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通过稳态和时间分辨荧光及二次谐波产生(SHG)的方法研究了2-硝基-5-(N-甲基-N-十八烷基)氨基苯甲酸(NMOB)分子朗缪尔-布罗基特(Langmuir-Blodgett,LB)多层膜的光谱及非线性光学特性。LB膜的稳态荧光谱较溶液红移大。而纯的NMOBY型LB多层膜与NMOB/花生酸交替的LB多层膜之间差别较小;由于分子间的相互作用,使得NMOB分子在溶液中比在LB膜中的荧光衰减时间大。在LB膜中,纯的NMOB和NMOB与花生酸交替的LB多层膜的荧光衰减时间相差不大,说明NMOB分子层内的相互作用较大,而层间的相互作用较小;由于苯环两侧的不对称取代,分子内部形成固有的偶极矩,使得NMOB/花生酸交替的LB多层膜具有较大的宏观偶极矩,因而具有大的二阶非线性极化率,其超分子极化率约为β=4×10-29esu。
The Langmuir of 2-nitro-5- (N-methyl-N-octadecyl) aminobenzoic acid (NMOB) was studied by means of steady state and time resolved fluorescence and second harmonic generation (SHG) Spectroscopic and Nonlinear Optical Properties of a Multilayer Film of Langmuir - Blodgett (LB). The steady-state fluorescence spectrum of LB film is larger than that of solution. However, the difference between pure NMOBY LB multilayer and LB / LBB with alternating NMOB / arachidic acid is small. Due to the intermolecular interactions, the fluorescence decay time of NMOB molecules in solution is larger than that in LB films. In the LB film, the fluorescence decay time of LB multilayer films with pure NMOB and NMOB alternating with arachidic acid shows no significant difference, indicating that the interaction in the NMOB molecular layer is larger but the interaction between layers is smaller; Asymmetric substitution of the two sides leads to the formation of intrinsic dipole moment inside the molecule, which makes the NMOB / arachidic alternating LB multilayers have larger macro dipole moment and thus has a large second-order nonlinear polarizability. The molecular polarizability is about β = 4 × 10-29esu.