Visual Detection of Cadmium and Glutathione by Dicyanoisophorone Fluorescent Probe and its Portable Application

A novel fluorescent probe XL derived from dicyanoisophorone was designed and synthesized, achieving successful sequential detection of Cd²⁺ and GSH. As probe XL interacted with Cd²⁺, the emission wavelength redshifted from 565 nm to 650 nm, accompanied by enhanced red fluorescence, which realising a fluorescence turn-on response in the near-infrared region. A large Stokes shift (121 nm) combined with low detection limit (0.484 µmol/L) were key advantages of the detection process. However, due to high affinity of GSH for Cd²⁺, as addition of GSH to complex XL-Cd²⁺, fluorescence response in NIR region was switched off and emission peak was blue-shifted back to 565 nm. Detection limit for GSH was calculated as 0.784 µmol/L, a value significantly lower than its normal intracellular concentration, and the assay process with good sensitivity. Notably, probe XL showed an immediate response (3 s) to Cd²⁺ and GSH, with a clear visual detection in natural light. In addition, XL could be used to detect Cd²⁺ and GSH in real samples and achieve linked applications with smartphones.