Spontaneous emission properties of organic film in plane optical microcavity

The spontaneous emission properties of a single layer organic film in plane optical microcavities were studied. Optical microcavity was formed by a Tris(8-quinolinolato) aluminium (Alq) film sandwiched between a distributed Bragg reflector (DBR) and a Ag metallic reflector. Two kinds of microcavities were devised by using a different DBR structure. Compared with a Alq film, significantly spectral narrowing and intensity enhancement was observed in the two microcavities, which is attributed to the microcavity effect. The spectra characteristics of the two microcavities showed that the structure of DBR has much influence on the emission properties of a microcavity. (C) 2000 Elsevier Science S.A. All rights reserved.

Calculation of second-order nonlinear optical coefficients of KTiOPO4 and KTiOAsO4

The second-order nonlinear optical tensor coefficients of both KTiOPO4 (KTP) and KTiOAsO4 (KTA) are calculated from the chemical bond viewpoint. All constituent chemical bonds of both crystals are considered, and contributions of each type of bond to the total linearity and nonlinearity are determined. Calculated results agree satisfactorily with experimental data in both signs and numerical values. The calculation shows that though TiO6 groups and P(1)O-4 or As(1)O-4 groups have relatively larger linear contributions, they can only produce an advantageous environment for KOx (x = 8, 9) groups and P(2)O-4 or As(2)O-4 groups in nonlinear optical contributions. The origin of nonlinearity of KTP family crystals comes from the KOx (x = 8, 9) and P(2)O-4 groups in their crystal structures. Furthermore, the difference in optical nonlinearities of KTP type crystals is analyzed, based on the detailed calculation of nonlinearities of both KTP and KTA. (C) 1999 Academic Press.

Thermally stable interpenetrating polymer networks for second-order nonlinear optical materials

We report several kinds of interpenetrating polymer networks (IPNs) with nonlinear optical (NLO) properties. DMA spectra show that the two components of the IPNs have good compatibility with each other. The NLO materials have good optical transparency. The thermal stability of alignment was improved and the poled order remained very high. (C) 1999 John Wiley & Sons, Inc.

Structure and order of the discotic compound 2,3,6,7,10,11-hexakispentyloxytriphenylene as revealed by diffraction and molecular simulation studies

The aggregate structure of the discotic compound 2,3,6,7,10,11-hexakispentyloxytriphenylene (HPT) was studied both for the crystalline state and the liquid crystalline state by using electron crystallography and a molecular simulation approach. In the crystalline state, HPT was found to adopt an orthorhombic P-2212 space group with cell parameters a = 36.73 Angstrom, b = 27.99 Angstrom and c = 4.91 Angstrom. Molecular packing calculations were conducted to elucidate the molecular conformation and mutual orientational characteristics in the different states. Phase transitions and relationships are discussed from a structural point of view.

Spontaneous assembly of the inclusion complexes of viologen-attached alkanethiols and alpha-, beta-cyclodestrin on gold electrode

Electroactive self-assembled monolayers (SAMs) with well-defined electrochemical responses were prepared by spontaneous assembly of the inclusion complexes (CD/C8VComegaSH) of viologen-attached alkanethiols (C8VComegaSH) and alpha- and beta-cyclodextrin (CD). They were characterized by X-ray photoelectron spectroscopy and cyclic voltammetry. The results demonstrate that the chemisorption process of CD/C8VComegaSH on gold substrate occurs through S-Au bonds, and that the redox sites in SAMs of CD/C8VComegaSH are in a much more uniform environment than those in SAMs of C8VComegaSH.

Study of molecular order in organo-soluble polyimide thin films

The changes in refractive indices (n(TE) and n(TM)) in a direction normal to the plane of thin films of an organo-soluble polyimide based on 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride and 2,2'-dimethyl-4,4'-methylene dianiline were measured by a prism coupler. The results implied that the molecules near the substrate-polyimide interface were much ordered, while those near the polyimide-air interface were less ordered, judging from the variation in the level of negative birefringence with the depth of the films. The molecules are more condensed near the substrate surface, as seen by the average refractive index increasing from the polyimide-air interface to the substrate-polyimide interface, which implies that the condensed states of polyimide molecules change gradually in the depth direction. (C) 1997 Elsevier Science B.V.

Effect of crystal-disrupting chlorohydroquinone on the first-order transitions of poly(aryl ether ketone)s containing biphenyl units

The novel poly(aryl ether ketone)s were synthesized by nucleophilic substitution reactions of 4,4'-difluorobenzophenone with 4,4'-biphenyldiol and chlorohydroquinone. As expected, the copolymers have lower melting transitions than the biphenyldiol-based homopoly(aryl ether ketone) because of the copolymerization effect of the crystal-disrupting monomer chlorohydroquinone. Copolymers containing 50 and 70% biphenyldiol show two first-order transitions which are associated with the crystal-to-liquid crystal transition and the liquid crystal-to-isotropic transition.

