Use of Single-Layer g-C₃N₄/Ag Hybrids for Surface-Enhanced Raman Scattering (SERS)

Surface-enhanced Raman scattering (SERS) substrates with high activity and stability are desirable for SERS sensing. Here, we report a new single atomic layer graphitic-C₃N₄ (S-g-C₃N₄) and Ag nanoparticles (NPs) hybrid as high-performance SERS substrates. The SERS mechanism of the highly stable S-g-C₃N₄/Ag substrates was systematically investigated by a combination of experiments and theoretical calculations. From the results of XPS and Raman spectroscopies, it was found that there was a strong interaction between S-g-C₃N₄ and Ag NPs, which facilitates the uniform distribution of Ag NPs over the edges and surfaces of S-g-C₃N₄ nanosheets, and induces a charge transfer from S-g-C₃N₄ to the oxidizing agent through the silver surface, ultimately protecting Ag NPs from oxidation. Based on the theoretical calculations, we found that the net surface charge of the Ag atoms on the S-g-C₃N₄/Ag substrates was positive and the Ag NPs presented high dispersibility, suggesting that the Ag atoms on the S-g-C₃N₄/Ag substrates were not likely to be oxidized, thereby ensuring the high stability of the S-g-C₃N₄/Ag substrate. An understanding of the stability mechanism in this system can be helpful for developing other effective SERS substrates with long-term stability.