Microwave-Activated Functionalization of Bare-Surfaced Metal Nanoparticles On Graphene Derivatives: Avenue for Carrier Manipulation, Enhanced Catalytic Activity and Raman Amplification

In this talk, we will demonstrate that a controlled Microwave (MW) exposure on an aqueous gold salt solution results in an instantaneous formation of ‘naked' gold nanostructures, which, (a) can be stabilized by covalent implantation on the micron scale large Graphene-oxide (GO) sheets that can be dispersed in several organic solvents, and (b) due to their bare exposed surface, exhibit an enhanced electrochemically active surface area as compared to similar shaped surfactant capped gold nanoparticles. Dispersing metal nanoparticles (MNPs) in solutions without compromising the density of surface catalytic sites has been a critical challenge in liquid-phase catalysis, because stabilizing MNPs requires their surface to be capped with surfactant or stabilizing groups. The confined dielectric heating induced by MW together with the stabilizing ability of oxy-functionalized graphene sheets enables an efficient solvent dispersion of bare surfaced gold nanoparticles (BSGNs). We illustrate and characterize, for the first time, the catalytic properties of these solvent-dispersed BSGNs and compare their efficiency with similarly shaped surfactant-capped gold nanoparticles. Further, this approach to functionalize graphene derivatives with metal NPs does not use any reducing agent, which is commonly required for synthesizing graphene-nanoparticle hybrids. We envision that the results presented here will spur a worldwide research effort and the scientific community will leverage them to produce next-generation hybrids and applications in areas including supported catalysts, nanoelectronics, optoelectronic devices, sensors, Raman multipliers, and molecular electronics.