materials through thermal reduction or annealing is a wellknown and efficient method to eliminate oxygen functional groups from GO, yielding 3DGAs with increased bulk volumes. This technique entails exposing GO precursors to elevated temperatures, usually between 800 and 1000°C, inducing a series of structural and chemical modifications. For 3D graphene, high-temperature annealing can trigger thermal exfoliation, causing the expansion of dried and pre-shaped GO bulk precursors. These precursors may appear in several forms, including granular GO, misaligned GO films, tape-cast layers, and bulk GO materials. During the thermal evolution of bulk GO, oxygen-containing functional groups such as carboxyl, hydroxyl, carbonyl, and ether groups are either partially removed or converted into more stable chemical bonds like anhydrides, quinones, and lactones. This leads to the emission of trace gases including CO2, CO, and H2O. The degree of purification of the graphene surface is augmented with increased annealing temperatures. At maximum temperatures of 1000°C, unstable oxygen species are efficiently eradicated, enhancing the electrical conductivity of the resultant rGO sheets significantly [24].

Concurrently, the GO mass morphs into honeycomb-esque 3D nanostructures composed of microscopic sheets and numerous pores. This enlargement process contributes to a notable amplification in the material's specific surface area. Depending on the specific precursor and the subsequent reaction, the surface area of 3D rGO structures can generally vary from 400 to 800 m<sup>2</sup> /g. Thermal annealing is also

#### *Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

utilized for the reduction of partially reduced 3D GO and 3DGAs achieved through dry processes and intense reduction procedures. In such instances, the main goal might not be the modification of 3D structures, but rather the expulsion of oxygen functional groups and conductivity augmentation. Nonetheless, exposing GO precursors to elevated temperatures swiftly, without a gradual heating process, can induce the creation of additional in-wall pores, increasing the surface areas. For instance, subjecting crumpled graphene spheres to thermal shock at 400°C can produce a surface area of roughly 567 m2 /g, whereas maintaining the sample at the same temperature without rapid cooling can yield a lower surface area of 344 m<sup>2</sup> /g. Thermal expansion through annealing is a flexible and popular approach to fabricating 3DGAs with enhanced bulk volumes and superior electrical conductivity. This technique involves the elimination of oxygen functional groups and the formation of porous 3D nanostructures, positioning it as a valuable technique for diverse applications in material science and nanotechnology.

#### **2.11 Solvothermal and hydrothermal reduction**

The solvothermal and hydrothermal reduction techniques are increasingly recognized for their effectiveness in transforming GO to rGO and crafting 3D graphene structures. These procedures revolve around high-temperature reactions in autoclaves, usually ranging between 100 and 250°C, using water or organic solvents as reducers. In hydrothermal treatments, supercritical water driven by thermal activation serves as the reducer, facilitating the transformation of GO sheets into 3D rGO hydrogels. Early in this process, the surface charges are reduced due to the extraction of carboxylic groups from GO sheets. As the reaction progresses, most carboxylic groups vanish, increasing hydrophobicity and enhancing the attractions and interactions among the rGO sheets. This facilitates the formation of a closely-knit 3D structure. By-products commonly include CO2, with minor amounts of CO and organic acid remnants. Even if some GO sheets remain intact post-treatment, their oxygen-functional groups help link the 3D rGO sheets, forming a monolithic design. Factors like the initial GO suspension's size, concentration, and surface traits can notably alter the final 3D rGO gel's makeup.

In solvothermal treatments, organic solvents take the place of water, leading to milder reaction temperatures and decreased GO sheet assembly. Given their inherent high pressure and the solvent's low surface energy, solvothermal processes are adept at shaping and reducing GO sheets. This results in 3D rGO products with superior conductivity but diminished surface areas and bulkier walls compared to their hydrothermal counterparts. For example, using ethanol in solvothermal reduction can yield 3D rGO aerogels with distinct features, like near-zero super-elasticity.

Post-reduction drying is vital in maintaining the eventual 3D shape. Traditional drying might induce significant volume contraction and cracks, stemming from substantial capillary pressure during solvent evaporation. To mitigate this, alternative techniques like freeze-drying or supercritical CO2 drying are adopted. They reduce structural degradation since ice or supercritical CO2 have minimal interactions with graphene. The capillary pressure experienced during solvent evaporation is influenced by aspects like solvent surface tension, contact angle, and pore size. Several methods are explored to achieve ambient drying while preserving the 3D structure and elevating material rigidity. While the degrees of reduction achieved in solvothermal and hydrothermal reactions are somewhat moderate due to their temperature constraints, further treatments like annealing or chemical reduction can be applied

to amplify reduction and reinstate π-conjugation. These augmentations also bolster electrical conductivity. Moreover, these processes can be employed to manufacture 3D graphene-infused composites by embedding nanoparticles like Fe3O4 or CO3O4 into the 3DGAs. Solvothermal treatments especially lead to a more evenly spread nanoparticle distribution within the 3D rGO, creating consistent composites. The solvothermal and hydrothermal reduction techniques are potent tools for devising 3D graphene structures, aerogels, and composites. The selection of solvents and drying methods remains essential in shaping the final material's attributes and structure.

