Search

The sensitivity evaluation of a vanadium pentoxide/poly-o-methoxyaniline hybrid material (V2O5/POMA) using casting deposition for the preparation of an ammonia gas sensor was investigated herein. V2O5/POMA was produced by the intercalation of V2O5 via sol–gel and o-methoxyaniline monomers. V2O5/POMA thin film deposition onto electrodes was performed by casting. The electrical studies confirmed that V2O5/POMA exhibited increased complex impedance as a function of increasing ammonia concentration. The conductivity of the film decreased with increasing ammonia concentration due to the de-doping process. According to theoretical adjustment, a significant increase in the bulk and interfacial electrical resistance in the presence of ammonia was observed. The combination of these effects contributed to the high sensitivity of the prepared film in both the real and imaginary components of the complex impedance for ammonia gas in a range of 0 to 100 ppm, which indicated that the film is a good candidate for use as an ammonia sensing material.

Conducting polymers such as polyaniline (PANi) have been widely investigated as ammonia gas sensors due to their intrinsic redox states, good environmental stability, and suitability for low-cost and variable changing in electrical conductivity when exposed to acid and basic gases. In this paper we used both a hybrid PANi derivative, poly(o-methoxyaniline) (POMA)-vanadium pentoxide (V2O5) film, and new ac electrical measurement strategies to increase the ammonia gas sensor performance. Complex impedance measurements of POMA/V2O5 hybrid film showed linearity in response and a high sensitivity to ammonia in the 0–20 ppm range in both real (around 800%) and imaginary (around 3000%) components, which indicated that the film is a good candidate to use as an ammonia sensing material. FTIR spectra presented typical V2O5 and POMA bands and also presented a shifting to higher wave numbers in bands referring to the vanadyl group and primary amines, which indicated the presence of hydrogen bonds between oxide and polymer. Finally, the Cole–Cole theoretical model with an interface effect provided a good fit for the experimental results from electrical ac measurements.

Studies of xerogel vanadium pentoxide hybrids in the presence of polyaniline (V2O5/PANI) for ammonia gas detection are presented. The hybrid materials were obtained in an oxidative polymerization/intercalation process, in which gel reacted with the monomers of the polymers. In situ characterization revealed V2O5/PANI hybrids with lamellar structure. Finally, the electric impedance technique was used for determining the optimal frequency band for operation of an Ag/V2O5/PANI/Ag amperometric ammonia gas sensor, to achieve linearity and stability. The results indicate that the sensor can detect gaseous ammonia in the 0–54 ppm range of concentrations. This characteristic is important for successful applications in easy to handle and low-cost ammonia gas sensors for animal confinement husbandry, for which current variation and difficulties related to electrode effects and dielectric absorption of V2O5 and PANI are negligible.

Hyperbilirubinemia is a systemic global problem and an often diagnosed pathology in newborns. In most cases, blue-light phototherapy (410–460 nm) is the only treatment required to prevent the bilirubin neurotoxicity, but its effectiveness is dose-dependent and is highly affected by the skills, knowledge, and attention of nurses and clinicians who implement the treatment. This paper presents a novel light-sensitive colorimetric dosimeter to simulate the effect of blue-light phototherapy on the optical properties of in vitro bilirubin. The dosimeter is based on a multilayered organic structure comprising a light-stable green-light emitter (copper phthalocyanine, C 32 Cl 16 CuN 8 ), and a blue-light-sensitive red emitter (poly{[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene]vinylene}, OC 1O C 6 -PPV). The optical and chemical properties of the dosimeter were investigated by fluorescence and FTIR spectroscopies and by color coordinates of CIE (1931) diagram chromatics, while the photochemical processing of bilirubin was evaluated by UV–vis absorption spectroscopy. The optical response of the dosimeter under conventional (10 μW/cm 2 ) and intensive (40 μW/cm 2 ) phototherapy was found to present the same photochemical kinetics as bilirubin. These findings highlight a cutting-edge solution for monitoring bilirubin elimination in neonates as a function of the dosimeter’s color evolution. This novel colorimetric dosimeter provides a standardized method of reporting and measuring phototherapy dose to promote an efficient use of available phototherapy units in health facilities.

This paper describes a variety of experiments that reveal the potential application of impedance spectroscopy (IS) measurements to enhance performance of ultrathin polyaniline (PANI)-based films on flexible substrate to control ammonia gas exposure in the 0–20 ppm range. Further, the device is mechanically robust for making electrical contact without lithography. We have employed the IS technique to proper adjust the optimal operation frequency of an easy-to-process, inexpensive and user-friendly PANI-based resistometric detectors in which drift current and delay problems related to electrode effects and dielectric absorption of PANI are insignificant. These requirements place emphasis upon the material and device configuration, and the range of frequencies from 10 to 100 Hz corresponds to the ideal working region to operate the device to unify sensibility inside 5%, reproducibility, linearity, stability and low response time (

Made available in DSpace on 2018-11-26T17:42:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) This paper describes a new statistical model to predict the frequency dependence of the conductivity of conjugated polymer-semiconductor nanoparticle composites. The model considers AC conduction in an inhomogeneous medium represented by a two-dimensional model of resistor network. The conductivity between two neighboring sites in the polymer matrix and the semiconductor particles is assumed to obey the random free energy barrier model and the Drude model, respectively. The real and imaginary parts of the AC conductivity were determined using the transfer-matrix technique, and the statistical model was applied to experimental data of thin films composed of polyaniline (PANI) and indium-tin-oxide (ITO) nanoparticles. The conductivity critical exponent (s) obtained in two dimensions for PANI/ITO films below the percolation threshold was found to be 2.7, which is greater than the universal value of s described by the classical percolation theory (s = 1.3). This non-universality is explained by the existence of a local electric field distribution in the bulk of the nanocomposite. Finally, these results are discussed in terms of the distribution of potential barriers that vary according to the concentration of ITO amount in the composite. Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil IFMG, Campus Ouro Preto, BR-35400000 Ouro Preto, MG, Brazil Univ Fed Ouro Preto, Dept Fis, BR-35400000 Ouro Preto, MG, Brazil Univ Estadual Paulista, Dept Fis & Quim, Campus Ilha Solteira, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista, Dept Fis & Quim, Campus Ilha Solteira, BR-15385000 Ilha Solteira, SP, Brazil

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable aliphatic-aromatic copolyester. In this paper, we report the radio induction of photoluminescence (PL) properties in PBAT, after exposure to high doses of gamma radiation. After the previous high-energy irradiation, the material shows the highest photo-stimulated luminescence emission when excited with a light-emitting diode (LED) source at wavelengths ranging from 370 to 405 nm. The PL intensities obtained after excitation with an LED source of 385 nm are proportional to gamma doses ranging from 100 to 1000 kGy in the preirradiation process. FTIR data revealed that the gamma-induced aromatic amine groups may be responsible for the appearance of the postirradiation PL character in PBAT samples. The results indicate that PBAT has great potential for applications in in vitro imaging of human cancer, bioimaging devices, and radiation dosimetry.

