Preparation of copper nanoparticles fluorescent probes and detection of hydrogen peroxide and glucose

Fluorescent copper nanoparticles (CuNPs) was synthesized by one-step chemical reduction method using ascorbic acid (AA) and copper sulfate (CuSO₄⋅5H₂O) as raw materials, which had good water solubility and fluorescence properties. A green, simple and safe CuNPs@Fe²⁺ fluorescence probe was developed for the detection of hydrogen peroxide and glucose using Fe²⁺ as a bridge. The prepared CuNPs could obtain the maximum fluorescence emission wavelength at 440 nm when the excitation wavelength was 360 nm. The average particle size of CuNPs was 10 nm, which had good photobleach resistance, stability and salt tolerance. The fluorescence intensity was quenched due to electron transfer (ET) process when hydrogen peroxide was added to CuNPs@Fe²⁺ system. This result was mainly because Fenton reaction occured between hydrogen peroxide and Fe²⁺, producing hydroxyl free radicals (OH) and Fe³⁺. Since glucose could be catalyzed by specific glucose oxidase (GOX) to produce H₂O₂ and corresponding oxidation products, the quantitative analysis of glucose was realized when glucose oxidase was introduced into the CuNPs@Fe²⁺ sensor system. Therefore, a novel CuNPs@Fe²⁺ fluorescent probe sensor study was constructed to further achieve quantitative detection of H₂O₂ and glucose. Under the optimized experimental conditions, the linear ranges for H₂O₂ and glucose were 28.219-171.562 μM and 1.237-75.771 μM, respectively. And the detection limits for H₂O₂ and glucose were 7.169 μM and 0.540 μM, respectively. In addition, the mechanism of fluorescence probe quenching caused by the interaction between H₂O₂ and CuNPs@Fe²⁺ was also discussed. The proposed sensing system had been applied successfully to the detection of glucose in human serum samples.