Highly Sensitive, Uniform, and Reusable Surface-Enhanced Raman Scattering Substrate with TiO₂ Interlayer between Ag Nanoparticles and Reduced Graphene Oxide

TiO₂ nanoparticles and Ag nanoparticles were successively deposited on reduced graphene oxide (rGO) by a two-step solvothermal process to develop a reusable surface-enhanced Raman scattering (SERS) substrate with high sensitivity and uniformity owing to the 2-dimensional planar structure of rGO, the photocatalytic activity of TiO₂, and the SERS function of Ag nanoparticles. The presence of TiO₂ interlayer efficiently diminished the interference from the Raman intensities of D-band and G-band of rGO and hence enhanced the sensitivity significantly. As compared to Ag/rGO nanocomposite, the detection limit of 4-aminothiophenol (4-ATP) for Ag/TiO₂/rGO nanocomposite could be lowered from 10^-10 to 10^-14 M, and its enhancement factor could be raised from 1.27 × 10¹⁰ to 3.46 × 10¹². Meanwhile, good uniformity remained, the relative standard deviation (RSD) value was about 10%. Furthermore, by UV irradiation in water, the photocatalytic property of TiO₂ could eliminate the Raman signal of 4-ATP efficiently and made this substrate reusable. After being reused five times, its excellent SERS performance was still retained. Thus, the Ag/TiO₂/rGO nanocomposite developed in this work was a promising SERS substrate with good reusability and high sensitivity and uniformity.