Temperature-Dependent SERS Detection Using CVD-Grown MoSe₂ Nanoflakes

MoSe2 is a promising surface-enhanced Raman spectroscopy (SERS) substrate because of its cost-effectiveness, simple synthesis, exceptional optical properties, high carrier mobility, tunable bandgap, and conducive biocompatibility. In this study, we synthesize MoSe2 nanoflakes with different morphologies over a large area (centimeter scale) on Mo and Si substrates using the chemical vapor deposition (CVD) technique. These pristine MoSe2 films are employed as SERS substrates to detect melamine, bilirubin, vitamin B12, and Rhodamine 6G (R6G). Strong vibronic coupling during the charge transfer (CT) process facilitates resonance in photoinduced charge transfer (PICT) to enhance SERS activity. We obtain the excellent detection limits of 10–9 M for melamine, 10–10 M for bilirubin, 10–9 M for vitamin B12, and 10–11 M for R6G with MoSe2/Si SERS substrate, while detection limits of 10–6 M for melamine, 10–9 M for bilirubin, 10–8 M for vitamin B12, and 10–10 M for R6G are observed with MoSe2/Mo as SERS substrate. We could observe near single molecule detection for R6G (2 and 11 molecules for MoSe2/Si and MoSe2/Mo substrates, respectively) and bilirubin (18 molecules for MoSe2/Si). Quantitative analysis of degree of charge transfer deepens understanding of SERS signal enhancement. As per our knowledge, this is the first demonstration of low-temperature SERS activity on pristine MoSe2 films, revealing enhanced SERS performance due to synergistic PICT and Fano resonance. The pristine MoSe2-based SERS substrate offers an in situ, efficient approach for trace detection, with medical and environmental monitoring, food safety, and surface contamination analysis applications.