Riskin Michael, Basnar Bernhard, Katz Eugenii, Willner Itamar
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Chemistry. 2006 Nov 15;12(33):8549-57. doi: 10.1002/chem.200600273.
Hg(2+) ions are bound to a 1,4-benzenedimethanethiol (BDMT) monolayer assembled on a Au electrode. Electrochemical reduction of the Hg(2+)-BDMT monolayer to Hg(+)-BDMT (at E degrees =0.48 V) and subsequently to Hg(0)-BDMT (at E degrees =0.2 V) proceeds with electron-transfer rate constants of 8 and 11 s(-1), respectively. The Hg(0) atoms cluster into aggregates that exhibit dimensions of 30 nm to 2 microm, within a time interval of minutes. Electrochemical oxidation of the nanoclusters to Hg(+) and further oxidation to Hg(2+) ions proceeds with electron-transfer rate constants corresponding to 9 and 43 s(-1), respectively, and the redistribution of Hg(2+) on the thiolated monolayer occurs within approximately 15 s. The reduction of the Hg(2+) ions to the Hg(0) nanoclusters and their reverse electrochemical oxidation proceed without the dissolution of mercury species to the electrolyte, implying high affinities of Hg(2+), Hg(+), and Hg(0) to the thiolated monolayer. The electrochemical transformation of the Hg(2+)-thiolated monolayer to the Hg(0)-nanocluster-functionalized monolayer is characterized by electrochemical means, surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact-angle measurements. The Hg(0)-nanocluster-modified surface reveals enhanced hydrophobicity (contact angle 76 degrees ) as compared to the Hg(2+)-thiolated monolayer (contact angle 57 degrees ). The hydrophobic properties of the Hg(0)-nanocluster-modified electrode are further supported by force measurements employing a hydrophobically modified AFM tip.
汞离子（Hg(2+)）与组装在金电极上的1,4-苯二甲硫醇（BDMT）单层相结合。Hg(2+)-BDMT单层电化学还原为Hg(+)-BDMT（在E° = 0.48 V时），随后再还原为Hg(0)-BDMT（在E° = 0.2 V时），其电子转移速率常数分别为8和11 s(-1)。Hg(0)原子在几分钟的时间间隔内聚集成尺寸为30纳米至2微米的聚集体。纳米团簇电化学氧化为Hg(+)并进一步氧化为Hg(2+)离子，其电子转移速率常数分别对应9和43 s(-1)，Hg(2+)在硫醇化单层上的重新分布在大约15秒内发生。Hg(2+)离子还原为Hg(0)纳米团簇及其反向电化学氧化过程中，汞物种不会溶解到电解质中，这意味着Hg(2+)、Hg(+)和Hg(0)对硫醇化单层具有高亲和力。通过电化学方法、表面等离子体共振（SPR）、X射线光电子能谱（XPS）、扫描电子显微镜（SEM）、原子力显微镜（AFM）和接触角测量对Hg(2+)-硫醇化单层到Hg(0)-纳米团簇功能化单层的电化学转变进行了表征。与Hg(2+)-硫醇化单层（接触角57°）相比，Hg(0)-纳米团簇修饰的表面显示出增强的疏水性（接触角76°）。采用疏水修饰的AFM探针进行的力测量进一步证实了Hg(0)-纳米团簇修饰电极的疏水性质。
