A near-infrared fluorescent probe for detecting Cu²⁺ and its versatile applications

Copper ions (Cu²⁺), although essential for biological systems, pose substantial environmental and health risks at elevated concentrations. Therefore, the detection of Cu²⁺ in the environment is of great significance. In order to develop a simple, rapid, convenient and reliable method for Cu²⁺ analysis, a simple fluorescent probe was successfully prepared, which incorporates the dicyanoisophorone fluorophore and the 2-aminonicotinic acid recognition group. This probe demonstrated stable near-infrared emission at 655 nm, large Stokes shift of 235 nm, exceptional selectivity (detection limit: 0.018 μM), and robust anti-interference capabilities across diverse environments. It enabled direct Cu²⁺ detection in real water matrices, food (rice and mung beans), plant tissues (onion roots), and soil samples. By integrating smartphone-based chromatic analysis and portable test strips, this probe demonstrated on-site visual quantification of Cu²⁺ without complex instrumentation. This study provides a cost-effective Cu²⁺ detection solution for environmental, agricultural, and food safety applications, particularly in resource-limited settings.