*3.1.1. Applications of CNTs in green electronics*

Single-walled carbon nanotubes (SWCNTs) also have unique properties which make them suitable for applications in a variety of imaging modalities, such as magnetic resonance, nearinfrared fluorescence, Raman spectroscopy, photoacoustic tomography, and radionuclidebased imaging.

The various features of carbon nanotubes are:


#### **3.2. Graphene**

The two-dimensional carbon material graphene find application for sensors, electronics and catalysis applications due to its exceptional electrical and mechanical properties. Some of these applications require the adsorption of metal clusters onto graphene and metalgraphene systems which are now become a subject of intense investigation. It show many interesting properties as the observable quantum Hall effect at room temperature [100, 101], existence of two-dimensional gas of massless Dirac fermions [102], ballistic transport properties on the sub micrometer scale [103], etc. As graphene is unique in nature, so researchers explore its unique properties in storage [104], spintronics [105], microelectronics [106], etc. A number of theoretical and experimental work have been carried out for the electronic and magnetic behaviors of dimers [107] and adatoms of different elements [108] adsorbed on graphene system, which have been found to yield many interesting results. Graphene also has immense potential to act as a key ingredient for new devices as single molecule gas sensors, ballistic transistors, and spintronic devices. Bilayer graphene, which consists of two stacked monolayers, has a quadratic low-energy band structure which generates very different scattering properties from those of the monolayer. It also presents the unique property i.e. *the tunable band gap can be opened and controlled easily by a top gate*. Another property of graphene is the high electronic mobility, which is crucial for many of its potential applications [109]. So, understanding the mechanism, which limit the mobility of carriers in graphene is extremely important. It is also of a high conceptual interest, since transport properties of chiral massless fermions are essentially different from those of conventional charge carriers in metals and semiconductors [110]. Charged impurity scattering has received the most attention [102], with the majority of studies modeling the impurities as point-like objects (1/r potential). Recently, it has been revealed in a theoretical study that the physical structure of the charged impurities and clusterization of charged impurities might be the an important factor, which influence their scattering properties [111]. Graphene nanoribbons (GNRs) present reactive edges which make GNRs not only more accessible to doping and chemical modification, but also more susceptible to structural defects [112]. In particular, for zigzag graphene nanoribbons (ZGNRs) terminated with one hydrogen atom on each zigzag edge, there are quite a few localized edge states near the Fermi energy level on both edges. Such localized edge states can lead to a spin induced energy gap [113] providing a significant effect on the electronic and transport properties [114]. The electronic and transport properties are thus very sensitive to the atomic structures and chemical modification of the edges. One of the natural ways of chemically modifying graphene is to include metal adatoms [115–117]. Motivated by the special transport properties of atomic wires of Al, Ag, Au and Cu, and inspired by the localized edge states of ZGNRs that greatly enhance the binding energy of adatoms, we also conducted the studies on (Al, Au and Cu) adatomed-objects on edge chlorinated nano graphenes to investigate the electronic, magnetic and adsorption and transport properties of these (C1 (C42CI18)/C2(C48CI18)/ C3(C60CI22))–metal systems (**Figure 6**). Metals adsorbed on nanoscale carbon surfaces have been reported experimentally and theoretically to form a variety of structures, such as continuous coatings or discrete clusters [118] and novel interesting phenomena were observed

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Metallic nanowires (namely, linear chains of metal atoms) have drawn significant attention due to the quantum confinement effect, as they represent the ultimate miniaturization of conductors. The nanoscales of metallic nanowires result in a number of novel and interesting phenomena different from their bulk materials [119–121]. Graphene based biosensors can be

to occur through suitable modification.

**1.** Graphene-based electrochemical biosensors [122]

**2.** Graphene-based enzymatic electrochemical biosensors **3.** Graphene-based bioaffinity electrochemical biosensors

**4.** Graphene-based DNA electrochemical sensors [123]

**7.** Graphene-based optical biosensors [126]

**5.** Graphene-based electrochemical immunosensors [124]

**6.** Graphene-based field-effect transistor (FET) biosensors [125]

classified as follows:

**Figure 5.** Representation of the role of CNTs in drug delivery. (a) Gene delivery by CNTs, (b) Normal drug delivery versus the efficient target drug delivery using CNTs.

