Multifunctional Reduced Graphene Oxide Wrapped Circular Au Nanoplatelets: Enhanced Photoluminescence, Excellent Surface-Enhanced Raman Scattering, Photocatalytic Water Splitting, and Non-Enzymatic Biosensor

Herein, we demonstrate the synthesis and multifunctional properties of reduced graphene oxide (RGO)-wrapped Au nanoplatelets. We have characterized the sample by field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive X-ray spectroscopy (EDS), high-angle annular dark-field scanning transmission electron microscopy (STEM-HAADF), electron energy-loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS) studies. It has been shown that the RGO wraps a large number of 2D circular Au nanoplatelets (diameter ∼15 nm). We have examined the optical property of the sample using Raman, UV-vis, and PL spectroscopic techniques. Large enhancement in intensity of Raman spectra was observed due to the surface enhanced Raman scattering (SERS) resulting from the Au nanoplatelets. The collective sway of surface plasmon resonance and fluorescence resonance energy transfer effect owing to Au gives rise to giant enhancement in intensity of photoluminescence emission spectrum. Upon visible-light irradiation, photocurrent flows through the sample due to interband 6sp transition within the Au nanoplatelets and it exhibits photocatalytic water splitting effect. The sample displays excellent nonenzymatic hydrogen peroxides (H₂O₂) and ascorbic acid (AA) sensing property. The value of sensitivity for H₂O₂ is 280.28 μA mM^-1 cm^-2 in the linear range of 1 μM to 0.8 mM and that for AA is 314.07 μA mM^-1 cm^-2 in the linear range of 25-300 μM. The lowest detection limit of both H₂O₂ and AA is 6.8 μM at S/N= 3. So, the sample can be used for multifunctional applications in SERS as substrate, photocatalytic water splitting, photodetectors, and nonenzymatic biosensing.