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

Abstract

From spanning bulks to nanoclusters, surfaceenhanced 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 C 3 N 4 nanosheets (Au 1 / ACNs). The Au 1 /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 × 10 4 . The SAERS effect is attributed to the synergistic effect of Au single atoms anchored on amorphous C 3 N 4 , 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.

Recent Progress of Amorphous Nanomaterials

“…Amorphous C 3 N 4 (ACN) was first prepared by the polycondensation method by Guo et al, and the 2D Au/ ACN loaded with 0.46 wt % Au single atoms was successfully prepared by the impregnation method (Figure a–d) . Au/ACN shows very strong Raman scattering enhancement with good spectral stability and reproducibility.…”

“…The high electron delocalization of amorphous materials is also the main factor to promote SERS performance. 261 Wu et al developed a novel amorphous N-doped carbon nanocage with a high enhancement factor (5.52 × 10 6 ) and explored the effects of electron delocalization and electronic state density on SERS in amorphous structures. 455 In summary, amorphous materials present excellent optical properties with the following features:…”

“…In this work, the mixture of iron acetoacetate, ruthenium acetoacetate, and potassium bromide was directly annealed in air at 260 °C, and then a salt template was removed with water. By controlling the precursor type and heating temperature, the Ru 1 /2DCF, amorphous iron oxide nanosheets (2DAF), and crystalline iron oxide (2DCF) modified crystalline iron oxide nanosheets were obtained.Amorphous C 3 N 4 (ACN) was first prepared by the polycondensation method by Guo et al, and the 2D Au/ ACN loaded with 0.46 wt % Au single atoms was successfully prepared by the impregnation method (Figure48a−d) 261. Au/ ACN shows very strong Raman scattering enhancement with good spectral stability and reproducibility.…”

2D carbon nitride as a support with single Cu, Ag, and Au atoms for carbon dioxide reduction reaction

“…[30][31][32] Moreover, single Au atom deposition on g-C 3 N 4 has been experimentally studied. 33 The single metal atoms deposited on different supports are often unstable, and the isolated metal atoms tend to aggregate into nanoparticles and small clusters. 34,35 However, g-C 3 N 4 is an excellent substrate to stabilize metal atoms mainly due to the strong metal-nitrogen interactions.…”

Boosting ultrasensitive SERS activity on quasi-metallic tungsten oxide through synergistic vibronic coupling and electromagnetic resonance

“…Consequently, SERS realized by the EM mechanism is difficult to occur but mainly dominated by the CT process in semiconductors. 9,10 There is broad consensus that the aim to overthrow the monopoly of noble metals in the current SERS eld poses formidable methodological challenges in the design of novel and reliable non-noble metal substrates.…”