Colorimetric sensor for thiocyanate based on anti-aggregation of citrate-capped gold nanoparticles

A convenient colorimetric sensor based on anti-aggregation of citrate-capped gold nanoparticles (AuNPs) is demonstrated for thiocyanate (SCN−) sensing. The citrate-capped AuNPs aggregated readily in the presence of sulfuric acid, leading to a color change from red to blue. This particle aggregation could be suppressed by SCN−, which had strong protective effect on the gold colloid. The thiocyanate recognition suffers insignificant interference from most of common ions. With this strategy, 1 μM of SCN− can be recognized within 5 min by naked-eye observation. This simple, selective, and sensitive approach can be potentially applied for SCN− assays in environmental aqueous samples.