Visible electroluminescence from p-n junction porous Si diode with a polyaniline film contact

We have fabricated a light emitting diode using a p-type conducting polyaniline layer deposited on a n-type porous silicon (PS) layer. The contact formed between a p-type conducting polyaniline layer and a n-type PS wafer has rectified behaviour demonstrated clearly by the I-V curves. The series resistance Rs in the p-type conducting polyaniline/n-PS diode is reduced greatly and has a lower onset voltage compared with ITO/n-PS diode. The PS has an orange photoluminescence (PL) band after coating with polyaniline. Visible electroluminescence (EL) has been obtained from this junction when a forward bias is applied. The emission band is very broad extending from 600-803 nm with a peak at 690 nm.     

Polymerization of aniline on bacterial cellulose and characterization of bacterial cellulose/polyaniline nanocomposite films

Bacterial cellulose/polyaniline nanocomposite film was prepared by the chemical oxidative polymerization of aniline with bacterial cellulose. Polyaniline conducting polymer nanocomposite films with bacterial cellulose fibers was prepared and characterized. In nanocomposite film, the bacterial cellulose was fully encapsulated with polyaniline by direct polymerization of the respective monomers using the oxidant and dopant. These bacterial cellulose/polyaniline nanocomposite films materials exhibited the inherent properties of both components. The deposition of a polyaniline on the bacterial cellulose surface was characterized by SEM. XPS revealed a higher doping level of the nanocomposite films doped with p-TSA dopant. From the cyclic voltammetry results, the polyaniline polymer was thermodynamically stable because redox peaks of electrochemical transitions in the voltagrams were maintained in bacterial cellulose/polyaniline nanocomposite films.     

导电聚苯胺的合成及其性能研究

化学氧化法合成了导电性聚苯胺 ,系统地研究了氧化剂种类、浓度、反应温度、反应时间、掺杂酸的种类和浓度等不同因素对聚合反应的影响 ,获得了苯胺聚合反应的最佳条件。     

Composites of multiwall carbon nanotubes and conducting polyaniline: Bulk samples and films produced from a solution in chloroform

Multiwall carbon nanotubes and conducting polyaniline, doped with dodecylbenzenesulfonic acid, are blended by employing the solubility of both materials in chloroform. Pellets are made by pressing the dried powder of the obtained composite, and films by sedimentary deposition onto a plastic substrate. In these composites, the advantageous properties of carbon nanotubes can be utilized in fully conducting bulk and planar structures while the strong decrease of the conductivity of doped polyaniline at low temperatures is simultaneously suppressed. The nanotube content in pellets can be as high as 40% by weight, and this wide range leads to a control over the shape and magnitude of the conductivity versus temperature curves. As the nanotube content grows, the temperature dependence of the conductivity becomes less steep, which is similar to the effect of annealing temperature on the conductivity of certain polycrystalline graphene films. In our case, this change is most likely caused by the increase of the density of highly conducting channels and not by homogeneous delocalization effects.     

Laser photoelectron projection microscopy of an organic conducting polymer

A conducting organic polymer is visualized on a laser photoelectron projection microscope, which is based on Letokhov’s concept and has a nanometer spatial resolution. Photoelectron images of polyaniline (which is the most promising representative of conducting polymers) with a magnification of ∼10⁵ have been obtained when a 100-nm quartz capillary coated with a film of this material was irradiated by femtosecond laser pulses. The projection photoelectron method using 400- and 800-nm laser radiation has made it possible to directly reveal the existence of the redox heterogeneity of the organic polymer, which is due to the contact of the sections of polyaniline with different oxidation degrees and strongly affects the electric conductivity of the sample.     

Charge transport across the metal–polymer film boundary

Thin polyaniline films were fabricated by thermal vacuum evaporation from a Knudsen effusion cell. The conducting properties of films synthesized under different evaporation conditions were studied. The enhancement of the emission capacity of a wolfram tip coated with a polyaniline film of a nanometer thickness was demonstrated experimentally. A model of the discovered effect was proposed. The obtained Fowler–Nordheim current–voltage characteristics were used to estimate the change in the electronic work function occurring when a thin film is deposited on the tip surface. The effective temperature of electrons emitted from the polyaniline film was determined based on the results of analysis of energy distributions, and the specific features of charge transport in the metal–polyaniline–vacuum system were examined. A model of energy bands of the metal–polymer film contact was also constructed.     

Preparation of conducting polyaniline colloids under ultrasonication

The effects of ultrasonication on the chemical polymerization of aniline leading to the formation of conducting polyaniline colloids were examined. The formation rate of the colloids was significantly increased under ultrasonication. Furthermore, it was also observed that the morphological structure of the colloids thus prepared was greatly affected by the sonication. The polyaniline colloids were further characterized by a range of techniques including electric resistance meter, gel permeation chromatography, FT-IR and cyclic voltammetry. It is noteworthy that the application of ultrasound to the polymerization resulted in a marked increase in the doping level, which reflected to the high electroconductivity of polyaniline colloids.     

