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In this paper, we report a simple procedure to decouple effects from temperature and volume on the emission properties of thin films of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). This procedure consists of applying a positive pressure close to the β-relaxation temperature, Tβ (∼220 K), of MEH-PPV, which controls the molecular movement to retain a disordered state for the polymer chains even after the sample is cooled from room temperature. Such decoupling could be confirmed by calculating the photoluminescence (PL) spectra line shape using a semi-empirical model based on molecular exciton and Franck-Condon transitions, and with electron-vibrational modes coupling being parameterized with the Huang-Rhys factor. We also show that the decoupling between temperature and volume effects does not occur if the molecular movement is restricted either by thermal annealing or by depositing the MEH-PPV film on a rigid substrate. This latter finding may be exploited in designing thermally stable devices.

Cervids show a high degree of abnormalities in their sperm cells. Thus, this study aimed to select high-quality spermatozoa using magnetic-activated sperm sorting (MASS) compared to density gradient centrifugation (DGC) by assessing the post-selection cell quality. Semen from six Mazama deer was collected by electroejaculation after chemical restraint. The semen was analyzed in four samples: Fresh, DGC, SEMgood - non-apoptotic fraction, and SEMpoor - apoptotic fraction. The material was analyzed for motility and vigor (light microscopy), concentration (Neubauer chamber), semen morphology (phase contrast), and supravital staining test (eosin/ nigrosine). The DGC method used 20 x 106 cells in 90% and 45% percoll® gradient. The MASS used 10 x 106 cells with 20 μl of iron nanoparticles attached to Annexin V and filtration in a magnetic separation column. Both processing methods (DGC and MASS) were effective in producing high-quality sperm samples, with a marked reduction in abnormalities from 41.83 ± 10.25 (fresh) to 14.83 ± 3.17(DGC) and 12 ± 3.01(SEMgood), with 80.3% ± 2.06 livings cells. These findings suggest that this nanotechnological method, using nanoparticles, effectively produces high-quality semen samples in cervids for use in assisted reproduction.

Objectives: Due to the crisis in protective equipment caused by a pandemic, it generates needs for equipment rationing among professionals working in the health area, with the need for many health professionals to use homemade masks. Therefore, this is a comparative study regarding the relative efficiencies of commercial respiratory masks (medical masks) and homemade fabric masks.Methods: A liquid aerosol line was created that passes through a chamber with 6 optical windows that allows the fixation of tissue or masks in the aerosol flow. The measures used two spectroscopic techniques that made it possible to relate the amount of aerosols with the scattering of light..Results: Fabrics with a higher percentage of cotton, and a greater number of layers and more closed wefts proved to be more efficient in blocking aerosols, however, fabrics without treatments obtained results far below the real needs of professionals working in the health area, with efficiency below 75% for liquid aerosols among the tissues tested.Conclusion: Homemade masks prove to be effective in reducing the spread of the virus among ordinary citizens in past infections, the efficiency of homemade masks is very low for health professionals who are directly exposed to the biological agent, so, it is necessary for public administrations to seek new alternatives with greater efficiency for this type of professional during the absence of surgical masks and n95.

This paper presents the results of a study conducted on the interaction between curcumin, a compound with several biomedical applications in traditional and modern medicine, and the acrylic polymers poly(methyl methacrylate), poly(ethyl methacrylate), and poly(n-butyl methacrylate), through photophysical experiments in curcumin/acrylic polymers casting films. Optical absorption intensity at ~340 nm increases relatively to its maximum at ~417 nm when the amount of curcumin in the polymeric film decreases, due to a significant change in the concentration of the isomers cis- or trans-form of curcumin, regardless of the acrylic polymer. Fluorescence (FL) spectra of the films depend on the curcumin concentration in the matrix with well-resolved line shape. They show two distinct bands, one at ~525 nm, for higher curcumin concentration (5.00 mmol.L-1), related to the aggregated curcumin species, and another at ~465 nm, for lower concentration of curcumin (0.10 mmol.L-1), related to the effects of the solvent on the conformational structure of the curcumin molecule and the presence of the trans-form of curcumin. The parameter Kagg, related to the contribution of the aggregated curcumin, shows the influence of the polymeric lateral chain length of the matrix in the de-aggregation of the curcumin. The Huang-Rhys factor indicates that curcumin aggregated species are conformationally more stable, and that the isolate species depends on the chemical environment and the matrix/curcumin interaction, decreasing its conformational degrees of freedom. Arrhenius plots, obtained via FL experiment in function of the sample temperature, show that, for higher curcumin concentration, the value for the relaxation energy process is not well defined, due the decrease in the interaction between the matrix and the curcumin molecules. With these results, it is possible to infer that the interaction matrix/curcumin must occur via lateral chemical alkyl groups.

