Abstract: As an effective way to detect quercetin, it is important to synthesize fluorescent probe with excellent performance by a simple method. In this work, a facile one-pot approach has been developed to prepare blue-emitting Cu nanoclusters (NCs) using ascorbic acid as a reducing agent and polyvinyl pyrrolidone (PVP) as a capping agent. The PVP-stabilized PVP-Cu NCs display good dispersion, high stability and strong fluorescence. It exhibits good water solubility, excellent photostability and high stability toward high concentration of sodium chloride. The optical performance and structure of PVP-Cu NCs were characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The characterization results show that PVP-Cu NCs have a strong symmetric emission at 429 nm with a maximum excitation at 366 nm. TEM analysis shows that the average diameter of PVP-Cu NCs is 2.0 nm. We construct a fluorescent sensor for the detection of quercetin on the basis of the quenching effect of quercetin on the fluorescence of PVP-Cu NCs. The experimental results show that the quercetin sensing system has a linear range of 0.1～0.9 μmol/L and 15～60 μmol/L with a low detection limit (S/N=3) of 0.053 μmol/L. The sensor has high sensitivity and good selectivity for the detection of quercetin, and can be applied for quercetin detection in real samples.

Key words: copper nanoclusters, polyvinyl pyrrolidone, quercetin, fluorescence quenching