Simulation Calculation Verification of Graphene Oxide-Decorated Silver Nanoparticles Growing on Titania Nanotube Array as SERS Sensor Substrate

Abstract

Graphene oxide-decorated silver nanoparticles growing on titania nanotube array (GO/Ag/TiO2 NTA) were designed as active Surface-enhanced Raman scattering (SERS) sensor substrates for sensitive determination of the organic compound bisphenol A. The theoretical simulation calculation and experimental measurements have been adopted to investigate the electronic and sensing properties of GO/Ag/TiO2 NTA SERS substrate. The molecule adsorption and surface energy are applied to investigate the interfacial interaction between the SERS substrate and the organic molecule. The Raman spectrum response intensity and the electron transfer behavior are applied to investigate sensing activity of GO/Ag/TiO2 NTA SERS substrate. The specific adsorption amount of BPA is 3.3, 7.1, and 52.4 nmol cm−2 for TiO2, Ag/TiO2, and GO/Ag/TiO2 NTA, respectively, presenting superior adsorption and aggregation capability. GO/Ag/TiO2 NTA SERS sensor accordingly achieves the low detection limit of 5 × 10−7 M for bisphenol A molecule. The density functional theory simulation calculation proves that GO/Ag/TiO2 reveals a higher density of states, lower HOMO-LUMO gap, stronger electrostatic interaction, and similar band gaps in comparison with Ag/TiO2. Binary-interfaced GO/Ag/TiO2 presents a more declined molecule structure surface energy of 5.87 eV rather than 4.12 eV for mono-interfaced Ag/TiO2. GO/Ag/TiO2 also exhibits a more declined surface adsorption energy of 7.81 eV rather than 4.32 eV for Ag/TiO2 in the adsorption of bisphenol A. The simulation calculation verification results well confirm the superior activity of GO/Ag/TiO2 NTA substrate for sensitive detection and quantitative determination of the organic compound bisphenol A.