A colorimetric sensing probe for chromium (III) ion based on domino like reaction

In this work, a gold nanobipyramid@Ag nanorod (AuNBP@Ag NR)-based sensor platform was developed for the quantitative, visual, and sensitive detection of Cr3+ ions in aqueous solutions. This assay provides quantitative detection of Cr3+, which relies on the absorbance change of AuNBP@Ag NRs due to morphological change of the AuNBP@Ag NRs induced by Cr3+. When AuNBP@Ag NRs and Cr3+ mix, the coordination reaction of the carboxyl groups of citrate and Cr3+ occurs, which leads to the collapse of Ag shell nanorods, similar to the domino effect, and obvious color changes from yellow to pink can be observed by the naked eye. When combined with UV–vis spectrophotometer-based colorimetric detection, a detection limit of 8.7 nM for Cr3+ in ultrapure water was achieved. With the advantages of high sensitivity, selectivity, and performance, we anticipate that the sensor will be helpful for the on-site, quantitative detection of Cr3+ ions in water samples.