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.     

PANI膜电聚合过程及电控分离苯酚的EQCM研究

通过电沉积方法在镀铂石英晶片上制备了导电聚苯胺(PANI)膜,采用电化学石英晶体微天平(EQCM)技术探讨了苯胺聚合机制及在苯酚溶液中的氧化还原特性.在0.5 mol/L硫酸溶液中结合循环伏安法考察了PANI膜在完全还原态(L)-半氧化态(E)-完全氧化态(P)之间的电活性和稳定性;在不同浓度的苯酚溶液中结合恒电压阶跃...     

Self-assembly of S-layer-enveloped cytochrome c polyelectrolyte multilayers

We report a study of the electrostatic layer-by-layer self-assembly of electroactive polyelectrolyte multilayers incorporating the redox protein cytochrome c (cyt c) combined with recrystallization of the bacterial cell wall surface layer from Bacillus sphaericus CCM 2177 SbpA (S-layer). The polyelectrolyte multilayer assembly was prepared on flat gold electrodes with a nanometer-scale roughness that allowed monitoring of the film formation throughout all the assembly stages by atomic force microscopy measurements in liquid with respect to topography and forces. The deposition of alternating layers of sulfonated polyaniline and cyt c was carried out by adsorption from the corresponding solutions on a cyt c monolayer electrode. The electroactivity of cyt c within the assembly was confirmed by cyclic voltammetry. We showed that the surface properties of the electrode terminating layer change after each adsorption step accordingly. We also found that S-layer recrystallization on the top of the multilayer film was feasible while electroactivity of cyt c within a polyelectrolyte matrix was partially maintained. This approach offers a new strategy to design a biocompatible and permselective outer envelope of a polyelectrolyte multilayer, promising sensor applications.     

Synthesis and Properties of Composite Polyaniline–Nafion Films on Platinum

Information on the synthesis of a polyaniline film on platinum covered with a Nafion film is obtained. The effect of electrochemical conditions on the synthesis is studied. The relationship between these conditions and properties of obtained composite polyaniline–Nafion films is revealed. It is established that on platinum covered with a Nafion film in certain electrochemical conditions in a polyaniline solution there occurs the formation of a composite polyaniline–Nafion film. The polyaniline in the film mainly retains its individual properties. It is demonstrated that the mechanism of the synthesis of polyaniline in the composite film substantially differs from that in the case of the formation of a film on platinum.     

Sensing Properties of Polyaniline Films Doped with Dawson Heteropoly Compounds

Polyaniline films doped with 2 : 18 series heteropoly compounds were used a material of gas-sensing films for chemical sensors. The technology of film fabrication was considered. The properties of modified polyaniline films with respect to ammonia were studied, and the effect of humidity and temperature on the film properties was examined. A high sensitivity of polyaniline-based sensors to ammonia was demonstrated.     

Conductive polymers as a new type of thermoelectric material

Thermoelectric properties were investigated for the films of electrically conductive doped polyanilines. The thermoelectric performance, evaluated by thermoelectric figure-of-merit (ZT = T (S² σ) / κ), of various protonic acid-doped polyaniline bulk films was found to depend on the electrical conductivity σ of the film. Thus, the higher the electrical conductivity, the higher the figure-of-merit is, because the thermal conductivity κ of polyaniline films does not depend on the electrical conductivity. Among the conductive bulk films of polyaniline, the highest figure-of-merit (ZT = 1 × 10⁻⁴) was observed for (±)-10-camphorsulfonic acid (CSA)-doped polyaniline in an emeraldine form (σ - 188 S cm⁻¹) at room temperature. The multilayered film, composed of electrically insulating emeraldine base layers and electrically conducting CSA-doped emeraldine salt layers, exhibited 6 times higher ZT at 300 K than that of a bulk film of CAS-doped polyaniline, showing the highest ZT value of 1.1 × 10⁻² at 423 K. Stretching of the CAS-doped polyaniline film also increased the figure-of-merit of doped polyaniline films along the direction of the stretching.     

Layer-by-layer self-assembled conducting polymer films at elevated pressure investigated by surface plasmon spectroscopy with electrochemistry

Polyaniline/sulfonated polyaniline (PANI/SPANI) multilayer films were fabricated using the layer-by-layer (LbL) technique. The electrochemical and optical properties of the film at elevated pressure were investigated by high-pressure surface plasmon spectroscopy combined with electrochemistry. Cyclic voltammograms of the PANI/SPANI films were performed at different hydrostatic pressure. It was found that the charge transfer currents decrease with elevated pressure. This indicates that the film becomes more compact with increasing hydrostatic pressure, which is confirmed by surface plasmon spectra, hinting at a substantial increase in the optical density.     

