Spectroscopic Study of Water Adsorption and Desorption on/from Oligo(ethylene glycol)-Substituted Alkanethiolate Self-Assembled Monolayers
Spectroscopic Study of Water Adsorption and Desorption on/from Oligo(ethylene glycol)-Substituted Alkanethiolate Self-Assembled Monolayers
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低聚（乙二醇）取代的烷硫醇自组装单分子层上水吸附和解吸的光谱研究
DOI：
10.1021/acs.jpcc.8b02514
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发表时间：
2018
影响因子：
3.7
通讯作者：
Michael
中科院分区：
文献类型：
--
作者：
Mustafa;Nefedov;Alexei;Zharnikov;Michael
用同步加速器X射线光电子能谱和近边X射线吸收精细结构谱研究了不同端基(−OH或−OMe)的低聚乙二醇烷基硫酸酯自组装膜(SAM)对水(D2O)的吸附和温度驱动脱附。监测了D2O的特征光谱特征，其中无定形冰在105-125K吸附并随后升温到脱附温度时具有明显的特征。吸附只发生在SAM表面，第一层(对于羟基端基表面)的光谱模式发生了强烈的扭曲，没有任何迹象表明D2O分子渗透到SAM的水凝胶状OEG部分。冰膜厚度随着D2O剂量的增加而线性增加，对于所有的羟基封端的自组装膜，冰膜的厚度增加的速率是相同的，而对于CH3封端的自组装膜，冰膜的厚度略低。在给定的准静态温升范围内，所有自组装膜在∼150K-155K发生D2O的脱附。NEXAFS谱的特殊特征可以初步解释为水合相的特征，这是由吸附的D2O分子在温度驱动下扩散到自组装膜的水凝胶状OEG部分而形成的。
Adsorption and temperature-driven desorption of water (D2O) on/from the surface of oligo(ethylene glycol) (OEG)-substituted alkanethiolate self-assembled monolayers (SAMs) with a variable length of the OEG segment and variable termination (−OH or −OMe) were studied by synchrotron-based X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The characteristic spectroscopic features of D2O were monitored, with a predominant signature of amorphous ice upon adsorption at 105–125 K and subsequent heating up to desorption temperature. The adsorption occurred exclusively onto the SAM surface, with a strong distortion of the spectral pattern for the first layer (for OH-terminated surfaces) and without any indication for the penetration of the D2O molecules into the hydrogel-like OEG part of the SAMs. The thickness of the ice films increased linearly with the D2O dose with the same rate for all OH-terminated SAMs and a slightly lower rate for the CH3-terminated films. The desorption of D2O in the given quasi-static temperature increase regime occurred at ∼150–155 K for all SAMs studied. Specific features of the NEXAFS spectra could be tentatively interpreted as a signature of a hydration phase, formed by the temperature-driven diffusion of the adsorbed D2O molecules into the hydrogel-like OEG part of the SAMs.