Ethylene diamine mediated cobalt nanoparticle studded graphene oxide quantum dots with tunable photoluminescence properties

Abstract

Preparation of graphene oxide quantum dot-inorganic nanoparticle hybrids is still an unexplored area of graphene-centred research. The present study demonstrates the ethylene diamine mediated in situ synthesis of cobalt oxide nanoparticles (Co₃O₄ NPs) studded on graphene oxide quantum dots (GOQDs). Ethylene diamine(en) is known to form a stable coordination complex with Co²⁺. CoCl₂ was used as a precursor material for Co-nanoparticle formation as small sized Co²⁺ ions can enter the interlayer spacing between the graphene sheets. Ethylene diamine gets attached to the GOQDs via ring opening of epoxy groups on the GOQDs and pulls the Co²⁺ ions from the medium onto the GOQDs. On treating this system with hydrogen peroxide, GOQDs-en-Co₃O₄ nanoparticle composites with enhanced optical properties could be successfully prepared. We also tried to explore the potential of our system as a reversible on/off fluorescence switching material based on oxidation–reduction chemistry and could find satisfactory results. Such systems we believe can prove to be model systems for quantum level graphene-inorganic nanoparticle hybrid nanocomposites with potential for application in optoelectronic devices.