Molecular assembled self-doped polyaniline interlayer for application in polymer light-emitting diode

Self-doped polyaniline (SPANI) ultrathin films were prepared by using a self-assembly process consisting of a self-doping monomer (o-aminobenzenesulfonic acid, SAN) and aniline (AN). SAN-AN copolymerization and film formation were simultaneously performed in aqueous solution. An immersing self-assembly method was developed to build up a SPANI nanofilm on an ITO glass, providing a hole injection layer in a double-layer electroluminescence (EL) device ITO/SPANI nanofilm//MEH-PV//Ca/Al. This device produces an orange EL as compared with a single-layer EL device of ITO//MEH-PV//Ca/Al. A double-layer device demonstrates that a SPANI film is capable of transporting holes in a polymer light-emitting diode (PLED).     

Development of an optical ammonia sensor based on polyaniline/epoxy resin (SU-8) composite

Polyaniline (PANI)/glycidyl ether of bisphenol A (SU-8) composite film is elaborated in order to detect ammonia gas. These composite films are characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The sensitivity to ammonia is measured by optical absorption changes. The ammonia sensing properties of PANI/SU-8 composite films are studied, and then are compared to pure PANI films elaborated by chemical way. Experimental results show that the PANI/SU-8 optical sensor has simultaneously a rapid response to ammonia gas and regenerates easily, that is advantageous compared to pure PANI films.     

Two liquid adsorptive entrapment of a pluronic polymer into the surface of polyaniline films

Pluronic triblock copolymers were entrapped on the surface of polyaniline (PANI) films by first immersing the latter in N-methylpyrrolidinone (NMP) solutions of one of the Pluronics for a short time. This softened the surface of the films and allowed the Pluronic molecules to entangle with PANI segments of the swollen film on the surface. Further, the films were taken out from the NMP solution and dipped into water, which is a nonsolvent for PANI. The rapid surface deswelling of PANI by the water resulted in the entrapment of the Pluronic on its surface, with the hydrophilic blocks toward water and the hydrophobic block imbedded in the PANI films. The modified PANI obtained was examined by X-ray photoelectron spectroscopy, water droplets contact angles, scanning electron microscopy, and wide angle X-ray diffraction. The surface of the Pluronic entrapped PANI films became more hydrophilic than the hydrophobic PANI films and decreased the amount of bovine serum albumin protein adsorbed on them. This means that, by reducing the biofouling, the life of the modified polyaniline film can be extended when the latter is employed as a biosensor.     

纳米纤维聚苯胺膜在不锈钢电极表面的生长过程

研究了脉冲电流法(PGM)聚合苯胺时, 纳米纤维聚苯胺(PANI)膜在不锈钢(SS)电极表面的生长过程. 用计时电位法和扫描电子显微镜(SEM)表征了聚苯胺生长过程的电化学特征和微观形貌; 并通过循环伏安(CV)法研究了苯胺的聚合速率. 结果表明, 聚苯胺的生长经历了两个阶段, 首先是在裸不锈钢电极表面上形成颗粒状聚苯胺, 此时聚合电位约为1.10 V, 经历了30 s后, 电极表面被一层颗粒状聚苯胺膜所覆盖; 在此基础上, 聚苯胺以纳米纤维状结构继续生长, 当颗粒状聚苯胺被纳米纤维状聚苯胺膜完全覆盖时, 聚合电位降至0.75 V左右并保持稳定.     

聚苯胺电致变色薄膜在不同颜色区间的电化学循环稳定性研究

本文采用电位阶跃和循环伏安法结合紫外可见光光度法研究了聚苯胺薄膜的电致变色性质. 聚苯胺薄膜颜色多变,颜色在浅黄色到绿色再到蓝色之间变化,本文研究在不同的颜色变化区间内聚苯胺薄膜的电化学循环稳定性. 研究结果表明,薄膜在黄色到蓝色(0.4 V ~ 1.2 V)以及绿色到蓝色(0.8 V ~ 1.2 V)区间变化时,电致变色循环性能较差,而在黄色和绿色(0.4 V ~ 0.8 V)之间变化时循环稳定性能良好,着色时间为4.5 s,着色效率高达159.48 cm²·C^-1.     

