Gibbs-Davis Julianne M, Hayes Patrick L, Scheidt Karl A, Geiger Franz M
Department of Chemistry and International Institute for Nanotechnology, Institute for Environmental Catalysis, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
J Am Chem Soc. 2007 Jun 6;129(22):7175-84. doi: 10.1021/ja068117w. Epub 2007 May 11.
We report resonantly enhanced surface second harmonic generation (SHG) measurements to track the interaction of the EPA priority toxic metal pollutant chromium(VI) with fused quartz/water interfaces containing tailor-made amino acids that serve as model systems for environmental and biological interfaces. chi3 measurements of amido acid functionalized fused quartz/water interfaces are consistent with two acid-base equilibria, suggesting the formation of a laterally hydrogen-bonded environment similar to what is observed for aliphatic carboxylic acids. Chromate adsorption isotherms recorded at pH 7 are suggestive of an intramolecular chelation mechanism that becomes important when four or more hydrogen-bonding moieties are displayed toward the incoming chromate. The strong binding affinities of the amido acid functionalized fused quartz/water interfaces toward chromate are consistent with nearly 50% slower transport rates with respect to free-flowing groundwater, indicating that, in the absence of redox processes, peptide materials in heterogeneous geochemical environments can significantly increase chromate residence times. The strong evidence for synergistic effects dominating the interactions of chromate with surface-bound amido acids indicates that chemical complexity can be systematically addressed using tailor-made organic surfaces and interfaces.
我们报告了共振增强表面二次谐波产生（SHG）测量结果，以追踪美国环境保护局（EPA）优先有毒金属污染物铬（VI）与含有特制氨基酸的熔融石英/水界面之间的相互作用，这些界面作为环境和生物界面的模型系统。对氨基酸功能化的熔融石英/水界面进行的三阶非线性光学极化率（χ³）测量结果与两种酸碱平衡一致，这表明形成了类似于脂肪族羧酸中所观察到的横向氢键环境。在pH值为7时记录的铬酸盐吸附等温线表明存在一种分子内螯合机制，当四个或更多氢键部分朝向进入的铬酸盐时，这种机制变得很重要。氨基酸功能化的熔融石英/水界面与铬酸盐之间的强结合亲和力与相对于自由流动的地下水近50%的较慢传输速率一致，这表明在没有氧化还原过程的情况下，非均相地球化学环境中的肽材料可显著增加铬酸盐的停留时间。铬酸盐与表面结合的氨基酸之间相互作用以协同效应为主导的有力证据表明，利用特制的有机表面和界面可以系统地解决化学复杂性问题。
