Fig. 7From: Colorimetric detection of Cr3+ based on gold nanoparticles functionalized with 4-mercaptobenzoic acidThe effect of the reaction time on the detection of Cr3+. a The UV-Vis spectra of 4-MBA modified AuNPs solutions with reaction time from 0 to 30 min. b The plot of the absorption ratio (A635nm and A520nm) versus reaction time. The Cr3+ concentration was 1 × 10−5 MBack to article page