Highly Stable and Sensitive Colorimetric Visualization of Trivalent Chromium Using Amido Black 10B-Stabilized Silver Nanoparticles

Here, we report a highly stable and sensitive colorimetric assay for Cr 3+ based on amido black 10B-stabilized silver nanoparticles (AgNPs) as the probes. The detection mechanism is that the coordination interaction between Cr 3+ and amido black 10B on the surface of AgNPs causes the cross-linking/aggregation of amido black-stabilized AgNPs, generating a redshift of the absorption peak and a color change from yellow to pink. Under the optimized assay conditions, this colorimetric assay displays a good linear relationship ( R 2  = 0.996) between relative absorbance ratios and the concentration of Cr 3+ in the range of 0.05–20 μM, and the limit of detection (LOD) was estimated to be 0.01 μM by the UV-Vis spectra and 15 μM by the naked eye. Additionally, the colorimetric assay shows a good selectivity over other metal ions, and it is successfully applied to detection of Cr 3+ in tap water, lake water, and river water samples with satisfactory recoveries.