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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.

The increasing energy and sustainable materials demand requires the development of renewable production technologies to meet current global demands. Certainly, the progress for a sustainable development goes through the use of renewable and versatile raw materials, as the lignocellulosic biomass, in terms of application in energy, materials and environment sciences. The key role in the use of lignocellulosic biomass as renewable raw material has been its conversion to C6 and C5 sugars, which can be converted in different materials by several biological and chemical routes. Although its recalcitrance nature and high cost of the enzyme that promotes such conversions, obtaining a magnetic cross-linked enzyme aggregates (MCLEAs) has emerged as a green and sustainable technology to overcome these problems. This class of nanohybrids materials can significantly improve enzyme stability, activity and its recovery, decreasing cost of the process and adverse consequence of use of fossil raw materials. So, this review intends to shows the potential and recently advances of MCLEAs applied to biomass conversion to value-added chemicals, fuels and materials.

Made available in DSpace on 2021-06-25T10:52:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Financiadora de Estudos e Projetos Cancer is responsible for many fatalities and it is considered a public health problem. The side effects caused by conventional treatment are aggressive and painful to patients and can be reduced using nanomaterials that allows action in specific sites, making the cancer treatment more efficient, improving patient life's quality. Many kinds of nanoparticles that can be used, among these the block copolymer functionalized iron oxide nanoparticles stand out due to their simultaneous interaction with hydrophobic and hydrophilic drugs. The evaluation of these platforms properties allows optimizing their action in the human body, enhancing its biodistribution and targeting a specific region in the organism. The encapsulation efficiency and the controlled release profile is strictly dependent on the size, morphology, and interactions of the copolymer blocks. In this work, it was studied the synthesis of a hybrid nanoplatform composed of an inorganic core (iron oxide) and a polymeric shell (PCL-co-PEGMA block copolymer modified with folic acid). FTIR and 1H NMR allowed the confirmation of the nanoplatform synthesis. Particles around 180 nm stable at physiological pH were obtained, allowing its application in different regions of the human body. The encapsulation efficiency of methotrexate was approximately 95%. The drug delivery assays indicated that the nanoplatform is less active at pH 2; the presence of reduced glutathione enhanced the methotrexate release, reaching almost 50% methotrexate release after 96 h of analysis. The release efficiency of the nanoplatform allowed to identify its potential as a controlled drug delivery system. Laboratory of Magnetic Materials and Colloids Department of Physical Chemistry Institute of Chemistry São Paulo State University (UNESP), Araraquara - SP Laboratory of Magnetic Materials and Colloids Department of Physical Chemistry Institute of Chemistry São Paulo State University (UNESP), Araraquara - SP

Made available in DSpace on 2018-12-11T17:15:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-01 This study analyzes the synthesis and characterization of functionalized Fe3O4 nanoparticles by ethylenediaminetetraacetic acid (EDTA). The syntheses were performed using the co-precipitation method under different experimental conditions: nitrogen atmosphere versus ambient atmospheric conditions, and temperatures of 25 °C versus 90 °C. X-ray diffraction techniques, Fourier transform infrared (FTIR) spectroscopy, zeta potential, and transmission electron microscopy (TEM) were used to characterize these nanoparticles. The co-precipitation method produced high homogeneity in nanostructure shape and size. The functionalization of the magnetite surface was confirmed by the FTIR analyses and the development of new bands associated with EDTA as well as by zeta potential change. The addition of EDTA was also found to change the mechanism of nucleation and nanostructure growth; EDTA was found to favor nucleation, thus decreasing nanoparticle size. Department of Chemistry School of Sciences São Paulo State University (UNESP), Campus of Bauru Department of Physical and Chemistry Institute of Chemistry São Paulo State University (UNESP), Campus of Araraquara Associate Dean's Office of Graduate Research (PRPPG) Sagrado Coração University (USC) Department of Physics School of Sciences São Paulo State University (UNESP), Campus of Bauru Department of Chemistry School of Sciences São Paulo State University (UNESP), Campus of Bauru Department of Physical and Chemistry Institute of Chemistry São Paulo State University (UNESP), Campus of Araraquara Department of Physics School of Sciences São Paulo State University (UNESP), Campus of Bauru

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.

