A nanocage reactor with dense shareable hot spots for in-situ and dynamic SERS tracking photocatalytic reaction bonds variations

•Controllable plasma nanogap structure formed by dense Au NPs results in exceptional SERS enhancement performance and full-band spectral response characteristics.•Highly sensitive localized surface plasmon resonance reactor de-Au@mTiO2 exhibits excellent photogenerated carrier separation capabilities.•The mechanism of benzylamine oxidative coupling and NADH photocatalytic cleavage is initially demonstrated through in-situ SERS. The construction of bifunctional nanomaterials containing high-density controllable plasma nanogaps (hot spots) integrated with photocatalysis has made it possible to monitor photocatalyzed reactions in-situ using Surface-Enhanced Raman Scattering (SERS). Additionally, in-situ SERS monitoring of the reaction process is high beneficial for understanding the underlying mechanisms of photocatalysis. In this study, we present the fabrication of a novel spherical nanocage reactor (de-Au@mTiO2) with an exterior composed of mesoporous titanium dioxide (TiO2). The nanoreactor contains a multitude of different sized gold nanoparticles (Au NPs) embedded as internal scaffolds, and the numerous nano-gaps form substantial shareable hot spots, thereby enhancing the SERS performance. Moreover, under light stimulation, the synergistic effect between the TiO2 semiconductor and the plasma nanoparticles can significantly expand the light absorption range and achieve a full-band spectral response. We then successfully employed the full-band bifunctional substrate to monitor the classical photocatalytic reaction of benzylamine oxidative coupling through in-situ SERS. The SERS dynamic change spectrum provided direct evidence for understanding the plasma-driven electron transfer mechanism, and density functional calculations then revealed the key steps and possible intermediate states in this catalytic reaction. Based on this experimental verification, we proceeded to employ this material for the photocatalytic cleavage of NADH, an important reduction oxidase involved in tumor cell metabolism. Remarkably, SERS was also utilized to uncover the molecular-level mechanism of NADH cleavage, offering a novel approach to impede the activity of tumor cells.