property i.e. *the tunable band gap can be opened and controlled easily by a top gate*. Another property of graphene is the high electronic mobility, which is crucial for many of its potential applications [109]. So, understanding the mechanism, which limit the mobility of carriers in graphene is extremely important. It is also of a high conceptual interest, since transport properties of chiral massless fermions are essentially different from those of conventional charge carriers in metals and semiconductors [110]. Charged impurity scattering has received the most attention [102], with the majority of studies modeling the impurities as point-like objects (1/r potential). Recently, it has been revealed in a theoretical study that the physical structure of the charged impurities and clusterization of charged impurities might be the an important factor, which influence their scattering properties [111]. Graphene nanoribbons (GNRs) present reactive edges which make GNRs not only more accessible to doping and chemical modification, but also more susceptible to structural defects [112]. In particular, for zigzag graphene nanoribbons (ZGNRs) terminated with one hydrogen atom on each zigzag edge, there are quite a few localized edge states near the Fermi energy level on both edges. Such localized edge states can lead to a spin induced energy gap [113] providing a significant effect on the electronic and transport properties [114]. The electronic and transport properties are thus very sensitive to the atomic structures and chemical modification of the edges. One of the natural ways of chemically modifying graphene is to include metal adatoms [115–117]. Motivated by the special transport properties of atomic wires of Al, Ag, Au and Cu, and inspired by the localized edge states of ZGNRs that greatly enhance the binding energy of adatoms, we also conducted the studies on (Al, Au and Cu) adatomed-objects on edge chlorinated nano graphenes to investigate the electronic, magnetic and adsorption and transport properties of these (C1 (C42CI18)/C2(C48CI18)/ C3(C60CI22))–metal systems (**Figure 6**). Metals adsorbed on nanoscale carbon surfaces have been reported experimentally and theoretically to form a variety of structures, such as continuous coatings or discrete clusters [118] and novel interesting phenomena were observed to occur through suitable modification.

Metallic nanowires (namely, linear chains of metal atoms) have drawn significant attention due to the quantum confinement effect, as they represent the ultimate miniaturization of conductors. The nanoscales of metallic nanowires result in a number of novel and interesting phenomena different from their bulk materials [119–121]. Graphene based biosensors can be classified as follows:

**1.** Graphene-based electrochemical biosensors [122]

**12.** Radionuclide-based imaging with SWCNTs [97, 98]

**14.** CNTs used as scaffolds in bone regeneration [99]

The two-dimensional carbon material graphene find application for sensors, electronics and catalysis applications due to its exceptional electrical and mechanical properties. Some of these applications require the adsorption of metal clusters onto graphene and metalgraphene systems which are now become a subject of intense investigation. It show many interesting properties as the observable quantum Hall effect at room temperature [100, 101], existence of two-dimensional gas of massless Dirac fermions [102], ballistic transport properties on the sub micrometer scale [103], etc. As graphene is unique in nature, so researchers explore its unique properties in storage [104], spintronics [105], microelectronics [106], etc. A number of theoretical and experimental work have been carried out for the electronic and magnetic behaviors of dimers [107] and adatoms of different elements [108] adsorbed on graphene system, which have been found to yield many interesting results. Graphene also has immense potential to act as a key ingredient for new devices as single molecule gas sensors, ballistic transistors, and spintronic devices. Bilayer graphene, which consists of two stacked monolayers, has a quadratic low-energy band structure which generates very different scattering properties from those of the monolayer. It also presents the unique

**Figure 5.** Representation of the role of CNTs in drug delivery. (a) Gene delivery by CNTs, (b) Normal drug delivery

versus the efficient target drug delivery using CNTs.

**13.** Scaffolds in tissue engineering

**15.** CNTs for neural applications

**3.2. Graphene**

178 Green Electronics


what we have set up for the mankind. Since electronics has now become an indispensable part of our life- for us and our future generations. The natural and nature inspired materials allow the "green" technologies to achieve the substantial goals in the electronics field: they embody low energy and have biodegradable and biocompatible materials as their backbone. Now the time has started to imagine and explore the new possibilities of "Green" organic electronics.

Biomolecules and Pure Carbon Aggregates: An Application Towards "Green Electronics"

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**Author details**

Ruby Srivastava

**References**

Capri, Italy. pp. 124-127

biosensor for CO and O<sup>2</sup>

10.1016/S1369-7021(02)05226-4

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Address all correspondence to: amitruby1@gmail.com

CSIR-Indian Institute of Chemical Technology, Hyderabad, India

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**Figure 6.** Potential adsorption sites and the most stable structures for Al, Au and Cu (dimers) on C1 (C42CI18), C2 (C48CI18) and C3 (C60CI22). Adapted from Ref. [117].

## **4. Conclusions**

In this chapter, we have discussed the role of DNA and CNTs in the field of green electronics. Metal nanoparticles and its interaction to the nucleobases and pure carbon aggregates are also described in detail. Current and future investigations of green nanotechnology will provide a more complete knowledge regarding various factors that influence green synthesis of nanoparticles and the most sophisticated technology that can be used for characterization of the synthesized nanoparticles for its more efficient future applications in environmental, optoelectronic and biomedical field.

"United Nations World Commission on Environment and Development" has stated that the sustainable development is established when humanity ensures its present needs without compromising the ability of future generations to meet their own needs. So the time has come when we have to bear the responsibility for the shape and type of environment our future generations will live in; a healthy environment, a non-toxic world. Right now the world is not what we have set up for the mankind. Since electronics has now become an indispensable part of our life- for us and our future generations. The natural and nature inspired materials allow the "green" technologies to achieve the substantial goals in the electronics field: they embody low energy and have biodegradable and biocompatible materials as their backbone. Now the time has started to imagine and explore the new possibilities of "Green" organic electronics.
