In-situ photodegradation monitoring from repeatable ultra-sensitive SERS fiber probes based on Ag nanoparticle and Ag3PO4 nanocube composite

Photocatalytic compound decomposition can be an effective protocol for the prominent and urgent solving of the environmental pollution and energy shortage problems. In-situ monitoring of the substance concentrations change during the process is of importance for understanding the decomposition process and final effects. In present research, a surface enhanced Raman spectroscopy (SERS) fiber probe based photocatalyst decomposition monitoring method is proposed. Ag nanoparticles and Ag 3 PO 4 microcube composites were synthesized by ion exchange and subsequent ion reduction method, and then they were coated on silica fiber end-tip for probe fabrication. The microstructures, elements distribution, and morphologies analysis confirm the formation of dense Ag nanoparticles with 30 nm diameter on 1 μm edge length Ag 3 PO 4 cubes. The localized surface plasmon resonance (LSPR) induced absorption peak of Ag nanoparticles is found at 318 nm, along with the band-gap absorption of Ag 3 PO 4 cubes. The Ag nanoparticles and Ag 3 PO 4 composites are homogeneously distributed on the fiber end-tip surface. The fiber probes show the lowest detection limit of 10 −14 M using crystal violet analyte, and as high as 5.3 × 10 11 calculated enhancement factor, due to the strong LSPR induced electrical field from the densely distributed Ag nanoparticles on Ag 3 PO 4 microcubes surface. Furthermore, the linear relationship between analyte concentrations and SERS intensities indicates a potential for quantitative analysis. The analytes crystal violet and 4-aminothiophenol can be photodegraded under UV and visible light irradiation by Ag 3 PO 4 . The Raman spectra of crystal violet and 4-aminothiophenol intensities decrease with longer irradiation durations, indicating the decomposition of organic compounds. The fiber probes also present repeatable using within several cycles. The research provides a potential method for photocatalyst decomposition monitoring.