Recyclable Ag-Deposited TiO₂ SERS Substrate for Ultrasensitive Malachite Green Detection

An ultrasensitive Ag-deposited TiO₂ flower-like nanomaterial (FLNM) surface-enhanced Raman scattering (SERS)-active substrate is synthesized via a hydrothermal method, and Ag nanoparticles (NPs) are deposited through electron beam evaporation. Malachite green (MG), which is widely used in aquaculture, is employed to assess the surface-enhanced Raman scattering (SERS) properties of TiO₂/Ag FLNMs. They exhibit ultrasensitivity (limit of detection (LOD) of MG reaches 4.47 × 10^-16 M) and high reproducibility (relative standard deviations (RSDs) are less than 13%); more importantly, the TiO₂/Ag FLNMs are recyclable, as enabled by their self-cleaning function due to TiO₂ photocatalytic degradation. Their recyclability is achieved after three cycles and their potential application is examined in the actual system. Finite difference time domain (FDTD) simulations and the charge-transfer (CT) mechanism further prove that the excellent SERS properties originate from localized surface plasmon resonance (LSPR) of Ag NPs and the coupling field between Ag and TiO₂ FLNMs. Therefore, TiO₂/Ag FLNMs show promising application in aquaculture.