Strong Visible Light Absorption and Abundant Hotspots in Au-Decorated WO₃ Nanobricks for Efficient SERS and Photocatalysis

Metal/semiconductor hybrids show potential application in fields of surface-enhanced Raman spectroscopy (SERS) and photocatalysis due to their excellent light absorption, electric field, and charge-transfer properties. Herein, a WO₃-Au metal/semiconductor hybrid, which was a WO₃ nanobrick decorated with Au nanoparticles, was prepared via a facile hydrothermal method. The WO₃-Au hybrids show excellent visible light absorption, strong plasmon coupling, high-performance SERS, and good photocatalytic activity. In particular, on sensing rhodamine B (RhB) under 532 nm excitation, bare WO₃ nanobricks have a Raman enhancement factor of 2.0 × 10⁶ and a limit of detection of 10^–8 M due to the charger-transfer property and abundant oxygen vacancies. WO₃-Au metal/semiconductor hybrids display a largely improved Raman enhancement factor compared to pure Au and WO₃ components owing to the synergistic effect of electromagnetic enhancement and charge transfer. The Raman enhancement factor and limit of detection are further improved, reaching 5.3 × 10⁸ and 10^–12 M, respectively, on increasing the content of Au to 2.1 wt %, owing to the strong plasmon coupling between the Au nanoparticles. Additionally, the WO₃-Au hybrids also exhibit excellent photocatalytic activity toward degradation of RhB under visible light irradiation. WO₃-Au (2.1 wt %) possesses the fastest photocatalytic rate, which is 6.1 and 2.0 times that of pure WO₃ nanobricks and commercial P25, respectively. The enhanced photocatalytic activity is attributed to the strong plasmon coupling and the efficient charge transfer between Au and WO₃ nanobricks. The as-prepared materials show great potential in detecting and degrading pollutants in environmental treatment.