**2.1 The synthesis of graphene**

The numerous chemical and physical methods have been proposed for the production of different types of graphene (from single layer to few layer) based on top-down and bottom-up approaches. Chemical vapor deposition (CVD) and epitaxial growth [15, 16], plasma-enhanced chemical vapor deposition (PECVD) [15], mechanical cleavage [14, 17], Scotch® tape technique [17], chemical synthesis [18], liquid exfoliation [19, 20], etc. have been widely used to produce graphene.

### **2.2 Graphene properties**

Considering the attention of scientists to graphene and the hope for its various applications in the near future, many research efforts have been devoted to understanding the structure and properties of graphene. Graphene is expected to

**Figure 3.** *Different forms of graphitic carbon [13].*

consist of only single layer, but there is a significant attractive force to bind layers and to form two-layer or few-layer graphene. Two- and few-layer graphene consist of two and three to ten layers of these 2D nanosheets, respectively. The graphene structure, which contains more than ten of these 2D sheets, is considered to be "thick graphene" and is less of a concern for scientists. The status of graphene has changed from an unknown to a superstar in various fields of science and technology [21]. This is due to graphene's exceptional characteristics including high current density, ballistic transport, chemical inertness, high thermal conductivity, optical transmittance, and superficial hydrophobicity on a nanometer scale [14].

Single-layer graphene, as previously discussed in this chapter, is defined as a 2D nanosheet of carbon atoms that are arranged in a hexagonal network. Each sp2 -hybridized carbon atom is bonded to three another atoms with strong covalent bond (σ) that are configured in the hexagonal structure and also has a π orbital perpendicular to the sheet that forms π bond out of plane. These bonds can control the interaction between different layers of graphene in few-layer graphene [21].

Graphene is a semimetal or a semiconductor with a bandgap of zero and also has very high electron mobility at room temperature. Single-layer graphene has an unexpected high degree of transparency so that it absorbs πα ≈ 2.3% the incident white light, in which α is a substructure factor [7]. Single-layer graphene is also considered as one of the strongest materials. Given these mechanical properties, more applications in nanocomposite and coating industries are expected to be opened [21].

Graphene nanosheets are demonstrated to exhibit high transparency in UV-Vis and IR radiation and could be used to produce transparent electrode in solar cells [22]. Graphene has a good ability to functionalize with different functional groups in the form of covalent and noncovalent which leads to its solubility in different solvents. On the other hand, the high surface area of graphene provides a lot of area for loading of functional groups, which leads to reach a higher-level loading of targeting group in the surface, so graphene is considered as a suitable agent for drug delivery. In addition, the high surface area of graphene allow for development of targeted drug delivery systems [23].

## **2.3 Graphene applications**

Different types of graphene, single-layer and few-layer, have potential applications in various fields. As stated above, graphene is the hardest and thinnest substance ever produced by human beings. Despite the fact that it has a dense structure, due to its very thin thickness, which is equal to the thickness of a carbon atom, it allows light to pass through and is highly transparent; it is also conductive, even more conductive than copper. Its ability to pass through heat and electricity makes it a new option for using on optical screens and computers.

It is 200–300 times stronger than steel and is even harder than diamond; however, it is very light and flexible. In addition, one of its properties is the great ability to move charge carriers. Electrons move relatively freely throughout graphene. With these features, graphene could be called supermassive, and it is expected that this material will create a revolution in the electronic, transistor, composite, coating, and sensor industries. Some examples of graphene applications can be:


**25**

*Two-Dimensional Nanomaterials*

*DOI: http://dx.doi.org/10.5772/intechopen.85263*

competitor of silicon [24].

• Used in optical electronics [28].

• Create supercapacitors [32].

(OLEDs) [35].

nanosheets (BNNSs).

ers, is called BNNSs.

• Make harder, stronger, and lighter plastics [29].

• Producing stronger implants (medical) [31].

• Application in flexible touch screens and displays [33].

• Application in liquid crystal display (LCD) [34].

• Making conductive inks for coating [36].