Research in hybrid electronics has included advances in materials, devices and architectures. However, in practice, controversy still exists on some details which limit hybrid materials to high-performance applications, such as processing–structure–design–property relations. This paper describes a practical approach to enhancing the sensing performance of a prototype ammonia gas sensor based on electrical conductivity changes, percolation theory and current limitation to a semiconducting polymer-metal oxide medium. This device is based on fully-gravure printed polyaniline/indium - tin oxide nanocomposites, Pani100−xITOx [0 ≤ x≤ 100% (wt/wt)], layers on a freestanding high-density polyethylene substrate. We find that the electrical current of the device decreases and tends to saturate as the gas concentration increases, and the value of this electrical current limit (IL) depends on x: the higher the value of x, the smaller the IL, when the current that flows through the electronic device was dominated by the ITO-nanoparticle filled PAni, which increase the concentration of hopping carriers and contribute to the desired electrical response of a heterogeneous gas sensor. In this regime, we find a good linear relationship between x and ammonia concentration. These findings suggest new directions for future research on the development and investigation of organic-inorganic devices in which the electrical current variation is desired for enhanced sensitivity and stability of hybrid sensors.

In the present work, we concentrate on the study of effects of metallic electrodes, multilayer thickness and temperature in ac and dc electrical conductivity of polyaniline/poly(vinyl sulfonic acid) (PANI/PVS) ultrathin films. The polymer system was obtained from layer-by-layer (Lbl) self-assembly technique on a glass substrate with an electrode array of adhesion layer of NiCr (20 nm) covered with Au (180 nm). We observed a significant and abrupt increase in the value of dc conductivity and a change of ac conductivity behavior of NiCr/Au–PANI/PVS–NiCr/Au structure when the thickness of PANI/PVS system reaches the Au layer. These effects were ascribed to the ideal contact of Au–PANI/PVS and the relative high interfacial contact resistance between PANI/PVS and NiCr, thus reducing the parallel resistance of NiCr/Au–PANI/PVS interfacial layer in an ideal parallel plate capacitor structure. Atomic Force Microscopy images confirm this assumption. Furthermore, the ac conductivity of Au–PANI/PVS–Au structure was typical of solid disordered materials. A model based on carrier hopping in a medium with randomly varying energy barriers was presented for the ac conductivity of the polymer system, which also encompasses the high dielectric constant of PANI/PVS blended films, the neutral contact Au–PANI/PVS, and the electrical resistance of NiCr–PANI/PVS interfacial layer. The model allowed separating the interface and the bulk effects in the electrical response of NiCr/Au–PANI/PVS–NiCr/Au structure and in addition the highest activation energy (35 MeV) correlated with an optimization of hopping distance (30 nm) for carriers jumps in PANI/PVS system.

In this paper, a detailed study of the capacitance spectra obtained from Au/doped-polyaniline/Al structures in the frequency domain (0.05 Hz–10 MHz), and at different temperatures (150–340 K) is carried out. The capacitance spectra behavior in semiconductors can be appropriately described by using abrupt cut-off models, since they assume that the electronic gap states that can follow the ac modulation have response times varying rapidly with a certain abscissa, which is dependent on both temperature and frequency. Two models based on the abrupt cut-off concept, formerly developed to describe inorganic semiconductor devices, have been used to analyze the capacitance spectra of devices based on doped polyaniline (PANI), which is a well-known polymeric semiconductor with innumerous potential technological applications. The application of these models allowed the determination of significant parameters, such as Debye length (≈20 nm), position of bulk Fermi level (≈320 meV) and associated density of states (≈2×1018 eV−1 cm−3), width of the space charge region (≈70 nm), built-in potential (≈780 meV), and the gap states’ distribution.

In this work, a new type of WO3 and V2O5 photovoltaic cell were fabricated. The oxides were obtained by sol-gel route. Both V2O5 and WO3 presented a lamellar structure with d = 1.17 nm and 0.69 nm, respectively. From SEM of V2O5 was observed ribbons and for WO3 noted a presence of platelets. For WO3, increasing the distance of lamp was observed a decreasing of light intensity: 164 mV in 44000 lux to 42 mV in 60 lux. For V2O5, in 1700 lux it was observed a voltage of 1418 mV and in 15000 lux a value of 1572 mV.

Poly( p -phenylene vinylene) (PPV) derivatives are well known for their applications in polymer light emitting diodes (PLEDs). PPV derivatives are highly susceptible to photo-oxidation though, which is mainly caused by the scission of the vinyl double bond on the polymer backbone. In this work, we show that Langmuir–Blodgett (LB) films are less degraded than cast films of a PPV derivative (OC 1 OC 6 -PPV). Both films had similar thickness (∼50 nm) to allow for a more realistic comparison. Degradation was monitored with UV–vis and FTIR spectroscopies. The results indicated that cast films were completely degraded in ca. 400 min, while LB took longer time, i.e. about four times the values for the cast films. The differences can be attributed to the more compact morphology in the LB than in the cast films. With a compact morphology the diffusion of oxygen in the LB film is hampered and this causes a delay in the degradation process.

We have developed a novel programmable, low cost, spin coater to be used for applications where flat substrates are coated with an uniform thin layer of a desirable material. The equipment is built with dc brushless motor present in most of the hard disk drivers (HDDs). The system offers manual control, wide speed range (from 0 to 10,000 rpm), spin speed stability and compact size. The paper also describes the use of such equipment for the fabrication of thin poly(o-methoxyaniline) (POMA) films, which are of particular interest for design organic electronic devices, such as diodes, transistor, sensors and displays.

