Self-assembled film of poly(4-carboxyphenyl)acetylene and diazoresin and its photoelectric conversion property

A novel multilayer film was assembled from water-soluble poly(4-carboxyphenyl)acetylene sodium salt (PCPA) and diazoresin (DR) in aqueous solution via electrostatic attraction. Under UV irradiation, following the decomposition of the diazonium group between the adjacent interfaces of the multilayers, the ionic bonds of the self-assembled film convert to covalent bonds and the film becomes very stable toward electrolyte aqueous solutions. Thus, the photoelectric conversion property of PCPA-containing film can be measured in a conventional three-electrode photoelectrochemical cell, and 0.5 mol/l KCl solution can be used as the supporting electrolyte. The photocurrent spectroscopy response coincides with the absorption spectrum of the irradiated self-assembled film, which indicates that the irradiated DR/PCPA film is responsible for the photocurrent generation.     

Covalently attached self‐assembly of ultrathin films from hydroxy‐containing porphyrin and diazoresin

Ultrathin films from 5,10,15,20‐tetrakis(4‐hydroxyphenyl) porphyrin (HPP) and diazoresin (DR) via a H bonding interaction were fabricated with the self‐assembly technique. Under UV irradiation, the H bonds between the layers will convert to covalent bonds following the decomposition of the diazonium group of DR. The stability of the film against the polar solvent and electrolyte aqueous solution increases a lot because of the formation of the covalent crosslinking structure. Thus, the photoelectric conversion property of DR/HPP film can be measured directly with a normal photoelectric chemical cell with potassium chloride as the electrolyte. The maximum of the anodic photocurrent was measured as 1.7 μ Å for an eight bilayer DR/HPP film deposited on an indium–tin oxide glass electrode. The action spectrum of the photocurrent generation indicated that the HPP contained in the film is responsible for the generation of the observed photocurrent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3103–3108, 2003     

重氮树脂-聚(4-羧酸苯基)乙炔自组装膜与光电转换

近年来 ,自组装及其形成的多层复合膜已经在导电、生物传感器及非线性光学等领域得到深入研究 ,特别是以聚阴离子与聚阳离子相互作用的静电自组装研究更为深入 .这一技术制备方法简单 ,无需特别的设备 ,对膜层厚度能随意调控 ,并以水作为介质 ,对环境无害 [1～ 3] .共轭高分子 (如聚苯胺、聚吡咯及聚苯亚乙烯等 )通过自组装形成共轭高分子膜 ,对制备具有导电、光电和传输等功能的薄膜半导体器件具有重要意义 .聚乙炔类是最早被发现且理论与应用研究最多的一类共轭高分子材料[4 ,5] .本文以聚 ( 4 -羧酸苯基 )乙炔 ( PCPA)为聚阴离子 ,以重…     

红外光谱法研究重氮树脂自组装膜的光化学反应

将具有导电功能的聚(4-羧酸钠苯基)乙炔阴离子(PCPA)与具有生物活性的DNA聚阴离子交替与重氮树脂聚阳离子(DR)进行自组装,可以得到层重复单元为DR／DNA／DR／PCPA的三夹层聚电解质自组装膜。重氮树脂聚阳离子在紫外光照射下可与聚阴离子发生光化学反应,使层与层之间的离子键连接转化为共价键连接,从而制备稳定的纳米级超薄膜。本文用红外光谱法对此类聚电解质自组装膜的光化学反应过程进行了研究。     

Photocrosslinkable diazoresin/pectin films – Synthesis and application as cell culture supports

Multilayer polymeric films composed of diphenylamine-4-diazoresin (DR), a synthetic polycation, and pectin (Pec), a polyanionic natural polysaccharide, were obtained using a layer-by-layer method (LbL). The films was photocrosslinked by the irradiation with 350 nm light which resulted in their stabilization against different solvents. The nanostructure of the films was studied using AFM microscopy. Irradiation of the films resulted also in the change of the zeta potential of both DR and Pec outermost layer to more negative values and in the increase of the film hydrophobicity as found from the contact angle measurements. The DR/Pec films have been shown to support cell growth and osteogenic potential of cell culture supports in tissue engineering, as found from the experiments with human bone marrow stromal cells (hMSCs).     

