SCALABLE PRODUCTION OF GRAPHENE OXIDE AND QUANTUM DOTS BY CHEMICAL ROUTE AND THEIR COMPARATIVE ANALYSIS.

Abstract

Graphene, the wonder material is known for it‘s excellent properties which are due to it‘s unique geometry, high mechanical and thermal strength and electrical conductivities. It has great electrical stability and impermeability. Among the various techniques that are available for its synthesis, modified hummers method is widely used for the scalable production of graphene oxide (GO). Recently, GO has attracted massive attention from the researchers due to it‘s unique properties like though it is an insulator it shows fluorescence behaviour due to the presence of oxygenated functional groups along it‘s edges and basal planes. The FT-IR spectrum of GO shows the presence of many functional groups which are confined into the sp2 and sp3 sites present on it‘s structure. Since, it is a monolayer sheet of graphite it‘s XRD peak clearly indicates how it doubles the inter-layer separation between the stacks. To improve it‘s conductivity we perform the oxidative cutting of GO sheets by strong acids to synthesize graphene quantum dots (GQDs). These GQDs are readily used for optoelectronic applications. The as prepared GQDs show excellent conductivity and reduction in bandgap. On contrary to GO the fluorescence in GQDs are due to defects and trap sites. Due to quantum confinement effect and reduction of size the GQDs are luminescent and they show green colour when exposed to ultra-violet light. Thus, though both GO and GQDs are fluorescent the emission spectra of GO is independent of excitation wavelengths but the fluorescence of GQDs depend not only on the excitation wavelengths but also on the pH value of the solution. Thus, in this thesis, we have synthesized both GO and GQDs by using chemical route and have evaluated their similarities and differences by various characterizing methods.