Self-assembled Films of Poly(4-diazosulfonate Styrene-co-4-vinylpyridine) with Polyaniline and Their Photoelectric Conversion Properties

Poly(4-diazosulfonate styrene-co-4-vinylpyridine) (P(DSS-co-VP)) can self-assemble (SA) with polyaniline via H-bond interaction. The SA film was then photo-crosslinked under UV irradiation to form a covalent crosslinking structure. The photocurrent of the crosslinked SA films was determined directly in aqueous salt solution. The results showed that the polyaniline SA films were materials with good photoelectron conversion properties.     

聚(4-偶氮磺酸苯乙烯-co-4-乙烯基吡啶)与本征态聚苯胺的氢键自组装及其光电转换性能

合成了一种新的共聚体——聚(4-偶氮磺酸苯乙烯-co-4-乙烯基吡啶), 它含有吡啶环, 能作为氢受体与本征态聚苯胺进行氢键自组装. 在紫外光照下, 组装膜通过偶氮磺酸基的光解, 形成稳定的共价交联结构, 在电解质水溶液中也不被破坏, 可用作光电转换膜, 并能在盐水溶液中直接测定它的光电流. 结果表明含有本征态聚苯胺的自组装膜是一种良好的光电转换材料.     

Optical,electrical, and thermochromic properties of polyazothiophene Langmuir–Blodgett films

The conductivity and luminescence of conjugated polymers may be combined with the photoisomerization capability of azobenzene materials to achieve unique properties for a variety of applications, particularly if conjugated polymers with azobenzene side chains are processed as nanostructured films. In this study, we report on Langmuir–Blodgett (LB) films of a polythiophene-bearing azobenzene moieties, which displayed photoluminescence, thermochromism, electroactivity, and photoinduced birefringence. The latter three properties were enhanced in the LB films, as compared to spin-coated films of the polyazothiophene, and this has been attributed to differences in film morphology that could be probed with atomic force microscopy.     

Polyaniline doped with modified gold nanoparticles and its electrochemical properties in neutral aqueous solution

Doping polyaniline with COO(-)-modified gold nanoparticles by forming stable layer-by-layer multilayer films can shift its electroactivity to neutral pH. The films can electrocatalyze the oxidation of NADH and offer potential applications in other fields, e.g., optoelectronics or biosensing.     

Extending electrochemical activity of polyaniline to alkaline media via electrostatic interaction and sol–gel route

The electroactivity of polyaniline was extended to pH = 14 alkaline media by preparation of a novel electrostatic interaction conductive hybrid from water-borne conductive polyaniline and silica network containing carboxyl groups via sol–gel process. In addition, the obtained conductive polyaniline hybrid film displayed very low conductivity threshold percolation and demonstrated excellent stability upon cycling.     

Dielectric Relaxation Phenomena and Electric Properties of Conductive Composite Polyurethane/Polyaniline Films

Summary: Composite polyurethane/polyaniline (PU/PANI) films have been chemically prepared by oxidative in-situ polymerization of aniline inside the previously swelled PU film. Swelling kinetic studies have shown that for PU films the swelling degree of aniline is 25 wt.%. The dielectric and electrical properties of the composite films were measured using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of a relaxation process for the composite PU/PANI-HCl film. This relaxation was explained in terms of interfacial polarization due to the double-layered structure of the composite film. The activation energy values found by dielectric and electrical measurements are close and this result confirms the conducting character of the PANI containing layer.     

In situ polymerized polyaniline films. 4. Film formation in dispersion polymerization of aniline

Polyaniline films were grown on glass supports during dispersion polymerizations of aniline using poly(N-vinylpyrrolidone) and hydroxypropylcellulose as stabilizers. The initiation of polyaniline chains is proposed to be heterogeneously catalyzed by the surfaces immersed in the reaction mixture. Film formations in dispersion and precipitation polymerizations are compared. Surfometry and optical absorption were used to assess the submicrometer film thickness, and FTIR spectroscopy was used to analyze the chemical structure of films and prove the absence of stabilizer. The film thickness was proportional to the dimensions of simultaneously produced colloidal polyaniline particles. The conductivity of films increased with increasing film thickness.     