Made available in DSpace on 2020-12-12T02:16:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 In this work, we report the synthesis of a new nanofluid (NF) based on magnetic nanoparticles (MNPS) synthesized by the coprecipitation method with high colloidal stability. The MNPS were functionalized with citric acid (Cac), and then, polyethylene glycol, 1000 (PEG1000), was bonded by polycondensation reactions with acid groups on the nanoparticles surface to increase the colloidal stability of the nanofluid. The MNPS were dispersed in an aqueous medium to obtain nanofluid-based magnetic nanoparticles in water (NF-MNPS-W) and in ethylene glycol to obtain nanofluid-based magnetic nanoparticles in ethylene glycol (NF-MNPS-E). The MNPS were characterized by X-ray diffraction and selected area electron diffraction, which confirmed the formation of the crystalline phase of Fe3O4. Transmission electron microscopy was used to confirm the size and morphology of the MNPS. The MNPS had an average diameter of 11.33 ± 3.68 nm. Infrared spectrum of the MNPS allowed the functionalization of the MNPS by Cac and then by PEG1000 to be proved. The colloidal stability of NF-MNPS-W (pH 8) and NF-MNPS-E was evaluated by measurement of Zeta potential (ζ) and dynamic light scattering (DLS) − 25 mV and 112 nm ± 1 nm, respectively. The DLS in the temperature function allowed the stability of the NF to be proved in working conditions. Laboratory of Magnetic Materials and Colloids Department of Physical Chemistry Institute of Chemistry São Paulo State University (UNESP) Goiano Federal Institute of Education Science and Technology, Rodovia Sul Goiana Km 01, Zona Rural Laboratory of Magnetic Materials and Colloids Department of Physical Chemistry Institute of Chemistry São Paulo State University (UNESP)

The lack of monitoring of food freshness during the cold chain has been reported in the literature as either a problem faced by meat industries enforcing stricter controls and public health security needs. This paper presents an innovative solution for real-time food freshness discrimination: a printable, easy-to-use, and non-toxic two-faced Janus color-indicator label. This sensor is based on the pink to purple variation of a multilayer pH-sensitive composite (cellulose acetate and black carrot anthocyanin) film in the turnover process of fresh to spoilage chicken. The microstructure and permeability of the composite, and also the impact of the psychrotrophic aerobic bacteria on the optical properties of the indicator label, were investigated. This sensor demonstrating a short response time (∼ 2 min), great color stability, and provides interactive information of food freshness, being capable of communicating directly with consumers via two simple images: “happy face” for fresh meat and “sad face” for spoilage. As far as we know, this is the first time that the Janus (or Emoji) principle is designed for tracking food quality to allow consumers to have easy information on food freshness.

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 (

The treatment of skin wounds is a worldwide problem due to possible complications of healing process, such as infections, sepsis and even death. Current treatment strategies involves the use of dressings, bandages and topical application of antibiotic to the wound. An ideal dressing should protect against bacterial contamination, while covering the wound. The aim of this study was to investigate the antibacterial activity of chitosan membranes associated to banana peel for potential wound dressing application, since both materials have previously demonstrated antimicrobial properties. The active principles of banana peel were extracted by two methods: decoction and drying. Membranes were prepared by chitosan association with the extracts of first and third days of decoction and with different concentrations of dried extract, by the casting/solvent evaporation techniques. All obtained membranes were uniform, flexible and easily unmolded. Antibacterial activity studies were performed by the Surface Plating technique. Inhibition of bacterial growth was evaluated against two bacteria Escherichia coli and Staphylococcus aureus, usually present in skin wounds. All membranes were able to inhibit S. aureus e E. coli growth by contacting. In addition to contacting inhibition of E. coli growth, an inhibition halo of 0.5 cm diameter was also observed around the chitosan-unripe banana peel membrane prepared with the extract of first day of decoction.