Covalentely Attached Multilayer Films Comprising Phthalocyanine and Their Photoelectron Conversion Properties

The photosensitive multilayer films from sulfonated metal-free, sulfonated copper-, and sulfonated nickel-phthalocyanines were fabricated with diazoresin layer by layer on a substrate via electrostatic interaction by the self-assembly technique. Under UV irradiation, the linkage nature between the layers of the film is converted from the electrostatic bonding to covalent bonding. The covalently attached multilayer films are very stable towards polar solvents and salt aqueous solutions. The photovoltaic properties of the covalently attached film can be determined by means of a traditional three-electrode photoelectrochemical cell in aqueous solutions with KCI as the supporting electrolyte. The photocurrent determination has shown that the sulfonated copper-containing phthalocyanine films possess a higher photocurrent value than sulfonated metalfree and sulfonated nickel-containing phthaloeyanine films.     

重氮树脂与牛血清白蛋白共价结合自组装膜及其表面细胞培养

细胞支架作为组织工程的组成部分为细胞生长提供了最佳微环境 ,并对细胞生长与功能进行控制 .由于细胞对支架表面的生物识别是细胞附着、生长和增殖的基本前提 ,所以对材料表面的功能化是一个重要的课题 [1,2 ] . Shoichet等 [3 ] 通过化学反应或等离子体处理的方法 ,将蛋白质引入到材料表面而使其功能化 .基片在两种带有相反电荷的聚电解质溶液中交替吸附 ,其表面形成致密有序的超薄自组装膜 ,这种层 -层自组装技术不仅制备方法简单 ,无需特殊的设备 ,而且对膜组成和厚度能随意调控 ,以水为介质 ,对环境友好 [4～ 6] ,无疑是一项重要的表…     

Fabrication of a stable inorganic-organic hybrid multilayer film with uniform and dense inorganic nanoparticle deposition

A stable inorganic-organic hybrid multilayer film with homogeneous and dense inorganic nanoparticle deposition was constructed by coating ZrO2 nanoparticles with poly(4-sodium styrenesulfonate) (PSS) and irradiating multilayer film assembled from PSS-coated ZrO2 nanoparticles and a diazo-resin (DR).     

聚(对乙烯基苯酚)的合成及其与重氮树脂的氢键自组装研究

带相反电荷的聚电解质,交替沉积在基片,形成超薄有序膜,通常称为静电自组装,自1991年由Decher首次阐明以来,静电自组装技术引起了广泛重视,利用氢键相互作用的氢键自组装1997年才有报道,沈家骢、张希等从聚丙烯酸和聚乙烯基吡啶通过氢键组装了有序超薄膜。和乙烯基吡啶通过氢键组装超薄膜的制备。由于静电力和氢键均很弱,此类膜对极性溶剂不稳定,如在DMF中会离解而遭破坏,我们曾报道重氮树脂（DR）与酚醛树脂间通过氢键的自组装,本文报道聚（对乙烯基苯酚）（PVPh）的制备及春与重氮树脂（DR）间的氢键相经作用,并结合光照,制备了对极性溶剂稳定的超薄膜。     

Layer-by-layer deposition of rhenium-containing hyperbranched polymers and fabrication of photovoltaic cells

Multilayer thin films were prepared by the layer-by-layer (LBL) deposition method using a rhenium-containing hyperbranched polymer and poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS). The radii of gyration of the hyperbranched polymer in solutions with different salt concentrations were measured by laser light scattering. A significant decrease in molecular size was observed when sodium trifluoromethanesulfonate was used as the electrolyte. The conditions of preparing the multilayer thin films by LBL deposition were studied. The growth of the multilayer films was monitored by absorption spectroscopy and spectroscopic ellipsometry, and the surface morphologies of the resulting films were studied by atomic force microscopy. When the pH of a PTEBS solution was kept at 6 and in the presence of salt, polymer films with maximum thickness were obtained. The multilayer films were also fabricated into photovoltaic cells and their photocurrent responses were measured upon irradiation with simulated air mass (AM) 1.5 solar light. The open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency of the devices were 1.2 V, 27.1 mu A cm(-2), 0.19, and 6.1x10(-3) %, respectively. The high open-circuit voltage was attributed to the difference in the HOMO level of the PTEBS donor and the LUMO level of the hyperbranched polymer acceptor. A plot of incident photon-to-electron conversion efficiency versus wavelength also suggests that the PTEBS/hyperbranched polymer junction is involved in the photosensitization process, in which a maximum was observed at approximately 420 nm. The relatively high capacitance, determined from the measured photocurrent rise and decay profiles, can be attributed to the presence of large counter anions in the polymer film.     

