Thermal Dynamics And The SERS Application Of 2D Materials

The thermal stability of four different two-dimensional materials(MoS2,MoSe2,WS2,WSe2)in air was investigated.When the thermal annealing temperature is high,WS2 and WSe2 are easily oxidized in the air,and on the contrary,MoS2 and MoSe2 are not oxidized,but they are easily volatilized in the air.MoS2 and MoSe2 still maintain relative good crystallinity at high temperatures before oxidization.We found that the thermally annealed two-dimensional materials can be used as a Raman-enhanced substrate,where the MoS2 substrate provides very efficient hot spots by using the Rhodamine 6G(R6G)molecule as a probe.Raman and photoluminescence spectra of modified MoS2 reveal the detailed mechanism for enhancing Raman signal of R6G.It is found that both the substrate roughness and the slight chemical bond broken on the surface are the main driven forces to-induce the surface enhanced Raman scattering(SERS)effects due to the breaking of symmetry of probed molecules.The minimum detectable concentration of R6G on the most optimized thermally treated-MoS2 can be as low as 10-8 M and enhancement factor(EF)value is 1.8×106.We successfully combined the thermally annealed bulk MoS2 with Au nanoparticles,further enhancing the Raman signal of R6G,and detecting the lowest concentration of R6G molecules is 10'9 M.This synthetic approach is facile,sensitive and reliable,which shows great potential to be an excellent SERS substrate for biological and chemical detection.