Synthetic materials based on calcium such as hydroxyapatite and beta-TCP are one of the main bone substitutes because of their biocompatibility. The starch consolidation is a simple and low cost technique which is based on using the starch as a gel former in the presence of water, turning possible its use as a conforming and main element to form pores. In this project,samples were produced trough starch conformation by fixing the percentage of solids (beta-TCP) in 50% and varying the amount and type of starch (corn and potato) in 10, 20, 30 and 40%. The results showed that it was possible to obtain porous samples by using corn and potato starches. Moreover, the percentage of starch added strongly influenced porosity and resistance of the samples. The addition of 30% or more of starch reduced the mechanical resistance of samples which limited their use.

This work evaluated on the structural modification during high-energy ball milling of the Si-50C, Si-42.9C-19.1B e Si-33.3C-44.4B (at.-%) powder mixtures from elemental powders. Electron images revealed on occurrence of continuous fracture mechanisms in brittle particles during their processing, which presented rounded particles lower than 10 μm. X-ray diffraction results of Si-50C powders indicated that the intensity of Si peaks was slightly reduced after milling for 17 h, which were moved to the direction of larger diffraction angles after 7 h of milling, suggesting that carbon atoms were dissolved into the Si lattice in order to form an extended solid solution. Following, these values were increased due to the discrete exothermic formation of the SiC compound. In Si-C-B powder mixtures, the SiC and B4C compounds were formed after milling for 7 h.

Made available in DSpace on 2020-12-12T02:48:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-15 A magnetic cross-linked enzyme aggregate (MCLEA) of cellulases and a non-magnetic analogue (CLEA) were synthesized and further investigated. The obtained MCLEA and CLEA showed a high enzyme loading efficiency of 90% and 88%, respectively. However, the MCLEA presented an activity 33% higher than the CLEA one, suggesting a catalytic enhancement effect as a result of magnetic nanoparticle presence in cross-linked cellulase aggregates structure. In addition, MCLEA shows an unusual behavior with highest enzymatic activity at low temperatures near to 37 °C. Lastly, a full factorial design (2x2) with two variables at two levels, frequency (203–420 kHz) and amplitude (3–6 kA m−1), was used in order to better investigate the effects of an alternating magnetic field (AMF) on MCLEA activity. AMF application decreased MCLEA activity, particularly in the highest values of frequency and amplitude, when compared to condition field free. In addition, frequency implied in more significant effects on MCLEA activity when compared to AMF amplitude. São Paulo State University (UNESP) Institute of Chemistry Magnetic Materials and Colloids Laboratory São Paulo State University (UNESP) Institute of Chemistry Institute for Bioenergy Research (IPBEN) São Paulo State University (UNESP) School of Pharmaceutical Sciences São Paulo State University (UNESP) Institute of Chemistry Center for Monitoring and Research of the Quality of Fuels Biofuels Crude Oil and Derivatives (CEMPEQC) São Paulo State University (UNESP) Institute of Chemistry Magnetic Materials and Colloids Laboratory São Paulo State University (UNESP) Institute of Chemistry Institute for Bioenergy Research (IPBEN) São Paulo State University (UNESP) School of Pharmaceutical Sciences São Paulo State University (UNESP) Institute of Chemistry Center for Monitoring and Research of the Quality of Fuels Biofuels Crude Oil and Derivatives (CEMPEQC)

This work reports the synthesization of nanoparticles cobalt oxide (Co3O4) with no secondary phase by a modified sol-gel method and its structural morphological and electrochemical characterizations. FTIR, XRD and Raman analysis showed the formation of spinel cobalt oxide with no secondary phase. TEM images revealed that an undefined morphology with average crystallite size estimated by Scherrer's equation was found to be 30 nm. Experiments of cyclic voltametric, galvanostatic charge-discharge and impedance spectroscopy were evaluated at 1 mol L-1 KOH and revealed an intrinsic pseudocapacitance. The studies of complex capacitance and complex power revealed the resistive and capacitive characteristics with a specific capacitance of 120 F g-1.

The present work demonstrates preparation of magnetic nanoparticles by a novel method. Magnetic nanoparticles with potential for biomedical and environmental applications were obtained by homogeneous coprecipitation method sonochemically assisted. The effect of ultrasonic cavitation on changing the reaction environment was studied. The chemical reaction media used here was very similar to those used for Sono-Fenton process. The ultrasonic energy has driven the growth of particles; smaller diameter nanoparticles were obtained by applying a higher power. For the first time, it was demonstrated the iron oxide nanoparticles synthesis at pH lower than 6.