Polyaniline film deposition from the oxidative polymerization of aniline using K2Cr2O7

The deposition of the polyaniline (PANI) films was monitored using the quartz crystal microbalance (QCM) technique. The films were grown from an aqueous dilute hydrochloric acid solution by the chemical oxidation of aniline using potassium dichromate (KDC). The effect of the initial molar ratio of the KDC/aniline on the yield and the growth rate of the PANI films were studied. There is no optimum initial molar ratio of KDC/aniline of PANI film deposition. Also there was a small depletion period and no degradation to the deposited PANI films. The order of the polymerization kinetics was studied with respect to KDC. The UV-visible spectra of the PANI films grown onto a glass support immersed into the bulk solution were measured. The absorption of the PANI film with the time of polymerization was compared to the growth of the PANI film thickness with time determined from the QCM technique. The characteristics of the PANI film deposition were compared to the corresponding ones that were observed during the oxidative polymerization of aniline with ammonium persulphate (APS).     

Ag-PVA和Ag-PVA/TiO2复合超薄膜的制备及性能研究

用3种方法制备了银纳米粒子-聚乙烯醇复合体系,其中用加热还原法所得体系中Ag纳米粒子的尺寸较大(15nm),其表面等离子体共振吸收峰较宽,最大吸收波长位于420nm;用室温硼氢化钠还原法得到的复合体系的吸收峰蓝移至409nm,且峰形较窄,Ag纳米粒子的平均粒径为8.7nm;低温NaBH4还原法所得体系吸收峰进一步蓝移至397nm,此时Ag纳米粒子粒径最小(3.5nm).将室温还原法所得Ag-PVA复合体系旋涂成膜,所得薄膜光滑、透明、均匀性好,该法适用于制备多层薄膜,以调控薄膜的厚度和光谱性质.将Ag-PVA复合体系与钛酸四丁酯(Ti(O_nBu)₄)的乙醇溶液交替旋涂得到Ag-PVA/TiO₂有机/无机复合薄膜.紫外-可见吸收光谱研究表明,随着Ag-PVA层数的增加,薄膜的表面等离子体共振吸收强度呈线性增加,但是TiO₂层数的增加对吸收光谱没有明显影响.Ag-PVA/TiO₂有机/无机复合薄膜将金属纳米粒子、有机高分子与无机半导体材料结合在一起,这种多层纳米结构在光电、催化功能薄膜等方面具有潜在的应用前景.     

铂粒子修饰单壁碳纳米管/聚苯胺复合膜对甲醛的电催化氧化

在溶有单壁碳纳米管(SWNTs)的苯胺溶液中, 通过电化学共聚合法成功制备了单壁碳纳米管(SWNT)/聚苯胺(PANI)复合膜. 用电沉积法将铂沉积到SWNT/PANI复合膜上. 样品的成分和形貌分别用XRD和SEM表征. 四探针和电化学交流阻抗的研究表明被PANI包裹的SWNTs整齐地排列在复合膜中, 从而提高了复合膜的电导率, 促进了电荷转移. 循环伏安(CV)说明Pt修饰的SWNT/PANI复合膜对于甲醛氧化具有良好的电催化活性及稳定性. 研究结果表明SWNT/PANI复合膜是一种非常好的催化剂载体, 有着广泛的应用前景.     

Active sol–gel thin film on nanostructured plasmonic surface

Sol–gel hybrid films based on alkyl bridged polysilsesquioxanes and doped with phenol red molecules, were synthesized for sensing purposes. Doped films changes colour from yellow to orange to red when exposed to hydrochloric acid (HCl) both in solution and gas phases. The synthesis was optimized in order to produce porous films after spin coating. The porosity increases reacting surface area and chemical reactivity of the sensing thin film. Porosity, optical and structural characterizations of these films were investigated by transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Spectroscopic Ellipsometry (SE). Variation of optical characteristics upon immersion of the film in the solution was characterized by UV–visible (UV–vis) spectroscopy. Moreover the same porous sensitive hybrid film was deposited on gold sinusoidal grating in order to detect variations of the dielectric film optical constant after HCl solution dip. This variation was revealed by monitoring surface plasmon polariton excitations.     