Multilayer nitroazobenzene films covalently attached to carbon. An AFM and electrochemical study

Nitroazobenzene films have been grafted to pyrolyzed photoresist films by electrochemical reduction of the corresponding diazonium salt in acetonitrile solution. Two component films were also prepared by electrochemically grafting methylbenzene layers to preformed NAB films. Voltammetric investigation of the films in aqueous acid medium and the measurement of film thickness using atomic force microscopy (AFM) lead to new insights into film structure. In aqueous acid solution, the azobenzene groups have no detectable electroactivity and not all nitro groups in the films can be reduced. These findings point to a compact film structure in which proton diffusion is limited. There may also be spatial inhibition of the conformational changes that accompany azobenzene reduction. For increasingly thick NAB films, the peak for reduction of the nitro groups moves to more negative potentials and the peaks become more asymmetric in shape. These changes are interpreted in terms of the dielectric properties and the rate of proton diffusion in the films. Film thickness was measured by ploughing through the film with an AFM tip. When an NAB film prepared in acetonitrile solution is reduced in aqueous acid, the film thickness decreases by more than 50%. The changes can be partially reversed by treatment in acetonitrile-electrolyte solution and hence are attributed to ion-solvent induced swelling and shrinking. Thus, the large decrease in thickness detected by AFM after treatment of the film in aqueous acid is consistent with the compact film structure revealed by electrochemistry.     

循环伏安法制聚(1,5-萘二胺)膜及其对紫外可见光吸收的研究

利用循环伏安法合成了1,5-萘二胺(1,5DAN)聚合物膜.从反应的介质、膜的厚度以及掺杂酸的种类等方面,讨论了制备电活性聚1,5-萘二胺(P1,5DAN)膜的影响,结果发现,在酸性水溶液中,初始的电活性比较高,但是,随着循环的继续,聚合物膜的电量损耗比较大,而在乙腈溶液中电量损耗较小;同时还发现,P1,5DAN电活性膜的厚度并不随总电量的增加而增厚;活性聚合物膜是受扩散控制,扩散系数(D)与酸根离子有关.最后,结合电化学,讨论了不同掺杂状态下的紫外可见吸收光谱(UV-Vis),并用FT-IR对所合成的聚合物作了结构表征.     

Impedance study of thiolated polyaniline

Covalent attachment of thiolated probes to conducting polymers such as polyaniline (PANI) is a promising approach towards the development of electrochemical sensors and biosensors. However, thiolation alters the conjugated polymer backbone and influences the electrochemical behavior of the conducting polymer. PANI studied in this work was electropolymerized on glassy carbon (GC) electrodes from a solution of 0.1 M aniline in 0.5 or 1.0 M H₂SO₄. The GC/PANI electrodes were then functionalized by covalent attachment of 2-mercaptoethanol to the PANI backbone. The progress of thiolation was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Thiolation of PANI was found to cause an initial decrease in electroactivity at 0–0.25 V and an increase in electroactivity at 0.25–0.6 V. However, prolonged thiolation caused a loss of electroactivity of PANI, which could be seen from EIS measurements as a dramatic decrease in the bulk redox capacitance of PANI.     

On the break-in and passivation phenomena in polypyrrole/sulfate films

The influence of different divalent cations (M²⁺) on the electrochemical charging/discharging process of polypyrrole/sulfate (PPy/SO₄) films has been investigated. In principle, two different types of M²⁺ were found: (a) cations that cause the break-in phenomenon in the PPy film during electrochemical cycling with a gradual increase of film electroactivity and (b) cations in whose solutions the PPy film remains mainly electroinactive. Certain correlations have been drawn between several physico-chemical properties of the investigated cations and the break-in and passivation phenomena. The break-in and passivation phenomena were found to be influenced by the size and deformability of the cation hydration shell, ion covalent index and softness, as well as by the pH value of the test solution.     

Nanoscale measurements of conducting domains and current-voltage characteristics of chemically deposited polyaniline films

Spatial variations in electric conductivity and evolutions of band structures of polyaniline (PANI) films have been studied by use of a so-called current-sensing atomic force microscope (CS-AFM) or atomic force microscope current image tunneling spectroscopy (AFM-CITS). PANI films were deposited chemically onto indium-tin oxide- (ITO-) glass substrates, and their thickness and doping levels were controlled by polymerization and acid-doping conditions. The conducting uniformity of the PANI films depends on their doping level and thickness. Conducting domains were observed in fully doped PANI film, even when the bias voltage was reduced to as small as 30 mV. High current flowing regions gradually disappeared when conducting PANI films were partially dedoped. The point-contact current-voltage (I-V) characteristics of conducting tip-polymer/ITO systems were investigated on PANI films with different thickness and degree of doping. Various types of I-V curves representing metallic, semiconducting, and insulating states were obtained depending on the aggregation of polymer chains and doping level of the polymer film. The band gap energies (estimated from the I-V or dI/dV-V curves) of emeraldine base (EB) (undoped polyaniline) films are all higher than 3.8 eV, and a wide distribution of the band gap energies (0-1.1 eV and 0.75-1.8 eV for fully and partially doped PANI thin films, respectively) was found in a single polymer film.