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Ultratrace Naked-Eye Colorimetric Ratio Assay of Chromium(III) Ion in Aqueous Solution via Stimuli-Responsive Morphological Transformation of Silver Nanoflakes

Li, Xuemei, Zhang, Shouting, Dang, Yanfeng, Liu, Zheyuan, Zhang, Zhen, Shan, Duoliang, Zhang, Xuehong, Wang, Tiansheng, Lu, Xiaoquan
Analytical chemistry 2019 v.91 no.6 pp. 4031-4038
absorbance, aqueous solutions, blood serum, chromium, color, colorimetry, environmental monitoring, humans, nanoparticles, nanosilver, silver, spectroscopy
In this work, we discover an effective domino-effect-based detection mechanism for the rapid, high-selectivity, and ultrasensitive naked-eye colorimetric ratio assay of chromium(III) ion (Cr³⁺) in aqueous solutions. This naked-eye colorimetric ratio assay to Cr³⁺ relies on changes in absorbance properties that are due to the stimuli response of Cr³⁺ for the morphological transformation of silver nanoflakes. In the presence of Cr³⁺, large silver nanoflakes can be stimulated to transform to small nanoparticles (NPs), which promoted a color change in solution from bright yellow to wine red that was detected by the naked eye and spectroscopic absorption methods. The proposed naked-eye sensing strategy was coupled with an ultraviolet (UV)-spectroscopic chemosensor for the detection of trace Cr³⁺. The detection method showed an ultralow detection limit of 1.4 nM (nanomole) for Cr³⁺ in ultrapure water and 11.5 nM in human serum sample, respectively. On the basis of colorimetry, the lowest concentration of ∼50 nM for Cr³⁺ in ultrapure water and human serum can be detected by the naked eye. This naked-eye-based colorimetric ratio assay for accurate and selective identification and high sensitivity of Cr³⁺ is expected to have large potential and wide applications such as pharmaceutical analysis, clinical diagnosis, and environmental monitoring.