Photoelectrochemical properties of alternating multilayer films composed of titania nanosheets and Zn porphyrin

Alternating multilayer films composed of titania nanosheets and Zn porphyrins were prepared by use of a previously reported Langmuir-Blodgett film-transfer method in order to fabricate photoelectrochemical devices. Closely packed titania nanosheet monolayers on indium tin oxide (ITO), mica, and quartz surfaces strongly adsorbed cationic [5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrinatozinc]4+ (ZnTMPyP4+) by electrostatic interactions. The alternating deposition process afforded nanometer-scale multilayer films with the following structure: solid surface/(titania nanosheet/ZnTMPyP4+)n (n is the number of layers). The multilayer films were characterized by various physical measurements, including AFM, XRD, and UV-visible spectra. The visible-light irradiation of this multilayer film on an ITO electrode in the presence of triethanolamine as an electron donor yielded an anodic photocurrent. The action spectrum was consistent with the absorption spectrum of ZnTMPyP4+, which indicates that the photoexcitation of ZnTMPyP4+ is responsible for the photocurrent generation. However, the photocurrent density decreased with an increasing number of layers, which indicates that the harvesting of photoexcited electrons vertically through the titania nanosheets in the ITO/(titania nanosheet/ZnTMPyP4+)n structure was not efficient. To overcome this problem, the use of a lateral interlayer connection to all of the titania nanosheets with Ag paste was examined. As a result, a dramatic improvement in the photocurrent density was obtained. Thus, for efficient photocurrent generation with the titania nanosheet-ZnTMPyP4+ composite material, the lateral connection to all of the titania nanosheet layers is effective.     

Enhancement of photocurrent in dye sensitized solar cells incorporating a cyclometalated ruthenium complex with cuprous iodide as an electrolyte additive

A new cyclometalated ruthenium complex, [Ru(6'-phenyl-4'-thiophen-2-yl-[2,2']bipyridinyl-4-carboxylic acid)(4,4',4'-tricarboxy- 2,2':6',2'-terpyridine)]Cl, for Dye Sensitized Solar Cells (DSSCs) is proposed. We have investigated the use of cuprous iodide (CuI) as an electrolyte additive, which in turn has shown photocurrent enhancements of more than 25% in our dye based cells. Using an ionic liquid based electrolyte, an efficiency of η = 5.7% has been accomplished under 1 sun irradiation. The origin of this photocurrent enhancement upon the CuI addition was studied by means of impedance spectroscopy and cyclic voltammetry under dark conditions. The reason behind such a photocurrent enhancement is attributed to an electrocatalytic effect of the CuI on the regeneration of the oxidized dye. Furthermore, the CuI addition did not affect the recombination processes between the injected electrons and the electrolyte nor the electron lifetime in the semiconductor TiO(2) film, which in turn resulted in no changes in the photovoltage.     

染料敏化太阳能电池TiO2电极的制备及电解质的影响

采用溶胶-凝胶水热法制备了锐钛矿型纳米晶TiO₂薄膜电极,在乙二醇碳酸酯(EC)/1,2-丙二醇碳酸酯(PC)电解液体系中,研究了I₂和KI含量对电极光电性能的影响,发现随着电解液中I₂含量的增加,电池的短路光电流呈现先增加后减小的趋势,但光电流增加和减少的幅度并不大,同时体系的暗电流不断增加,光电压不断下降;随着电解液中KI含量的增加,电池的短路光电流也不断增加,当KI的含量大于0.2 mol/L时,电池的短路光电流的增加的趋势减缓.并对电解液中I₂和KI含量对电池光电性能影响的原因进行了初步的探讨.     

