A colorimetric assay for measuring iodide using Au@Ag core-shell nanoparticles coupled with Cu(2+).

Anal Chim Acta

Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Published: September 2015

Au@Ag core-shell nanoparticles (NPs) were synthesized and coupled with copper ion (Cu(2+)) for the colorimetric sensing of iodide ion (I(-)). This assay relies on the fact that the absorption spectra and the color of metallic core-shell NPs are sensitive to their chemical ingredient and dimensional core-to-shell ratio. When I(-) was added to the Au@Ag core-shell NPs-Cu(2+) system/solution, Cu(2+) can oxidize I(-) into iodine (I2), which can further oxidize silver shells to form silver iodide (AgI). The generated Au@AgI core-shell NPs led to color changes from yellow to purple, which was utilized for the colorimetric sensing of I(-). The assay only took 10 min with a lowest detectable concentration of 0.5 μM, and it exhibited excellent selectivity for I(-) over other common anions tested. Furthermore, Au@Ag core-shell NPs-Cu(2+) was embedded into agarose gels as inexpensive and portable "test strips", which were successfully used for the semi-quantitation of I(-) in dried kelps.

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http://dx.doi.org/10.1016/j.aca.2015.06.043DOI Listing

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