Effect of surface pressure on oxygen transfer across molecular monolayers at the air/water interface: Scanning electrochemical microscopy investigations using a mercury hemispherical microelectrode probe
Effect of surface pressure on oxygen transfer across molecular monolayers at the air/water interface: Scanning electrochemical microscopy investigations using a mercury hemispherical microelectrode probe
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DOI：
10.1021/jp036286m
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发表时间：
2004-03-25
影响因子：
3.3
通讯作者：
Unwin, PR
中科院分区：
文献类型：
--
作者：
Ciani, I;Burt, DP;Unwin, PR
研究分子在液/气界面上的转移动力学和分子单层的作用，作为某些生物和环境过程的模型，具有相当大的兴趣。在这项工作中，使用了扫描电化学显微镜(SECM)-Langmuir槽技术来研究分子单层的化学性质和机械压缩对空气/水（a /W）界面氧传递速率的影响。具体来说，考虑了由脂肪醇1-十八醇和磷脂l - α -双棕榈酰磷脂酸组成的单分子层。汞半球形微电极探针用于测量SECM中的界面动力学，并建立了该配置中质量传递的数值模型，以便对实验数据进行定量分析。结果表明，对于两种单层膜来说，界面上的氧传递速率都比干净界面上的氧传递速率低，并且随着单层膜表面压力的增加，阻塞效应变得更加明显。用一个简单的能垒模型成功地解释了氧转移速率常数与表面压力的关系。实验数据也证明了SECM探头对A/W界面附近水面变形的影响。
Investigations of the kinetics of molecular transfer across the liquid/gas interface and the effect of a molecular monolayer are of considerable interest as a model for certain biological and environmental processes. In this work, a combined scanning electrochemical microscopy (SECM)-Langmuir trough technique has been used to investigate the effect of the chemical character and mechanical compression of molecular monolayers on the rate of oxygen transfer across the air/water (A/W) interface. Specifically, monolayers comprising the fatty alcohol 1-octadecanol and the phospholipid L-alpha-dipalmitoyl phosphatidic acid were considered. A mercury hemispherical microelectrode probe has been used to measure interfacial kinetics in SECM, and a numerical model has been developed for mass transport in this configuration to allow quantitative analysis of experimental data. The results obtained suggest that, for both monolayers, the oxygen-transfer rate across the interface decreased compared to that across the clean interface, with the blocking effect becoming more pronounced as the surface pressure of the monolayer increased. A simple energy-barrier model was used successfully to interpret the dependence of the rate constant of oxygen transfer on the surface pressure. The experimental data also provide evidence for the effect of the SECM probe on the deformation of the water surface at very close distances to the A/W interface.