Optical switching of azobenzene sidechain molecules observed by surface plasmon spectroscopy

The use of surface plasmons is reported for the optical characterization of thin organic films, in particular thin polymer films at a metal dielectric interface. The basic properties of PSP are presented, including excitation and the technique of surface plasmon microscopy, which allows to obtain an image. As an example studies are presented on the trans-cis photoisomerization of azobenzene sidechain polymers in ultra thin films, prepared by the Langmuir-Blodgett-Kuhn technique. The transition from the trans to the cis state induces a change in the refractive index of the film. These changes were detected and their kinetics measured by a surface plasmon spectroscopy technique. A refractive index pattern could be written into the films and the areas of different refractive indices have been detected by surface plasmon microscopy.     

负偏压下Ag@AgBr/Ni膜电极光电催化降解罗丹明B的性能和机理

用电化学方法制备Ag@AgBr/Ni表面等离子体薄膜电极,以扫描电子显微镜（SEM）、X射线衍射（XRD）和紫外-可见漫反射光谱（UV-Vis DRS）对薄膜的表面形貌、晶相结构、光吸收特性进行了表征,在负偏压和可见光作用下,以罗丹明B为模拟污染物对薄膜的光催化活性和稳定性进行了测定,采用电化学技术和向溶液中加入活性物种捕获剂的方法对薄膜光电催化降解机理进行了探索。结果表明：最佳工艺下制备的Ag@AgBr/Ni膜电极是由表面沉积纳米Ag的纳米晶AgBr颗粒构成的薄膜,具有显著的表面等离子共振效应。薄膜具有优异的光电催化活性和良好的催化稳定性,在最佳负偏压和可见光照射下反应12 min,薄膜光电催化罗丹明B（c=5 mg·L^-1）的降解率是多孔TiO₂（P25）/ITO纳米薄膜的10.2倍。相对于未加偏压的光催化,降解率提高了2.0倍;在保持薄膜光催化活性基本不变的前提下可循环使用5次。电极表面纳米Ag粒子的等离子体共振对于光阴极反应（价带反应）的活化作用是光电催化活性提高的重要原因。提出了负偏压下Ag@AgBr/Ni表面等离子体薄膜光电催化降解罗丹明B的反应机理。     

负偏压下Ag@AgBr/Ni膜电极光电催化降解罗丹明B的性能和机理

用电化学方法制备Ag@Ag Br/Ni表面等离子体薄膜电极,以扫描电子显微镜(SEM)、X射线衍射(XRD)和紫外-可见漫反射光谱(UV-Vis DRS)对薄膜的表面形貌、晶相结构、光吸收特性进行了表征,在负偏压和可见光作用下,以罗丹明B为模拟污染物对薄膜的光催化活性和稳定性进行了测定,采用电化学技术和向溶液中加入活性物种捕获剂的方法对薄膜光电催化降解机理进行了探索。结果表明:最佳工艺下制备的Ag@Ag Br/Ni膜电极是由表面沉积纳米Ag的纳米晶Ag Br颗粒构成的薄膜,具有显著的表面等离子共振效应。薄膜具有优异的光电催化活性和良好的催化稳定性,在最佳负偏压和可见光照射下反应12 min,薄膜光电催化罗丹明B(c=5 mg·L~(-1))的降解率是多孔Ti O2(P25)/ITO纳米薄膜的10.2倍。相对于未加偏压的光催化,降解率提高了2.0倍;在保持薄膜光催化活性基本不变的前提下可循环使用5次。电极表面纳米Ag粒子的等离子体共振对于光阴极反应(导带反应)的活化作用是光电催化活性提高的重要原因。提出了负偏压下Ag@Ag Br/Ni表面等离子体薄膜光电催化降解罗丹明B的反应机理。     

