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1.
LB膜的制膜条件优化及其对光学性能的影响   总被引:1,自引:1,他引:0  
通过紫外-可见吸收光谱、二次谐波振荡和稳态荧光的测量,研究了半花菁(DAEP)Langmuir-Blodgett(LB)膜在不同制膜条件(压膜速度、半花菁和花生酸混合、亚相中加入碘离子)下,LB膜样品中半花菁分子的聚集体性质的改变和对非线性光学性能的影响.实验发现,纯半花菁LB膜中分子形成H-聚集体,从而导致吸收峰、荧光峰的蓝移和分子二阶非线性极化率β的减少.分子聚集程度的减少和分子二阶非线性系数β的增加可以通过增大压膜速度、半花菁和花生酸混合、亚相中加入碘离子等方法实现.  相似文献   

2.
采用稳态和时间分辨芝光研究了不同类型的LB多层膜中分子聚集特性。在半花菁/花生酸交替膜中,花生酸层的隔离使得半花菁分子之间的相互作用主要发生在同一层中,形成H形成H聚集体,荧光光谱蓝移;在纯半花菁Y型和Z型膜中,较强的层间相互作用使分子形成J聚集体,导致荧光光谱发生显著红移。  相似文献   

3.
周广朋  韩奎 《光学学报》1997,17(1):1-96
用光学线性和非线性方法研究了Y型半花菁/花生酸交替LB多层膜的光致光学各向异性。在纳秒紫外偏振脉冲激光照射下,LB多层膜中半花菁分子发色团长轴向紫外光偏振方向重新取向。加热可以使LB多层膜平面内各向异性消失及H-聚集体分解。  相似文献   

4.
本文利用不同波段的时间分辨荧光和三维荧光谱对半花菁分子激发态的动力学特性进行了研究。在半花菁/花生酸交替的Y型多层膜中,半花菁分子形成的H-聚集体引起其三维荧光谱蓝移,并且荧光峰随时间的变化逐渐向红光方向移动。由于聚集体内所有分子间的相互作用(耦合)相干叠加,使得LB膜中的半花菁分子的激发态寿命比溶液寿命要短,由激发态较高振动能级向低能级过渡较快,因而不同波段的起始发光时间相差也较小。  相似文献   

5.
研究了不同活性分子(半花菁和氐盐)混合聚集体的形成以及紫外光照射对LB交替多层膜光致荧光(PL)特性的影响。在半花菁和氐盐混合的LB膜中,由于不同分子间较强的相互作用使混合膜的荧光光谱较纯半花菁和氐盐分子膜分别发生了蓝移和红移。利用紫外光照射可以使分子的聚集体部分分解甚至破坏分子的结构,导致光致荧光强度明显减弱。  相似文献   

6.
余靖  刘丽英 《光学学报》1997,17(10):294-1299
用溶胶-凝胶技术制备的掺入半花菁染料的二氧化硅薄膜在不加电场极化条件下,由半花菁分子的自取向导致光学二次谐波产生,定量测得厚度为50nm薄膜的二阶非线性系数x(2)为6.6pm/V,着重研究了薄膜稳定前的溶剂挥发过程中,膜结构的变化以及相应二阶光学非线性的变化,在成膜后的四个小时中,质子化半花菁逐步转化为单体和聚集体态,同时,光学二次谐波信号也不断增大,还观察到在这一过程中出现了单体和聚集态半花菁  相似文献   

7.
利用稳态荧光谱和时间分辨荧光技术研究了温度对半花菁Langmuir-Blodgett(LB)多层膜光致荧光特性的影响.半花菁分子在半花菁/花生酸、半花菁/花生酸镉交替及纯半花菁Z-型LB多层膜中均形成了H-聚集体,加热能使聚集体部分离解.由于Z-型膜中没有花生酸或花生酸镉的屏蔽,分子间具有较强的偶极相互作用,加热使聚集体的离解的程度较小.镉离子的加入对半花菁LB多层膜的稳态荧光谱也有一定的影响.  相似文献   

