Abstract
Large-area mildly reduced graphene oxide (MR-GO) monolayer films were self-assembled on SiO2/Si surfaces via an amidation reaction strategy. With the MR-GO as templates, MR-GO-Ag nanoparticle (MR-GO-Ag NP) hybrid films were synthesized by immersing the MR-GO monolayer into a silver salt solution with sodium citrate as a reducing agent under UV illumination. SEM image indicated that Ag NPs with small interparticle gap are uniformly distributed on the MR-GO monolayer. Raman spectra demonstrated that the MR-GO monolayer beneath the Ag NPs can effectively quench the fluorescence signal emitted from the Ag films and dye molecules under laser excitation, resulting in a chemical enhancement (CM). The Ag NPs with narrow gap provided numerous hot spots, which are closely related with electromagnetic mechanism (EM), and were believed to remarkably enhance the Raman signal of the molecules. Due to the co-contribution of the CM and EM effects as well as the coordination mechanism between the MR-GO and Ag NPs, the MR-GO-Ag NP hybrid films showed more excellent Raman signal enhancement performance than that of either Ag films or MR-GO monolayer alone. This will further enrich the application of surface-enhanced Raman scattering in molecule detection.
Highlights
Surface-enhanced Raman scattering (SERS) is an alternative to fluorescence (FL) detection
It was found that the mildly reduced graphene oxide (MR-GO) monolayer with a thickness of approximately 0.65 nm is uniformly assembled on silicon surface
Some negligible overlapping MR-GO films can be observed on the silicon surface, which could be avoided by adjusting the concentration of the MR-GO solution during the assembly process
Summary
Surface-enhanced Raman scattering (SERS) is an alternative to fluorescence (FL) detection. It greatly amplifies the Raman signal of analytes adsorbed on metal surface [1]. Due to their good chemical stability and bio-compatibility, Au and Ag films are typically regarded as the good SERS substrates [2,3]. To enhance the Raman signal from adsorbed molecules, a rough metal surface with different morphologies is normally needed for highly sensitive SERS substrates [4]. The fabrication processes either have the rigorous requirement for equipment or give a limited Raman sensitivity Both the Au and Ag films have a strong photoluminescence (PL)
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