Photochemical synthesis of ZnO@Au nanorods as an advanced reusable SERS substrate for ultrasensitive detection of light-resistant organic pollutant in wastewater

The prospect of wielding surface-enhanced Raman spectroscopy (SERS) as a powerful technique for ultrasensitive detection of organic molecules in wastewater has received extensive attention in environmental surveillance. Based on ultraviolet (UV, 405 nm) laser irradiation of ZnO nanorods in HAuCl 4 solution, ZnO@Au nanorods with controllable Au nanoparticles were successfully fabricated and established as an advanced SERS-based substrate. The reduction of Au ions was driven by the generation of electron-hole pairs via UV laser excitation of semiconductor-based nanomaterials , resulting in the moderate overgrowth of Au nanoparticles on the ZnO nanorods. The Au composition-dependent SERS analysis of crystal violet (CV) molecules revealed that the ZnO@Au nanorods with 16.21% Au contents exhibited optimized SERS activity in comparison with other nano-substrates in this paper. Furthermore, the detection limit of light-resistant methyl blue (MB) dye molecules was achieved at nanomole (nM) level of 10 −9 M (0.8 μg/L), providing ultrasensitive detection of organic pollution in wastewater. Even after twenty recycles, the excellent reusability of this novel substrate with 65% original SERS intensity was achieved by subsequently eliminating the residual MB molecules via photocatalytic degradation. Therefore, the as-prepared ZnO@Au nanorods can serve as a cost-effective, clean, reusable and active SERS substrate for ultrasensitive monitoring of light-resistant organic pollutant in natural ecosystems.