Made available in DSpace on 2018-11-26T16:04:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01. Added 1 bitstream(s) on 2021-07-15T15:01:17Z : No. of bitstreams: 1 S1516-14392018000600207.pdf: 5767388 bytes, checksum: ec46d42a9613a5d9eb8daa06e6a952cc (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this paper, a novel wound dressing membrane for controlled release of gentamicin (GE), while covering and protecting the wound was investigated. Chitosan (CHI) was associated with methoxy polyethylene glycol - polycaprolactone copolymer (mPEG-PCL) to prepare the blended wound dressing membranes. The use of copolymer mPEG-PCL was necessary to improve the compatibility between CHI and PCL. The association of CHI and PCL was required to control the water retention and release rate of encapsulated GE. In vitro release studies were performed with the mPEG-PCL/ CHI-GE membranes in order to evaluate the effect of copolymer concentration on the kinetics of GE release and water uptake. Reduced burst release rates and swelling ratios were observed for the 1/2 and 1/4 mPEG-PCL/CHI-GE membranes. In addition, all gentamicin-loaded membranes inhibited S. aureus and E. coli growth, and demonstrated color, moisture and thermal stability. Therefore, mPEG-PCL/CHI-GE membranes showed important features for potential wound dressing and drug delivery applications. Univ Fed Alfenas, Inst Ciencia & Tecnol, Pocos De Caldas, MG, Brazil Univ Estadual Paulista, Inst Quim, Araraquara, SP, Brazil Univ Estadual Campinas, Fac Engn Quim, Campinas, SP, Brazil Univ Estadual Paulista, Inst Quim, Araraquara, SP, Brazil

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

Made available in DSpace on 2018-11-26T17:40:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) FAP/DF INCT in Nanobiotechnology In this study we report on successful production of two samples (BR15 and BR16) comprising magnetite (Fe3O4) nanoparticles (similar to 10 nm) surface-functionalized via hydrolysis and condensation of alkoxysilane agents, namely 3-aminopropyl-trimethoxisilane (APTS) and N-propyl-trimethoxisilane (NPTS). The as-produced samples were characterized using transmission electron microscopy (TEM), x-ray diffraction (XRD), magnetization measurements (5 K and 300 K hysteresis cycles and zero field-cooled/field-cooled measurements), and Mossbauer spectroscopy (77 and 297 K). The Mossbauer data supported the model picture of a core-shell magnetite-based system. This material system shows shell properties influenced by the surface-coating design, either APTS-coated (BR15) or APTS+NPTS-coated (sample BR16). Analyses of the Mossbauer spectra indicates that the APTS-coated sample presents Fe(III)-rich core and Fe(II)-rich shell with strong hyperfine field; whereas, the APTS+NPTS-coated sample leads to a mixture of two main nanostructures, one essentially surface-terminated with APTS whereas the other surface-terminated with NPTS, both presenting weak hyperfine fields compared with the single surface-coated sample. Magnetization measurements support the core-shell picture built from the analyses of the Mossbauer data. Our findings emphasize the capability of the Mossbauer spectroscopy in assessing subtle differences in surface-functionalized iron-based core-shell nanostructures. Univ Fed Acre, Postgrad Studies Biotechnol & Biodivers, Rio Branco, Acre, Brazil Univ Estadual Paulista, Inst Chem, Dept Phys Chem, Sao Paulo, Brazil Univ Brasilia, Inst Ciencias Biol, BR-70910900 Brasilia, DF, Brazil Univ Brasilia, Inst Fis, BR-70910900 Brasilia, DF, Brazil Anhui Univ, Sch Chem & Chem Engn, Hefei 230601, Anhui, Peoples R China Univ Estadual Paulista, Inst Chem, Dept Phys Chem, Sao Paulo, Brazil

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.