#### **2.12 Freeze-casting process (pre- or post-reduction)**

The freeze-casting process is a well-established solution-phase technique widely employed for the fabrication of 3D structures from GO or partially reduced GO suspensions or gels. This method leverages the freezing point of water and capitalizes on ice crystallization to arrange GO or partially reduced GO sheets into a continuous 3D framework. For this to occur, it is crucial to exceed the percolation threshold by concentrating GO or partially reduced rGO sheets. After freeze-casting, a subsequent reduction step is usually necessary to transform the porous GO monolith into a 3D rGO framework, thereby modifying the surface properties of the sheets. However, it should be noted that the freeze-casting process and subsequent reduction may have a marginal effect on the microscopic morphology of the final product. In the freezecasting of GO suspensions, the chemical characteristics of GO sheets play a pivotal role. When GO suspensions are frozen directly, they produce monoliths that are brittle and randomly oriented. In contrast, when freeze-drying is applied to GO-filtered gels or specific partially reduced GO dispersions, it results in super-elastic structures with a honeycomb-like cellular orientation. In part, this contrast in monolith structure can be explained by the heightened attraction between partially reduced GO sheets. Furthermore, the capacity of partially reduced GO sheets to adsorb onto ice surfaces, owing to their hydrophobic properties and the presence of abundant oxygen-containing groups, facilitates the development of these super-elastic configurations [25].

The term "super-elasticity," as applied to freeze-cast partially reduced GO monoliths, characterizes their exceptional ability to endure substantial deformation and rapidly recover, rendering them exceptionally resilient materials. These materials exhibit remarkable load-bearing capabilities, sustaining loads up to 450,000 times their weight and rebounding from 480% compression quite quickly. Moreover, the freezing process's temperature holds a significant role in shaping the 3D structure during freeze-casting. Various freezing temperatures affect ice crystal growth dynamics, resulting in different wall thicknesses, overall dimensions, and pore architectures. Through precise control of the freezing temperature, researchers gain the ability to tailor the freeze-cast material's properties to precise specifications. In recent years, bidirectional freezing technologies have also emerged as valuable tools for controlling the freezing process precisely. This innovative approach facilitates the creation of distinctive structures, such as fan-shaped arrangements of GO, which find applications across diverse fields, including water purification. Moreover, freeze-casting can use alternative solvents, such as those characterized by high vapor pressures and melting points slightly higher than room temperature. This variation, known as room-temperature freeze gelation, presents significant energy-saving advantages compared to freeze-drying with water. However, it's worth noting that the cost associated with these organic solvents may present challenges for large-scale applications. The freeze-casting method stands as a versatile and efficient technique for producing

3D structures from GO or partially reduced GO suspensions or gels. The method allows the fabrication of super-elastic, highly resilient materials that can be tuned by manipulating freezing parameters and applying bidirectional freezing methodologies. This approach holds great promise across a broad spectrum of applications, encompassing domains like water purification and the development of lightweight structural materials.

#### **2.13 3D printing before reduction**

The extrusion-based 3D printing method, also known as robot-assisted deposition, robocasting, direct ink writing, or continuous extrusion, stands out for its ability to fabricate complex 3D rGO structures that are challenging to achieve using alternative manufacturing techniques. This technique involves the layer-by-layer deposition of GO or partially reduced GO inks, enabling the creation of intricate 3D structures. The effectiveness of extrusion-based 3D printing depends on the rheological properties of the GO ink. Specifically, the ink should exhibit shear-thinning behavior and viscoelastic characteristics to ensure proper adhesion between layers while maintaining the desired print shape. The rheological properties of GO inks are influenced by various factors, including flake size and GO concentration. Smaller lateral sizes of GO sheets, typically in the range of 150–400 nm, display non-Newtonian fluid behavior at a concentration of 20 mg/mL. Higher concentrations result in increased viscosity and improved printability. To enhance printability further, modified GO suspensions are often used, incorporating additives such as pH-sensitive polymers, hydrophobic fumed silica powder, and basic compounds. These additives help regulate viscosity and shear-yield stress, making it possible to 3D print the inks effectively. In addition to extrusion-based 3D printing, optical 3D printing has emerged as a precise technique for manipulating micrometer-scale structures. This approach combines photo-excited polymerization with layer-by-layer 3D printing to generate complex macro-3D rGO architectures. The photocurable resin used in this process is created by blending diluted GO dispersion with photocurable acrylates and a photoinitiator. This resin can rapidly solidify through light-initiated polymerization. During optical 3D printing, thin layers of the resin are deposited, cross-linked, and solidified using patterned light irradiation. This process is repeated for subsequent layers, resulting in the gradual construction of 3D structures. A light source with a wavelength of 405 nm is typically employed, along with a spatial light modulator, to enable precise control over 3D patterns and resolutions. This technology allows for the fabrication of intricate 3D structures with controlled micron-scale dimensions, maintaining a high resolution of approximately 10 μm (**Figure 4**) [26].

#### **2.14 Wet-spinning before reduction**

Wet-spinning is a widely employed technique for the fabrication of 3D rGO structures, encompassing a range of forms such as fabrics, films, cylinders, spheres, and fibers. This method offers continuous alignment of rGO materials, resulting in the development of materials with distinctive properties. The wet-spinning process involves extruding a GO suspension through a nozzle into a coagulation bath. The concentration of GO within the suspension plays a crucial role in the successful formation of fibers. High concentrations of GO in the suspension foster strong interactions among GO sheets, promoting alignment and coagulation. Conversely, low concentrations can lead to the formation of brittle fibers and collapsed structures. It's important

**Figure 4.** *Illustration of the optical 3D printing process [26].*

to note that the formation of graphene fibers through wet-spinning follows a multistep mechanism. Initially, a multilayer GO film is generated as negatively charged GO sheets repel each other. As the charge neutralizes within the coagulation bath, the film undergoes bending and folding, resulting in highly aligned fine particles. The versatility of wet-spinning allows for the production of 3D graphene materials with diverse shapes and structures by controlling the rotation process. For instance, the wet-spinning of liquid GO crystals into a rotating coagulation bath can yield superelastic graphene aerogel millispheres. These millispheres possess continuous shell and core structures, exceptional mechanical strength, and unique jumping properties. Wet-spinning, when followed by a reduction step, emerges as a versatile and efficient approach for manufacturing a wide array of 3D rGO structures with tailored properties. The selection of GO concentration, spinning conditions, and parameters for the reduction process can be finely tuned to achieve specific characteristics in the final material. This method finds applications across various domains that demand highperformance graphene-based materials, showcasing its versatility and adaptability.

