Microwave-Reduced Uncapped Metal Nanoparticles on Graphene: Tuning Catalytic, Electrical, and Raman Properties

Abstract

This work addresses a major challenge in liquid-phase catalysis by enabling the synthesis of solvent dispersible “uncapped” metal nanoparticles (NPs) with enhanced density of accessible catalytic sites. We demonstrate that graphene oxide’s (GO's) high density of accessible and bondable oxy-functional groups and the high steric hindrance from its micrometer-scale area covalently implant, stabilize, and support bare-surfaced gold nanoparticles (BSGNs) produced in situ by a unique microwave reduction process. Comparing the efficiency of catalytic reduction of p -nitroaniline ( p -NA) by BSGNs and similar sized surfactant-capped gold NPs showed that the uncapped surface on GO-supported NPs, (a) opens up 258% more active sites, and (b) enhances the catalytic reduction of p -NA by 10−100 fold. Further, BSGN implantation on GO, (a) amplifies the Raman signal of bare GO by ∼3 fold, and (b) increases the conductivity of native p-type GO by >10 fold via injection of 1.328 × 10 12 electrons/cm 2, consequently transforming it into an n-type semiconductor.