Electrical transport and optical properties of vanadyl phosphate—polyaniline nanocomposites

The nanocomposites of conducting polyaniline and layered vanadyl phosphate, VOPO₄·2H₂O are synthesized by redox intercalation method. Water content decreases with insertion of polyaniline molecules. In scanning electron micrographs plate like structures are observed for both VOPO₄·2H₂O and intercalated nanocomposites. Protonation of polyaniline and interaction with vanadyl phosphate are observed in infrared and UV absorption spectroscopy. Intercalation improves conductivity of pristine vanadyl phosphate. Thermally activated electrical dc conductivity at low temperature shows two distinct slopes around 210 K for both the nanocomposites. The optical band gap of vanadyl phosphate decreases from 4.0 to 3.7 eV due to insertion of polyaniline.     

Desorption of an organic conducting polymer by soft X-ray radiation created by a femtosecond laser

The possibility of the desorption of complicated molecular complexes by soft X rays resulting from a solid target irradiated by a single sharply focused femtosecond laser pulse with an energy of several millijoules has been experimentally demonstrated for polyaniline, which is an organic conducting polymer. X-ray desorption and photodesorption of polyaniline by femtosecond laser pulses have been compared using a time-of-flight mass spectrometer. The results provide the possibility of studying surfaces with spatial nanoresolution and high elemental (chemical) selectivity, as well as observing the photodesorption with a high temporal resolution.     

The effect of ultrasonic waves in conducting polymer solution

The effects of ultrasonic wave on the conducting polymer polyaniline dissolved in DMSO were observed. The UV-visible, infrared and NMR analysis show that the polymer undergo a redox and doping transition when the ultrasound wave interacts with the polymer dissolved into the solvent. The proposed mechanism to explain these effects is based on the solvent's hygroscopicity properties. The interaction with the ultrasonic wave, homolitically dissociates the water molecule producing radical species, and these species interact with the dissolved conducting polymer changing its oxidation and doped state. The resulting effects of that interaction are the modification of oxidation state of the conducting polymer and the decrease of the amount of water molecule in the solvent. From those results, we have proposed one straightforward method to eliminate water contamination in the solvent DMSO using ultrasonic waves.     

Freestanding conducting polyaniline film for the control of electromagnetic radiations

Electromagnetic interference is pollution generated due to dense nature of circuitry in electronic devices and is required to be control at its source. Polyaniline is an environmentally stable conducting polymer which can be cast as thin film, which can replace the corrosive metals as a shield for the control of electromagnetic radiations. In this communication we discuss our results on the preparation of flexible freestanding conducting polyaniline film of varied thickness using either p-toluenesulphonic acid (PTSA) or camphor-10-sulphonic acid as a primary dopant and 4-chloro-3-methyl phenol (CMC) as a secondary dopant. The resulting films were characterized by conductivity, scanning electron micrograph and shielding effectiveness measurements (SE). The SE measurements were carried out using co-axial transmission line method in the frequency range of 0.1–1000 MHz. We noticed that only the change of 2% in the shielding effectiveness of these films over the period of 3 years indicating the environmental stability of polyaniline films.     

TEM,XRD and AFM study of poly(<Emphasis Type="Italic">o</Emphasis>-ethoxyaniline) films: new evidence for the formation of conducting islands

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism.     

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF DIMENSIONALITY OF POLYANILINE FILMS

The line shape analysis of electron paramagnetic resonance (EPR) spectra for low-dimensional solids are calculated. A comparison is carried out between the experimental EPR results of polyaniline samples and theoretical calculation. The dimension evolution of the samples from nonconducting to conducting states is obtained. It is found that the dimensional properties determined by EPR are in good accordance with those obtained using previous ellipsometric methods.     

Effect of cerium ions on corrosion inhibition of PANI for iron in 0.5 M H2SO4

In recent years conducting polymers such as polyaniline are used as corrosion inhibitors for metals in acids. The performance of the inhibitor can be enhanced either by the addition of halide ions or metal cations. A study has been made on the effect of addition of ceric ions on the corrosion inhibition performance of polyaniline for iron in 0.5 M H₂SO₄. Techniques such as electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization resistance methods have been employed to study the corrosion inhibition. The polyaniline has been used in the concentration range of 10-100 ppm and the ceric ions concentration has been maintained at 1 × 10⁻³ M. The inhibition efficiency of polyaniline at 10 ppm has been increased from 53 to 88% and for 50 ppm from 71 to 90% in the presence of ceric ions. The enhanced inhibition of polyaniline in presence of ceric ions is due to the higher coverage of polyaniline-cerium complex.     

