Colorimetric detection of sulfide ions in water samples based on the in situ formation of Ag2S nanoparticles

In this work, a facile approach to sensitively detect sulfide ions is developed. The proposed method is based on the findings that silver ions could oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to induce a blue color and an absorption peak centered at 652   nm. The introduction of sulfide ions leads to the formation of Ag 2 S nanoparticles which act as catalyst to enhance the oxidation capacity of silver ions, resulting in a blue color burning and increase of the absorbance at 652   nm. Based on the above facts, a facile method is developed to qualitatively and quantitatively detect sulfide ions by naked eyes and UV–vis spectroscopy, respectively. The color changes of the detection system in the presence of nanomolar level of sulfide ions could be distinguished by naked-eyes, demonstrating the high sensitivity of the method. Highly sensitive detection of sulfide ions can be achieved in the range of 1.0   ×   10 −9   M to 8.0   ×   10 −8   M, with a detection limit of 0.2   nM. In addition, this method shows excellent selectivity toward sulfide ions detection and has been successfully applied to detect sulfide ions in tap water and lake water samples. Moreover, this method is simple without the preparation of nanomaterials and the need of complex readout instruments.