**4.3 Gene therapy**

Gene therapy is a big breakthrough in medical science. Gene therapy is a new technique to treat various genetic diseases such as cystic fibrosis, Parkinson's, and various cancers. Efficient gene therapy includes a gene vector that protects the desired gene from nuclease degradation and allows cellular uptake of DNA with high transfection efficiency. The selection of an appropriate gene vector is the main obstacle in the development of gene therapy. The non-toxic nanocarrier in efficient gene therapy is Graphene and graphene-coated substrates. Graphene-based nanosheets have sp2 hybridized orbitals, which are capable to interact with drugs and other molecules like nucleic acids such as DNA and RNA. Thus, they can be used for gene delivery or as carriers and protectors of probes involved in identifying miRNAs [74]. Hyunwoo et al. synthesized GO-based polyethyleneimine (PEI) composite and used it as an efficient gene delivery carrier in gene therapy [75]. Among different carriers, polyethyleneimine (PEI) has been typically recognized as the "golden standard" cationic polymer in gene transfection, because of its strong binding to DNA and RNA and effective uptake by cells. However, due to high cytotoxicity and poor biocompatibility, applications of PEI polymers in gene therapy is limited [76].

#### **4.4 Catalyzed organic reactions**

Carbon-based nanocomposite materials have been extensively used as heterogeneous catalysts in many organic chemical reactions. In chemical industries, less than 10% of the chemical reactions are still conducted without the addition of specific catalysts [77]. The catalytic products such as organic building blocks, pharmaceuticals, natural products, and agricultural derivatives are very valuable in chemical industries [78]. In many industrial chemical reactions, different types of supported and unsupported metal catalysts have been investigated. In the last few decades, the researchers gave more importance to using carbon nanostructure-based composites as heterogeneous catalysts in organic transformations. The highlighted advantages of carbon-based nanocomposites catalysts are high surface area, stability, fine dispersion, reusability, and easy recovery after completion of reactions. Furthermore, the introduction of metal nanoparticles onto the carbon support has shown more usefulness in carrying out the highly selective catalytic organic reactions [79]. In comparison with CNTs, graphene or GO has been preferred due to its low cost, large-scale preparation, and less health risk.

#### **4.5 Radar absorbing materials**

Electromagnetic wave absorbing materials are widely used in radar-absorbing technology. The absorbing of electromagnetic waves has many widespread applications, including minimizing the radar signature of a target, protection of human eyes, protective shielding of computers, consumer electronics, and optical sensors from intense laser pulses. Composites, in which polymer matrix having embedded multiwalled carbon nanotubes (MWCNTs), have been studied in multi-frequency detection mode instruments. Their applications in the microwave frequency range are anti-reflection, microwave absorbers, and electromagnetic interference shielding. The use of CNTs in radar-absorbing nanocomposite materials is more prominent due to their attractive properties i.e., electrical capacity, stiffness along large electromagnetic wave absorption tendency in the microwave range [80]. Zakharychev et al. [81]

have investigated the radar absorbing properties of epoxy binder and CNT nanocomposites in the frequency of 52–73 GHz.

#### **4.6 Actuators**

Shape memory alloys or liquid crystal elastomers have latent ability for activation under the right conditions. However, blending of two or more materials is required by other systems to report a new physical response leading to activation process. Recently, it has been proven that the polymer nanocomposite seems to be the best candidate for mechanical activation processes. The reported literature showed that most of the studies were concerned with the activation of the already described polymer matrix by introducing nanotubes. A new activator response was reported by Courty and their team by an electrical field due to the presence of CNTs in an elastomer polysiloxane [82]. Koerner et al. fabricated new polydimethylsiloxane (PDMS)/ MWCNT nanocomposite material which showed a mechanical response to infrared radiation [83]. The mechanical response of (PDMS)/MWCNT was due to absorption of photons from irradiation and not due to slight heating of material. Moreover, the nature of activator mechanism is not known. Mylvaganam and Zhang [84] developed a method for the preparation of activating nanocomposite material i.e., polyimide and CNT nanocomposite.