压力对聚苯胺导电性的影响

 导电高聚物聚苯胺薄膜经过定向拉伸后，其有序度、电导及跃迁势垒都发生了很大变化。本文研究了准静水压力对定向拉伸前后，聚苯胺薄膜电学性质的影响。发现未定向拉伸的聚苯胺薄膜的电导随压力单调增加，跃迁势垒T₀随压力单调减少，而定向拉伸后的聚苯胺薄膜则在0.47 GPa出现电导的极大值，在0.35~0.71 GPa之间出现T₀的极小值，这个异常行为与聚乙炔、聚噻吩等导电高聚物均不相同。     

Analysis of infrared reflectivity of conducting polymers: example of camphor-sulphonic-acid-doped polyaniline

The reflectivity spectrum of a polyaniline CSA-doped in presence of m-cresol has been measured over the wide wavenumber range of 15- 9 000 cm ^-1 (0.002-1.1 eV) at room temperature. Experimental data compare well with similar experiments performed by another group. The conductivity spectrum of this conducting polymer has been deduced from the reflectivity spectrum by means of two methods, Kramers-Kronig transformation and best fit of an “extended Drude” model to the reflectivity spectrum. Whereas the deviation from Drude behavior was interpreted in terms of Anderson localization or by inhomogeneous disorder by other groups, it is shown here that a different model developed for conducting oxides that also exhibit non-Drude behavior, applies very well to this example of conducting polymer. Received 11 February 1999 and Received in final form 26 April 1999     

Doping dependence of infrared conductivity of camphor-sulphonic-acid-doped polyaniline

The reflectivity spectrum of a polyaniline CSA-doped in presence of m-cresol has been measured over the wide wavenumber range 25-15,000 cm^-1 (0.003-1.9 eV) for three different doping levels. Since spectra cannot be fitted correctly with the conventional Drude model, several extensions are tested. A model derived from the factorized form of the dielectric response and including the effect of Anderson localization in disordered metals, is proposed and found to yield good fit to data with a satisfactory physical meaning. Data are reduced to a small number of parameters potentially useful for further comparison with other conducting polymers or even other non-Drude conducting media like oxides. Received 6 February 2002 / Received in final form 12 August 2002 Published online 27 January 2003 RID="a" ID="a"e-mail: gervais@delphi.phys.univ-tours.fr RID="b" ID="b"UMR 6157 CNRS/CEA     

Spin dynamics in conducting polymers studied by μSR

We report studies of spin dynamics in the conducting polymers polyaniline and polypyrrole using both μ⁺SR and μ^-SR techniques. These measurements reveal characteristic field dependences and cutoff frequencies for the muon spin relaxation which can be related to the spin diffusion process. Clear evidence is seen for increased spin localisation at low temperatures where a crossover occurs from two or three dimensional spin diffusion to a one dimensional diffusion regime. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation and characterization of conducting polymer/silver hexacyanoferrate nanocomposite

In this work, we present an alternative route to prepare silver hexacyanoferrate(II)/polyaniline (PANI) composite thin films. Differently from the electrochemical method, used to synthesize the conducting polymer film on a electrode surface, this new chemical route makes use of dialysis membrane as a solid support to synthesize the silver hexacyanoferrate(III) compound, and subsequently uses this composite membrane as oxidizing agent to polymerize the aniline monomer. The spectroscopic (UV-vis and IR region) and electrochemical characterization (cyclic voltammetry) indicates that the polymeric composite remains optically active and conductive. The X-ray analysis shows that the composite membrane/Ag₃[Fe_III(CN)₆] has an crystalline structure that can be assigned to the Ag₃[Fe_III(CN)₆] structure, and after reaction with aniline solution it became less crystalline. Additionally the SEM measurements shown that the reaction of silver ions with hexacyanoferrate(III) across the membrane results in a well defined and aliened Ag₃[Fe_III(CN)₆] crystals and when this crystalline compound reacts with aniline monomer silver wire of 100 nm of diameter by 6 μm longer are formed together with the conducting polymer polyaniline/Ag_x[Fe_II(CN)₆] composite.     

Photophysical characteristics of polyaniline with photochromic azobenzene side groups

Photochromic characteristics and optical molecular reorientation in conducting polymer such as polyaniline derivatives containing photochromic azobenzene moieties (PAPNPAPOA) in side chain are studied. Changes in the UV—vis absorption, refractive index, thickness, contact angle and morphology of these films after irradiation of a linearly polarized light with a wavelength of 365nm are measured. The trans-cis isomerization of PAPNPAPOA is proved irreversible even after withdrawing the UV light for a long time. That the structure of main-chain attends by the trans-cis isomerization of side-chain is confirmed by the absorption and the solution colour during the UV irradiation. These effects are discussed by taking the trans-cis isomerization of azobenzene into consideration.