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 H 2 O 2 . The horseradish peroxidase (HRP) catalyzes H 2 O 2 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 ( F 445 / F 665 ) 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%. Graphical abstract