Graphene is an allotrope of carbon which has a two-dimensional structure. It is in the form of a hexagonal lattice (see
Figure 1) that resembles honeycomb structure
[1]. It has some unique properties that have interested the researchers since its discovery by Geim and Noveselov
[2]. Due to its high versatility and relatively huge specific surface region
[3], graphene is sought as a good option in sensing applications
[4]. Main advantages of graphene are: (a) it is the finest and toughest material known; (b) it has carbon monolayered atoms that are both flexible and transparent in colour; (c) it is an excellent thermal and electrical conductor; (d) its main usage is in the manufacture of high-speed electronic gadgets; (e) explosives detection through chemical sensors; (f) membranes for more proficient separation of gases and is produced using sheets from which nanoscale pores have been made; (g) for manufacturing of transistors operating at high frequencies; (h) it has boosted the manufacture of low-cost display screens of cell phones replacing the indium-based electrodes in organic light emitting devices (OLED); (i) to produce lithium-ion batteries that use graphene on the anode surface and these batteries recharge faster; (j) stockpiling hydrogen for cars powered by fuel cells; (k) cheaper water desalination techniques by using graphene films with nanoscale holes to separate water from ions in brine; and (l) Graphene condoms are produced to increase the sensation and is thinner than conventional latex condoms.
The very first examinations on exfoliated graphene done by Schedin et al.
[6] have showcased graphene’s capability on identifying single gas particles based on estimations under Hall effect. The basic guideline behind the usage of graphene in gas sensors is the transfer of charge between the molecule adsorbed to its surface and the material
[7]. The carrier concentration of graphene is changed by the absorbed particles which cause the electrical properties to change and the concentration of particles is determined. The response of the system largely depends on the nature of the particle donor or the acceptor
[6][8]. Graphene electrical conductivity increases as a result of adsorption of the acceptor compounds (e.g., H
2O or NO
2). On the other hand, conductivity decreases when the donor compounds get absorbed to the graphene surface (e.g., CO, NH
3). Due to the 2D structure, every carbon atom in graphene lattice turns into a surface atom. It makes graphene extremely delicate to the outside environment, yet in addition also restricts its gas selectivity simultaneously
[9][10]. Its properties like high intrinsic mobility, enormous surface area, excellent conductor of electricity and heat, and its ability to resist a current density of 108A/cm
2 is the main driving basis of utilizing graphene and its subsidiaries
[5]. Properties shown by graphene, make them ideal for biomedical application as well.
Graphene was isolated by passing power through crystals that were cut off from mass graphite and were moved onto fine SiO
2 or silicon wafer
[5]. Further, with the current emergence of green chemistry and sustainable, non-polluting approaches, graphene was manufactured by using biomolecules as a substrate. Recently, biomolecules and biosimilars are being capitalized in a wide reach due to the non-poisonous and biocompatibility nature forthe production of graphene. According to the underlying property of graphene-based nanomaterials (GBNs), graphene is a water resisting material. So, it needs a modification in its functional groups making it bio-medically suitable. The modifications are covalent and non-covalent functionalization. The non-covalent functionalization assists detection, biocompatibility, dispersibility, reactivity and mixing efficiency
[11]. Between the polar points present on the surface of graphene oxide and water molecule, hydrogen bonds are available which makes it suitable for biomedical packings
[12][13]. In the course of the most recent twenty years there has been a tremendous and sudden development in the utilization of nanotechnology in analysis and therapeutics areas. In addition to this, GBNs have an affable physicochemical property which makes them a great therapeutic molecule. The partially soluble drugs are aided in loading with high productivity and intensity by pi-pi stacking, electrostatic collaboration, and huge explicit area of GBNs
[14]. Hence GBNs hold a substantial position in the applications in biomedical field. Since GBNs manage the rate at which drugs are released, it has an incredible practicality in drug delivery frameworks
[15]. GBNs-based nanocomposites utilizing polymers, biomolecules, are less toxic in nature, and enhances proficiency against microorganisms. Materials required for bio imaging must have properties likehigh specificity, non-poisonous, and sensitivity which are displayed by graphene quantum dots (GQDs). Besides, they demonstrate extraordinary photophysical and spectrofluorometric properties needed for producing images of biological segments
[16]. Graphene also found applications in photodynamic therapy (PDT), which is a non-intrusive technique for cancer therapy. PDT technique uses hydrophobic photosensitizer (PS) and near infrared (NIR) light to form an active form of oxygen inside the tumour cells to destroy the malignant cells
[17][18]. It is additionally helpful in the detection and treatment of infections and in transporting explicit medications to the target organs. Being a lightweight material that can be synthesised, it helps inconveyance of medications and genes easily without any critical convolutions. The extraordinary mechanical and other useful properties of graphene shows that it has a high potential to create predominant gadgets and has grabbed the title of “wonder material”
[19]. Graphene materials are widely used in the field of electromechanical devices
[20], field-effect semiconductors (FET)
[21], strain sensing devices
[22], electronics devices
[23], super-capacitors
[24][25], H
2 storage
[26] and solar power-driven cells
[27][28]. It is typically converted into quantum dots
[29] and nanoribbons
[30] for its utilization in hydrogels
[31], froths
[32][33] and semiconductor gadgets for various energy applications. The most promising effect in the latest innovations have been created from the creative transformations of various graphene supported polymers and metal-based grid nanocomposite. Henceforth, over the most recent few decades, various innovative work identified with graphene-based nanocomposite have been expanded at a quick rate. These researches showed that various graphene materials can be added to the polymer framework to enhance electrical, mechanical, thermal and numerous other functional properties of thecomposite substances which in turn boosts the total efficacy of the substances manufactured using these composites
[34]. The polymer-graphene nanocomposite working greatly improves as a result from the creation of large particle interfacial areas. This is done so by the fusion of nanofiller in the matrix, thus changing their significant properties and rearranging the nanoparticles
[19]. Graphene materials operate as either agile medium or as well distributed and aligned electrode material in light to other energy conversion fields such as solar to thermal power, solar to electricity conversion, catalysis in presence of light and so forth, contributing widely in renewable energy production. The technological improvements have developed a 3D graphene material having cross linking bonds which absorbs radiations from the sun and converts it to thermal energy
[35]. It produces productivity as high as around 87% in one sun intensity and over 80% in the surrounding daylight. However, this impressive proficiency can be further evolved by changing the underlying model of the material.