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 x 10(10) to 3.46 x 10(12). 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.