We systematically investigated and quantified how gold (Au) metal nanoparticles (NPs) optical spectra change upon introduction into biological tissue phantoms environment, in which the AuNPs can agglomerate. Quantitative knowledge of how the AuNPs spectra and plasmon resonance wavelength change inside a phantom environment can provide many in-vitro and in-vivo plasmonic NPs-mediated applications. Because the plasmonic properties of metal NPs are dependent on their size, morphology, concentration and local environment, tuning the incident photon wavelength may increase the AuNPs plasmonic properties, on which applications such as plasmonic photothermal therapy and photonic gene circuits are based. Quantitatively analyzing optical absorption and scattering data, we were able to observe changes in the resonance peak positions and breadths, which are related to the distribution of the spherical AuNPs within the chitosan phantoms as a function of the particles size and concentration., Comment: 17 pages, 3 figures, 1 table

This paper reports the influence of the molecular relaxation temperature and electric field on the emission efficiency of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) in Organic Light-Emitting Diode (OLED) structure. We observe that the photoluminescence (PL) depends on the OLED polarization (forward and reverse) and on MEH-PPV molecular β-relaxation ( T β ∼ 220 K) and α-relaxation ( T α ∼ 330 K) temperatures. Above T β unbalance in charge carrier concentration in the device have a significant effect on the emission efficiency. The exciton energy transfer as a function of the sample temperature was determined using emission ellipsometry within the Stokes’ theory scope. Regardless of the OLED voltage polarization, the emission is partially linearly polarized and the polarization degree decreases significantly above T β and T α temperatures. Finally, we propose an approach to enhance the emission efficiency of luminescence polymers by controlling the molecular relaxation temperatures of the multilayer polymer OLEDs.

Nesta dissertação realizamos a síntese eletroquímica e a caracterização eletroquímica e óptica de polímeros conjugados eletroluminescentes no azul, como o poli(p-fenileno) (PPP) e alguns copolímeros. Filmes de PPP, poli(pirrol) (PPI), poli(3-metiltiofeno) (P3MET) e os copolímeros, copoli(p-fenileno-pirrol) (CPPI) e copoli(p-fenileno-3-metiltiofeno) (CP3MET), foram preparados por voltametria cíciica (VC) e cronoamperometria (CR) em eletrodos de óxido de estanho dopado com índio sobre vidro (ITO) em uma solução não-aquosa de acetonitrila e perclorato de tetrabutilamônio contendo os monômeros a diferentes concentrações. Durante a síntese eletroquímica dos filmes de PPP, PPI, P3MET, CPPI e CP3MET, foi usado CaC12 como agente secante em uma caixa-seca para reduzir a umidade do ar. Um tratamento de secagem permitiu um melhor controle sobre o crescimento dos filmes e a presença de umidade na síntese eletroquímica foi correlacionada as diferentes respostas eletroquímicas dos filmes. Os valores de potencial de ionização (PI) e de afinidade eletrônica (AE) foram calculados através da medida dos potenciais no início das curvas voltamétricas direta e inversa, quando foram obtidos os potenciais de oxidação e redução (Eoxd\' e Ered\'). Os valores de energia de gap eletrônico (EgapE) ara esses filmes foram também obtidos por medidas eletroquímicas. Através dos espectros de absorção no UVVIS, foi possível se calcular a energia de gap óptico (EgapO) para os diferentes filmes poliméricos. In this work we describe the electrochemical and optical aspects of a series of electrochemically synthesized blue-electroluminescent conjugated polymers. The materials employed here comprised poly(p-phenylene) (PPP), poly(pyrro1e) (PPI), poly(3-methylthiophene) (P3MET), poly(p-pheny1ene-pyrrole) (CPPI) copolymer and poly(p-phenylene3methyIthiophene) (CP3MET) copolymer. The films were electrochemically synthesized and deposited onto indium-tin-oxide covered glass (ITO) electrodes. The latter was carried out using either cyclic voltammetry (VC) or cronoamperometry (CR) in a acetonitrile nonaqueous medium containing tetrabutilammonium perclorate and different concentration of the respective monomers. As a further film quality control, the synthesis was carried out within a glove box containing a CaCI2 salt, which acted as drying agent. The latter procedure allowed us to correlate the amount of moisture present within the glove box with the electrochemical properties of the films. The ionization potential (PI) and the electronic affinity (AE) were calculated using the oxidation and reduction on-set potentials of the films (Eoxd\' e Ered\'). The electronic gap (EgapE)d the optical gap energies were calculated using electrochemical and UV-VIS. spectroscopy respectively.

