![]() ![]() Zhao’s group reported SERS response of adsorbed molecules on TiO 2 nanoparticles and proposed the enhanced Raman scattering can be attributed to the plasmon resonance absorption of Ag and the CT of TiO 2-to-molecule 24, 25. ![]() prepared flower-shaped Au–ZnO hybrid nanoparticles with strong charge-transfer-induced SERS property and used as biocompatible and recyclable SERS-active substrate 23. fabricated of Au–Cu 2O/rGO nanocomposites as efficient SERS substrate which origin from the synergistic effect of CE and EE 22. Moreover, the additional studies have been carried out to investigate the SERS enhancement from the hybrid system composed of noble metal nanostructure and metal–oxide semiconductor 20, 21. It has been suggested that the SERS enhancement is owing to the CT increased by Herzberg–Teller coupling, which provides a profound understanding on the defect-assisted CE 18, 19. However, in terms of CE, the high SERS enhanced factor (EF) has been measured recently for the molecule adsorbed on the metal–oxide semiconductor substrates fabricated through various defect engineering 14, 15, 16, 17. Empirical evidence shows that SERS produced by CT is usually weak, comparing with that of EE 13. As for CE, a clear picture is still in debate, and one of the popular explanations is attributed to the charge transfer (CT) between the substrate and adsorbate 10, 11, 12. In generally, EE is considered to be the dominated factor for SERS and is derived from the localized surface plasmon resonance in noble metal nanostructure 8, 9. And it is widely accepted that the electromagnetic enhancement (EE) and the chemical enhancement (CE) are two main mechanisms to contribute the SERS 6, 7. Due to its high sensitivity and selectivity on the designated analyte adsorbed on the noble metal and/or semiconductor substrates, SERS has been used as a powerful and useful tool for fingerprint tracing of biological and chemical molecules, such as tumor markers 2, extracellular metabolites 3, and pesticide residues 4, even explosives 5. ![]() Surface-enhanced Raman scattering (SERS) has been intensive studied since it was first observed by a roughened silver electrode decorated by pyridine 1. A microscopic understanding of the time-dependent SERS behavior is derived based on the microanalysis of the Ag/Ag-doped TiO 2 nanostructure and the molecular dynamics, which is attributed to three factors: (1) higher crystallinity of Ag/Ag-doped TiO 2 substrate (2) photo-induced charge transfer (3) charge-induced molecular reorientation. With increasing irradiation time, the SERS intensity of 4MBA shows an irreversible exponential increase, and the Raman signal of the Ag/Ag-doped TiO 2 substrate displays an exponential decrease. Herein, we report an irreversible accumulated SERS behavior induced by near-infrared (NIR) light irradiating on a 4-mercaptobenzoic acid linked with silver and silver-doped titanium dioxide (4MBA/Ag/Ag-doped TiO 2) hybrid system. ![]() However, the underlying mechanism is still to be revealed in detail. In recent years, surface-enhanced Raman scattering (SERS) of a molecule/metal–semiconductor hybrid system has attracted considerable interest and regarded as the synergetic contribution of the electromagnetic and chemical enhancements from the incorporation of noble metal into semiconductor nanomaterials. ![]()
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