**3. Introduction of hexagonal boron nitride**

It is not present in nature and is synthesized.

electrons present in silicon, which is why potentially graphene have many applications in the electronics industry. This material is currently the main

• Embedding graphene in plastics to enable them to conduct electricity [25, 26].

• Applications in light-emitting diodes (LEDs) and organic light-emitting diodes

hBN is structurally similar to graphite and has hardness comparable to graphite. Since hBN is the isoelectric analog of graphite structure and shares very similar structural characteristics and many physical properties, is so-called white graphite.

Due to its unique properties, including high resistance to oxidation, high thermal conductivity, good thermal insulation, chemical inertness, excellent lubrication, non-toxicity, and environmental friendliness, hBN has diverse industrial applications in surface coatings, composites, lubricants, and insulators. Due to the impressive properties of nanoscale materials and the development of the application of nanomaterials in the industry, ongoing research is carried to develop new methods for synthesis of nanomaterials. However, until now, there is no ensured large-scale and high yield method to achieve a significant amount of boron nitride

Although researches on 2D nanomaterials have been began several decades ago, the wave of interest and attention to these materials get started in 2004 when Novoselov discovered single-layer graphene with superb electronic properties [1]. Many efforts have been made to achieve 2D materials including graphene, boron nitride, and several dichalcogenides. Boron nitride (BN) is one of the most promising systems ever to be the lightest compound of the three and four groups in the periodic table. BN is composed of equal numbers of N and B atoms, which are configured in hexagonal arrange, similar to carbon atoms in graphene. For naming, the term "single-layer BN" is used for monolayer of BN, and in the case of multilay-

• To increase the durability of batteries using graphene dust [27].

• As conductive transparent coating for solar cells and screens [30].

*Nanostructures*

sp2

opened [21].

targeted drug delivery systems [23].

**2.3 Graphene applications**

consist of only single layer, but there is a significant attractive force to bind layers and to form two-layer or few-layer graphene. Two- and few-layer graphene consist of two and three to ten layers of these 2D nanosheets, respectively. The graphene structure, which contains more than ten of these 2D sheets, is considered to be "thick graphene" and is less of a concern for scientists. The status of graphene has changed from an unknown to a superstar in various fields of science and technology [21]. This is due to graphene's exceptional characteristics including high current density, ballistic transport, chemical inertness, high thermal conductivity, optical transmittance, and superficial hydrophobicity on a nanometer scale [14]. Single-layer graphene, as previously discussed in this chapter, is defined as a 2D nanosheet of carbon atoms that are arranged in a hexagonal network. Each


Graphene nanosheets are demonstrated to exhibit high transparency in UV-Vis and IR radiation and could be used to produce transparent electrode in solar cells [22]. Graphene has a good ability to functionalize with different functional groups in the form of covalent and noncovalent which leads to its solubility in different solvents. On the other hand, the high surface area of graphene provides a lot of area for loading of functional groups, which leads to reach a higher-level loading of targeting group in the surface, so graphene is considered as a suitable agent for drug delivery. In addition, the high surface area of graphene allow for development of

Different types of graphene, single-layer and few-layer, have potential applications in various fields. As stated above, graphene is the hardest and thinnest substance ever produced by human beings. Despite the fact that it has a dense structure, due to its very thin thickness, which is equal to the thickness of a carbon atom, it allows light to pass through and is highly transparent; it is also conductive, even more conductive than copper. Its ability to pass through heat and electricity

It is 200–300 times stronger than steel and is even harder than diamond; however, it is very light and flexible. In addition, one of its properties is the great ability to move charge carriers. Electrons move relatively freely throughout graphene. With these features, graphene could be called supermassive, and it is expected that this material will create a revolution in the electronic, transistor, composite, coating,

• As reinforcement in composites instead of carbon fiber, this results in the

• Used instead of semiconductor silicones in transistors due to superb conductivity properties. In this case, electrons can move 100 times faster than the

makes it a new option for using on optical screens and computers.

and sensor industries. Some examples of graphene applications can be:

creation of lighter and stronger aerocrafts and satellites.

**24**

electrons present in silicon, which is why potentially graphene have many applications in the electronics industry. This material is currently the main competitor of silicon [24].

