2H Tantalum Disulfide Nanosheets as Substrates for Ultrasensitive SERS-Based Sensing

Single-molecule detection with ultrahigh sensitivity and selectivity is one of the purposes of surface-enhanced Raman spectroscopy (SERS)-based sensing. Compared with the semiconducting and semimetallic phases, the metallic charge density wave transition-metal dichalcogenides (TMDs) are more promising as SERS plasmon-free substrates. However, as their intrinsic chemical and physical properties vary from each other, they show a different molecular selectivity and SERS activity. This study shows how metallic TMDs, especially 2H tantalum disulfide (2H-TaS2) nanosheets, can be used as SERS-based sensor substrates to detect the extremely low concentration of rhodamine 6G (R6G) and Nile blue A (NBA) with a very high Raman enhancement. The minimum detectable concentration or the limit of detection is 3.01 × 10–18 and 4.05 × 10–21 for R6G and NBA, respectively. In addition, the maximum enhancement factor is up to 1.3 × 1014 for R6G. The huge Raman enhancement can be attributed to the strong interaction between the molecular probes and 2H-TaS2, the alignment between the Fermi level and the highest occupied orbital, the abundance density of states, and the resonance effect of the molecular probes and the substrate.