Several cements are used as biomaterials. Biopolymers such as chitosan and collagen exhibit excellent biocompatibility and can be used in the remodeling of bone tissue. The cement must have high mechanical strength and compatibility with original tissue. In this context, the objective of this study was to extract, characterize and cross-link collagen from bovine tendon, forlater associate it with chitosan and calcium phosphate to obtain cements for bone regeneration. Glutaraldehyde was used as cross-linker in 0.1, 0.5, 1.0 and 10% concentration. Infrared analysis confirmed the presence of functional groups characteristic of collagen, whereas the capacity of water absorption decreased with the increasing of cross-linking degree. Denaturation temperatures of collagen samples were obtained by Differential Scanning Calorimetry and Scanning Electron Microscopy showed the fiber structure characteristics of collagen, which were more organized for high degree of cross-linking samples.

The present work reports on the preparation of Al2O3-TiO2 ceramics by high-energy ball milling and sintering, varying the molar fraction in 1:1 and 3:1. The powder mixtures were processed in a planetary Fritsch P-5 ball mill using silicon nitride balls (10 mm diameter) and vials (225 mL), rotary speed of 250 rpm and a ball-to-powder weight ratio of 5:1. Samples were collected into the vial after different milling times. The milled powders were uniaxially compacted and sintered at 1300 and 1500°C for 4h. The milled and sintered materials were characterized by X-ray diffraction and electron scanning microscopy (SEM). Results indicated that the intensity of Al2O3 and TiO2 peaks were reduced for longer milling times, suggesting that nanosized particles can be achieved. The densification of Al2O3-TiO2 ceramics was higher than 98% over the relative density in samples sintered at 1500°C for 4h, which presented the formation of Al2TiO5.

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.

Apatite coatings were deposited on titanium surfaces modified by Nd:YVO 4 laser at different energy densities in environment atmosphere. Apatite was synthesized by sol–gel method using calcium nitrate and phosphoric acid as precursors. The titanium modified surfaces were dip-coated into precursor solution and pre-fired at 700 °C in air for 3 h. Analyses by XRD, FTIR and SEM showed the formation of a mixture of phases: hydroxyapatite (HA) and tricalcium phosphate (β-TCP) onto the surfaces submitted to laser ablation. Surface Rietveld analysis showed that a larger amount of non-stoichiometric oxides produced by laser ablation resulted in greater formation of HA on the coating. However, more of the β-TCP phase than HA was observed on surfaces with low amounts of oxides.

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.

Mossbauer spectroscopy was used in this study to investigate magnetite nanoparticles, obtained by spray pyrolysis and thermal treatment under H2 reduction atmosphere. Room temperature XRD data indicate the formation of magnetite phase and a second phase (metallic iron) which amount increases as the time of reduction under H2 is increased. While room temperature Mossbauer data confirm the formation of the cubic phase of magnetite and the occurrence of metallic iron phase, the more complex features of 77 K-Mossbauer spectra suggest the occurrence of electronic localization favored by the different crystalline phase of magnetite at low temperatures which transition to the lower symmetry structure should occur at T ∼120 K (Verwey transition).

SiC fiber-reinforced SiC matrix composite (SiCf/SiC) is one of the leading candidates in ceramic materials for engineering applications due to its unique combination of properties such as high thermal conductivity, high resistance to corrosion and working conditions. Fiber-reinforced composites are materials which exhibit a significant improvement in properties like ductility in comparison to the monolithic SiC ceramic. The SiCf/SiC composite was obtained from a C/C composite precursor using convertion reaction under high temperature and controlled atmosphere. In this work, SiC phase presented the stacking faults in the structure, being not possible to calculate the unit cell size, symmetry and bond lengths but it seem equal card number 29-1129 of JCPDS.

Bacterial cellulose (BC) hydrated membranes present nanometric reticulated structure that can be used as a template in the preparation of new organic–inorganic hybrids. BC–silica hybrids were prepared from BC membranes and tetraethoxysilane, (TEOS) at neutral pH conditions at room temperature. Macroscopically homogeneous membranes were obtained containing up to 66 wt.% of silica spheres, 20–30 nm diameter. Scanning electron micrographs clearly show the silica spheres attached to cellulose microfibrils. By removing the cellulose, the silica spheres can be easily recovered. The new hybrids are stable up to 300 °C and display a broad emission band under UV excitation assigned to oxygen-related defects at the silica particles surface. Emission color can be tuned by changing the excitation wavelength.

