含偶氮苯长链脂肪酸浸涂在银镜上的薄膜的激发波长依赖性表面增强拉曼光谱。

Excitation wavelength dependent surface-enhanced Raman spectra of a dipping film of azobenzene-containing long-chain fatty acid on a silver mirror.

作者信息

Jung Young Mee, Sato Hidetoshi, Ikeda Teruki, Tashiro Hideo, Ozaki Yukihiro

机构信息

Department of Chemistry, School of Science and Technology, Kwansei Gokuin University, Sanda, Japan.

出版信息

Spectrochim Acta A Mol Biomol Spectrosc. 2004 Jul;60(8-9):1941-5. doi: 10.1016/j.saa.2003.10.010.

Abstract

Surface-enhanced Raman scattering (SERS) of dipping films of azobenzene-containing long-chain fatty acids, nAmH (n=8, 12, m=3, 5), on silver mirrors measured with a wide range of excitation wavelengths in the 457.9-1064 nm region is reported. The obtained Raman spectra show great SERS effect even with the 1064 nm excitation, and the excitation with 457.9, 476.5, and 488.0 nm gives surface-enhanced resonance Raman scattering (SERRS) due to the resonance effect of the symmetry-forbidden n-pi* transition of the azo group. Of particular note in the present study is that the SERS spectra with the excitation in the 532-1064 nm region yield Raman bands whose frequencies are almost identical to those bands in Raman spectra of nAmH in solid state while the SERRS spectra with the excitation in the 457.9-514.5 nm region show not only a set of bands which correspond to those of nAmH in the solid state but also a set of bands whose frequencies show a significant shift from those of the bands of nAmH in the solid state. These observations lead us to conclude that there are two kinds of molecular aggregates in the dipping films of azobenzene-containing long-chain fatty acid in which azobenzene moieties are condensed to form small bundles.

摘要

报道了在457.9 - 1064 nm区域内,用多种激发波长测量含偶氮苯的长链脂肪酸nAmH(n = 8, 12,m = 3, 5)浸涂膜在银镜上的表面增强拉曼散射(SERS)。即使在1064 nm激发下,所获得的拉曼光谱也显示出很大的SERS效应,而457.9、476.5和488.0 nm的激发由于偶氮基团对称禁阻的n - π*跃迁的共振效应而产生表面增强共振拉曼散射(SERRS)。本研究中特别值得注意的是,在532 - 1064 nm区域激发的SERS光谱产生的拉曼带频率几乎与固态nAmH拉曼光谱中的那些带相同,而在457.9 - 514.5 nm区域激发的SERRS光谱不仅显示出一组与固态nAmH对应的带,还显示出一组频率与固态nAmH的带频率有显著偏移的带。这些观察结果使我们得出结论,含偶氮苯的长链脂肪酸浸涂膜中有两种分子聚集体,其中偶氮苯部分缩合形成小束。

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