Cerium ion(III)-triggered aggregation-induced emission of copper nanoclusters for trace-level p-nitrophenol detection in water

Abstract

Herein, we provide the first report on the effects of Ce3+ addition on the fluorescence of copper nanoclusters (CuNCs), which have excellent optical properties and lower toxicity as compared to AgNCs and AuNCs. We synthesized glutathione-encapsulated copper nanoclusters (GSH-CuNCs) using a simple one-pot chemical reduction approach. The excitation/emission wavelengths of the GSH-CuNCs were 350/650 nm. Introduction of Ce3+ triggered an aggregation-induced emission of GSH-CuNCs due to formation of GSH-CuNCs-Ce3+ complexes, resulting in a prominent fluorescence enhancement (~42-fold) of the mixed system. Fluorescent intensities (FIs) for the GSH-CuNCs-Ce3+ system were significantly quenched by introduction of p-nitrophenol (p-NP). The aforementioned quenching mechanism resulted from an inner-filter effect producing nearly unchanged fluorescence lifetime and overlap between UV–Vis absorption of Ce3+ and the excitation wavelength of GSH-CuNCs. Consequently, a GSH-CuNCs-Ce3+-based “ON-OFF” platform was constructed for fluorescent detection of p-NP in water matrices. Under optimized conditions (5-min incubation time, pH = 5.6, 20 mM Ce3+), the FIs of the GSH-CuNCs-Ce3+ system were linear for p-NP concentrations from 0.5 to 500 μM and achieved a low detection limit of 0.17 μM. Moreover, the as-constructed nanofluoroprobe demonstrated high stability and specificity to p-NP, thereby offering a simple, cheap and robust experimental method for conventional monitoring of p-NP at trace levels in real-world water samples.