#### **3. Properties of 3D graphene**

Since their initial creation in 2011, 3DGAs have consistently showcased exceptional properties. The Table below provides an overview of the physical characteristics that define various 3DGAs, encompassing attributes such as specific surface area (SSA), electrical conductivity, pore structure, density, and mechanical properties. It highlights the remarkable qualities inherent to three-dimensional graphene networks, with a specific focus on GFs, graphene sponges (GSs), and graphene aerogels (GAs). These materials stand out for their impressive features, including substantial surface areas and pore volumes, reduced densities, noteworthy electrical conductivities, and robust mechanical performance. In a general context, it is evident that 3DGAs characterized by chemically bonded structures exhibit notably superior properties in comparison to those relying on physically assembled structures. As a result of these chemically bonded variants, they consistently demonstrate advantages such as reduced contact resistance, enhanced electrical conductivity, and superior mechanical properties, such as heightened strength, toughness, and flexibility. As illustrated in the **Table 1**, chemically bonded GAs have a bulk electrical conductivity of approximately 1 S/cm. This level of conductivity outperforms what has been reported for


*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

#### **Table 1.**

*The physical characteristics of various 3DGAs have been synthesized through diverse methods.*

macroscopic 3DGAs exclusively constructed using physical cross-linkers or partial chemical bonding. For instance, GO hydrogel, with a conductivity of 5 × 10−3 S/cm, and 3D RGO, with a conductivity of 2.5 × 10−3 S/cm, significantly lag in this regard. In contrast, GFs exhibit significantly higher electrical conductivity due to their continuous and interconnected networks. Notably, GAs consistently demonstrate high electrical conductivities of around 1 S/cm, regardless of whether or not an organic cross-linker is employed.

This phenomenon may be attributed to the cross-linking interactions that occur among functional groups present on the surfaces and edges of the graphene oxide

during the sol–gel process. Alterations in fabrication conditions lead to variations in structural features, including the orientation of graphene sheets, physical or chemical interconnections between these sheets, pore size, porosity, and the number of graphene sheet layers. Consequently, these structural changes affect the properties of the material. For example, GFs possess an isotropic structure due to the absence of specific graphene sheet orientation, while GSs exhibit anisotropic structures. In the case of GSs, large graphene films align nearly parallel to one another, resulting in an anisotropic arrangement. The adaptable manufacturing process employed for GFs provides precise control over both their macrostructure and microstructure [31]. The pore structure within Ni foam can be carefully manipulated to tailor the pore size and porosity to meet specific requirements. Simultaneously, the adjustment of CH4 concentration plays a vital role in influencing several key characteristics of GFs, including the average number of graphene layers, surface area, and overall density. The concentration of CH4 enables more graphene layers to be formed, resulting in a substantial change in SSA, density, and electrical conductivity. Intriguingly, it is noteworthy that the electrical conductivity of GFs exhibits an initial increase followed by a subsequent decrease as the number of graphene layers escalates.

In a similar vein, the microstructure and characteristics of graphene sponges (GSs) can be finely tailored by making adjustments to the synthesis conditions. Particularly, when GSs are fabricated through the freeze-drying process using graphene hydrogels (GH), the freezing temperature emerges as a crucial factor (**Figure 5**). Changing freezing temperatures cause significant pore size and wall thickness changes, changes in pore morphology from anisotropic lamellar to uniform cellular structures, and changes in Young's modulus. It's worth emphasizing that the mean pore size exerts a direct influence on water absorption properties, where larger pores impart water resistance to the sponge, while smaller pores facilitate water absorption. This tunable aspect of GS properties, contingent on freezing temperature, offers remarkable versatility for an array of applications [32].

#### **Figure 5.**

*(a–d) SEM images of the porous structures of four 3DGAs fabricated at different freezing temperatures of −170, −40, −20, and − 10°C, respectively. (e) Enlargement of the square area in image (a) [32].*

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

#### **4. Applications of 3D graphene**

#### **4.1 Drug delivery and cancer treatment**

 In conventional drug delivery methods, a range of challenges can arise, including low solubility, insufficient selectivity, and toxicity concerns. To address these limitations, researchers have increasingly used carbon nanotubes (CNTs), a subgroup of graphene, as drug delivery platforms. CNTs offer a substantial surface-to-volume ratio, enabling the incorporation of significant drug volumes, encompassing both hydrophilic and lipophilic drugs. Drugs can be loaded either on the exterior or inside of CNTs, making this a viable option for multidrug therapies. Of notable importance, drugs attached to the surface of CNTs possess the capability to recognize specific cell receptors and traverse cellular barriers without inducing toxicity. This innovative approach has demonstrated significant potential in the delivery of medications such as methotrexate, epirubicin, and doxorubicin, particularly in the context of cancer treatment [ 33 ].

#### **4.2 Tissue engineering**

 Tissue engineering constitutes the development of functional tissues for purposes such as transplantation and regenerative medicine. Materials based on graphene have proven valuable in the design of scaffolds in this domain. The scaffolds promote crucial cellular processes, such as adhesion, proliferation, and differentiation. As a noteworthy example, the utilization of graphene oxide-modified 3D acellular cartilage extracellular matrix (ACM) scaffolds has yielded substantial advancements in the realm of cartilage regeneration. These scaffolds were found to promote good cell behavior and biocompatibility, making them promising for repairing cartilage

 **Figure 6.**  *Graphene-based scaffolds have been explored for bone tissue engineering [ 34 ].* 

injuries [34]. Additionally, as shown in **Figure 6**, graphene-based scaffolds have been extensively investigated in various tissue engineering applications, including bone tissue engineering, cardiac tissue engineering, neural tissue engineering, and skin tissue engineering. The versatility and potential of graphene-based scaffolds in tissue engineering are underscored by this multifaceted application.