Poly(p-phenylene/pyrrole) (PPP-PPY) films were electrochemically synthesised on transparent indium-tin-oxide-covered glass (ITO) electrodes. The presence of two monomers, p-phenylene and pyrrole, in the polymerisation medium facilitated the synthesis process, yielding electroactive, uniform and stable films. In order to obtain materials with improved quality, PPP, PPY and PPP-PPY films were prepared in a mild, dry atmosphere. The morphological, electrochemical and optical properties were compared for different films obtained by varying the number of cycles with and without controlling humidity.

Poly( p -phenylene) (PPP) and poly( p -phenylene-pyrrole) (PPP-Ppy) films were electrochemically polymerized on indium-tin-oxide glass (ITO) and platinum electrodes. Their optical properties were studied by UV-vis and photoluminescence spectroscopy. The influence of the final potential applied during synthesis (E f ) on the optical properties of PPP films was also studied. The PPP film prepared at 1.5 V showed an absorption band at 540 nm which was attributed to a p-doping process. Stable films with a similar emission band at 420 nm (blue region) were obtained after polymerization of p -terphenyl, and p -terphenyl/pyrrole monomers.

Poly(p-phenylene) (PPP), polypyrrole (PPY), and poly(p-phenylene-pyrrole) (PPP-PPY) films were electrochemically synthesized in acetronitrile by cyclic voltammetry. For comparison purposes, the films were characterized by cyclic voltammetry in a monomer-free solution, and their optical responses were also obtained in the UV-VIS range of energy after varying the applied potentials. The absorbance spectra of the PPP-PPY film exhibited bands typically seen in the spectra of the homopolymers, PPP and PPY films, but better defined, intense, and related to reversible color transitions. Although it was not possible to confirm by using infrared and Raman spectroscopy that a copolymer was in fact obtained, the presence of both monomers, pyrrole and biphenyl, in the polymerization medium turned easier the process of film formation, yielding darker, more uniform, and rougher films as it was verified by photographic images and AFM (atomic force microscopy) images.

The suitability of the layer-by-layer (LbL) technique, based on the alternate adsorption of oppositely charged materials, for immobilization of biomolecules has been well established. Achieving optimized results depends on the experimental conditions for film fabrication, and in most cases on the film architecture. In this paper we exploit the high catalytic activity of glucose oxidase (GOD) immobilized in LbL films with chitosan in oxidation reactions of glucose to gluconic acid. In addition to confirming previous works that these LbL films can be used in biosensors, we used the films in the reduction of a gold salt to yield metallic gold nanoparticles. The reaction kinetics was monitored by measuring the plasmon resonance band of gold nanoparticles, where the enzyme catalytic activity was found to be 92% of the activity in a homogeneous environment. This high degree of activity preservation for immobilized GOD is promising for various systems involving catalysis by GOD.

A theoretical approach is used here to explain experimental results obtained from the electrosynthesis of polypyrrole-2-carboxylic acid (PPY-2-COOH) films in nonaqueous medium. An analysis of the Fukui function (reactivity index) indicates that the monomer (pyrrole-2-carboxylic acid, PY-2-COOH), and dimers and trimers are oxidized in the C4 or C5 positions of the heterocyclic ring of the PY-2-COOH structure. After calculating the heat of formation using semiempirical Austin Model 1 post-Hartree–Fock parameterization for dimer species, both C4 and C5 positions adjacent to the aromatic rings of PPY-2-COOH were considered the most susceptible ones to oxidative coupling reactions. The ZINDO-S/CI semiempirical method was used to simulate the electronic transitions typically seen in the UV–VIS–NIR range in monomer and oligomers with different conjugation lengths. The use of an electrochemical quartz crystal microbalance provides sufficient information to propose a polymerization mechanism of PY-2-COOH based on molecular modeling and experimental results.

Instituto de Fsica de S¼o Carlos, Universidade de S¼o Paulo, Av. Trabalhador S¼o-carlense 400, S¼o Carlos, SP, postcode 369,13560-970, Brazil*e-mail: gdebora@ifsc.usp.brReceived: October 17, 2012Accepted: December 4, 2012Published online: February 22, 2013AbstractThe process for obtaining polypyrrole-2-carboxylic acid (PPY-2-COOH) films in acetonitrile was investigated usingcyclic voltammetry, electrochemical quartz crystal microgravimetry (EQCM), and infrared spectroscopy (FTIR).Different potential ranges were applied during cyclic voltammetry experiments with the aim of obtaining films with-out and with the presence of controlled amounts of water added in acetonitrile. The FTIR spectra of the films haveevidenced that cations and anions from the electrolyte solution were incorporated into the PPY-2-COOH structure,with a preferential adsorption of cations. After chemically immobilizing polyphenoloxidase (tyrosinase, PPO), PPY-2-COOH/PPO films were build for amperometric detection of catechol, establishing a linear limit of concentrationsranging from 5.010