A ZINDO-SOS study on the nonlinear second-order optical properties of substituted silanes series molecules

On the basis of ZINDO methods,according to the sum - over - states( SOS) expression, we divise the program for the calculation of nonlinear second - order optical susceptibilities beta(ijk) and study how the different substituents on the phenyl ring attached to the atom silicon influence or; the nonlinear second - order optical properties for substituted silanes series molecules. The property of (CH3)(3)Si is Studied particularly. The effect of length of silica chains on the calculated beta values is studied too. The regularity summarized from calculated results has been explained micromechanically.

A theoretical study on the nonlinear optical second-order properties of azobenzene series molecules

On the basis of AM1 and INDO/CI methods, we devise the program for the calculation of nonlinear second-order optical susceptibilities beta(ijk) and perform systematic theoretical studies on the nonlinear optical second-order properties of azobenzene series molecules, i. e. on the basis of [GRAPHICS] we induced different donors on the left side of phenyl ring, and different accepters on the right side of phenyl ring, and examined the rule of beta variation. The regularity summarized from the calculated results has been explained micromechanically. Finally, a molecule having a big nonlinear second-order optical susceptibility has been designed.

SYNTHESIS OF CROSS-LINKED 2ND-ORDER NONLINEAR-OPTICAL POLYMERS WITH HIGH T-G

Synthesis and characterization of a diamino dihydroxyl azo compound were reported, The crosslinking reaction process of the diamino dihydroxyl azo compound with the biuret of hexamethylene diisocyanate was studied by FTIR, The glass transition temperatures of crosslinked polymers were measured by DSC, The orientation and oriented stability of crosslinked and poled polymers were studied by UV-Vis spectra.

SYNTHESIS AND CHARACTERIZATION OF CROSS-LINKED 2ND-ORDER NONLINEAR-OPTICAL POLYMER

The present paper reports the synthesis of glycidyl monoether of 4-[(p-nitrophenyl) azo] phenol (GMNA) and crosslinking reaction of GMNA with hexamethylene diisocyanate biuret (HDIB). The Tg of crosslinked polymer was investigated by DSC. The orientation and stability of the poled and crosslinked polymer film were studied by UV-Vis spectra and Maker fringe method.

THE APPLICATION OF ULTRAMICROELECTRODE IN HOMOGENEOUS CATALYTIC REACTION .5. ELECTROCHEMICAL-BEHAVIOR OF MACRO-MICRO-MACRO TRIPLE AND MICRO-MICRO TWIN ELECTRODES AND THE QUASI-FIRST-ORDER HOMOGENEOUS CATALYTIC REACTION (EC') AT GENERATION/COLLECTION ELECT

A new type of macro-micro-macro triple electrode has been fabricated, the steady-state currents of solution redox species have been observed at an ultramicroband electrode by linear potential scan voltammetry, and generation/collection experiments have al

APPLICATION OF ULTRAMICROELECTRODES IN STUDIES OF HOMOGENEOUS CATALYTIC REACTIONS .2. A THEORY OF QUASI-1ST AND 2ND-ORDER HOMOGENEOUS CATALYTIC REACTIONS

The analytical expressions of quasi-first and second order homogeneous catalytic reactions with different diffusion coefficients at ultramicrodisk electrodes under steady state conditions are obtained by using the reaction layer concept. The method of treatment is simple and its physical meaning is clear. The relationship between the diffusion layer, reaction layer, the electrode dimension and the kinetic rate constant at an ultramicroelectrode is discussed and the factor effect on the reaction order is described. The order of a catalytic reaction at an ultramicroelectrode under steady state conditions is related not only to C(Z)*/C(O)* but also to the kinetic rate constant and the dimension of the ultramicroelectrode; thus the order of reaction can be controlled by the dimension of the ultramicroelectrode. The steady state voltammetry of the ultramicroelectrode is one of the most simple methods available to study the kinetics of fast catalytic reactions.

APPLICATION OF ULTRAMICROELECTRODES IN STUDIES OF HOMOGENEOUS CATALYTIC REACTIONS .3. THE CONDITION FOR QUASI-1ST AND 2ND-ORDER HOMOGENEOUS CATALYTIC REACTIONS AT ULTRAMICRODISK ELECTRODES IN THE STEADY-STATE

The conditions for quasi-first and second order homogeneous catalytic reactions and their variation with each other at an ultramicrodisk electrode in the steady state are discussed in this paper. The order of reaction can be controlled by changing the dimension of the ultramicroelectrode: the second order reaction can be changed to quasi-first by decreasing the dimension of the ultramicroelectrode. An example of this is given. The main factor effect on the reaction order is the dimension of the ultramicroelectrode. The K4Fe(CN)6-aminopyrine system is selected to confirm the theory, the experiments showing that the system is a second order reaction at a 432 mum microelectrode, and a quasi-first order reaction at a 19 mum ultramicroelectrode. The kinetic constant of the system can be determined by applying the previous theory of homogeneous catalytic reaction.