SERS sensitivity improvement of molybdenum oxide nanosheets via the lightning rod effect and application in detecting methylene blue.

MoOnanomaterials show superior surface-enhanced Raman scattering (SERS) property due to their high concentration of free electrons and low resistivity. However, the physical process of semiconductor-based SERS is still elusive because there are many factors to affect the local electromagnetic field intensity and the subsequent Raman intensity of the molecules in close proximity to the semiconductor nanomaterials. Herein, we investigate the important contribution of surface morphology to the molybdenum oxide SERS. The MoO/MoOnanosheets (NSs) are synthesized by oxidizing MoONS, and the surface roughness of MoOcan be controlled through adjusting the oxidizing time. Compared with the MoONS before oxidizing, the MoO/MoONSs exhibit much more strong SERS signal, which favors their application as a SERS substrate to detect trace amounts of methylene blue (MB) molecular. The minimum detectable concentration is up to 10M and the maximum enhancement factor (EF) is about 1.4×10. Meanwhile, excellent signal reproducibility is also observed using the MoO/MoONSs as SERS substrate. Simulated electric field distribution shows that a stronger electric field enhancement is formed duo to the lightning rod effect in the gap of corrugated MoONSs. These results demonstrate that the surface topography of molybdenum oxide may plays a more important role than their oxidation state in SERS signal enhancement.