Entropy Engineering on 2D Metal Phosphorus Trichalcogenides for Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) spectroscopy is an ultrasensitive detection technique for molecular identification in both biology and chemistry. 2D materials have displayed increasing potentials as SERS substrates based on chemical enhancement, where optimization of the band structure to promote the charge transfer is exceptionally important. Here, the regulation of band structure of 2D metal phosphorus trichalcogenides (MPCh3) via entropy engineering is demonstrated. The optimized high-entropy MnFeCuAgInPS3 nanosheets (NSs) with narrowed bandgap (Eg) show significant SERS performance with a low detection limit with 10-9 m for both rhodamine 6G and crystal violet. Combined spectral characterizations and density functional theory (DFT) calculations reveal that the combination of multiple hetero-element provides continuous d orbitals and endows high-entropy MPCh3 NSs with high population of electrons at the energies near Fermi level (EF), which allows highly efficient photo-induced charge transfer (PICT) between the SERS substrates and target molecules. This work affords a new strategy for high-performance 2D SERS materials and also reveals the origin of the band structure regulation by entropy engineering. Through optimizing band structure and thus increasing the population of electrons at states near the Fermi level, entropy engineering can significantly improve the SERS performance of 2D metal phosphorus trichalcogenides. The optimal MnFeCuAgInPS3 nanosheets exhibit remarkable SERS signals with a detection limit down to 10-9 m and excellent stability for trace analysis.image