Colorimetric detection of Cr3+ using gold nanoparticles functionalized with 4-amino hippuric acid

A facile and effective technique for monitoring Cr3+ concentration based on 4-amino hippuric acid (PAH) decorated Au nanoparticles (PAH-AuNPs) is introduced. The modified AuNPs were easily aggregated in the presence of Cr3+, resulting in the color change from red to violet or blue, which is in response to the surface plasmon absorption of dispersed or aggregated nanoparticles. Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.998) was obtained between the ratio of the absorbance at 635 nm to that at 520 nm (A 635 nm/A 520 nm), and the concentration of Cr3+ was over the range of 5.0–120 µM with detection limit of 1.17 µM. This method exhibited excellent selectivity for Cr3+ over other tested heavy metal ions. Furthermore, there was no significant difference for the parameters of calibration equation between the presence and absence of ethylenediamine tetraacetic acid (EDTA), which suggests that the method can be applied in various real samples owing to the strong masking ability of EDTA. The assay was used to detect the concentrations of Cr3+ in liquid milk, milk power, and lake water samples with recoveries ranging from 93.5 to 114 %, indicating that the method could be used for extensive practical application. A facile and effective technique for monitoring Cr3+ based on 4-amino hippuric acid decorated Au nanoparticles is introduced. The modified AuNPs were aggregated in the presence of Cr3+ resulting in the color change from red to violet or blue, which is in response to the surface plasmon absorption of dispersed or aggregated nanoparticles.