Chemical vapor generation colorimetric system for visual/smartphone RGB dual-mode detection of sulfide

A chemical vapor generation (CVG)-colorimetric system is proposed to realize the on-site detection of sulfide (S^2-). Through the process of CVG, S^2- was converted to H₂S, and the volatile H₂S escaped to undergo a redox reaction with HAuCl₄ on the test paper. The generated Au NPs changed the color of the test paper from pale yellow to brownish black, which could be read out by the naked eye and smartphone-assisted color detection. Under the optimized conditions, the limits of quantification were 0.5 µg/mL and 0.2 µg/mL for the naked eye and smartphone modes, respectively. The proposed colorimetric analytical system was further applied to the rapid and on-site analysis of several real samples, including environmental water samples, species, and certified water sample (BWZ6676-2016C). Recoveries of 97-106% were obtained for those samples and their spiked samples.