Dithiothreitol-capped red emitting copper nanoclusters as highly effective fluorescent nanoprobe for cobalt (II) ions sensing

Herein, red emitting copper nanoclusters (Cu NCs) were synthesized by employing dithiothreitol (DTT) as both the capping and reducing agent at room temperature. The synthesis route was facile, rapid and efficient. The DTT-Cu NCs were thoroughly characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transient and steady-state fluorescence, and UV–vis absorption spectroscopy. The water soluble DTT-Cu NCs exhibited small size, good storage stability and high salt tolerance. Significantly, the fluorescence intensity was effectively quenched by cobalt (II) ions, and a novel sensitive and selective fluorescent assay was developed for the label-free determination of cobalt (II) ions with a detection limit of 25 nM. The sensing mechanism was ascribed to the aggregation-induced fluorescence quenching effect. Moreover, practicability of the proposed assay to determine the cobalt content in real samples was validated with satisfactory recoveries. Additionally, it was further demonstrated that a visual paper sensor could be manufactured by immobilizing the DTT-Cu NCs probe on a piece of filter paper with great potential application in on-site visual detection of Co (II) ions.