Fig. 1. Schematic of fluorescence detection of GSH based on Au@MnO₂-OPD system

Fig. 2. Structural characterization of Au@MnO₂ nanoparticles. (a) SEM image, (b) TEM image, and (c) linear scanning electron microscopy of UFO shaped Au@MnO₂ nanoparticles; (d) TEM image of Au@MnO₂ nanoparticles etched by 1 mmol/L GSH

Fig. 3. Effect of solution pH on system fluorescence intensity

Fig. 4. Effect of OPD concentration on system fluorescence intensity

Fig. 5. Effect of incubation time of 0.1 mmol/L GSH on system fluorescence intensity

Fig. 6. Sensing results of different concentrations of GSH in buffer solution by Au@MnO₂-OPD system. (a) Fluorescence spectra of Au@MnO₂-OPD system before and after reaction with different concentrations of GSH; (b) fluorescence photos under ultraviolet light and curve of fluorescence intensity changing with GSH concentration; (c) linear relationship between change value of fluorescence signal and logarithmic value of GSH concentration

Fig. 7. Exploration of interference experiments. (a) Color photos and (b) fluorescence intensity histogram of Au@MnO₂-OPD system for 5 mmol/L interfering substances (amino acids and metal ions) and 0.5 mmol/L GSH

Fig. 8. Sensing results of different concentrations of GSH in serum samples by Au@MnO₂-OPD system. (a) Fluorescence spectra of Au@MnO₂-OPD-serum system before and after the reaction with different concentrations of spiked GSH with different concentrations (0, 10 nmol/L, 100 nmol/L, 500 nmol/L, 10 µmol/L, 50 µmol/L, 0.1 mmol/L, 0.5 mmol/L, 1 mmol/L); (b) fluorescence photos under ultraviolet light and variation curve of fluorescence intensity with GSH concentration in serum; (c) linear relationship between the change value of fluorescence signal and logarithmic value of GSH concentration in serum; (d) comparison of fluorescence intensity caused by different concentrations of GSH in PBS solution and serum