In this work, a plasma-enhanced chemical vapor deposition (PECVD) system was used to deposit carbon nitride at low deposition temperatures (ca. 100 °C) to improve the lifetime of polymer light-emitting diodes (PLEDs) and to decrease photo-degradation of MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinilene]) in air. The characteristics of the carbon nitride and MEH-PPV films are investigated with FTIR and UV–Visible spectroscopies, with particular emphasis on the degradation process of MEH-PPV under illumination. It was shown by absorbance measurements that the coating protects the polymer film since the damage caused by photo-oxidation diminishes considerably. Current vs. voltage curves for PLEDs also indicated that the protection of a carbon nitride layer enhances the device lifetime.

The properties of a commercial indium-tin-oxide (ITO) layer deposited on glass substrates were evaluated as a function of the treatment time in diluted aqua regia solution. The samples were characterized by atomic force microscopy (AFM), bulk conductivity, ellipsometry, energy-dispersive X-ray analysis (EDX), contact angle/surface energy, and work function measurements. The results show that shorter times of treatment do not affect significantly the ITO properties but decrease the ITO thickness. For longer times (more than 30 min), although the work function and In/Sn ratio are not affected by the treatment, conductivity, roughness, UV–VIS absorption spectra, and refraction index values are greatly affected. Contact angle and surface energy data indicated that the dispersive component of the surface energy was not affected by the treatments. However, a strong decrease in the polar contribution occurred, indicating that ITO surface becomes more hydrophobic as the chemical treatment proceeds. These treated surfaces can interact more strongly with nonpolar materials, such as poly-(p-phenylene-vinylene) derivatives, resulting in a strong polymer ITO adhesion that can improve the efficiency of polymer light-emitting diodes (PLEDs).

Poly(p-phenylenevinylene) (PPV) and its derivatives exhibit strong luminescence, being serious candidates to be used as active layers in organic light-emitting diodes. However, the structural degradation caused by photo-oxidation is an obstacle for commercial applications of such materials. Here, we show that spectroscopy ellipsometry is a useful technique to investigate the photo-oxidation of poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] (MH-PPV), a PPV derivative, which emits a red color light. Spectroscopy ellipsometry enables determination of the complex dielectric function ∈ * (E) of MH-PPV thin-layer films exposed to air, in the 2.1-4.2 eV energy range, as a function of the light exposure time (t e ). By using the Lorentz model to fit the experimental ∈*(E) curves, it was inferred that the interactions among polymeric chains increase with t e . From ∈*(E), it is also possible to obtain the complex refractive index, N*(E) = n + ik. At higher energies (where k << n), n increases from 1.32 to 1.40 with the photo-oxidation progress. The behavior of n was investigated by using the Lorenz-Lorentz equation, taking into account the contribution for n by the chromophores of MH-PPV. The effect of photo-oxidation, mainly due to the replacement of vinyl C=C by the ketone C=O bonds, is confirmed by Fourier transform infrared measurements, an effect that reduces the average effective polymer conjugation length.

This article presents a novel radiochromic film for selective detection of low-medium (0–10 kGy) gamma radiation (60Co) doses. This dosimeter is based on a printed fluorescent multilayer structure comprising a paper substrate having layers of copper phthalocyanine (DY220) (a green emitter material) on the bottom, and layers of poly[2-methoxy-5(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) (a green-light absorber, red emitter, and radiation sensitive polymer) on the top. The effect of gamma radiation on the optical properties of DY220/MEH-PPV was described: it was observed as a strong correlation between radiation dose and fluorescent, color coordinates for CIE (1931) chromatic diagram, and Pantone color reference of the dosimeter. The rate of these changes can be altered by manipulation of top–bottom layers to represent easily the radiation dose to be determined in a wide range. This versatile dosimeter has many uses in the field of food radiation for monitoring, quality assurance, and control of the gamma radiation process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45729.

In this paper we present the photoconduction effect of the poly( p -phenylenevinylene) (PPV) and its derivative, the poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] (MH-PPV). The structures used to study photoconductivity were prepared using solutions of either PPV-precursor in methanol or MH-PPV in chloroform, both spin-coated on an interdigitated chromium-gold line array previously deposited onto glass substrate. Currents vs. voltage curves were carried out as well as of the films optical characteristics have been studied by UV-Vis, and photoluminescence and eletroluminescent spectroscopies.

A report is made of Langmuir film of a new semi-amphiphilic alternating N-hexylpyrrole-thiophene AB copolymer (PHPT) that is amenable to transfer as Langmuir–Blodgett (LB) films. PHPT was synthesized by condensation copolymerization via Stille coupling between N-hexyl-2,5-bis(trimethylstannyl)pyrrole and 2,5-dibromothiophene in the presence of Pd(PPh3)2Cl2 as a catalyst in dry DMF and characterized with various analytical techniques. In contrast to homopolymers (e.g. poly(N-alkylpyrrole)s and poly(3-alkylthiophene)s), PHPT formed a reasonably stable monolayer, as inferred through surface pressure and surface potential isotherms, and Brewster angle microscopy (BAM). The dependence of monolayer characteristics on the spreading volume, subphase temperature and compression speeds was also investigated. Electrical characterization revealed the possibility of using PHPT LB films as gas sensors.

Optical absorption and fluorescence measurements have been done on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]/[aluminum-tris(8-hydroxyquinoline)] solutions. The authors show that there is a visible response that covers the electronic absorption of bilirubin ( 350 – 500 nm ) , and hence, this material is applicable for managing the radiation doses planning before treatment of jaundice of neonates, which is one of the most common reasons of hospital readmission of newborns infants. The results show that the material presents a gradation of color from orange to yellow clearly, while its peak position emission shifts from orange-red ( λ max = 571 nm ) to green ( λ max = 540 nm ) with the radiation exposure time. The rate of these changes can be altered by manipulations of organic solution concentration and they are usually slow (from 2 to 8 h ), suggesting these color and emission changes can be used to design an easy to make, easy to read, easy to operate, low cost ( US $0.50) and accuracy for individual monitoring indicator dosimeter in order to represent easily the radiation exposure time usually used in management of neonatal jaundice.

