Integrating Fluorescent Copper Nanoclusters into Hydrogel for Onsite Point-of-Care Testing of Cr(VI).

Copper nanoclusters (Cu NCs) have promising applications in fluorescence sensors due to their excellent optical properties. However, their efficient application in point-of-care testing (POCT) remains a challenge due to the limited development of solid-state fluorescence platforms. In this study, a POCT platform for Cr(Ⅵ) was fabricated based on a Cu NCs hydrogel by assisting of a smartphone. The Cu NCs hydrogel was facilely synthesized by integrating cysteine (Cys)-Cu NCs into agarose- hydrogel via a self-assembly process. The prepared Cu NCs hydrogels display more stronger emission at 600 nm and stability. Moreover, the fluorescence of the Cu NCs hydrogel could be selectively quenched by Cr(Ⅵ) with the fluorescence color change from red to blue. With the assistance of a smartphone, a solid-state fluorescence platform could be developed based on the Cu NCs hydrogel directly for POCT of Cr(Ⅵ). The fluorescence color change was transduced into the RGB that displayed two linear relationships to Cr(VI) concentration between 1-10 and 10-1000 µM, with a detection limit of 1 µM. This platform also displayed great anti-interference ability and reproducibility, and was successfully used for quantifying Cr(Ⅵ) in real water samples. This study demonstrates the application potential of Cu NCs hydrogel in POCT.