Detachment behavior of Langmuir-Blodgett films of arachidic acid from a gold surface studied by the quartz crystal microbalance method
Detachment behavior of Langmuir-Blodgett films of arachidic acid from a gold surface studied by the quartz crystal microbalance method
复制标题
石英晶体微天平法研究花生酸 Langmuir-Blodgett 薄膜从金表面的脱离行为
DOI：
10.1016/s0927-7757(01)00856-1
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
M. Tagawa
中科院分区：
文献类型：
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作者：
K. Gotoh;M. Tagawa
利用石英晶体微天平（QCM）和Langmuir-Blodgett （LB）技术构建的模型系统，研究了含油污染物从金表面的剥离过程。以长链脂肪酸花生酸为模型油类污染物。通过垂直浸渍法将花生酸在水中的固体浓缩单层转移到QCM上。各浸提周期下QCM的频率变化表明，单层膜成功沉积在QCM的金表面，形成y型多层膜。在含有氯化钠、氢氧化钠、表面活性剂和/或乙醇的水溶液中应用超声波清洗具有花生四烯酸LB膜的QCM。表面活性剂为十二烷基硫酸钠（SDS）和正辛基β-d-葡萄糖苷（OGP）。通过分离引起的QCM频率变化来评价LB膜与金表面的分离效率。效率随时间增加而增加，在20 ~ 30 min达到饱和。发现分离随着氢氧化钠、SDS、OGP和乙醇浓度的增加而增加。在SDS和OGP的临界胶束浓度下，或在约50%的乙醇浓度下，LB膜从金表面完全去除。通过实验确定的接触角和表面自由能，可以计算出LB膜与金表面之间由于液体渗透而产生的自由能变化。花生酸在碱作用下的皂化作用和液体的渗透作用是导致LB膜脱落的主要原因。在超声洗涤前，用172nm紫外准分子光照射对LB膜的去除是有效的。
The detachment process of an oily contaminant from a gold surface was investigated using a model system constructed by the application of the quartz crystal microbalance (QCM) method and the Langmuir–Blodgett (LB) technique. Long-chain fatty acid, arachidic acid, was used as a model oily contaminant. The solid-condensed monolayers of arachidic acid on water were transferred onto the QCM by the vertical dipping method. The frequency change of the QCM at each immersion–withdrawal cycle indicated that the monolayers were successfully deposited on the gold surface of the QCM as Y-type multilayers. The QCM having the LB films of arachidic acid was cleaned in aqueous solutions containing sodium chloride, sodium hydroxide, surfactants and/or ethanol by applying ultrasonic waves. Surfactants used were sodium dodecyl sulfate (SDS) and n-octyl β-d-glucopyranoside (OGP). The detachment efficiency of the LB films from the gold surface was evaluated from the frequency change of the QCM due to the detachment. The efficiency increased with time and showed saturation at 20–30 min. The detachment was found to increase with increasing concentrations of sodium hydroxide, SDS, OGP, and ethanol. At the critical micelle concentrations of SDS and OGP or at ca. 50 vol.% of ethanol, the LB films were perfectly removed from the gold surface. The detachment efficiencies obtained in all systems were correlated with the free energy change due to liquid penetration between the LB films and the gold surface, which was calculated from the experimentally determined contact angles and surface free energies. The saponification of arrachidic acid by alkali as well as the liquid penetration was found to contribute to the detachment of the LB films. The exposure of the 172 nm ultraviolet excimer light prior to the ultrasonic washing was effective for the removal of the LB films.