The ac complex conductivity σ*(f) of polyaniline (PAN) films at different doping levels and different temperatures, in the 1–100 KHz frequency range, are reported. The results are typical of a disordered medium where the real component of ac conductivity is frequency independent at low frequencies, rising for higher values of frequencies. In order to interpret both the real and the imaginary components of σ*(f), we developed a model which considers the doped PAN as a disordered insulating matrix, sprinkled with conductive islands generated by doping, as indicated by energy dispersed x-ray microanalysis. The conduction through the insulating matrix obeys the random free energy barrier model, while in the conductive islands a metallic frequency-independent conductivity is considered. From the fittings we obtained the activation energy value of the maximum energy barrier of the doping mechanism and estimated the concentration of hopping sites.

This paper presents a methodology for the preparation of a-HgI2 by Physical Vapor Transport and of PbI2 crystals using the Bridgman technique. The results of the growth of HgI2 diluted in PbI2 by the Bridgman technique are shown for the first time, its limit of solubility having been determined at 600 ppm of HgI2 in the PbI2 matrix. Optical absorption, photoluminescence and electrical conductivity measurements show that the crystals prepared are of good crystalline quality.

The control of the photo degradation of a fluorene–vinylene–phenylene based-polymer, poly(9,9-di-hexylfluorenediylvinylene- alt -1,4-phenylenevinylene) (LaPPS16) was achieved by addition of a radical scavenger (RS) (enhancing photo resistance) or a radical initiator (RI) (reducing photo resistance). Photoluminescence, UV–Vis absorption, 1 H NMR spectroscopies and gel permeation chromatography (GPC) revealed that the incorporating small amounts of RS or RI is an efficient way to control the rates of the photo-oxidation reactions, and thus to obtain the conjugated polymer with foreseeable degradation rates for applications in blue-light sensitive detectors for neonatal phototherapy.

In this paper, we report our experimental design in searching a smart and easy-to-read dosimeter used to detect 6MV X-rays for improving patient safety in radiation oncology. The device was based on an organic emissive solutions of poly(2-methoxy-5(2′-ethylhexyloxy)- p -phenylenevinylene) (MEH-PPV), aluminum-tris-(8-hydroxyquinoline) (Alq 3 ) and additive components which were characterized by UV–Vis absorption, photoluminescence and CIE color coordinate diagram. The optical properties of MEH-PPV/Alq 3 solutions have been examined as function of radiation dose over the range of 0–100Gy. It has shown that MEH-PPV/Alq 3 solutions are specifically sensitive to X-rays, since the effect of radiation on this organic system is strongly correlated with the efficient spectral overlap between Alq 3 emission and the absorption of degraded MEH-PPV, which alters the color and photoemission of MEH-PPV/Alq 3 mixtures from red to yellow, and then to green. The rate of this change is more sensitive when MEH-PPV/Alq 3 is irradiated in the presence of benzoyl peroxide than when in the presence of hindered phenolic stabilizers, respectively, an accelerator and an inhibitor to activate or inhibit free radical formation. This gives rise to optimize the response curve of the dosimeter. It is clear from the experimental results that organic emissive semiconductors have potential to be used as dedicated and low-cost dosimeters to provide an independent check of beam output of a linear accelerator and therefore to give patients the opportunity to have information on the dose prescription or equipment-related problems a few minutes before being exposed to radiation.

In this work we investigate the radio-degradation of MEH-PPV polymer film as a tool for measuring high doses of gamma radiation. In order to produce film samples with thickness in the micron range, we have mixed the photoluminescent poly(2-methoxy-5(2'-ethylhexyloxy)-p-phenylenevinylene) copolymer (MEH-PPV) with a biodegradable poly(butylene adipate-co-terephthalate) copolymers (PBAT). The system was irradiated with a Co-60 source with doses ranging from 1 to 1,000 kGy. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy have been used to investigate the radiation induced changes in the absorption and photon-emission spectra of the irradiated samples. Results indicate that the PL emission intensity varies exponentially with the applied gamma radiation dose for doses ranging from 30 to 500 kGy. The unambiguous relationship between PL & Dose together with the good flexibility of the copolymer films indicate that MEH-PPV/PBAT blends have great potential for applications in high gamma dose dosimetry.

A novel approach for studying the thermal conversion of poly-p-xylylidene tetrahydrothiophenium chloride (PTHT) into poly(p-phenylenevinylene) (PPV) films has been proposed on the basis of calculated optical parameters. Spin-cast PTHT films were thermally converted into partially conjugated PPV films over conversion temperatures ranging from 22 °C to 200 °C. A strong correlation between refractive index (n) and damping constant extinction coefficient (k) was verified by spectroscopic ellipsometry (SE) for the films studied in the visible range of energy. The conversion temperature has a strong influence on the values of n and k, which were theoretically modeled using a Lorentz harmonic oscillator analysis. The films were also studied by spectroscopic techniques (photoluminescence, FTIR, and UV–VIS), and it was verified that the values of n decrease with increasing the amount of C C groups present along the polymer chains, as a strong evidence that both structure and optical properties of thermally converted PPV films can be directly compared. The optical properties of the PPV films were also compared with those of two electroluminescent derivatives in which side chains are introduced into the phenyl ring of PPV, poly(2-methoxy-5-hexyloxy)-p-phenylenevinylene) (MH-PPV) and poly(3-methoxy-5-dodecyloxy-p-phenylene–vinylene) (MD-PPV).

