Selective and cyclic detection of Cr3+ using poly(methylacrylic acid) monolayer protected gold nanoparticles

A colorimetric gold nanoparticle-based sensor, a monolayer of poly(methylacrylic acid)-modified gold nanoparticles (PMAA@Au NPs), was developed for selective detection of Cr3+ ions in aqueous solution. In the presence of Cr3+, PMAA@Au NPs are aggregated by a chelation process, which caused the prominent color changes in response to carboxyl groups in the sensor. Furthermore, the selective detection of Cr3+ in aqueous solution was achieved over 11 other metal ions. The metal complexes were characterized by UV-vis spectroscopy and transmission electron microscopy. In addition, the chelation-dissociation process was reversible via addition of a strong metal ion chelator such as EDTA. The colorimetric sensor used for detecting Cr3+ was able to be recycled at least three times by monitoring optical changes of the PMAA@Au NPs.