Photocurrent generation in heterostructured ultrathin films fabricated by layer-by-layer deposition of polyelectrolytes bearing tris(2,2'-bipyridine)ruthenium(II) and ferrocene moieties

The photoelectrochemical properties of single-component and heterostructured layer-by-layer deposited films bearing tris(2,2'-bipyridine)ruthenium(II) (Ru) moieties were investigated by photocurrent measurements in solutions in the presence of sacrificial reagents. The photocurrent increased with an increase in the thickness of the films and then had a maximum at a thickness of 10 nm. This increase demonstrates a light-harvesting effect based on excitation energy migration among the Ru moieties to the film/electrolyte interface. A cathodic photocurrent was observed for a heterostructured film where bilayers bearing ferrocene (Fc) moieties and bilayers bearing Ru moieties were deposited on an indium tin oxide (ITO) substrate in the order (ITO/Fc/Ru). On the other hand, an anodic photocurrent was observed for the reverse order film (ITO/Ru/Fc). These results show that the direction of the photocurrent is determined by the gradient of the redox potentials formed in the heterostructured films. The internal quantum efficiency for the ITO/Ru/Fc film was twice that for the single-component film (ITO/Ru). This enhancement of the quantum efficiency is due to suppression of charge recombination by successive electron transfers in the heterostructured film.     

Identification of Skim Milk Electroacidification Fouling: A Microscopic Approach

The self-assembly film fabricated via the layer-by-layer technique was studied by the dynamic contact angle (DCA) method (wilhelmy plate method). The used polyelectrolytes are poly(diallyl-dimethylammonium chloride) (PDDA), poly(etheleneimine) (PEI), diphenylamine-4-diazonium-formaldehyde resin (DR), 2-nitro-N-methyl-4-diazonium-formaldehyde resin (NDR), and poly(sodium-p-styrenesulfonate) (PSS). For the self-assembly systems of PDDA/PSS, PEI/PSS, DR/PSS, and NDR/PSS, their individual contact angle fluctuates regularly with the fabrication of each layer, while the magnitude of different systems' contact angle depends on the participant polycation. The re-organization of components and the adjacent layer interpenetration are presented here to explain this phenomena. We also found that DR or NDR can adsorb itself via the layer-by-layer method to form multilayer film, and the hydrophobic interaction is put forward to effect this process. Moreover, the procedure of washing and drying after adsorption was studied and considered as a prerequisite for the successful fabrication, especially of the same charge carried components. Copyright 2001 Academic Press.     

Fabrication of an ESA Multilayer Film from a Diazo Resin by Direct Surface Charge Reversal

An electrostatic self‐assembly (ESA) multilayer film of a diazo resin (DR) was fabricated by direct surface charge reversal. DR is first adsorbed onto the substrate via electrostatic interaction, and in the chemical activation step, the sign of the surface charge is directly reversed by converting the positively charged diazonium ion to the negatively charged diazo sulfonate ion under mild conditions. By repeating adsorption and chemical activation step, the film grows regularly layer by layer.     

Photocurrent generation in multilayer self-assembly films fabricated from water-soluble poly(phenylene vinylene)

A novel, water-soluble, cationic PPV derivative poly[(2,5-bis(3-bromotrimethylammoniopropoxy)-phenylene-1,4-divinylene)-alt-1,4-(2,5-bis(2-(2-hydroxyethoxy)ethoxy))phenylene vinylene] (BH-PPV) has been synthesized by a Heck coupling reaction. Multilayered assemblies of the BH-PPV and the sodium salt of hexa(sulfobutyl)fullerenes (C(60)-HS) were fabricated successfully by an alternate deposition technique. The multilayer structures were studied by UV/Vis spectroscopy, small angle X-ray diffraction, and atomic force microscopy. The photoinduced charge transfer property of the self-assembled multilayer film was also measured by a three-electrode cell technique. A steady and rapid cathodic 5.5 microA cm(-2) photocurrent response was measured as the irradiation of the multilayer film was switched on and off. Importantly, the response of on/off cycling is prompt and reproducible. A possible mechanism for the electron-transfer process is proposed.     