Neste trabalho são apresentadas a fabricação e a caracterização óptica de um novo detector de raios X para monitoramento da dose nos processos de radioterapia empregando fótons de alta energia (6,0 MV). O dispositivo foi fabricado a partir de materiais orgânicos luminescentes consolidados como elemento ativo de displays eletroluminescentes nanoestrurados, mas que, até esse momento, têm sido pouco investigados como detectores de radiação ionizante. Para tanto, foram preparadas soluções à base de tris(8-hidroxiquinolato) de alumínio - Alq3 e poli(2-metóxi-5-(2-etilhexiloxi)-pfenilenovinileno) – MEH-PPV, cujo espectro de emissão do primeiro material se sobrepõe ao de absorção do segundo. Os resultados obtidos mostram que os espectros de emissão do sistema MEH-PPV/Alq3 desloca-se do vermelho-laranja (λmax = 598 nm) para o verde (λmax = 545 nm) quando a dose de radiação vai de 0 a 100 Gy. Essa mudança, consequência da degradação induzida pela radiação do MEH-PPV, foi usada no desenvolvimento de dosímetros para possível futura aplicação no controle do tratamento de pacientes oncológicos. In this work it is presented the characterization and fabrication of a novel ionizing radiation detector for high energy photon beam (6.0 MV). It is used organic luminescent materials usually applied in light-emitting and nanostructure device, but still few explored in radiation dosimetry. Organic solutions of tris(8-hydroxyquinolinato) aluminum - Alq3 and poly[2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene] - MEH-PPV were prepared to better study the impact of spectral overlap between the Alq3 emission and MEH-PPV absorption. It is observed a blue-shift on the photoluminescence of the MEH-PPV/Alq3 solution system from red-orange (λmax = 598 nm) to green (λmax = 545 nm) when the radiation dose changes from 0 to 100 Gy. This effect is attributed to the photoxidation process of MEH-PPV and was employed to design dose accumulation detector in order to represent easily the radiation dose for cancer treatment.

We report on the design, fabrication and performance of a poly (2-methoxy-5(2_-ethylhexyloxy)- p-phenylenevinylene)/tris-(8-hydroxyquinoline)aluminum (MEH-PPV/Alq3) X-ray dose detector for improving safety for cancer patients shortly before radiation therapy. The detector consists of an inexpen-sive (

We report on the investigations about the modification of optical properties induced by X-rays onto film detectors of cadmium tungstate (CdWO4), poly[2-methoxy-5(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and polystyrene (PS) This device takes advantage of reduction of spectral overlap between the radioluminescence (RL) of CdWO4 and the absorption of MEH-PPV as it is exposed to radiation, forming the basis of a new dosimeter that is capable of converting the orange-red radioluminescence of PS:MEH-PPV:CdWO4 into green. We propose an explanation of the optical processes occurring in MEH-PPV:CdWO4 in terms of the radiation hardness of CdWO4 combined to the RL-induced degradation of MEH-PPV.

A fototerapia com luz azul (460 nm - 490 nm) é o procedimento mais utilizado para o tratamento da icterícia em recém-nascidos. Contudo, dois fatores alteraram drasticamente a eficiência desse tratamento: (1) o espectro da fonte luminosa e (2) a dose de radiação absorvida pelos neonatos. Este trabalho apresenta o desenvolvimento de detectores de radiação orgânicos e flexíveis, de baixo custo, de bom desempenho e de fácil operação para monitoramento da radiação incidente em neonatos ictéricos sob tratamento fototerápico. O princípio de funcionamento dos dispositivos baseia-se na resposta óptica de filmes finos à base de dois materiais orgânicos luminescentes: o tris (8-hidroxiquinolinato de alumínio) - Alq3 e o poli[2-metóxi-5-(2’-etilóxi)-p-fenilenovinileno] - MEH-PPV, dispersos em matriz de poliestireno – PS sob efeito de luz azul. Os resultados obtidos mostram que a radiação atua no sentido de alterar a intensidade de máxima emissão do vermelho ao verde, passando pelo amarelo, dos filmes de PS/MEH-PPV/Alq3. Esse resultado é atribuído à fotodegradação do MEH-PPV e, consequentemente, as mudanças na sobreposição entre os espectros de emissão do Alq3 e de absorção desse polímero. A resposta óptica dos filmes com a radiação foi usada para fabricar um sensor orgânico flexível, inédito e de custo inferior a R$ 0,50, para controle das condições de exposição de neonatos ictéricos à fototerapia com luz azul. Blue-light therapy (460 nm - 490 nm) is the most common treatment of jaundice in newborns. However, the efficiency of this treatment is dependent of two factors: (1) the spectrum of light source and (2) the delivered dose to the neonates. This work presents the development of a low-cost, flexible, good performance and an easy detector operation based on organic materials for evaluation of radiation dose delivered by the phototherapy units to jaundice newborns. The operation principles of the device is based on the optical response of poly [2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene - MEH-PPV, tris (8-hydroxyquinolinato aluminum)-Alq3 and polystyrene-PS thin films under the effects of blue-light. It is observed that the optical response of the PS/MEH-PPV/Alq3 films changes from red to yellow, and then to green with the radiation exposure. It is attributed to the photodegradation process of MEH-PPV and also to the spectral overlap between the photoemission of Alq3 and the absorption of MEH-PPV. The optical response of PS/MEH-PPV/Alq3 films was used to develop a novel organic flexible and low cost (

Neste trabalho, é apresentado o desenvolvimento de um novo equipamento para fabricação de filmes finos orgânicos, baseado na tecnologia automotiva de injeção eletrônica. Tal sistema apresenta, dentre as vantagens de disponibilidade comercial e baixo custo, baixas taxas de corrosão química e de problemas de entupimento dos bicos injetores, bem como o controle de taxas de temperatura de deposição. Portanto, apresenta versatilidade para utilização de diversas soluções orgânicas usadas em microeletrônica e eletrônica orgânica, tais como Fotoresistes e polímeros semicondutivos, como o poli(etileno-dioxitiofeno) - PEDOT. Ensaios obtidos com esses materiais mostram que o desempenho do sistema proposto depende de parâmetros como frequência da válvula injetora, diâmetro do orifício ejetor, pressão aplicada na solução impressa e das características da superfície dos substratos, que influenciam diretamente na qualidade dos filmes obtidos. This paper presents the development of a new equipment for manufacturing organic thin-films based on the technology of electronic fuel injection. This system presents, among the advantages of commercial availability and low cost, low rates of chemical corrosion and problems of nozzle clogging, as well as a temperature rate control system for material deposition. Thus, the developed equipment presents the versatility of using several organic solutions, such as Photoresistes and semiconducting polymers, for microelectronic and organic electronics, such as polyethylenedioxythiophene - PEDOT. Tests obtained with these materials show that system performance depends of parameters such as frequency of the injector valve, ejector orifice diameter, pressure applied in the printed solution and the substrates surface characteristics that influence directly in the quality of films obtained.

