Plasmonic 3D Semiconductor-Metal Nanopore Arrays for Reliable Surface-Enhanced Raman Scattering Detection and In-Site Catalytic Reaction Monitoring.

It is urgent to develop a rapid, reliable, and in-site determination method to detect or monitor trace amounts of toxic substances in the field. Here, we report an alternative surface-enhanced Raman scattering (SERS) method coupled with a portable Raman device on a plasmonic three-dimension (3D) hot spot sensing surface. Plasmonic Ag nanoparticles (AgNPs) were uniformly deposited on 3D TiO ₂ nanopore arrays as a sensitive SERS substrate, and further coated with graphene oxide (GO). We demonstrate the plasmon-induced SERS enhancement (5.8-fold) and the improvement of catalytic activity by incorporation of plasmonic AgNPs into the 3D TiO ₂ nanopore arrays. The modification of GO on the TiO ₂ -Ag nanopore array further increases by a 6.2-fold Raman enhancement compared to TiO ₂ -Ag while maintaining good uniformity (RSD < 10%). The optimized TiO ₂ -Ag-GO substrate shows powerful quantitative detection potential for drug residues in fish scales via a simple scrubbing method, and the limit of detection (LOD) for crystal violet (CV) was 10 ^-8 M. The SERS substrate also showed detection practicability of pesticide residues in banana peel with an LOD of 10 ^-7 M. In addition, our TiO ₂ -Ag-GO substrate exhibits excellent SERS self-monitoring performance for catalytic reduction of multiple organics in NaBH ₄ solution, and the substrate shows good recyclability of 6 cycles. Such a 3D TiO ₂ -Ag-GO substrate is a promising SERS substrate with good sensitivity, uniformity, and reusability, and may be utilized for further miniaturization for point of analytical applications.