Sequential Visual Sensing of H2O2 and GSH Based on Fluorescent Copper Nanoclusters Incorporated Eggshell Membrane

Digital imaging technology provides a unique advantage for the portable on-site detection of targeted analytes. In this work, copper nanoclusters (CuNCs) based on the eggshell membrane (ESM) were combined with the photograph-taking and color recognition functions of a smartphone to build an “ON-OFF-ON” detection platform, which realized the dual visual detection of hydrogen peroxide ( $\text{H}_{{2}}\text{O}_{{2}}$ ) and glutathione (GSH). First, a red fluorescent nanocomposite membrane (GSH-CuNCs@ESM) was prepared by in situ synthesis with GSH as the protective and reducing agent. The physical characterization results confirmed its long fluorescence (FL) lifetime ( $23.77 \mu \text{s}$ ), high quantum yield (QY, 23.79%), large Stokes shift, and good stability. In addition, it is found that $\text{H}_{{2}}\text{O}_{{2}}$ has a specific response to the GSH-CuNCs@ESM, which can quench its FL. However, the FL of the quenched membrane was restored after it was put into the GSH solution. So, visual detection of $\text{H}_{{2}}\text{O}_{{2}}$ and GSH was developed based on this phenomenon integrating with a smartphone and color recognition functions. Consequently, the limit of detection (LOD) of $\text{H}_{{2}}\text{O}_{{2}}$ is as low as 63 nM when the concentration of $\text{H}_{{2}}\text{O}_{{2}}$ is between 0 and $100 \mu \text{M}$ . The LOD of GSH is as low as $1.0 \mu \text{M}$ when the concentration of GSH was between 0 and $800 \mu \text{M}$ .