A hindered phenol type radical scavenger (Irganox 1010®) was used to improve the resistance to photo-oxidation in PPV-type polymers. The degradation was performed under blue light (460 nm), and the effect of the added compound was investigated following the intensity variation of absorbance and photoluminescence spectra. The results showed that the addition of the compound brought about a significant enhancement in photodegration resistance without interfering in the electronic properties of the polymers. These results suggest that the free radical scavenger attenuates the decrease of the polymer conjugation length induced by the radiation. FTIR measurements confirm this evidence.

Nesse trabalho filmes ultrafinos de PANI/PVS foram caracterizados óptica, elétrica e morfologicamente para estudo da viabilidade desses sistemas como elemento ativo de sensores de amônia. Os filmes automontados foram depositados entre microeletrodos metálicos formados por uma fina camada de NiCr recoberto com Au. Medidas de absorção na região do UV VIS mostraram o crescimento linear dos filmes, enquanto a análise das imagens de microscopia de força atômica mostrou o aumento da rugosidade, do tamanho de grão e do tamanho da partícula com a espessura dos filmes. A caracterização elétrica dc evidenciou uma significativa mudança na resistência elétrica do sistema quando a espessura do filme tornou-se equivalente à espessura do eletrodo de NiCr. Esse efeito foi atribuído à alta resistência elétrica da interface NiCr-filme. A impedância complexa obtida foi típica de materiais sólidos desordenados, com influência da interface NiCr-filme em baixas frequências. Por fim, os filmes mostraram ainda aumento de resistência elétrica em cerca de três vezes quando expostos às condições ambientais de galpões de criação avícola ([NH3] < 50 ppm), bem como em outras aplicações agropecuárias onde a necessidade do monitoramento desse gás é de grande importância. Esses resultados demonstram o potencial que filmes de PANI/PVS apresentam para aplicações agropecuárias. In this work we investigated the optical, electrical and morphological properties of ultrathin PANI/PVS films as active material of ammonia sensor for a poultry house. The layer-by-layer polymer films were deposited onto NiCr interdigitated microelectrode recovered with Au (NiCr/Au) line arrays. The buildup of the multilayers was monitored at each deposition step by UV-VIS spectroscopy while the atomic force microscopy (AFM) was employed to monitor the change in the roughness, in the grain and particle sizes. We observed a significant change in the dc conductivity when the thickness of the films was close to that of the NiCr layer. This effect is attributed to the higher interfacial electrical resistance between NiCr and the polymer film, compared to the resistance of the Au-film interface and polymer bulk. The alternating conductivity of the polymer was typical of solid disordered materials, under the influence of the NiCr electrode at low frequencies. Finally, the electrical sensitivity of the system under the exposure of NH3 reveals PANI/PVS films as a feasible active element for use in poultry house control systems.

Growth of the vanadium pentoxide xerogel in the presence of the polyaniline thin film (V2O5/PANI) in different chemical treatment on substrate are presented. The in situ characterization studies revealed the presence of a lamellar structure for the V2O5/PANI hybrid material. The intercalation reaction was evidenced on the basis of the increase in the d-spacing as well as the displacement of the absorption bands toward lower energy levels. The growth of V2O5/PANI thin film, from direct reaction, on glasses substrate using pre-treated with cationic surfactant cetyl pyridinium chloride (CPC) and cetyl trimethylammonium bromide (CTAB) presented layers with a surface homogeneous. The UV/ozone and RCA treatment showed that the film had low adhesion on substrate compared with CPC and CTAB treatment. Furthermore, these results suggests that the CTAB and CPC treatment can be used, further, for V2O5/PANI LbL films using V2O5 gel as first layer as well as a promising candidate for applications as sensor for ammonia detection in poultry shed.

The present work details, to our knowledge, the first examination of the influence of blue-light radiation on the optical properties of organic luminescent films in attempting to develop an indicator dosimeter for phototherapy of neonatal jaundice. Jaundice is the most common problem encountered in newborns due to immature functioning in the liver. The operating principle of the device is based on the optical response of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene (MEH-PPV) and tris(8-hydroxyquinolinato) aluminum (Alq3) materials dispersed in polystyrene (PS) matrix (denoted as PS/MEH-PPV/Alq3). It is observed a blue-shift on the photoluminescence of PS/MEH-PPV/Alq3 system from red to orange-yellow, and then to green as function of the blue-light radiation exposure time. The result is attributed to the spectral overlap between emission of Alq3 and absorption of MEH-PPV. The optical response of PS/MEH-PPV/Alq3 to radiation was investigated to design a low-cost (< US$ 0.05) “smart” sensor to represent easily the radiation dosage normally used in blue-light phototherapy. The basic idea behind this concept considers the sensor as a traffic light device, where red represents underdose and green the prescription dose or overdose, while orange-yellow suggests that radiation therapy is an ongoing process. This personal real-time radiation dosimeter appears here as a key requirement for successful development of innovations in effective management of the radiation dose planning before treatment of neonatal where control of dose absorption of infants is extremely important.

Luminescent polymers are commonly employed in light-emitting displays because of their good processability and higher luminance with low power consumption. However, even though they are candidates for lighting applications, they are susceptible to photoxidation processes which dramatically change their colour with light exposure. In this work we use the light instability of luminescent polymers in order to design a blue-light dosimeter which indicates dose accumulation by multicoloured changes of photodegraded poly(2-methoxy-5(2′-ethylhexyloxy)- p -phenylenevinylene) (MEH-PPV). Photoluminescence and absorbance spectra measurements were carried out on MEH-PPV solutions under the effect of blue-light provided by phototherapy systems. All measurements were done maintaining chief conditions of jaundice treatments. It is observed that changes from orange-red to yellow clearly on colour solutions, while its peak position emission shifts from orange-red to blue and decreases in intensity with increasing radiation exposure time. Experiments performed with oxygen enriched solutions were shown to improve these effects, which is mainly caused by the competition between two possible mechanisms: a light induced polymerization of MEH-PPV and replacement of C C by C O bonds on the polymer backbone. Analyses of the relation between the irradiance produced by phototherapy systems and CIE (1931) chromatic diagram of MEH-PPV reveal this polymer as an easy to operate blue-light dosimeter, and the results reported here clearly demonstrated the possibility to produce self-adhesive patch of luminescent polymers in order to attach such organic dosimeter safety and placed closer to the skin of jaundiced infants.