有机钌螯合物/TiO_2杂化膜修饰电极上Pt纳米团簇的光电流增强效应

利用LB膜技术可控制备了纳米单层和多层的二氧化钛-有机钌螯合物杂化膜,并研究了上述无机-有机杂化膜修饰电极在Pt纳米团簇敏化后的光电流增强效应.实验结果表明:(1)纳米单层TiO2/[Ru(phen)2(dC18bpy)]2+(简称为TiO2-Ru)杂化膜的平均厚度为(3.6±0.5)nm;(2)在光照条件下TiO2-Ru杂化膜能有效催化还原[Pt(NH3)6]4+形成粒径位于20～160nm之间的Pt纳米团簇;(3)Pt纳米团簇的引入消除了金属钌螯合物中配体对电子传递的阻碍作用,改变了电子传递途径,从而有效减少了电子空穴对的复合,提高了Pt纳米团簇敏化的n层杂化膜修饰电极(ITO/(TiO2-Ru)n/Pt)在支持电解质中的光电流.与纳米单层TiO2-Ru杂化膜修饰的ITO电极(ITO/TiO2-Ru)相比,当工作电压为900mV时,ITO/TiO2-Ru/Pt在0.1mol·L-1的NaClO4电解质溶液中和光照(λ360nm)条件下,单位面积的光电流提高了约5倍;(4)ITO/(TiO2-Ru)n/Pt电极光电流的大小与杂化膜的层数密切相关,当TiO2-Ru杂化膜的层数从一层、二层增加到四层时,光电流呈现先升高后下降行为,这表明ITO/(TiO2-Ru)n/Pt电极的电子传递过程直接通过非电活性的二氧化钛纳米单层进行.     

纳米尺度TiO2微粒多孔膜电极光电化学

用光电流作用谱、光电流-电势图和瞬态光电流谱等光电化学方法研究了TiO2多孔膜电极在含不同氧化还原体系的电解质溶液中的光电转换过程.结果说明TiO2多孔股为n-型半导体，其禁带宽度为3.26eV.当在电解质溶液中加入醌二苯酸（BQ／HQ），TiO2多孔膜电极的光电流作用谱形基本与没加氧化还原对时类似。在可见光区的光电流拖尾是由于醌被光激发，然后给出电子到TiO2多孔膜导带而产生阳极光电流.而在电解质溶液中加入Fe（CN）3-6-／4-时，TiO2多孔膜电极的光电流作用谱有明显的改变.除了在小于380nm短波区有光电流峰外，还在400-600nm的可见光区观察到宽的光电流峰，大大增加了光电流转换效率.同时在小于-0.2V下为阳极光电流，在-0.2V～0.3V电势区间为明显阴极光电流，在大于0.3V下可观察到较弱的阳极光电流.当电极电势大于-0.2V时，光电流瞬态谱在开始光照时有一阴极瞬态光电流尖峰，然后转变为阳极稳态光电流.这是因为当电极电势较负时，Fe（CN）4-6与TiO2的电子传递络合物可以吸收光子，光生电子迅速注入TiO2导带，然后还原溶液中的而产生阴极光电流.     

Artificial photosynthesis by using chloroplasts from spinach adsorbed on a nanocrystalline TiO2 electrode for photovoltaic conversion

Photovoltaic conversion has been achieved by use of chloroplasts (photosynthetic organs) from spinach adsorbed on a nanocrystalline TiO₂ film on an indium tin oxide (ITO) glass electrode (chloroplast/TiO₂ electrode). The shape of the absorption spectrum of the chloroplast/TiO₂ electrode is almost the same that of a dispersion of the chloroplasts. Absorption maxima of the chloroplast/TiO₂ electrode observed at 430, 475, and 670 nm were attributed to carotenoid and chlorophyll molecules, suggesting that chloroplasts have been adsorbed by the nanocrystalline TiO₂ film on the ITO electrode. The photocurrent responses of chloroplast/TiO₂ electrodes were measured by using a solution of 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile as redox electrolyte in the presence or absence of water and 100 mW cm^?2 irradiation. The photocurrent of the chloroplast/TiO₂ electrode was increased by adding water to the redox electrolyte. The photocurrent responses of chloroplast/TiO₂ electrodes irradiated with monochromatic light (680 nm, the absorption band of photosystem II complexed with evolved oxygen) were measured by use of a solution of 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile as redox electrolyte in the presence or absence of water. A chloroplast/TiO₂ electrode photocurrent was observed only when the redox electrolyte containing water was used, indicating that the oxygen evolved from water by photosystem II in chloroplasts adsorbed by a nanocrystalline TiO₂ film on an ITO electrode irradiated at 680 nm is reduced to water by the catalytic activity of the platinum electrode. The maximum incident photon-to-current conversion efficiency (IPCE) was 0.8 % on irradiation at 670 nm.