Glutathione-stabilized copper nanoclusters mediated-inner filter effect for sensitive and selective determination of p-nitrophenol and alkaline phosphatase activity.

A simple and highly selective fluorescence biosensor has been exploited for p-nitrophenol (p-NP) and alkaline phosphatase (ALP) activity detection based on the glutathione-stabilized copper nanoclusters (GSH-CuNCs) mediated-inner filter effect (IFE). The GSH-CuNCs were prepared by employing GSH as stabilizer and ascorbic acid (AA) as reductant. The obtained GSH-CuNCs exhibited a strong blue fluorescence emission at 420 nm with an excitation wavelength of 365 nm, which overlapped largely with the absorption spectra of p-nitrophenol (p-NP). Therefore, the luminescence of GSH-CuNCs could be quenched by p-NP through inner filter effect. In addition, ALP catalyzed the substrate p-nitrophenyl phosphate (p-NPP) to form p-nitrophenol (p-NP), which also leading to the fluorescence quenching of GSH-CuNCs. The fluorescent strategy was realized for the sensitive determination of p-NP and ALP activity with the promising limit of detection of 20 nM (for p-NP) and 0.003 mU⋅mL (for ALP). Furthermore, the method could be applied to detect the p-NP content in river water samples and ALP activity in human serum samples.