Modification of Graphitic Carbon Nitride/Pyromellitic Diimide as a Robust Fluorescent Probe for Silver Detection in Water

Silver ions (Ag⁺), though valuable in industry and medicine, become hazardous at high concentrations, requiring reliable monitoring in environmental media. In this study, a sensitive and selective fluorescent probe is developed by modifying a graphitic carbon nitride/pyromellitic diimide (g‐C₃N₄/PDI, CNP) composite with dithiothreitol via a simple ring‐opening reaction. The introduction of SH and OH groups improves the probe's water dispersibility and affinity for Ag⁺, enhancing its adsorption capacity and detection performance. This leads to a twofold increase in fluorescence intensity, significantly improved selectivity, and a 36% increase in the Stern–Volmer quenching constant (Ksv). Furthermore, the optimized probe exhibits excellent stability (relative standard deviation <1%) and a substantial decrease in the limit of detection from 7.59 to 1.38 μM, confirming its high sensitivity. This green, cost‐effective, and easily prepared probe presents a promising solution for accurate and reliable Ag⁺ monitoring in environmental and complex matrices.