Controlled growth of silver nanoparticles through a chemically assisted photocatalytic reduction process for SERS substrate applications

Abstract

The deposition of Ag° nanoparticles (NPs) has been performed through a photocatalytic reduction process on the surface of sol–gel deposited TiO2 thin films. So-formed Ag°/TiO2 heterostructures are intended for Surface-Enhanced Raman Scattering (SERS) substrate applications. The photocatalytic growth of Ag° NPs has been chemically assisted by tri-sodium citrate (TSC) and a seeded growth procedure based on ascorbic acid (AA) has been developed. Field Emission Gun-Scanning Electron Microscopy, Transmission Electron Microscopy, and Energy Dispersive X-ray characterizations have been used to assess how the chemical assistance of the photocatalytic reduction process enables an enhanced uniformity of the Ag° NPs deposition. Then, Raman spectroscopy studies have been performed to assess the SERS performances of Ag°/TiO2 heterostructures on rhodamine 6G (R6G). It is shown that a TSC-based photocatalytic reduction process associated to an AA-based seeded growth is a low cost liquid solution elaboration procedure leading to good SERS performances, i.e. a 106 enhancement factor and a detection limit of R6G ranging between 10−8 and 10−10 M, as well as a good reproducibility of the SERS spectra on rather large dimension substrates.