Nanocrystalline Pd–Co alloys were obtained by electrodeposition from an ammoniacal chloride bath. The influence of the crystallite size and the residual stress on the magnetic properties of the alloys was investigated. The residual stress increased as the applied current density was increased. It was associated to the high nucleation rate during electrodeposition and correlated to the lattice strain, estimated from the XRD patterns. Also from the XRD patterns the average crystallite size and the lattice constant were determined by Scherrer's and Rietveld's methods, respectively. Both parameters were directly influenced by the applied current density. Magnetic properties such as coercivity, remanence, saturation magnetization and squareness showed strong dependence on the residual stress and crystallite size. Coercivity higher than 1 kOe was achieved when a high current density was applied. High coercivity was attributed to the presence of residual stress and to the small crystallite size of deposits.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:05:37Z No. of bitstreams: 1 S1516-14392007000300005.pdf: 1100963 bytes, checksum: 493d41a9e406bd2b283ea7ab58ff3171 (MD5) Made available in DSpace on 2013-08-22T19:05:37Z (GMT). No. of bitstreams: 1 S1516-14392007000300005.pdf: 1100963 bytes, checksum: 493d41a9e406bd2b283ea7ab58ff3171 (MD5) Previous issue date: 2007-09-01 Made available in DSpace on 2013-09-30T20:09:32Z (GMT). No. of bitstreams: 2 S1516-14392007000300005.pdf: 1100963 bytes, checksum: 493d41a9e406bd2b283ea7ab58ff3171 (MD5) S1516-14392007000300005.pdf.txt: 23505 bytes, checksum: 045a4bde3b4855be573eec1b59a63747 (MD5) Previous issue date: 2007-09-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:17:43Z No. of bitstreams: 2 S1516-14392007000300005.pdf: 1100963 bytes, checksum: 493d41a9e406bd2b283ea7ab58ff3171 (MD5) S1516-14392007000300005.pdf.txt: 23505 bytes, checksum: 045a4bde3b4855be573eec1b59a63747 (MD5) Made available in DSpace on 2014-05-20T15:17:43Z (GMT). No. of bitstreams: 2 S1516-14392007000300005.pdf: 1100963 bytes, checksum: 493d41a9e406bd2b283ea7ab58ff3171 (MD5) S1516-14392007000300005.pdf.txt: 23505 bytes, checksum: 045a4bde3b4855be573eec1b59a63747 (MD5) Previous issue date: 2007-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Biomaterials (composites and blends) play a major role in the health of modern society. This paper reports on the preparation and characterization of polyvinylidene fluoride (PVDF) and hydroxyapatite (HAP) composites, analyzing the incorporation of HAP in PVDF and investigating their mechanical properties and cytotoxicity (biocompatibility) for use in bone restoration and filling. The material was prepared in film form by the casting method. PVDF pellets were dissolved in dimethylacetamide (DMA), a HAP/DMA emulsion was prepared. The materials were mixed in proportions of 100/00, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70 in weight and left to dry in an oven, resulting in homogeneous, flexible films which were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X ray diffractometry (XRD), contact angle measurement, and by mechanical and cytotoxicity tests. Instituto de Pesquisas Energéticas e Nucleares Centro de Ciência e Tecnologia de Materiais UNESP Instituto de Química Departamento de Físico-Química Universidade Estadual de Campinas Faculdade de Engenharia Química Departamento de Tecnologia de Polímeros UNESP Instituto de Química Departamento de Físico-Química

Surface modifications have been applied in endosteal bone devices in order to improve the osseointegration through direct contact between neoformed bone and the implant without an intervening soft tissue layer. Surface characteristics of titanium implants have been modified by addictive methods, such as metallic titanium, titanium oxide and hydroxyapatite powder plasma spray, as well as by subtractive methods, such as acid etching, acid etching associated with sandblasting by either AlO2 or TiO2, and recently by laser ablation. Surface modification for dental and medical implants can be obtained by using laser irradiation technique where its parameters like repetition rate, pulse energy, scanning speed and fluency must be taken into accounting to the appropriate surface topography. Surfaces of commercially pure Ti (cpTi) were modified by laser Nd:YVO4 in nine different parameters configurations, all under normal atmosphere. The samples were characterized by SEM and XRD refined by Rietveld method. The crystalline phases αTi, βTi, Ti6O, Ti3O and TiO were formed by the melting and fast cooling processes during irradiation. The resulting phases on the irradiated surface were correlated with the laser beam parameters. The aim of the present work was to control titanium oxides formations in order to improve implants osseointegration by using a laser irradiation technique which is of great importance to biomaterial devices due to being a clean and reproducible process.