Confinement of polyaniline chains in capillary layers: an ordering effect of the uniaxially aligned surfaces

An ordering effect of uniaxially aligned poly(tetrafluoroethylene) (PTFE) substrates prepared by rubbing on polyaniline (PANI) molecules at the interfaces of PTFE/PANI film and PTFE/PANI solution has been investigated using electronic absorption spectroscopy. It was observed slight dichroism in electronic spectra from only very thin (thickness approximately 20 nm and less) PANI films as well as from PANI solutions of capillary thickness (10 to 30 microm) confined by oriented PTFE surfaces. The ordering effect is discussed in terms of a hydrodynamic flow arising upon sample formation and steric factors at the PTFE surface, which cause uniaxial deformation of the polymer coil on the rubbed PTFE surface.     

Theoretical analysis of gold-deposited optical fiber sensor and characterization of the gold film.

Gold-deposited optical fiber sensors with film thicknesses from 30 to 60 nm were prepared, and the responses to a wide range of a refractivity (1.33-1.54 refractive index (RI) units) were investigated both experimentally and theoretically. The response curve of the sensor has two minima in the refractivity range from 1.33 to 1.44 and at 1.462 RI units. The former minimum is due to surface plasmon resonance (SPR) in the thin gold film, and shifts to a lower refractivity as the film becomes thicker. The response curves of the sensors with film thicknesses of 45 and 60 nm agreed well with those calculated from SPR theoretical equations. Morphology observations of the surfaces of deposited gold films on glass by atomic force microscopy (AFM) and a variation in resistance of the films with various thicknesses show the structure of the gold films. We concluded that the thin deposited gold films have many defects, and that the core of the gold-deposited optical fiber leaks light through the defects to the sample solution with the same refractivity (1.462 RI units) as that of the core.     

Conducting polymer films fabricated by oxidative graft copolymerization of aniline on poly(acrylic acid) grafted poly(ethylene terephthalate) surfaces

A conductive polyaniline/poly(ethylene terephthalate) (PANI/PET) composite film was fabricated via the oxidative graft copolymerization of aniline (ANI) onto the plasma-induced poly(acrylic acid) (PAAc) grafted PET surface. The attenuated total reflectance Fourier transform infrared spectroscopy spectra (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed that PANI was successfully grafted onto the surface of the PAAc-g-PET films. The effects of the experimental conditions on the percentage of PANI grafted onto the PAAc-g-PET films were extensively investigated. A very high grafting percentage of ANI can be obtained through the acid-base reaction between the aniline monomer and PAAc on the PAAc-g-PET surface at high temperature. As a result, the grafting percentage of PANI can be increased to as high as 12.18 wt %, which causes the surface resistance of the PANI-g-PAAc-g-PET film to be reduced to about 1000 Omega/sq. We predicted that this is because of the high flexibility of the PAAc molecular chains and high solubility of aniline, both of which facilitate the binding of aniline to PAAc during this high temperature acid-base reaction. It was observed by atomic force microscopy (AFM) that the PANI-modified PET surface exhibits higher size irregularity and surface roughness, which further indicated that a much greater number of aniline molecules can be reactively bonded to and distributed along the grafted AAc chains and that the PANI-g-PAAc-g-PET surface resulting from the sequential oxidative graft copolymerization can possess higher electrical conductivity.     

Tailoring the refractive indices of thin film polymer metallic nanoparticle nanocomposites

We demonstrate how to tailor the spatial distribution of gold nanoparticles (Au-NPs) of different sizes within polystyrene (PS) thin, supported, film hosts, thereby enabling the connection between the spatial distribution of Au-NPs within the polymer film and the optical properties to be determined. The real, n, and imaginary parts, k, of the complex refractive indices N = n(λ)+ik(λ) of the nanocomposite films were measured as a function of wavelength, λ, using multivariable angle spectroscopic ellipsometry. The surface plasmon response of films containing nearly homogeneous Au-NP distributions were well described by predictions based on classical Mie theory and the Drude model. The optical spectra of samples containing inhomogeneous nanoparticle distributions manifest features associated with differences in the size and interparticle spacings as well as the proximity and organization of nanoparticles at the substrate and free surface.     

