Hierarchical Assembly of Gold Nanoparticles on Graphene Nanoplatelets by Spontaneous Reduction: Implications for Smart Composites and Biosensing

The uniform decoration of plasmonic nanoparticles for example, gold nanoparticles (AuNPs) on graphene sheets, can potentially lead to hybrid materials with unique photothermal responses, which are attractive for use in applications such as optoelectronic devices, smart polymer composites, sensing, and catalysis devices. Here, we demonstrate a simple, room temperature and reagent-free approach to achieving colloidally stable, few-layered graphene nanoplatelets (GNPs) decorated with AuNPs. Spontaneous reduction of gold acetate onto GNPs is confirmed from UV–vis spectra, high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), where the concentration of gold acetate can control the size of the AuNPs. The anchored AuNPs show crystalline lattice fringes in HR-TEM images, bright diffraction spots in selected area electron diffraction (SAED) patterns, and peaks in the XRD patterns, confirming their metallic crystallinity. A study of the interaction of these hybrid structures from Raman spectroscopy confirms the charge transfer between the AuNPs and graphene and the reduction of defect density upon the reaction of AuNPs with the GNPs. In addition, the colloidal stability of the synthesized AuNPs/GNPs is examined in various organic solvents and characterized by using UV–vis and AFM techniques. This highlights the simple and effective methodology for synthesizing hybrid structures stable in common organic solvents, opening up the possibility for processing and promising for a wide range of applications such as smart composites and biosensing.