#### **4.3 Sensors for magnetic resonance imaging (MRI)**

Graphene's unique properties have made it suitable for use in medical MRI sensors. Traditional sensors made from metals can introduce distortion and inhomogeneity to the magnetic field, leading to misdiagnosis. Graphene's high conductivity, strain resilience, and non-toxic nature make it an excellent candidate for replacing traditional metallic conductors in piezoelectric sensors used in MRI. Graphene-based sensors have shown promising results in providing clearer images with minimal distortion during MRI scans [35].

#### **4.4 Stem cell-based transplant**

Transplant therapy based on stem cells holds significant promise for the restoration of damaged tissues and organs, particularly within the realm of neural regeneration. Neural stem cells (NSCs) can self-renew and differentiate into a variety of neural cell types, making them invaluable for treating nerve damage, promoting neurogenesis, and stimulating axonal growth. Within the sphere of regenerative medicine, carbon-based materials, including CNTs, carbon nanofibers, and 3DGAs, have attracted considerable attention owing to their distinctive electrical, mechanical, and biological properties [36].

#### **4.5 Dental and oral application**

There has been considerable interest in graphene-based materials in the field of dentistry due to their exceptional properties, particularly their potential antibacterial properties [37]. These materials have demonstrated their effectiveness against a broad spectrum of bacterial pathogens, including both gram-positive and gram-negative bacteria [38]. The utilization of 3D GAs in dentistry presents various applications and advantages, as outlined below:


*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*


Thus, a variety of dental procedures may benefit from graphene-based materials, including antibacterial properties, biocompatibility, and imaging enhancement. These properties make graphene-based materials promising candidates for improving oral health and dental treatments [42].

#### **4.6 Supercapacitors**

Due to their distinctive properties, such as high power density and extended cycle life, supercapacitors have received substantial attention as energy storage devices. These devices are categorized into two primary groups: pseudo-capacitors and electrochemical double-layer capacitors (EDLCs). Pseudo-capacitors, such as transition metal oxides and conducting polymers, store charges via chemical reactions on their surfaces. In contrast, EDLCs, frequently incorporating carbonbased materials such as graphene, store energy through ion adsorption at the electrode-electrolyte interface. Because of its large surface area and varied dimensions, graphene has gained widespread use in EDLC electrodes [44]. Recently, 3D graphene structures have emerged as compelling candidates for supercapacitors, thanks to their porous nature, expansive surface area, and interconnected networks, which enhance electrolyte ion accessibility and bolster electrical conductivity. The following 3D graphene configurations have been investigated for applications in supercapacitors:


So, 3DGAs have shown promise in supercapacitor applications, offering enhanced performance, high energy density, and excellent cycling capability. These structures, whether in the form of spheres, networks, or films, hold great potential for energy storage in various electronic devices and portable applications. The utilization of graphene in flexible supercapacitors further expands their range of applications, making them suitable for emerging technologies like electronic textiles and wearable devices [44].

#### **4.7 Lithium-ion batteries**

In recent years, 3DGAs have become the focus of extensive research due to their potential application as active electrodes in batteries, particularly in lithium-ion batteries (LIBs). These 3DGAs offer numerous advantages, including enhanced lifetime, higher energy density, and improved electrochemical performance, addressing some of the challenges typically associated with batteries, such as low reversible capacity and limited cyclic life. In the design of batteries, such as LIBs, it is crucial to consider the role of different components, including electrodes and electrolytes, in enhancing overall battery performance. In addition to its exceptional properties, 3D graphene is a highly promising candidate for achieving high-performance LIBs due to its large surface area, porous structure, rapid mass and charge transfer, and interconnected network. Among the key strategies for harnessing 3D graphene's potential for LIBs is to incorporate metal or metal oxides such as Sn, NiO, Fe3O4, and LiFePO4, along with CNTs into graphene sheets. 3D graphene composites were formed as a result of these efforts, which exhibit remarkable electrochemical properties and significantly improve the performance of LIB electrodes. The incorporation of conductive nanomaterials such as graphene into Fe3O4 has attracted considerable attention, primarily due to the appealing characteristics of Fe3O4 as a prospective electrode material for LIBs. Aside from its high theoretical capacity, Fe3O4 has the advantage of being costeffective and non-toxic.

Stable electrode performance has been hindered by previously encountered challenges, such as Fe3O4's low conductivity and high volume expansion. To tackle these issues, researchers have pioneered the development of 3D GFs-supported Fe3O4 LIBs. This innovative approach has yielded LIB electrodes with an impressive capacity of 785 mA h/g at a 1 C charge–discharge rate, demonstrating stable performance over 500 cycles [47]. 3D graphene's incorporation into LIB electrodes confers several advantages in all the aforementioned studies. Firstly, it establishes a shorter path length for lithium ion transport, expediting charge and discharge processes. Secondly, it enhances electron transport and electrode conductivity. Lastly, it curbs the agglomeration of active materials, ensuring uniform and consistent electrode performance over extended cycling. The 3D graphene structures can significantly enhance LIB

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

performance. Through the integration of diverse metal or metal oxide composites and CNTs, researchers have harnessed the distinctive attributes of 3D graphene, resulting in improved electrode materials characterized by enhanced capacity, stability, and rate capability. These advancements pave the way for the development of high-performance batteries, with applications spanning from portable electronics to electric vehicles [48].

