Sum frequency generation from Langmuir-Blodgett multilayer films on metal and dielectric substrates.
Sum frequency generation from Langmuir-Blodgett multilayer films on metal and dielectric substrates.
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DOI：
10.1021/jp051564y
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发表时间：
2005-09
期刊：
影响因子：
--
通讯作者：
J. Holman;P. Davies;T. Nishida;S. Ye;D. Neivandt
中科院分区：
文献类型：
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作者：
J. Holman;P. Davies;T. Nishida;S. Ye;D. Neivandt
研究了吸附在高非共振磁化率基底（即金）和低非共振磁化率基底（即熔融石英）上的花生酸镉多层膜在空气中 C-H 拉伸区域的和频发生 (SFG) 振动光谱。这些薄膜通过 Langmuir-Blodgett (LB) 沉积形成，并使用 SFG 光谱仪记录其光谱，该光谱仪采用 532 nm 纳秒和 800 nm 飞秒激光器，分别具有反向传播和同向传播的光束几何形状。通过用全氘化十八烷硫醇（金）或全氘化花生酸镉（熔融石英）单层涂覆两种基材，使它们具有疏水性。使用全氘化 10 层薄膜中的单个全质子化花生酸酯层表明，SFG 共振仅来自由偶数个全质子化层组成的 LB 薄膜的最顶层和最下层，尽管来自两个疏水基底的 SFG 光谱彼此不同。沉积在两种类型疏水基底上的相同十层全质子化薄膜的光谱差异已通过解释共振和非共振贡献的简单模型来解释。
Sum frequency generation (SFG) vibrational spectra of cadmium arachidate multilayer films adsorbed on a substrate with high nonresonant susceptibility, i.e., gold, and on a low nonresonant susceptibility substrate, i.e., fused quartz, have been investigated in the C-H stretching region in air. The films were formed by Langmuir-Blodgett (LB) deposition and their spectra recorded using SFG spectrometers employing both 532-nm nanosecond and 800-nm femtosecond lasers, with counter-propagating and co-propagating beam geometries, respectively. Both kinds of substrate were rendered hydrophobic by coating them with per-deuterated octadecanethiol (gold) or per-deuterated cadmium arachidate (fused quartz) monolayers. Single per-protonated arachidate layers in otherwise per-deuterated 10-layer films were used to show that the SFG resonances arise only from the topmost and lowermost layers in a LB film comprised of an even number of per-protonated layers, although the SFG spectra from the two hydrophobic substrates are different from each other. The differences in the spectra from the same ten-layer per-protonated films deposited on the two types of hydrophobic substrate have been explained in terms of a simple model that accounts for resonant and nonresonant contributions.