4-Mercaptobenzoic acid-modified Au@Ag nanoparticle-based colorimetric Cr3+ ions detection in aqueous solution

Abstract Heavy metal ions pose a threat to both ecological balance and human health owing to the non-biodegradable and poisonous characteristics. A simple, convenient and rapid metal ion monitoring plays a significant role for eliminating metal ions pollution. In this work, we prepared 4-mercaptobenzoic acids (4-MBA)-functionalized silver-coated gold nanoparticles (Au@Ag NPs) as colorimetric probes to construct colorimetric Chromium III (Cr 3+ ) ions detection platform. The results showed that 4-MBA-Au@Ag NPs could effectively coordinate with the low-concentration Cr 3+ ions with the group of -COOH, generating the obviously colorimetric reaction. To detection system, the optimal concentration of 4-MBA and pH was 5 μM and 9, respectively. Signal response was found to be proportional to Cr 3+ ions concentration in the range from 10 to 500 μM with a correlation coefficient of 0.993, with UV–Vis and colorimetric detection limits determined as 9 μM and 10 μM, respectively. In addition, the recovery of the system was estimated to be from 88.2 to 112.1%, which was satisfactory for practical analysis of samples. The platform would have great potential applications in many areas.