title: Membrane-based assay for iodide ions based on anti-leaching of gold nanoparticles.
abstract: We report a label-free colorimetric strategy for the highly selective and sensitive detection of iodide (I(-)) ions in human urine sample, seawater and edible salt. A poly(N-vinyl-2-pyrrolidone)-stabilized Au nanoparticle (34.2-nm) was prepared to detect I(-) ions using silver (Ag(+)) and cyanide (CN(-)) ions as leaching agents in a glycine-NaOH (pH 9.0) solution. For the visual detection of the I(-) ions by naked eye, and for long time stability of the probe, Au nanoparticles (NPs) decorated mixed cellulose ester membrane (MCEM) was prepared (Au NPs/MCEM). The Au NPs-based probe (CN(-)/Ag(+)-Au NPs/MCEM) operates on the principle that Ag(+) ions form a monolyar silver atoms/ions by aurophilic/argentophilic interactions on the Au NPs and it accelerates the leaching rate of Au atoms in presence of CN(-) ions. However, when I(-) is introduced into this system, it inhibits the leaching of Au atoms because of the strong interactions between Ag/Au ions and I(-) ions. Inductively coupled plasma mass spectrometry, surface-assisted laser desorption/ionization time-of-flight mass spectrometry were used to characterize the surface properties of the Au NPs in the presence of Ag(+) and I(-). Under optimal solution conditions, the CN(-)/Ag(+)-Au NPs/MCEM probe enabled the detection of I(-) by the naked eye at nanomolar concentrations with high selectivity (at least 1000-fold over other anions). In addition, this cost-effective probe allowed the determination of I(-) ions in complex samples, such as urine, seawater, and edible salt samples.
authors.affiliation: Institute of Bioscience and Biotechnology, National Taiwan Ocean University , 2 Beining Road, Keelung, 20224, Taiwan.
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Shen
authors.forename: Pang-Hung
authors.initials: PH
authors.lastname: Hsu
authors.forename: Binesh
authors.initials: B
authors.lastname: Unnikrishnan
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Li
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Huang