摘要
Plasmon-free surface-enhanced Raman scattering (SERS) based on two-dimensional materials is a promising approach for nondestructive analysis. However, the smooth surfaces commonly formed during chemical vapor deposition (CVD) limit the generation of localized high electromagnetic fields and reduce chemical interactions with adsorbed molecules, even in metallic 2D materials. In this study, 2D Mo2C was synthesized by CVD, and MoOx/Mo2C, MoS2/Mo2C, and MoSe2/Mo2C heterostructures were fabricated through thermal oxidation, plasma-assisted sulfurization, and selenization, respectively. The MoS2 and MoSe2 top layers were phase-engineered into 1T-rich and 2H-rich structures at 350 degrees C and 550 degrees C, respectively, under the same plasma power of 150 W. The heterostructures exhibit improved SERS activity, mainly due to chemical enhancement (CM) arising from increased surface roughness, defect/edge-rich nanostructures, and heterointerfaces that provide abundant localized chemically active sites for molecular adsorption and interfacial charge transfer. The 1T-rich MoS2/Mo2C shows a detection limit of up to 10-10 M and a Raman enhancement factor of 9.1 & times; 104, while the 1T-rich MoSe2/Mo2C displays a detection limit of up to 10-9 M and a Raman enhancement factor of 8.9 & times; 104 for rhodamine B (RhB), attributed to the presence of a high density of states and localized chemically active sites on the 1T-rich MoS2 and MoSe2 surfaces.