#### **4.8 Sensors**

In recent years, graphene-based materials adorned with metals and metal oxides have emerged as highly promising contenders for a diverse array of sensing devices, encompassing electrochemical sensing and biosensing. As a result of graphene's exceptional optoelectronic attributes and the remarkable catalytic activity conferred by metals and metal oxides, graphene is attracting a growing amount of attention. Several applications involving these materials have yielded impressive results in terms of sensitivity, selectivity, and detection limits. Presented below are noteworthy instances of graphene-based sensing materials and their respective applications [49–52].


serves as an outstanding sensing platform for the highly sensitive determination of guanine and adenine. Beyond its applicability to guanine and adenine, this versatile platform lends itself to the determination of a multitude of other analytes, particularly within the realm of bioanalytical and clinical applications. These exemplars underscore the adaptability and potential of graphene-based materials to diverse sensing applications. Due to their unique properties, such as extensive surface areas, excellent electrical conductivity, and amenable functionalization, they are ideal candidates for sensor development. Furthermore, the integration of metals and metal oxides serves to bolster their catalytic prowess, broadening the horizon of possibilities in environmental monitoring, healthcare, and beyond. A graphene-based sensor can detect a wide range of analytes and has several advantages, such as fast response times, greater sensitivity, selectivity, and a wide range of analytes. As continued research in this domain advances, the anticipation of even more intricate and efficient sensing devices, spanning industries from electronics to biomedicine, becomes increasingly foreseeable.

#### **4.9 Fuel cells**

In the pursuit of sustainable energy sources and the transition away from finite fossil fuels, scientists and researchers have been exploring various avenues to develop renewable energy technologies. Among these, 3DGAs have garnered significant attention for their potential applications in fuel cells and microbial fuel cells (MFCs), where they serve as catalysts or catalyst carriers. In particular, these graphene structures improve the performance of oxygen reduction reactions (ORRs) in these energy conversion devices. In addition, they have shown promise for improving the power density and efficiency of MFCs, which can be applied to both energy production and environmental bioremediation [56–60].

a.Fuel cells: enhancing catalyst performance with 3D graphene.

Fuel cells serve as electrochemical devices, directly converting the chemical energy stored in fuels like hydrogen or methanol into electricity. Fundamentally, they operate by catalyzing reactions: anodes oxidize fuel, and cathodes reduce oxygen. The efficacy and performance of fuel cells heavily depend on the catalyst materials employed. Researchers are actively studying the potential of 3DGAs as catalyst supports or even as catalysts. One illustrative case involves the integration of 3D graphene as an anode electrode within microbial fuel cells (MFCs). MFCs represent devices designed to harness the chemical energy embedded in biodegradable organic compounds through a bio-oxidation process, simultaneously yielding electricity and contributing to environmental bioremediation. Nevertheless, conventional MFCs have issues such as low power density and low bacterial adhesion to electrodes. To tackle these issues, Yong et al. introduced an innovative anode electrode featuring a macroporous and monolithic structure, constructed from a hybrid material merging PANI with 3D graphene. As a result of graphene's generous surface area, it is more robustly integrated with bacterial films, resulting in enhanced electron transfer along multiple conductive pathways.

b.Microbial fuel cells (MFCs) offer an innovative avenue for converting organic substances, including wastewater, into electricity via microbial-driven processes. There are, however, several challenges associated with MFCs, including *Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

low power density and limited bacterial adhesion to electrode surfaces. Recent investigations have delved into the utilization of 3DGAs to tackle these hurdles and enhance MFC performance. To illustrate, researchers developed freestanding anodes for MFCs by adorning 3DGA with platinum (Pt) nanoparticles. This inventive configuration yielded an exceptional power density of 1460 mW/m<sup>2</sup> . The superior performance of these MFCs can be attributed to several factors, including a heightened bacterial loading capacity, streamlined electron transfer between bacteria and the 3D graphene/Pt anode, and expedited ion diffusion facilitated by the porous 3D structure.

c.Applications of 3DGAs in MFCs related to the environment and energy.

The integration of 3DGAs in microbial fuel cells holds significant promise for both energy generation and environmental bioremediation. These advancements not only enhance the efficiency of MFCs but also contribute to sustainable energy production while mitigating environmental issues through the treatment of organic waste. As a result, the use of 3D graphene in fuel cells and microbial fuel cells represents an important advancement in the field of renewable energy and environmental technology. These graphene structures contribute to improving catalyst performance, power density, and overall efficiency in energy conversion devices. As research continues in this area, we can anticipate further innovations and applications of 3DGAs in addressing global energy and environmental challenges.

#### **5. Conclusion**

3DGAs are noble materials for their distinctive 3D porous architectures, expansive specific surface areas, remarkable adsorption capabilities, exceptional electrical conductivity, mechanical robustness, and swift mass and electron transport properties. 3DGAs represent a transformative technology with far-reaching implications across various facets of human life. This review provides a comprehensive overview of recent advancements in 3DGA synthesis and their burgeoning applications in fields such as sensors, fuel cells, lithium-ion batteries, supercapacitors, dental materials, tissue engineering, drug delivery systems, and many other domains. The synthesis of 3DGAs has evolved significantly, embracing methods like electrospraying, 3D printing, and chemical and electrochemical reduction, among others. Efforts aimed at achieving cost-effective large-scale production and utilization of various 3D graphene materials are essential for their widespread adoption in industrial settings. It also holds the promise of mitigating toxicity concerns and ensuring safer applications by prioritizing the development of biocompatible 3DGAs.

