Au@Ag NPs-based probes with enhanced quenching effect immobilized on polymer platforms as solid-phase fluorescent sensors for malachite green detection

Malachite green (MG) used in aquaculture is highly toxic and poses a serious risk to human health. Therefore, a novel solid-phase biosensor was developed for the detection of MG in this study. We loaded upconversion nanomaterials with a core/shell/shell structure (CSS-UCNPs) on polydimethylsiloxane as a fluorescence donor and Au@Ag nanoparticles as a fluorescence acceptor. The fluorescence quenching of CSS-UCNPs was caused by fluorescence resonance energy transfer. With MG present, the fluorescence of CSS-UCNPs was restored so that MG could be detected by fluorescence spectroscopy and smartphones. Under the optimal conditions, the limit of detection of MG based on image and fluorescence was 0.037 and 0.029 ng/mL, respectively. In addition, the dual-mode method had a broad linear range of 0.05–500 ng/mL and was not significantly different from the results of high-performance liquid chromatography. Therefore, the solid-phase biosensor developed in this study can be applied in the field of food safety and provides insight for rapid on-site detection.