8.
利用紫外-可见吸收,稳态和时间分辨荧光等方法研究了半花菁与花生酸交替Y型LB膜中分子聚集体的性质;吸收光谱和稳态荧光光谱峰位的蓝移说明LB膜中H聚集体的存在。从荧光衰工线得到了聚集体的组份含量、大小和寿命。  相似文献   

9.
双亲性席夫碱金属配合物LB膜的制备和结构特征   总被引:1,自引:0,他引:1  
合成了双亲性席夫碱配体与Zn^2+,Cd^2+的配合物,用元素分析,红外光谱和紫外光谱对配合物进行了鉴定,以L-B技术得到了层状有序多层膜。LB膜的紫外可见吸收光谱表明膜中分子形成了H-聚集体,且具有特定取向,该膜在紫外光的照射下,膜内配体分子发生的烯醇-醌式结构转变能够提高分子的非线性极化率,该结果有利于这类配合物薄膜材料非线性光学性质研究。  相似文献   

10.
李加  郭玉斌 《光学学报》1995,15(10):346-1350
研究了芪盐在不同表压下制备的LB膜的二阶光学非线性。测量得到在低表压增强的二次谐波信号。对比芪盐的π-A曲线和透射光谱,认为在LB膜中芪盐以固相态存在,低表压时的固相态聚集体的吸收峰351nm使四阶非线性极化率X^(4)(-2ω:ω,ω,ω,-ω)产生共振强,四阶光学非线性现象对二次谐波信号产生影响。  相似文献   

11.
采用紫外可见吸收和二次谐波产生技术研究了“推-拉”型偶氮苯分子Langmuir-Blodgett(LB)膜的光谱和二阶非线性光学特性.4-硝基-4′-氨基偶氮苯(NAA)分子能制成很好的LB多层膜,在稀溶液中以单体的反式异构体形式存在,在膜中主要以J-聚集体的形式存在,LB膜的紫外可见吸收谱的吸收峰较之溶液的发生了52 nm的红移.NAALB膜的二阶非线性极化率χ(2)为19.59×10-8 esu,一阶超极化率β值较大,约为1.974×10-29 esu.其光学二阶非线性起源于电偶极子机制.  相似文献   

12.
The hemifused state on the pathway to membrane fusion   总被引:1,自引:0,他引:1  
Fusion of compartments enclosed by membrane bilayers enables secretion and other vital cellular processes and is widely studied in model synthetic membrane systems. Experiments suggest the fusion pathway passes through a hemifused intermediate where only outer monolayers are fused. Here we show membrane tension and divalent cations drive vesicles to hemifused equilibrium with expanded hemifusion diaphragms (HDs) where inner monolayers engage. Predicted HD sizes agree with recent measurements of Nikolaus et al. [Biophys. J. 98, 1192 (2010).]. The fusion pathway is completed by HD lysis provided HD tension is sufficiently high.  相似文献   

13.
The relative stability and the first and second hyperpolarizabilities of various conformers of four 1,1′-diarylethenylferrocenes have been evaluated at the MP2 computational level. Relative stability on the basis of the minimum polarizability principle is in complete agreement with the conclusion from the minimum energy criterion at the higher computational levels. Since the pi–pi interaction is an attractive force, the conformer with the intramolecular pi–pi interactions belongs to the lowest energy structure and is most likely to be populated. The calculated second hyperpolarizability is in excellent agreement with the experimental data available. There appear two low-energy absorption bands in electronic absorption spectra, where the lower-energy band shifts to the red and is enhanced by molecular distortion. This band is responsible for the largest linear polarizability and second hyperpolarizability of the conformer with inversion symmetry and the magnitude of the latter is dominated by one-photon transition.  相似文献   

14.
A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4′-cyanobiphenyl (8CB) and trans-4-octyl(4′-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates’ geometry was found.  相似文献   

