Optical waveguide spectrometry of acridine orange in monolayer and Langmuir-Blodgett film
Optical waveguide spectrometry of acridine orange in monolayer and Langmuir-Blodgett film
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DOI：
10.1021/la0112864
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发表时间：
2002-03-05
期刊：
影响因子：
3.9
通讯作者：
Shimomura, M
中科院分区：
文献类型：
--
作者：
Ohno, H;Yoneyama, S;Shimomura, M
采用光波导（OWG）光谱法研究了吖啶橙在单层膜和LB膜中的吸收光谱。十八烷基吖啶橙（C-18-AO）被整合到十八烷基腺嘌呤（C-18-Ade）和十八烷基胸腺嘧啶（C-18-Thy）的堆叠碱基对中，这两种碱基对已知在空气-水界面形成稳定的单层。单层膜的可见吸收光谱是常规光谱法难以获得的，而用OWG光谱法容易得到。C-18-AO的吸光度与沉积在衬底上的单层的数量呈线性关系。这表明单分子膜的定量分析可以用OWG光谱法进行。还可以对LB膜的结构进行定量分析。500nm处的吸光度，这是吖啶橙的一个特征，与衬底上的层数成比例地增加。OWG光谱法的主要优点是可以检测任何底物上分子的吸光度。C-18-AO在500 nm处的吸收随LB膜与波导表面的距离呈指数减小，这是由于倏逝波的强度随距离波导表面的距离呈指数减小。在非接触条件下，当波导与样品板之间的间隙小于0.5 μ m时，获得了可见光谱。
The absorption spectrum of acridine orange in a monolayer or an LB membrane is studied using optical waveguide (OWG) spectrometry. Octadecyl acridine orange (C-18-AO) is incorporated into the stacked base pairs of octadecyl adenine (C-18-Ade) and octadecyl thymine (C-18-Thy), which are known to form a stable monolayer at air-water interfaces. Visible absorption spectra of the monolayer, which are difficult to obtain by conventional spectrometry, are easily generated by OWG spectrometry. A linear relation between the absorbance Of C-18-AO and the amount of monolayer deposited on the substrate was clearly discerned. This suggests that quantitative analysis of the monolayer can be performed by OWG spectrometry. Quantitative analysis can also be made of the structure of LB films. The absorbance at 500 nm, which is a characteristic of acridine orange, increased proportional to the number of layers on the substrate. The principal advantage of OWG spectrometry is in detecting the absorbance of molecules on any substrate. The absorption at 500 nm based on C-18-AO decreases exponentially with the gap between the LB film and the waveguide surface, because the intensity of the evanescent wave falls off exponentially with distance from the waveguide surface. The visible spectra were obtained under noncontact conditions when the gap between the waveguide and sample plate was less than 0.5 mum.