Au Atoms Anchored on Amorphous C3N4 for Single-Site Raman Enhancement

From spanning bulks to nanoclusters, surface-enhanced Raman scattering (SERS) substrates of noble metals have frequently been explored for a long time. However, further downsizing nanoclusters to the atomic level, the surface plasmon resonance effect disappears, making the research on the SERS effect of atom-scale noble metal still lacking. Here, we discover a single-atom enhanced Raman scattering (SAERS) effect based on Au single atoms anchored on amorphous C3N4 nanosheets (Au1/ACNs). The Au1/ACN exhibits an excellent spectral stability and reproducibility, as the uniform dispersed Au single atoms avoid the agglomeration of Au atoms to generate nonuniformly dispersed "hotspots" that suffer from poor SERS stability and reproducibility. Even only ∼2.5% Au-coated area in the laser illuminated area can yield an enhancement factor of 2.5 × 104. The SAERS effect is attributed to the synergistic effect of Au single atoms anchored on amorphous C3N4, which increases the dipole moment and polarizability of molecules, enhancing the Raman signal of probe molecules. Furthermore, we propose a novel single-atom charge transfer mechanism that single-atom Au dominates higher electron delocalizability and higher electronic density of states near the HOMO level than the Au cluster. Our results will erect a new milepost for the application of single-atom materials in the field of enhanced Raman spectroscopy.