#### **Author details**

Md. Nizam Uddin1 \*, Md. Aliahsan Bappy2 , Md Fozle Rab3 , Faycal Znidi1 and Mohamed Morsy1

1 Department of Engineering and Physics, Texas A & M University-Texarkana, Texarkana, TX, USA

2 Department of Industrial Engineering, Lamar University, TX, USA

3 Bangladesh Railway, Rajshahi, Bangladesh

\*Address all correspondence to: muddin@tamut.edu

© 2024 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

#### **References**

[1] Sun Z, Fang S, Hu YH. 3D graphene materials: From understanding to design and synthesis control. Chemical Reviews. 2020;**120**(18):10336-10453. DOI: 10.1021/ acs.chemrev.0c00083

[2] Ding M, Li C. Recent advances in simple preparation of 3D graphene aerogels based on 2D graphene materials. Frontiers in Chemistry. 2022;**10**:1-9. DOI: 10.3389/fchem.2022.815463

[3] Qiu L, He Z, Li D. Multifunctional cellular materials based on 2D nanomaterials: Prospects and challenges. Advanced Materials. 2018;**30**(4):1704850. DOI: 10.1002/adma.201704850

[4] Shao Q, Tang J, Lin Y, Zhang F, Yuan J, Zhang H, et al. Synthesis and characterization of graphene hollow spheres for application in supercapacitors. Journal of Materials Chemistry A. 2013;**1**:15423-15428

[5] Liu H, Pang X, Ding W, Guo S, Ding Z. Preparation of nano-SiO2 modified graphene oxide and its application in polyacrylate emulsion. Materials Today Communications. 2021;**27**:102245. DOI: 10.1016/j. mtcomm.2021.102245

[6] Wu L, Feng H, Liu M, Zhang K, Li J. Graphene-based hollow spheres as efficient electro-catalysts for oxygen reduction. Nanoscale. 2013;**5**:10839-10843

[7] Huang X, Qian K, Yang J, Zhang J, Li L, Yu C, et al. Functional Nanoporous graphene foams with controlled pore sizes. Advanced Materials. 2012;**24**(32):4419-4423. DOI: 10.1002/ adma.201201680

[8] Uddin MN, Huang ZD, Mai YW, Kim JK. Tensile and tearing fracture properties of graphene oxide papers intercalated with carbon nanotubes. Carbon. 2014;**77**:481-491. DOI: 10.1016/j. carbon.2014.05.053

[9] Uddin MN, Desai FJ, Rahman MM, Asmatulu R. Highly efficient fog harvester of electrospun permanent Superhydrophobic-hydrophilic polymeric nanocomposite Fiber Mats. Nanoscale Advances. 2020;**2**:4627-4638. DOI: 10.1039/D0NA00529K

[10] Uddin MN, Desai FJ, Asmatulu E. Biomimetic electrospun nanocomposite Fibers from recycled polystyrene foams exhibiting Superhydrophobicity. Energy, Ecology, and Environment. 2020;**5**(1):1-11. DOI: 10.1007/ s40974-019-00140-7

[11] Bhuyan MSA, Uddin MN, Islam MM, Bipasha FA, Hossain SS. Synthesis of graphene. International Nano Letters. 2016;**6**:65-83. DOI: 10.1007/ s40089-015-0176-1

[12] Poudeh LH, Okan BS, Zanjani SMJ, Yildiz M, Menceloglu YZ. Design and fabrication of hollow and filled graphene-based polymeric spheres via core-shell electrospraying. RSC Advances. 2015;**5**:91147-91157

[13] Zhang Z, Scherer GW. Evaluation of drying methods by nitrogen adsorption. Cement and Concrete Research. 2019;**120**:13-26. DOI: 10.1016/j. cemconres.2019.02.016

[14] Zhang F, Pant D, Logan BE. Longterm performance of activated carbon air cathodes with different diffusion layer porosities in microbial fuel cells. Biosensors and Bioelectronics. 2011;**30**(1):49-55. DOI: 10.1016/j. bios.2011.08.025

[15] Fang Q, Shen Y, Chen B. Synthesis, decoration and properties of three-dimensional graphene-based macrostructures: A review. Chemical Engineering Journal. 2015;*264*:753-771. DOI: 10.1016/j.cej.2014.12.001

[16] Hu H, Zhao Z, Wan W, Gogotsi Y, Qiu J. Ultralight and highly compressible graphene aerogels. Advanced Materials. 2013;**25**(15):2219-2223. DOI: 10.1002/ adma.201204530

[17] Li H, Jia D, Ding M, Zhou L, Wang K, Liu J, et al. Robust 3D graphene/cellulose nanocrystals hybrid lamella network for stable and highly efficient solar desalination. Solar RRL. 2021;**5**(8):2100317. DOI: 10.1002/solr.202100317

[18] Zhang X, Sui Z, Xu B, Yue S, Luo Y, Zhan W, et al. Mechanically strong and highly conductive graphene aerogel and its use as electrodes for electrochemical power sources. Journal of Materials Chemistry. 2011;**21**(18):6494. DOI: 10.1039/c1jm10239g

[19] Williams G, Seger B, Kamat P. TiO2-graphene Nano-composites. UV-assisted photocatalytic reduction of graphene oxide. ACS Nano. 2008;**2**(7):1487-1491

[20] Smirnov VA, Arbuzov AA, Shulga YM, Baskakov SA, Martynenko VM, Muradyan VE, et al. Photoreduction of graphite oxide. High Energy Chemistry. 2011;*45*(1):57-61. DOI: 10.1134/S0018143911010176

[21] Chen W, Yan L. In situ self-assembly of mild chemical reduction graphene for three-dimensional architectures. Nanoscale. 2011;**3**:3132-3137

