Determination of xanthine using a ratiometric fluorescence probe based on boron-doped carbon quantum dots and gold nanoclusters.

A dual-emission ratiometric fluorescent sensing system based on boron-doped carbon quantum dots (B-CQDs) and gold nanoclusters (AuNCs) has been developed for the determination of xanthine. The blue fluorescence of B-CQDs at 445 nm is then reduced by the AuNCs through the inner filter effect (IFE) under a single excitation wavelength of 370 nm. By the catalysis of xanthine oxidase (XOD), xanthine is oxidized by oxygen dissolved in the solution to produce H2O2. The horseradish peroxidase (HRP) catalyzes H2O2 to generate hydroxyl radicals, which can quench the fluorescence of AuNCs, leading to the recovery of the fluorescence of B-CQDs. Based on the relationship between the fluorescence intensity ratio (F445/F665) and the concentration of xanthine, the designed method exhibits a good linearity range of 1.2-500.0 μmol L -1 and a limit of detection of 0.37 μmol L -1. The ratiometric fluorescent is applied to determine xanthine in human urine samples. Good recoveries of spiked samples in the range 99.2-105.0% are obtained by the proposed assay, with relative standard deviations (RSD) ranging from 0.9 to 2.6%.