Dual fluorometric and colorimetric sensor based on quenching effect of copper (II) sulfate on the copper nanocluster for determination of sulfide ion in water samples

A new dual function sensor was developed for the sensitive and selective detection of sulfide ion in aqueous media. The proposed indirect measurement was based on the copper ion (Cu2+) mediated the fluorescence intensity of tannic acid-capped copper nanoclusters (TA-CuNCs) in the presence of sulfide ion. Under the optimal conditions, the fluorometric sensing of sulfide ion was carried out over the concentration ranges of 0.7-80.0 mu M, without needing any etching time. Furthermore, fluorescence quenching is accompanied by color changing from sky blue to brown by increasing sulfide ion concentration that attributed to the formation of copper sulfide (CuS). The variations in the visible color of TA-CuNCs/Cu2+ in the presence of sulfide ion was recorded with a smart phone camera. The RGB color changes show a linear relationship with sulfide concentrations in the range of 6.0 - 130.0 mu M. The fluorometric and calorimetric detection limit values were calculated as 0.1 mu M and 2.0 mu M, respectively. The estimated detection limits in both methods are lower than the permitted value reported by World Health Organization (WHO). The prepared TA-CuNCs/Cu2+ probe was successfully applied to the sensitive fluorometric and colorimetric determination of sulfide ion in different types of natural waters. The proposed probe is highly sensitive, selective and particularly useful for the fast and cost effective diagnosis of sulfide ion in environmental samples.