Area of Contribution:

a) Design and development of Graphene and other 2D nanocomposite materials: A simple, cost-effective and green chemical approach for the synthesis of fine and uniform metallic/bimetallic/metal oxide/metal sulfide nanoparticles onto graphene oxide/reduced graphene oxide nanosheets and other 2D materials such as graphitic carbon nitride (g-C3N4), hexagonal boron nitride (h-BN), h-boron carbon nitride (h-BCN), MoS2 and other transition metal chalcogenides (TMC) are explored. These 2D nanocomposites not only possess favourable properties of 2D sheets and nanoparticles, but also greatly enhance their individual intrinsic properties due to the synergistic effect between them. However, some challenges remain associated with the practical applications of graphene; one of them being the tendency of graphene to agglomerate and restack to regenerate three dimensional graphitic structures. Introducing of nanoparticles onto graphene oxide or reduced graphene oxide sheets prevents them from undergoing restacking and at the same time provides an innovative way for developing advanced composite materials that are useful in a myriad of applications. The novel 2D nanocomposite materials are used as an efficient material for diverse applications like organic catalysis, photocatalytic degradation, removal of pollutants from water, sensors, etc.

b) 2D nanocomposite materials as efficient Nanozymes and their and Sensing application: The 2D nanocomposite materials are established as nanozyme through the intrinsic peroxidase mimicking activity which is utilized towards the colorimetric detection of the biomolecules, toxic metal ion in water, pesticides and other water pollutants, etc. These artificial nanozymes are low cost, mass-produced and stable as compared to the natural enzymes. Graphene and other 2D nanocomposite materials have been successfully established as artificial nanozymes and utilized for environmental pollutant detection and treatment. The synthesized nanozymes were utilized for a simple, sensitive and selective colorimetric and fluorescence analytical method aimed at detection of toxic metal ions (Hg(II), Cr(VI), As(III), F ions etc.), pesticides in aqueous medium and important biomolecules like glucose, ascorbic acid, dopamine and glutathione based on their peroxidase mimic like activity. The work has been successfully demonstrated in the reputed international publications like ACS- Applied Materials and Interfaces, ACS Sustainable Chemistry and Engineering, Journal of Hazardous Materials, Chemosphere, Journal of Environmental Chemical Engineering, etc.

c) Photocatalytic phenomenon for removal of water pollutants: The photocatalytic degradation phenomenon under the irradiation of the natural sunlight is successfully demonstrated for the removal of the model organic pollutants in aqueous medium using graphene-based nanocomposite materials. The interesting properties such as electron conductivity and mobility, high surface area, or high adsorption capacity, make graphene a material of choice for photocatalysis in the degradation of environmental pollutants. The incorporation of the bimetallic, metal oxide and metal sulfide nanoparticles on the graphene sheets enhanced the degradation of the organic pollutant under the irradiation of the natural sunlight due to synergistic effects. These graphene-based nanocomposites have successfully demonstrated the removal of the model organic pollutants like phenolic compounds, pesticides, etc. and photoreduction of toxic heavy metal Cr(VI) ion in aqueous medium which is reflected in the work published in Nanoscale, Journal of Hazardous Materials, ACS Sus Chem and Eng, Chemosphere, J. colloids & Interf. Sci., J. Env. Chem Eng. etc.

d) Photothermal therapy therapeutic application against cancer cell using 2D nanocomposite materials: Considering the need of an efficient treatment towards curing deadly disease cancer, it is highly desirable to develop novel material which can destroy cancer cells without damaging the surrounding normal cells. We intend to develop novel nanosystems that could be potential alternates for existing gold based photothermal agents to treat cancer. We have successfully demonstrated the photothermal activity of bimetallic nanoparticles decorated on the functionalised graphene sheets under the irradiation of near infrared (NIR) laser sources of wavelength 915 nm. The temperature rises nearly 51 ± 3 °C within 3 min of irradiation NIR laser light resulting in the ablation of model cancer cells like HeLa and MDAMB-231 cells with very low concentration. The work has been published in J. Material Chemistry B, J. Photochemistry and Photobiology B, Advances Colloids and Interface Science.

e) Fabrication of the microfluidic paper-based analytical device (µPAD) for sensing application:

The process of fabricating prototypes of µPADs is tedious, error-prone and time consuming. The chemical methods of fabrication such as photolithography are expensive and require multiple process steps. Many of the physical methods of fabrication such as inkjet printing are more complex and methods like wax printing and screen printing offer low resolution. We have adopted the fabrication of µPAD utilizing Laser/Thermal based cutting and engraving technique. The laser/thermal energy would remove the hydrophilic portion from the cutline of the CAD based designed structures, thus creating a hydrophobic barrier along the edge of the cutline. The process would allow fabricating high resolution structures that can define hydrophilic channels, fluid reservoirs and reaction zone. The challenge of this work is to design and develop highly sensitive paper-based nanosensor device which does not require any lithographic or microfabrication steps. Another challenge of this work is to significantly lower the detection limit beyond the nanomolar (nM) or part per billion (ppb) level. The paper-based analytical device will be of practical use to public health department, food and beverage industries, food safety and standard authority of India, tea industries, dairy industries and the common people in our society.

f) Graphene-based nanocomposite as a highly efficient catalyst for the electrochemical hydrogen generation: Platinum (Pt) and Pt- group metals are well recognized as the most powerful catalysts for the hydrogen evolution reaction. However, the high cost of Pt and its limited supply make the search for alternatives an important target. With this idea in mind, we have successfully designed bimetallic nanoparticles and metal sulfide on the graphene and other 2D nanomaterials and established as highly efficient electrocatalyst for the electrochemical hydrogen evolution reaction. These works have been highly cited from our published paper in Journal of Materials chemistry A, ACS-Applied Energy Materials, International J. Hydrogen Evaluation, etc.