Rapid synthesis of multifunctional copper nanoclusters for selective and sensitive detection of hexavalent chromium and anti-counterfeiting

In this work, a copper nanocluster (His-Cu NCs) with green fluorescence, which uses histidine (His) as the template agent, was developed. This nanomaterial was characterized using methods such as transmission electron microscopy (TEM). Based on this nanocluster, a fluorescence sensing platform was developed for the linear detection of Cr(VI) ions in solution. The surface of His-Cu NCs contains a large number of oxygen-containing and nitrogen-containing functional groups, which can react with Cr(VI), leading to charge transfer between ligands and metal ions, thereby quenching the fluorescence of His-Cu NCs. The sensor exhibits excellent sensitivity and selectivity for detecting Cr(VI), with a 0.31 μM detection limit for Cr(VI). Additionally, a fluorescent filter paper was created to detect Cr(VI). The fluorescence color of the fluorescent filter paper changed from green to blue with the increase in Cr(VI) concentration under the irradiation of a UV lamp at 365 nm. Furthermore, this His-Cu NCs’ fluorescence exhibits good stability, making it possible to employ the NCs as fluorescent ink for writing and drawing anti-counterfeiting icons on paper.