Quantitating the Balance between Enthalpic and Entropic Forces in Alkanethiol/Gold Monolayer Self Assembly
Quantitating the Balance between Enthalpic and Entropic Forces in Alkanethiol/Gold Monolayer Self Assembly
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DOI：
10.1021/ja961565r
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发表时间：
1996-10
影响因子：
15
通讯作者：
H. M. Schessler;and D. S. Karpovich;G. Blanchard
中科院分区：
文献类型：
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作者：
H. M. Schessler;and D. S. Karpovich;G. Blanchard
我们已经研究了温度和吸附质浓度的依赖性烷基乙醇/金单分子层形成原位和真实的时间使用石英晶体微天平监测反应速率。实验速率常数的温度依赖性，对于一个给定的浓度，表明这些单分子膜的形成是不扩散速率限制的条件下，我们在这里报告。我们的数据精确地模拟了Langmuir吸附等温线，并使用该模型，我们已经确定了单层自组装的吸附和解吸速率常数。我们从这些数据中提取了单层形成的热力学量ΔGads、ΔHads和ΔSads。对于正己烷吸附到金上的1-十八烷乙烷，ΔGads是温度依赖性的，约为。−5.5 kcal/mol，ΔHads = −20 ± 1 kcal/mol，ΔSads = −48 ± 1 cal/（mol·K）。这些数据对更广泛的界面化学领域有直接的影响，因为它们强调了熵在界面化学中的主导作用。
We have studied the temperature and adsorbate concentration dependence of alkanethiol/gold monolayer formation in situ and in real time using a quartz crystal microbalance to monitor the rate of reaction. The temperature dependence of the experimental rate constants, for a given concentration, demonstrates that the formation of these monolayers is not diffusion rate limited for the conditions we report here. Our data are modeled accurately by the Langmuir adsorption isotherm and, using this model, we have determined the adsorption and desorption rate constants for monolayer self assembly. We have extracted from these data the thermodynamic quantities ΔGads, ΔHads, and ΔSads for monolayer formation. For 1-octadecanethiol adsorption from n-hexane onto gold, ΔGads is temperature dependent and is ca. −5.5 kcal/mol, ΔHads = −20 ± 1 kcal/mol, and ΔSads = −48 ± 1 cal/(mol·K). These data have direct bearing on the broader field of interface chemistry because they underscore the dominant role that entropy plays in...