[22] Niu Z, Chen J, Hng H, Ma J, Chen X. A leavening strategy to prepare reduced graphene oxide foams. Advanced Materials. 2012;**24**:4144-4150

[23] Chen K, Chen L, Chen Y, Bai H, Li L. Three-dimensional porous graphene-based composite materials: Electrochemical synthesis and application. Journal of Materials Chemistry. 2012;**22**:20968-20976

[24] Wu Z-S, Ren W, Gao L, Zhao J, Chen Z, Liu B, et al. Synthesis of graphene sheets with high electrical conductivity and good thermal stability by hydrogen arc discharge exfoliation. ACS Nano. 2009;**3**(2):411-417. DOI: 10.1021/nn900020u

[25] Cote LJ, Cruz-Silva R, Huang J. Flash reduction and patterning of graphite oxide and its polymer composite. Journal of the American Chemical Society. 2009;**131**(31):11027-11032. DOI: 10.1021/ ja902348k

[26] Hensleigh RM, Cui H, Oakdale JS, Ye JC, Campbell PG, Duoss EB, et al. Additive manufacturing of complex microarchitected graphene aerogels. Materials Horizons. 2018;**5**(6):1035-1041. DOI: 10.1039/C8MH00668G

[27] Chen Z, Ren W, Gao L, Liu B, Pei S, Cheng H-M. Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapour deposition. Nature Materials. 2011;**10**(6):424-428. DOI: 10.1038/ nmat3001

[28] Bi H, Xie X, Yin K, Zhou Y, Wan S, He L, et al. Spongy graphene as a highly efficient and recyclable sorbent for oils and organic solvents. Advanced Functional Materials. 2012;**22**(21):4421- 4425. DOI: 10.1002/adfm.201200888

[29] Worsley MA, Pauzauskie PJ, Olson TY, Biener J, Satcher JH, Baumann TF. Synthesis of graphene aerogel with high electrical conductivity. Journal of the American Chemical Society. 2010;**132**(40):14067-14069. DOI: 10.1021/ja1072299

#### *Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

[30] Xu Y, Sheng K, Li C, Shi G. Selfassembled graphene hydrogel via a onestep hydrothermal process. ACS Nano. 2010;**4**(7):4324-4330. DOI: 10.1021/ nn101187z

[31] Tang Z, Shen S, Zhuang J, Wang X. Noble-metal-promoted threedimensional macroassembly of singlelayered graphene oxide. Angewandte Chemie International Edition. 2010;**49**(27):4603-4607. DOI: 10.1002/ anie.201000270

[32] Xie X, Zhou Y, Bi H, Yin K, Wan S, Sun L. Large-range control of the microstructures and properties of threedimensional porous graphene. Scientific Reports. 2013;*3*(1):2117. DOI: 10.1038/ srep02117

[33] Dhanasekaran PS, Uddin MN, Wooley P, Asmatulu R. Fabrication and biological characterization of highly porous PEEK bio-nanocomposites incorporated with carbon and hydroxyapatite nanoparticles for scaffold applications. Molecules. 2020;**25**(16):3572. DOI: 10.3390/ molecules25163572

[34] Ambekar RS, Kandasubramanian B. Progress in the advancement of porous biopolymer scaffold: Tissue engineering application. Industrial & Engineering Chemistry Research. 2019;**58**(16):6163- 6194. DOI: 10.1021/acs.iecr.8b05334

[35] Raslan A, Saenz del Burgo L, Ciriza J, Pedraz JL. Graphene oxide and reduced graphene oxide-based scaffolds in regenerative medicine. International Journal of Pharmaceutics. 2020;**580**:119226. DOI: 10.1016/j. ijpharm.2020.119226

[36] Zhu W, Ye T, Lee S-J, Cui H, Miao S, Zhou X, et al. Enhanced neural stem cell functions in conductive annealed carbon nanofibrous

scaffolds with electrical stimulation. Nanomedicine:Nanotechnology, Biology, and Medicine. 2018;**14**:2485-2494

[37] Karahan HE, Wiraja C, Xu C, Wei J, Wang Y, Wang L, et al. Graphene materials in antimicrobial Nanomedicine: Current status and future perspectives. Advanced Healthcare Materials. 2018;**7**(13):e1701406. DOI: 10.1002/ adhm.201701406

[38] Shahnaz T, Hayder G. Exploring graphene's antibacterial potential for advanced and sustainable solutions in water treatment. Journal of Water Process Engineering. 2023;**56**:104530. DOI: 10.1016/j.jwpe.2023.104530

[39] Aati S, Chauhan A, Shrestha B, Rajan SM, Aati H, Fawzy A. Development of 3D printed dental resin nanocomposite with graphene nanoplatelets enhanced mechanical properties and induced drug-free antimicrobial activity. Dental Materials. 2022;**38**:1921-1933. DOI: 10.1016/j.dental.2022.10.001

[40] Dreanca A, Sarosi C, Parvu AE, Blidaru M, Enacrachi G, Purdoiu R, et al. Systemic and local biocompatibility assessment of graphene composite dental materials in experimental mandibular bone defect. Materials. 2020;**13**(11):2511. DOI: 10.3390/ma13112511

[41] Antoine C, Pijeira MSO, Ricci-Junior E, Alencar LMR, Santos-Oliveira R. Graphene quantum dots as bimodal imaging agent for X-ray and computed tomography. European Journal of Pharmaceutics and Biopharmaceutics. 2022;**179**:74-78. DOI: 10.1016/j. ejpb.2022.08.020

[42] Li X, Liang X, Wang Y, Wang D, Teng M, Xu H, et al. Graphene-based nanomaterials for dental applications: Principles, current advances, and future Outlook. Bioengineering and