In this work we investigated the effect of visible radiation on the electrical properties of poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene]- MH-PPV films and light emitting diodes. Complex impedance measurements of (Au or ITO)/MH-PPV/(Au or Al) samples were carried out at room temperature and exposed to white light. Over the frequency range from 100 mHz to 2 MHz, the electrical results of Au/MH-PPV/Au was dominated by the Cole-Cole approach, where the electrode influence is negligible. However, some additional influence of the interface was observed to occur when Al was used as electrode. These effects were observed under both dark and visible-light illumination conditions. A simple model based on resistor-capacitor parallel circuits was developed to represent the complex impedance of the samples, thereby separating bulk and interface contributions. We observed that the polymer electrical resistivity decreased while the dielectric constant of the polymer and the thickness of the Al/MH-PPV layer were almost constant with increasing light intensity. The decrease of the polymer layer resistance comes from a better charge injection due to a light induced dissociation of positive charge carriers at the electrode.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:01:46Z No. of bitstreams: 1 S0104-14282007000400014.pdf: 147329 bytes, checksum: 3f893157c74ab6ca6c55c1e6b6861912 (MD5) Made available in DSpace on 2013-08-22T19:01:46Z (GMT). No. of bitstreams: 1 S0104-14282007000400014.pdf: 147329 bytes, checksum: 3f893157c74ab6ca6c55c1e6b6861912 (MD5) Previous issue date: 2007-12-01 Made available in DSpace on 2013-09-30T20:02:07Z (GMT). No. of bitstreams: 2 S0104-14282007000400014.pdf: 147329 bytes, checksum: 3f893157c74ab6ca6c55c1e6b6861912 (MD5) S0104-14282007000400014.pdf.txt: 21104 bytes, checksum: 2e00cd9e8faf5bb60bad2ebe8648ff72 (MD5) Previous issue date: 2007-12-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:22:59Z No. of bitstreams: 2 S0104-14282007000400014.pdf: 147329 bytes, checksum: 3f893157c74ab6ca6c55c1e6b6861912 (MD5) S0104-14282007000400014.pdf.txt: 21104 bytes, checksum: 2e00cd9e8faf5bb60bad2ebe8648ff72 (MD5) Made available in DSpace on 2014-05-20T13:22:59Z (GMT). No. of bitstreams: 2 S0104-14282007000400014.pdf: 147329 bytes, checksum: 3f893157c74ab6ca6c55c1e6b6861912 (MD5) S0104-14282007000400014.pdf.txt: 21104 bytes, checksum: 2e00cd9e8faf5bb60bad2ebe8648ff72 (MD5) Previous issue date: 2007-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Nesse trabalho descrevemos a arquitetura e a operação de filmes finos de polianilina (PAni) usados como elemento ativo de sensores flexíveis de pH e de deformação mecânica. Tais dispositivos apresentam grande interesse tecnológico devido aos seus baixos custos de produção e à possibilidade de integração com outros sistemas orgânicos e inorgânicos, incluindo transistores, diodos e baterias. Filmes finos de PAni foram preparados pelo método de polimerização in-situ sobre microeletrodos de Cr/Au previamente depositados sobre substratos de polietilenoteraftalato (PET). As características elétricas do sistema foram investigadas como função do nível de dopagem da PAni. Os dispositivos apresentaram boa resposta elétrica para diferentes soluções ácidas e básicas, bem como para pequenas variações de deformações mecânicas. In this work we describe the design and operation of thin polyaniline (PAni) films as active material for strain gauge and pH-monitoring flexible electronic devices. These devices are interesting due to their low cost and possible integration with other organic or inorganic systems, including diodes, transistors and batteries. Thin PAni films were prepared using the in-situ polymerization method on interdigitated chromium-gold microelectrodes previously deposited on poly(ethylene terephthalate) - PET substrates. The electrical characteristics of the polymer devices were obtained as a function of the PAni doping level. The devices showed high sensitivity for small strains and acid/base solutions. UFOP Departamento de Física EPUSP Departamento de Engenharia de Sistemas Eletrônicos UNESP Faculdade de Ciências e Tecnologia UNESP Faculdade de Ciências e Tecnologia

The alternating conductivity, σ *( f ) = σ ′( f ) + iσ ″( f ), of in situ polymerized polyaniline thin films doped with hydrochloric acid, deposited on top of an interdigitated gold line array previously deposited on glass substrates, were measured in the frequency ( f ) range between 0.1 Hz to 10 MHz and in the temperature range from 100 to 430 K. The results for σ ′( f ) are typical of a disordered solid material: for frequencies lower than a certain hopping frequency γ hop , log[ σ ′( f )] is frequency-independent rising almost linearly for in log f > γ hop . A master curve was thus obtained by plotting the real component of the conductivity using normalized scales σ ′( f )/ σ dc and f / γ hop , which is indicative of a single process operating in the whole frequency range. An expression encompassing the conduction through a disordered structure taken from previous random free energy barrier model for hopping carriers, as well a dielectric function to represent the capacitive behavior of the PAni was employed to fit the experimental results. The dielectric constant and activation energy for hopping carriers were obtained as function of the polymer doping level.

Neste trabalho foram observadas mudanças nas propriedades de emissão e de absorção de soluções de poli[2-metoxi-5-(2’etil-hexiloxi)-p-fenilenovinileno] – MEH-PPV com a exposição à radiação na região espectral do visível na faixa de 425 a 500 nm. Os resultados demonstram a possibilidade do uso de sistemas luminescentes como elemento ativo de detectores de radiação não ionizante, sobretudo na região empregada na profilaxia e no tratamento fototerápico da hiperbilirrubinemia neonatal. In this work, we observed changes in the emission and absorption properties of poly[(2-methoxy-5-hexyloxy)-pphenylenevinylene] - MEH-PPV solutions in the visible range from 425 to 500 nm. The main results demonstrated the possibility of using luminescent polymers as active material of non-ionizing radiation dosimeter, in such a way that MEH-PPV is promising for use in a management system to monitor radiation absorbed by newborns during phototherapy treatment of neonatal hyperbilirubinemia.

