Novel Red-Emitting Copper Nanoclusters as Fluorescence-Quenching Probes for Selective Detection of Congo Red

Abstract

Congo red poses significant toxicity to both humans and the environment, and its persistence in natural habitats for prolonged periods exacerbates these risks. Therefore, accurate detection of Congo red is crucial. In this study, red-emitting copper nanoclusters (Cu NCs) were synthesized through a novel strategy at room temperature within 15 min, using polyvinylpyrrolidone (PVP) as the protective ligand and 3-mercaptophenylboronic acid (3-MPBA) as both stabilizing and reducing agents. When excited at 335 nm, the Cu NCs exhibited a prominent red emission peak centered at 635 nm, along with remarkable water solubility, superior fluorescence stability, and a prolonged fluorescence lifetime. The fluorescence of Cu NCs was efficiently quenched by Congo red due to both static and dynamic quenching mechanisms. Based on this principle, Cu NCs were employed as fluorescent sensors for the rapid, selective, and sensitive detection of Congo red. A linear decrease in fluorescence intensity was observed with increasing Congo red concentrations in the ranges of 2–100 μM and 100–180 μM, with a detection limit of 0.68 μM. Significantly, the application of this method for detecting Congo red in water samples demonstrated satisfactory results, highlighting the practical potential of Cu NCs in real sample analysis.