title: Strong inclusion of inorganic anions into β-cyclodextrin immobilized to gold electrode.
abstract: The inclusion of inorganic anions such as SO(4)(2-), NO(3)(-), and HPO(4)(2-) into the cavity of β-cyclodextrin monolayers on Au was examined by X-ray photoelectron spectroscopy (XPS), a quartz crystal microbalance (QCM), and chronocoulometric measurements of the competitive inclusion with ferrocene. The inclusion amounts of ferrocence in 0.2 M Na(2)SO(4), NaNO(3), and Na(2)HPO(4) solutions were less than 6% of the adsorption amount of β-cyclodextrin on Au, resulting in the apparent inhibition of the ferrocene redox reaction. The surface association constants of these anions reached about 10 on a logarithmic scale and were much higher than those for the inclusion of common organic guest compounds. A stronger anion inclusion was also demonstrated by the QCM response corresponding to the replacement of a preincluded organic guest with sulfate upon the injection of the sulfate solution. Quantitative analysis of the XPS data suggested a 1:1 association for each of these anions per surface β-cyclodextrin. There was no detectable inclusion for ClO(4)(-), Cl(-), and Br(-).
authors: Division of Environmental Materials Science, Graduate School of Environmental Science, Faculty of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Yasuhiro
authors: Y
authors: Domi
authors: Kentaro
authors: K
authors: Ikeura
authors: Kazumasa
authors: K
authors: Okamura
authors: Katsuaki
authors: K
authors: Shimazu
authors: Marc D
authors: MD
authors: Porter
mesh_terms: D000838:Anions / Q000737:chemistry; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D013499:Surface Properties; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000838:Anions; D009566:Nitrates; D010710:Phosphates; D013431:Sulfates; D047392:beta-Cyclodextrins; D006046:Gold; C031215:betadex