#### **4.7 Wind turbine blades**

In the last few decades, it has been proved that the fastest-growing installed energy generation technology is wind energy. The energy department of US has set a goal for their researchers to produce at least 20% of its electrical energy up to 2030. To achieve the goal, the focus of the wind industry is to manufacture large blades. This is because the square of rotor radius increases the wind turbine energy output. This is a big challenge for the researchers to make such a large-sized blade with excellent mechanical properties i.e., excellent stiffness and strength, long fatigue life, and low weight. To enhance the strength of polymer matrices used for wind turbines, CNTs are the best candidate because of their excellent properties. Most of the previous work showed that CNTs used in polymer matrices have enhanced the strength and stiffness of composites materials. Recently this is also been reported that the use of CNT increased the fatigue and tensile properties of thermoset resins used in wind industry. To improve such type mechanical properties CNTs are the best candidates among the discovered fillers. It was reported that incorporating a small quantity of CNTs (0.2 wt%) improved the fatigue resistance of an epoxy system which is extensively used in the wind-energy industry. Tensile and dynamical mechanical analyses were performed on neat epoxy and on epoxy/CNT nanocomposite. The CNT composites had long fatigue life as compared to neat epoxies under the same conditions [85].

#### **4.8 Organic pollutant removal**

With rapid industrialization and untreated wastewater disposal, water pollution has become a serious threat to both flora and fauna. The contaminants which affect the water quality badly are synthetic organic dyes, petroleum, antibiotics, drugs, pesticides, polyaromatic hydrocarbons, heavy metal ions, etc., which have brought a lot of adverse effects on human health and social development. The most used method for decontamination of polluted water is the biological method. There are

some limitations of the biological method i.e., some refractory organic and inorganic pollutants in wastewater are not effectively removed [86]. Therefore, some other methods have been developed to remove refractory organic and inorganic pollutants from wastewater such as adsorption and advanced oxidation processes (APS). In the last few decades, CNTs and graphene-based materials have been widely used by many researchers in wastewater treatment. Carbon nanomaterials-based nanocomposites can be used as an adsorbent in adsorption studies while in AOPS they are used as effective catalysts due to their unique physical and chemical properties. In a word, the CNTs-based materials may have potential application prospects in water treatment [87].

#### **4.9 Aerospace industry**

In recent years, the dependence of humans on speedy transportation has boosted many folds. The high demands make the research of this area very fast and more fascinating. In aerospace industry, keen interest is shown in the mechanical, thermal, chemical along with electrical and biodegradable properties. In chemical properties, the focus is to stop the corrosion of the system. The lightweight of the aerospace structure is vital, but the role of mechanical properties cannot be ignored. The role of mechanical properties is crucial for design like impact and scratch tolerance, toughness, strength, etc. The high thermal emissivity decreased solar absorption, electric conductivity, and resistance for radiations are also the key parameters, which are kept in focus while designing the aircrafts [88]. In the last few decades, the use of various epoxy resins in the aerospace industry had enhanced enormously. Almost in all these applications, carbon nanostructures are considered as advanced materials, which may be used incorporation with other nanomaterials or simply as the replacement of them [89]. In certain nanocomposites, carbon fibers were replaced by CNTs, the reason was to reduce the weight of composite materials. The use of epoxy nanocomposites is valued in aircraft/aerospace industry due to its high strength-to-weight ratio and enhanced temperature resistance. The best example is the wingtip fairings of Lockheed's F-35 which is made of CNT/epoxy nanocomposite. In the present situation, the application of CNT-based epoxy nanocomposites in the aeronautical and aerospace industry is obvious from their use in the space shuttle and advanced commercial aircraft (such as Boeing 787 and Airbus A380). In 2010, NASA published a report which showed the road maps for the future applications of nanomaterials and utilization of CNTs in aerospace industries. This report reveals that CNTs have tremendous potential to be used in aerospace applications which includes reduced vehicle mass, superior functionality, improved self-healing characteristics, improved control and damage tolerance, durability, and greater thermal protection. The use of CNT in the aerospace industry represents a very bright picture [90].

#### **4.10 Conductive plastic**

Plastic is one of the important materials used in the modern world as a metal replacement. The mechanical properties of plastics have been improved up to a maximum extent, but their limitations are arising when electrical conductivity is needed, as plastics are mostly nonelectrical conductors. To remove this deficiency different filling agents like carbon black and bigger graphite fibers have been incorporated in plastic polymers [91]. The loading of polymers with traditional filler to enhance the electrical conductivity results in weighty parts with high degraded construction properties

*Improved Nanocomposite Materials and Their Applications DOI: http://dx.doi.org/10.5772/intechopen.102538*

[92]. For this reason, carbon nanostructures i.e., CNT is exceptional with the greatest carbon fiber aspect ratio. In addition, their intrinsic inclination to shape cords provides naturally very lengthy leading routes even at extremely low loads [93]. This property of CNTs makes it the best choice to use in applications, such as gasket, enclosure, composite EMI (electromagnetic interference), electrostatic dissipation (ESD), shielding, and other usage coatings, low-observance radar absorption materials, and conductive (even transparent) antistatic and material coatings [94].
