Fluorescence resonance energy transfer between NH2–NaYF4:Yb,Er/NaYF4@SiO2 upconversion nanoparticles and gold nanoparticles for the detection of glutathione and cadmium ions

Dual-functional nanosensors based on small molecule regulation can be widely used due to their simplicity, high sensitivity and selectivity. Herein, glutathione (GSH) calibrated dual-functional system for GSH and cadmium ions (Cd 2+ ) detection based on fluorescence resonance energy transfer (FRET) between NH 2 –NaYF 4 :Yb,Er/NaYF 4 @SiO 2 upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs) is designed. Unmodified AuNPs are easy to aggregate in high-salt solution and thereby quenching the red emission of UCNPs. The presence of GSH prevents the aggregation of AuNPs, so GSH can be detected by the changes in the color of solution and the recovery of red emission of UCNPs. However, Cd 2+ can interact with GSH, which makes AuNPs easy to aggregate, resulting in a gradual decrease in red emission of UCNPs. The fluorescence response of the system is linear with the concentrations of GSH and Cd 2+ in a wide range of concentrations, with low detection limits of 0.016 μM and 0.059 μM, respectively. Furthermore, the nanosensor demonstrates high selectivity for GSH and Cd 2+ detection and can be applied for the detection of GSH in human plasma and Cd 2+ in drinking water .