Dual hydrogen-bond network-enhanced sensor of recycle SERS substrate using MXene/hydrogel for sensitive detection of malachite green residues in fish

Malachite green (MG), with teratogenic and reproductive toxicity, is widely misused as an antimicrobial agent, posing a serious threat to animal and human health. Therefore, this study developed a novel recyclable Surface-enhanced Raman scattering (SERS) hydrogel substrate, TiO₂/MXene/PAA-PAM@AuNPs (TMPA), by forming a dual hydrogen-bond network using a PAA-PAM hydrogel matrix with TiO₂/MXene and embedding AuNPs, for detecting MG residues in aquatic products. This hydrogel exhibits high sensitivity, with a detection limit for MG of 8.13 × 10⁻⁶ mg/L. Additionally, it can completely degrade surface-adsorbed MG within 60 min under light irradiation, achieving self-cleaning and enabling reuse for more than seven cycles, and can be stored for over 50 days while maintaining its SERS activity due to the support and preservation provided by the hydrogel network. Additionally, this substrate can rapidly detect MG residues on or within fish, offering a new strategy for monitoring MG residues in aquatic products.