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Anal Chem. 2019 Mar 19;91(6):4031-4038. doi: 10.1021/acs.analchem.8b05472. Epub 2019 Mar 6.

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

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Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering , Northwest Normal University , Lanzhou 730070 , People's Republic of China.
Tianjin Key Laboratory of Molecular Optoelectronic Science, Department of Chemistry, School of Science , Tianjin University , Tianjin , 300072 , People's Republic of China.


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.

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