Biotechnology. 2022;**10**:804201. DOI: 10.3389/fbioe.2022.804201

[43] Mobarak MH, Hossain N, Hossain A, Mim JJ, Khan F, Rayhan MT, et al. Advances of graphene nanoparticles in dental implant applications-a review. Applied Surface Science Advances. 2023;**18**:100470. DOI: 10.1016/j. apsadv.2023.100470

[44] Cao X, Yin Z, Zhang H. Threedimensional graphene materials: Preparation, structures and application in supercapacitors. Energy & Environmental Science. 2014;**7**(6):1850- 1865. DOI: 10.1039/c4ee00050a

[45] Lei S, Liu X, Zhang X, Huang Z, He C, Yang Y. One-pot hydrothermal approach to graphene/poly(3,4 ethylenedioxythiophene) composites for high-capacitance supercapacitors. Materials Today Communications. 2019;**20**:100549. DOI: 10.1016/j. mtcomm.2019.100549

[46] He Y, Chen W, Li X, Zhang Z, Fu J, Zhao C, et al. Freestanding threedimensional graphene/MnO2 composite networks as ultralight and flexible supercapacitor electrodes. ACS Nano. 2013;**7**(1):174-182. DOI: 10.1021/ nn304833s

[47] Luo J, Liu J, Zeng Z, Ng CF, Ma L, Zhang H, et al. Three-dimensional graphene foam supported Fe3O4 lithium battery anodes with long cycle life and high rate capability. Nano Letters. 2013;**13**(12):6136-6143. DOI: 10.1021/ nl403461n

[48] Bagoole O, Rahman M, Younes H, Shah S, Al Ghaferi A. Three-dimensional graphene interconnected structure, fabrication methods and applications: Review. Journal of Nanomedicine & Nanotechnology. 2017;**8**(2):438-445. DOI: 10.4172/2157-7439.1000438

[49] Agudosi ES, Abdullah EC, Numan A, Mubarak NM, Aid SR, Benages-Vilau R, et al. Fabrication of 3D binder-free graphene NiO electrode for highly stable supercapattery. Scientific Reports. 2020;**10**(1):1-13. DOI: 10.1038/ s41598-020-68067-2

[50] Uddin MN, Nageshkar VN, Asmatulu R. Improving water-splitting efficiency of electrolysis process via highly conductive nanomaterials at lower voltages. Energy, Ecology and Environment. 2020;**5**:108-111. DOI: 10.1007/s40974-020-00147-5

[51] Asmatulu R, Veisi Z, Uddin MN, Mahapatro A. Highly sensitive and reliable electrospun polyaniline nanofiber based biosensor as a robust platform for COX-2 enzyme detections. Fibers and Polymers. 2019;**20**(5):966- 974. DOI: 10.1007/s12221-019-1096-x

[52] Salahuddin M, Uddin MN, Hwang G, Asmatulu R. Super-hydrophobic PAN nanofibers for gas diffusion layers of proton exchange membrane fuel cells for Cathodic water management. International Journal of Hydrogen Energy. 2018;**43**(25):11530-11538. DOI: 10.1016/j.ijhydene.2017.07.229

[53] Yavari F, Castillo E, Gullapalli H, Ajayan PM, Koratkar N. High sensitivity detection of NO2 and NH3 in air using chemical vapor deposition grown graphene. Applied Physics Letters. 2012;**100**:203120. DOI: 10.1063/1.4720074

[54] Kung CC, Lin PY, Buse FJ, Xue Y, Yu X, Dai L, et al. Preparation and characterization of threedimensional graphene foam supported platinum–ruthenium bimetallic nanocatalysts for hydrogen peroxide based electrochemical biosensors. Biosensors and Bioelectronics. 2014;**52**:1- 7. DOI: 10.1016/j.bios.2013.08.025

*Recent Progress on Synthesis of 3D Graphene, Properties, and Emerging Applications DOI: http://dx.doi.org/10.5772/intechopen.114168*

[55] Yang T, Guan Q, Li Q, Meng L, Wang L, Liu C, et al. Large-area, threedimensional interconnected graphene oxide intercalated with self-doped polyaniline nanofibers as a free-standing electrocatalytic platform for adenine and guanine. Journal of Materials Chemistry B. 2013;**1**(23):2926-2933. DOI: 10.1039/c3tb20171f

[56] Kumar SSA, Uddin MN, Rahman MM, Asmatulu R. Introducing graphene thin films into carbon Fiber composite structures for lightning strike protection. Polymer Composites. 2018;**40**(S1):E517-E525. DOI: 10.1002/ pc.24850

[57] Bhuyan MSA, Uddin MN, Bipasha FA, Islam MM, Hossain SS. A review of functionalized graphene. Properties and its Applications, International Journal of Innovation and Scientific Research. 2015;**17**(2):303-315

[58] Pang Y, Jian J, Tu T, Yang Z, Ling J, Li Y, et al. Wearable humidity sensor based on porous graphene network for respiration monitoring. Biosensors and Bioelectronics. 2018;**116**:123-129. DOI: 10.1016/j.bios.2018.05.038

[59] Uddin MN, Le L, Zhang B, Nair R, Asmatulu R. Effects of graphene thin films and nanocomposite coatings on fire Retardancy and thermal stability of aircraft composites: A comparative study. Journal of Engineering Materials and Technology. 2019;**141**(3):031004-1-7. DOI: 10.1115/1.4042663

[60] Xu Z, Peng M, Zhang Z, Zeng H, Shi R, Ma X, et al. Graphene-assisted electrochemical sensor for detection of pancreatic cancer markers. Frontiers in Chemistry. 2021;**9**:733371. DOI: 10.3389/ fchem.2021.733371

Section 2