ZnO-聚苯胺复合膜的制备和性能研究

利用溶胶-凝胶法在Au膜、聚苯胺膜(PANI)和ITO(导电玻璃)基体上制备ZnO纳米微粒膜,初步研究了该微粒膜的形貌,结构和紫外-可见吸收等性质.结果表明,PANI的孔洞结构抑制了ZnO颗粒的团聚,因此,ZnO-PANI复合膜的紫外-可见吸收光谱和荧光光谱相对于ZnO-Au微粒膜有一定程度的蓝移.光电流谱研究同时表明,ZnO-聚苯胺复合膜有望在光电化学方面得到应用.     

Fabrication of metal nanoparticle monolayers on amphiphilic poly(amido amine) dendrimer Langmuir films

A newly designed 1.5th generation poly(amido amine) dendrimer with an azacrown core, hexylene spacers, and octyl terminals was spread on gold nanoparticle (Au-NP) suspension. The surface pressure-area isothermal curves indicated that the molecular area of dendrimer on Au-NP suspension was significantly smaller than that on water, indicating the formation of dendrimer/Au-NP composites. The dendrimer Langmuir films on the Au-NP suspension were transferred to copper grids at various surface pressures and observed by transmission electron microscopy. The transferred films consisted of a fractal-like network of nanoparticles at low surface pressure and of a defect-rich monolayer of nanoparticles at high surface pressure. From these results, it was suggested that the dendrimers bind Au-NPs, and dendrimer/Au-NP composites formed networks or monolayers at the interface. From the intensity decrease of the Au plasmon band of Au-NP suspension after the formation of composite, it was estimated that some (approximately 14) dendrimer molecules bind to one Au-NP. Furthermore, neutron reflectivity at the air/suspension interface and X-ray reflectivity of the film transferred on a silicon substrate revealed that the dendrimer molecules are localized on the upper-half surface of Au-NP. Metal affinity of azacrown, flexibility of hexylene spacer, and amphiphilicity of dendrimer with octyl terminals played important roles for the formation of dendrimer/Au-NP hybrid films. The present investigation proposed a new method to fabricate the self-assembled functional polymer/nanoparticle hybrid film.     

Surface-enhanced Raman scattering on silver nanostructured films prepared by spray-deposition

Silver nanostructured films were directly prepared by spray deposition of preformed polyol-based Ag-PVP nanoparticles. These homogeneous films of high optical quality were tested as SERS-active substrates. Laser excitation at 514.5 nm within the red part of the plasmon band leads to intense and reproducible SERS spectra of acridine, used as the probe molecule. From SERS measurements at different pH values, it was possible to determine the apparent pK(a) of acridine and to obtain specific surface properties of the film. Finally, these SERS titrations along with enhancement factor estimates allowed us to further depict the nature of the films.     

Novel optical techniques for the analysis of polymer surfaces and thin films

Summary We report on novel optical techniques, based on evanescent waves, for the characterization of polymer surfaces and thin films. We first describe photo-ablation studies with polysilane films investigated by surface plasmon microscopy, a technique which is particularly well-suited for ultrathin samples. Thicker films that are homogeneous enough to carry optical waveguide modes can be characterized with high lateral resolution by the recently developed waveguide microscopy. We demonstrate this for a thin film of a solid polyelectrolyte. Finally, we report on surface plasmon field-enhanced Raman-spectroscopic and -imaging investigations of ultrathin Langmuir-Blodgett-Kuhn-layers of cadmium arachidate.W. Hickel is now with HOECHST AG, Angewandte Physik, W-6230 Frankfurt 80