Cellulose–phosphate composite membranes have been prepared from bacterial cellulose membranes (BC) and sodium polyphosphate solution. The structure and thermal behavior of the new composites were evaluated by X-ray diffraction (XRD), 31P-nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG) and thermomechanical analysis (TMA). From XRD analyses the Iα and Iβ cellulose crystalline phases were identified together with crystalline sodium phosphate that covers the cellulose microfibrils as revealed by SEM. 31P NMR spectra show peaks assigned to Q0 and Q1 phosphate structures to be compared to the Q2 units that characterize the precursor polyphosphate. Glass transition temperature, Tg, obtained from TMA curves and thermal stability obtained from TG and DSC measurements, were observed to be dependent on the phosphate content.

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.

SnO2-based varistors doped with ZnO and WO3 were prepared by mixed oxide method. Experimental evidence shows that the increase in ZnO amount increases the volume and microstrain of unit cell while the WO3 promotes a decrease. The effect of ZnO and WO3 additives could be explained by the substitution of Sn 4+ by Zn 2+ and W 6+ . The addition of WO3 inhibits the grain growth due to the segregation in the grain boundary without influence in the densification of the samples. Besides that, an increase in the electrical resistance of the SnO2–ZnO– WO3 system was observed independent of the WO3 concentration. D 2005 Elsevier B.V. All rights reserved.

In this work, the electrical properties of polymeric light-emitting diodes (LEDs) based on poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene), MEH-PPV, were studied by dc current–voltage (I–V) curves and impedance/admittance spectroscopy, at different temperatures. ITO/polymer/metal (Al and Au) structures were used to study the effect of the barrier height on the charge injection at the polymer/metal interfaces. For ITO/MEH-PPV/Al devices, strong temperature influence on the dc conductivity was observed in the forward direction whereas, in the reverse direction, the conductivity was almost temperature independent. On the other hand, ITO/MEH-PPV/Au devices presented temperature dependent conductivities for both polarities. This indicates that, for low barrier height at the interfaces (

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.

We present a detailed study of the electric mechanism of a thin poly(o-methoxyaniline) (POMA) field-effect transistor. The device was prepared using Al-Si/SiO2/(interdigitated gold lines array)/POMA structure as the gate electrode, insulating layer, source-drain electrodes, and active layer, respectively. A model is presented for the electrical characteristics of such a device that encompasses the disordered properties of the POMA, the source-drain electrical-field dependence of hole mobility, and the carrier and mobility gradients in directions perpendicular to the polymer–oxide interface. The fittings of source-drain current versus source-drain voltage, having as parameters the gate voltage, is in good agreement with the experimental data, and the dependence of both the carrier saturation velocity and of the carrier mobility with the gate voltage are obtained. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 74–78, 2005

The Generator Coordinate Hartree – Fock (GCHF) method is applied to generate extended (20s14p), (30s19p13d), and (31s23p18d) Gaussian basis sets for the O, Mn, and La atoms, respectively. The role of the weight functions (WFs) in the assessment of the numerical integration range of the GCHF equations is shown. These basis sets are then contracted to [5s3p] and [11s6p6d] for O and Mn atoms, respectively, and [17s11p7d] for La atom by a standard procedure. For quality evaluation of contracted basis sets in molecular calculations, we have accomplished calculations of total and orbital energies in the Hartree– Fock – Roothaan (HFR) method for 5 MnO 1þ and 1 LaO 1þ fragments. The results obtained with the contracted basis sets are compared with values obtained with the extended basis sets. The addition of one d polarization function in the contracted basis set for O atom and its utilization with the contracted basis sets for Mn and La atoms leads to the calculations of dipole moment and total atomic charges of perovskite (LaMnO3). The calculations were performed at the HFR level with the crystal [LaMnO3]2 fragment in space group C2v: The values of dipole moment, total energy, and total atomic charges showed that it is reasonable to believe that LaMnO3 presents behaviour of piezoelectric material. q 2003 Elsevier B.V. All rights reserved.

Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab Quim Teor & Computac, BR-66075110 Belem, Para, Brazil

Pure yttrium oxide or mixed with europium oxide (3 at%) were treated in supercritical isopropanolic suspension at 500°C for 20 h and filling degree of 50%. Products were supercritically dried and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and luminescence spectroscopy (LS). Particle shape is irregular with an equivalent diameter of ca. 5 μm. Cubic crystalline phase is mainly obtained and hydroxide ion in low concentration is detected by IR vibrational spectrum. Europium in this concentration does not extensively change such observed characteristics from the pure yttrium oxide. Luminescence spectra show that the doped product is a mixture of the two oxides added by oxyhydroxide impurities. Nevertheless, this precursor sample, after being heated at 900°C during 1 h, has all characteristics, especially luminescent ones, of the P22 commercial phosphor.

Powder X-ray diffraction (XRD) data were collected for La0.65Sr0.35MnO3 prepared through an alternative method from a stoichiometric mixture of Mn2O3, La2O3, and SrO2, fired at 1300 °C for 16 h. XRD analysis using the Rietveld method was carried out and it was found that manganite has rhombohedral symmetry (space group R3c). The lattice parameters are found to be a=5.5032 Å and c=13.3674 Å. The bond valence computation indicates that the initial inclusion of Sr occurs at higher temperature.

In this work the electron spin resonance (ESR) and electron detected magnetic resonance (EDMR) are applied in MH-PPV and MEH-PPV, respectively. The ESR measurements revealed that there is a change of lineshape and a clear reduction of spin density on MH-PPV degraded by light and air. This result is in agreament with the fact that the spin density resides predominantly on vinylic carbon. The EDMR measurements in MEH-PPV LEDs provided evidences that there is a spin-dependent fusion of two polarons to spinless bipolaron.

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.

In this paper we study the photo-oxidation phenomenon in the structure of a PPV derivative, the poly[(2-methoxy-5-hexyloxy)- p -phenylenevinylene] - (MH-PPV), using ellipsometry and infrared spectroscopy techniques. Ellipsometric measurements were carried out in MH-PPV films previously exposed to light irradiation in air. It was observed a variation of both real and imaginary components of the refractive index. These variations are related with the replacement of the vinyl C=C bounds by the carbonyl C=O bounds, as confirmed by the infrared absorption measurements.

The photodegradation of soluble electroluminescent polymers is one of the greatest problems to be overcome in order to improve their technological applications. Here we will report on preliminary evaluation of the effects of commonly used solvents on the photodegradation of poly(3-methoxy-5-dodecyloxy- p -phenylene-vinylene), MD-PPV. We prepared solutions of similar concentration of MD-PPV in different solvents and recorded the ultraviolet-visible spectra before and after the exposure to a 250 mW/cm 2 light intensity. Also, we prepared cast films with the same solutions (with similar thickness) in order to observe if the solvent also affects the properties of the films. The results showed that the solvent polarity seems to be not the unique factor affecting the photodegradation, since no direct correlation could be made. Among the solvents tested, tetrahydrofuran was the best solvent for preparing films in order to minimize the photodegradation process.

The purpose of this work is to obtain micrometer sized spherical particles of silica and silica–chromium from sodium silicate. Spherical particles were prepared by sol–gel method from hydrolysis to polycondensation of aqueous sodium silicate in alcohol medium. Chromium was added to the system for some samples. Compositions and morphologies were achieved by changing the precipitation agent. X-ray diffractometry, electrophoretic mobility, infrared spectroscopy and scanning electron microscopies were carried out on these particles to identify phases, determine particle mobility, morphology, particle sizes, shapes and order at short distance. Non-crystalline silica particles with spherical shapes and micrometric size were obtained. The surface potentials of the silica particles differed from that of the silica–chromium particles.

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.

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).