A new and facile preparation of 3D urchin-like TiO2@graphene core@shell SERS substrates for photocatalytic degradation of RhB†

Abstract

Here, we present a new and facile method to grow a graphene (Gr) shell layer on the surface of a 3D urchin-like TiO₂ core layer (TiO₂@Gr) on a silicon (Si/SiO₂) substrate as a surface enhanced Raman scattering (SERS) substrate for detecting and degrading rhodamine B (RhB) under UV irradiation. The core layer of 3D urchin-like TiO₂ (UT) was fabricated by a hydrothermal method and a Gr shell layer was grown on the surface of the TiO₂ core layer by a thermal chemical vapor deposition (CVD) method with sodium deoxycholate (SDC) surfactant as a carbon source. The obtained results indicated that the minimum detectable concentration of RhB on the TiO₂@Gr/SERS substrate-coated graphene (UTG) can reach 1 × 10⁻⁹ M with an enhancement factor (EF) of 1.3 × 10⁵. The enhancement of the Raman signals of the UTG can be generated because the graphene acts as the electron acceptor of TiO₂ and prevents charge recombination, and provides indirect charge transfer from TiO₂ to RhB molecules. The UTG SERS substrate can almost completely decompose RhB with a degradation rate of 0.069 min⁻¹ under UV irradiation at 254 nm within 80 min. The photocatalytic degradation mechanism of UTGs towards RhB was also presented in detail. The results show that the UTG SERS substrate can be further employed for detecting substances and degrading hazardous pollutants.