15.
《Surface science》1994,314(1):L849-L856
Ultrathin layers of aminophenylthiol on Cu(100) were prepared by vapour phase deposition of 4,4'-diaminodiphenyldisulphide (DAPS). Composition and molecular orientation in the films were determined by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. DAPS molecules adsorb on Cu(100) by dissociation of the intramolecular S-S bond and the formation of aminophenylthiolate at the copper surface. NEXAFS spectra indicate the presence of well-ordered monolayers with the plane of the phenyl ring tilted by 24° with respect to the surface normal. The same tilt-angle is found in the submonolayer regime.  相似文献   

16.
Meshulam G  Kotler Z  Berkovic G 《Optics letters》2002,27(13):1132-1134
The standard electric-field-induced second-harmonic (EFISH) technique for measurement of the first hyperpolarizability (beta) of nonlinear optical molecules is limited by the fact that the second hyperpolarizability (gamma) also contributes to the second-harmonic signal from which beta is deduced. We present a modified time-resolved EFISH in which the first and the second hyperpolarizabilities can be determined separately and accurately in the same experiment. We studied para-nitro aniline dissolved in a highly viscous solvent, glycerol, under conditions whereby the electric field was applied faster than the characteristic time for molecular rotation. This technique enabled the gamma contribution to the signal to be resolved separately from the beta contribution. The results confirm that for this molecule gamma contributes only ~10% of the total EFISH hyperpolarizability.  相似文献   

17.
The third-order optical nonlinearities of [(CH3)4N]Au(dmit)2 (dmit = 4,5-dithiolate-1,3-dithiole-2-thione) at 532 nm and 1064 nm are investigated using the Z-scan technique with pulses of picoseconds duration. The Z-scan spectra reveal a strong nonlinear absorption (reverse saturable absorption) and a negative nonlinear refraction at 532 nm. No nonlinear absorption is observed at 1064 nm. The molecular second-order hyperpolarizability γ for the [(CH3)4N]Au(dmit)2 molecule at 532nm is estimated to be as high as (2.1 ±0.1) × 10^-31 esu, which is nearly three times larger than that at 1064 nm. The mechanism responsible for the difference between the results is analysed. Nonlinear transmission measurements suggest that this material has potential applications in optical limiting.  相似文献   

18.
采用实时测量光学二次谐波产生(SHG)和吸收光谱的方法对苯腙类有机分子NDA及一种新合成的经氰基团修饰的有机分子CNDA掺杂PMMA极化聚合膜的非线性光学性质进行了研究。实验中发现两种掺杂极化聚合膜的最佳电晕极化温度均低于它们的玻转温度,CNDA/PM-MA极化掺杂聚合膜的χ(2)较NDA/PMMA极化聚合膜的大。结合极化前和极化后吸收峰强度的变化,得到CNDA分子的非线性极化率β约为146×10-30esu。在撤离极化场后,CNDA/PMMA的二次谐波强度的弛豫也比NDA/PMMA的慢  相似文献   

19.
设计了9种4-N-甲基苯乙烯砒啶盐衍生物分子,以密度泛函B3LYP/6-31G方法优化的构型为基础,采用耦合微扰(CPHF)方法研究了体系的非线性光学性质,对体系的电荷布居、吸收光谱及前线分子轨道等性质进行了分析,发现用线性关系对各分子一阶静态超极化率、基态和激发态偶极矩差、激发能及取代基给电子能力之间的关系进行描述是可行的,而且该分子体系的非线性光学响应完全可用二能级模型近似处理.  相似文献   

20.
We present a study on dielectric response of Ag14 nanocluster dimer using first principles methods. The interaction energy, (hyper)polarizability of dimer are predicted under various separations of the two identical Ag14 nanoclusters. The appropriate separation makes the second-order hyperpolarizability of Ag14 dimer is about 70 times larger than the Ag14 monomer. The increase of polarizability and hyperpolarizability is ascribed to reconfiguration of molecular electronic state from Ag cluster monomer to dimer. Nonlinear response is more susceptible to the steady intermediate state compared to linear response. The crucial transitions contributed to hyperpolarizability are assigned to be from highest occupied molecular orbitals to the lowest unoccupied molecular orbital (HOMOs-LUMO) of nanocluster dimer. Binding character of LUMO plays an important role in determining nonlinear optical properties.  相似文献   

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