Understanding Chemical versus Electrostatic Shifts in X-ray Photoelectron Spectra of Organic Self-Assembled Monolayers
Understanding Chemical versus Electrostatic Shifts in X-ray Photoelectron Spectra of Organic Self-Assembled Monolayers
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DOI：
10.1021/acs.jpcc.5b12387
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发表时间：
2016-02-18
影响因子：
3.7
通讯作者：
Zojer, Egbert
中科院分区：
文献类型：
--
作者：
Taucher, Thomas C.;Hehn, Iris;Zojer, Egbert
本文的重点是了解的洞察力，X射线光电子能谱（XPS）测量可以提供研究自组装单分子膜时。比较密度泛函理论计算的实验数据故意选择的模型系统，我们表明，无论是化学环境和静电效应所产生的叠加的分子偶极子影响测得的核心水平的结合能到一个显着的程度。极性自组装单分子膜（SAM）中经常被忽视的静电效应的关键作用是通过改变SAM覆盖率来改变偶极密度。由于这种效应，当从有序有机吸附物层的XP光谱中提取化学信息时必须小心。我们的研究结果，此外，意味着XPS是一个强大的工具，探测局部变化的静电能在纳米系统，特别是在自组装膜。
The focus of the present article is on understanding the insight that X-ray photoelectron spectroscopy (XPS) measurements can provide when studying self assembled monolayers. Comparing density functional theory calculations to experimental data on deliberately chosen model systems, we show that both the chemical environment and electrostatic effects arising from a superposition of molecular dipoles influence the measured core-level binding energies to a significant degree. The crucial role of the often overlooked electrostatic effects in polar self-assembled monolayers (SAMs) is unambiguously demonstrated by changing the dipole density through varying the SAM coverage. As a consequence of this effect, care has to be taken when extracting chemical information from the XP spectra of ordered organic adsorbate layers. Our results, furthermore, imply that XPS is a powerful tool for probing local variations in the electrostatic energy in nanoscopic systems, especially in SAMs.