Photogenerated charge carrier profiles in poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) light-emitting diodes were determined from steady-state photocurrent spectra and transient photocurrent decay measurements. The observation that the photocurrent spectra behavior is strongly dependent on the bias polarity and amplitude suggests the existence of an intrinsic electric field, determined by the difference in the work function of the metallic electrodes, as well as a field dependence on the free charge carrier generation rates. The obtained results reveal built-in voltages of +0.2 and −0.6 V for Au and Al electrodes, respectively. The photocurrent spectra can be semi-quantitatively explained using a simple model which takes into account the internal built-in electric field of the device structure, the band gap energy and the migration/diffusion of the photogenerated charge carriers through the polymeric film. The drift mobility of carriers was investigated by the time-of-flight technique (TOF). The value for the mobility of holes was obtained from the change of slopes in the double logarithmic plot of the transient current and was independent of the applied field. The TOF transients for electrons showed no change of slopes in the double logarithmic plot and the drift mobility of electrons could not be calculated.

Solid-state nuclear magnetic resonance methods were used to study molecular dynamics of MEH-PPV at different frequency ranges varying from 1 Hz to 100 MHz. The results showed that in the 213 to 323 K temperature range, the motion in the polymer backbone is predominantly slow (Hz--kHz) involving small angle librations, which occurs with a distribution of correlation times. In the side chain, two motional regimes were identified: Intermediate regime motion (1--50 kHz) for all chemical groups and, additionally, fast rotation $(\ensuremath{\sim}100\phantom{\rule{0.3em}{0ex}}\mathrm{MHz})$ for the terminal $\mathrm{C}{\mathrm{H}}_{3}$ group. A correlation between the motional parameters and the photoluminescent behaviors as a function of temperature was observed and is discussed.

Complex resistivity measurements in dark and under vacuum were carried out to study the electrical behavior of luminescent polymer diodes (LEDs) having ITO or gold as hole injector electrodes, aluminium as the cathode, and poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] - MH-PPV as the luminescent layer. The results obtained were analysed by a model based on resistor-capacitor circuits, which made possible to distinguish between bulk from interface effects, and the contribution of each phenomenon to the electrical current. It was also shown that bulk properties already exist in a film of 0.4 /spl mu/m thick, and from the theoretical fittings it was obtained the dielectric constant and resistivity of MH-PPV.

In this work, we study the influence of organic solvents on the absorption and emission spectra of solutions and films of a soluble poly-(p-phenylenevinylene)- PPV derivative, the poly(3-methoxy-5-dodecoxy-p-phenylene-vinylene)- MD-PPV. We carried out absorption in the UV-Vis range, photoluminescence (PL) and photoluminescence excitation (PLE) measurements of MD-PPV solutions and cast films from five different solvents at room temperature. UV-Vis measurements show a solvatochromic effect, presenting a blue shift of the lowest-energy edge of the φ-φ* transition band for different solvents. PL spectra, on the other hand, show a multi-peak behavior, which is fitted considering an excitonic transition model followed by vibronic structure replica. It is observed that the first vibronic peak intensity tends to increase in comparison to the excitonic peak as δH increases, indicating that the solubility parameter of the solvent has a direct influence on the electron-phonon coupling. In addition, deviations from the intrachain model were observed for aromatic solvents, suggesting that aggregate formation can take place in the emission spectrum. Excitation spectra show that a new excitation peak comes out around 550 nm for poorer solvent solutions at higher PLE detection wavelengths, which is consistent with aggregate states emission.

This paper describes a new approach to improve the analysis of surface modification of free-standing semiconducting polymer films emerged from the interfacial interaction between aluminium electrode and HCl-doped polyaniline (PANI) films. The Al–PANI–Al structure was prepared by casting PANI/N-methyl-2-pirrolidone onto a glass substrate and then being sandwiched between Al electrodes after immersion in HCl aqueous solutions and then dried. The Al–polymer interface was investigated by means of complex impedance spectroscopy in the frequency domain on HCl-doped PANI films. The dc conductivity of the interfacial layer between the Al and PANI surface exposed to air during the film processing is higher than those obtained with Al and PANI surface exposed to glass. Raman spectroscopy data confirm this evidence. Here, it is speculated that some dissociated chlorine and aluminium-salt-containing species have contributed as ionic carriers increasing the electrical conductivity of the polymer bulk, and by the formation of an Al2O3 thin layer between the Al and PANI films. An equivalent circuit model considering the influence of Al–PANI reactions on the electrical behaviour of the Al–PANI–Al structure was proposed. Additionally, it was demonstrated that the impedance spectroscopy facilitates the identification of interface modification in the Al–PANI–Al films.

A field-effect transistor (FET) having poly(o-methoxyaniline) (POMA) as the active layer was built on a SiO 2 -Si substrate which acts as the gate. The POMA layer was deposited by spin coating on the substrate interdigitated with gold lines and which acts either as the source or drain contact. A tentative theoretical model based on the Schottky gold/polymer interface contact and on the electronic properties of the POMA film was developed to explain the characteristic behavior of the FET device.

Schottky diode structures employing chlorine doped MH-PPV (Methoxy-Hexiloxy-P-Phenylene-Vinylene) as active layers were prepared to study the electronic possibilities of this conjugated polymer. MH-PPV films were deposited by spin-coating technique on ITO (indium tin oxide) coated glass substrates. Aluminum contact was then vacuum evaporated. Dark conductivity characteristic is that of a rectifier diode. Upon illumination the device shows photovoltaic characteristics. When a voltage is applied, however, the structure shows electroluminescence with a peak at 606nm. In this sense, it is a reversible photonic device.

Alternating conductivity measurements of polyaniline, in the 1–10 5 Hz range, were carried out in samples under different temperatures. It was observed that for low frequencies the real component, σ'(ƒ), of ac conductivity is frequency-independent, however obeying the relation σ'(ƒ) ∝ ƒ s , beyond a critical value; the imaginary component increases with frequency in the whole measurements frequency range. The Random Free Energy Barrier Model approach was used to explain the experimental results, and from the theoretical-experimental fittings, it was concluded that the temperature acts in the sense of increasing the carrier mobility.