Ultrathin layer solid transformation-enabled surface enhanced Raman spectroscopy for trace harmful small gaseous molecules
Detection of trace harmful small gaseous molecules (or h-SGMs), based on surface enhanced Raman spectroscopy (SERS), has been expected but in challenge due to the extremely small Raman cross section (RCSs) and weak metal affinity of the h-SGMs. Here, a new strategy, ultrathin layer solid transformation-enabled (ULSTE)-SERS, is proposed. It uses the chemical reaction between the target h-SGM and an ultrathin layer of solid sensing matter coated on a plasmonic metal SERS substrate. This reaction in situ produces a new solid matter with large RCS, which ensures the detection of trace h-SGMs via SERS. The validity of this strategy has been demonstrated by detecting trace H2S gas with ultrathin CuO layer-wrapped Au nanoparticles (NP). Furthermore, this strategy allows fast and ultrasensitive detection. The detection limit can be down to ppb (even ppt) levels with a 10 min preprocessing. Importantly, this strategy has good universality for various other h-SGMs, such as SO2, CS2, CH3SH, and HCl, etc., via using appropriate sensing matters. Additionally, the ULSTE-SERS is also very suitable for vulnerable molecules and fast portable detection due to the stable solid layer. This work provides highly efficient SERS-based detection of trace h-SGMs, which is easily applied in practical.