Environmental remediation using graphene based nanomaterials

Abstract

Graphene, one-atom-thick planar sheet of carbon atoms packed in hexagonal lattice, is a well-designed form of a two-dimensional organic macromolecule consisting of benzene rings for a chemist, a perfect example of a two-dimensional electron system for a physicist, and a material with enormous potentials for an engineer primarily due to its excellent multiple functionalities. Graphene is the basic structural unit for all other dimensionalities of graphitic materials. Controllable synthesis is in close agreement with the several prospective ways of enormous futuristic beneficial applications of graphene. With its intriguingly fascinating history, many are astonished and somewhat bewildered about the future of graphene.Chapter 2 details the use of graphene based material for carbon dioxide gas adsorption and its storage. It is shown that sulfur doped graphene can be used to efficiently trap CO2. The S-doped graphene material was synthesized by the chemical/thermal activation of a polythiophene-reduced graphene oxide material. This study reveals that S-doped graphene materials can be more effective than N-doped graphene materials for CO2 capture and storage which is primarily due to the stronger interaction between the CO2 molecule and S dopant as compared to that of the N dopant. Furthermore, this study displays imminent ways that can be followed for similar doped graphene materials to increase the gas adsorption capacity.In Chapter 3 and 4, the use of graphene materials for water remediation is presented. Chapter 3 details the synthesis of micro-graphene-based hydrogels by green chemistry applied in photocatalysis as well as its beneficial usage for bio sensing. The conservation of exclusive properties of SnO2-decorated graphene platelets leads to considerably higher adsorptive and photocatalytic activities. Nanoparticle decoration and surface hydration paves the way for reversible self-assembly and aqueous-phase exfoliation by preventing irreversible π-π stacking of graphene based platelets. The colloidal stability of the nanoparticle/graphene microgels in aqueous and organic media permits these materials to function as basic building blocks besides useful nanomaterials in wet-chemistry applications. The dye-hydrogel complex can be utilized as a sensor for detection of DNA by manipulating the fluorescence quenching effect. Furthermore, the study initiates an advanced synthetic approach to produce high-quality graphene-based nanomaterial.In Chapter 4 it is shown that by depositing a SnO2 nanoparticles onto a reduced graphene oxide substrate leads to efficiently decompose the organic dye methylene blue under visible light irradiation. Graphene water remediation materials can fall into two main water purification groups which are adsorption and photocatalytic. Moreover, the decomposition of methylene blue in the visible region is due to an induced shift in the band gap of SnO2 by electronic modulation between the adhered SnO2 nanoparticles and graphene substrate.In this thesis various studies display that graphene based materials are being applied in the environmental remediation with an emphasis on gas adsorption and water remediation which depends on the intrinsic properties such as surface area and conductivity of graphene. It leave us to conclude that the graphene field and its multiple composite graphene material applications have yet to reach its full potential and thus it paves a way for a further futuristic exploration.