Neste trabalho, apresentamos a eletrossíntese de um novo polímero condutor derivado do polipirrol (PPI) funcionalizado com um grupo carboxílico, o polipirrol-2-ácido carboxílico (PPI-2-COOH), e o seu uso como transdutor amperométrico em biossensores pelo uso da polifenol oxidase (PFO). São apresentadas todas as etapas de síntese e de caracterização dos filmes poliméricos em microeletrodos e o preparo e a resposta dos biossensores montados para a detecção de um composto fenólico. Nossos estudos sobre eletrossíntese, respostas eletroquímicas dos filmes, juntamente com resultados de microgravimetria e modelagem molecular de dímeros e trímeros derivados de PI-2-COOH, permitiram com que pudéssemos sugerir pela primeira vez um mecanismo de eletropolimerização deste monômero em meio não aquoso. Na caracterização dos filmes por espectroscopia in situ no UV-visível e infravermelho próximo foram observadas duas bandas idênticas às transições pi-pi* características dos filmes de PPI no seu estado neutro e de maior dopagem, confirmando a possibilidade de haver duas conformações na cadeia do PPI-2-COOH. Com a modelagem molecular de um oligômero formado a partir da oxidação do PI-2-COOH, verificamos que para cada 4 anéis heterocíclicos acoplados entre si na posição 4-5, um par de anéis se encontrava em um plano diferente do segundo par de anéis, mantendo este padrão em toda a extensão da cadeia polimérica. A resposta redox dos filmes nos permitiu observar a preferência do polímero pela entrada de cátions em sua estrutura. Nos espectros de FTIR também comprovamos a presença do grupo carboxílico na estrutura do polímero, o que permitiu uma imobilização enzimática por ligação covalente. A confecção de microeletrodos destinados para a análise por injeção em fluxo (FIA) nos possibilitou uma economia de reagentes, praticidade e boa reprodutibilidade das medidas. Os biossensores amperométricos obtidos pela imobilização covalente da PFO sobre filmes de PPI-2-COOH apresentaram um pH ótimo de funcionamento em 9,4 e um potencial ótimo de trabalho em +70 mV vs Ag/QRE. Finalizamos nosso trabalho obtendo as respostas amperométricas dos biossensores para a detecção de um composto fenólico, pirocatecol, com uma linearidade entre as concentrações de 5x10-4 até 2,5x10-2 mol/L. In this work, we present the electrochemical synthesis of a new conducting polymer derived of polypyrrole (PPI) functionalized by carboxylic group, the polypyrrole-2-carboxylic acid, and its application as amperometric transducer in biosensor by use of polyphenol oxidase (PFO). All the steps of syntheses and characterization of the polymer film in microelectrodes and response of the biosensor build for detection of phenolic compost. Our study about electrosyntheses, electrochemical response of the films (PPI-2-COOH) together with microgravimetry result and the molecular modeling of dimer and trimer derived from PI-2-COOH allowed one to suggest, for the first time, the mechanism of electropolymerization of this monomer in non-aqueous medium. When the technique of in-situ ultraviolet-visible spectroscopy (UV-VIS in-situ) was observed two bands, identical to the transition pi-pi* which are characteristics of the PPI films on their neutral state and of bigger doping, confirming the possibility that there may be two conformations in the PPI-2-COOH chain. With the molecular modeling of an oligomer formed by PI-2-COOH oxidation, we verified that for each four heterocyclic ring coupled together in the position 4-5, there´s a pair of rings, maintaining this pattern in all the extension of the polymeric chain. The redox response through the electrochemical measurement we could observe in FTIR the polymer preference for the cations adsorption. On the FTIR measurements, we could also observe the presence of the carboxylic group in the polymers structure, which is needed for the enzymatic immobilization by covalent binding. The fabrication of the microelectrode destined to flow injection analysis (FIA), made possible not only to save a lot of reagents, but also demonstrated praticity in the experimental set up and good reproducibility of results. Hence, the obtaining of amperometric biosensor by covalent binding of PFO on the PPI-2-COOH film, presented good pH in 9.4 and great work potential in +70 mV vs Ag/AgCl. We finish the work with the amperometric response of the biosensor in the detection of pyrocatechol, forming a straight line between the concentrations of 5x10-4 to 2.5x10-2 mol/L.

The molecular engineering capability of the layer-by-layer (LbL) method for fabricating thin films has been exploited in order to immobilize glucose oxidase (GOD) in films with alternating layers of chitosan. Chitosan was proven a good scaffolding material, as GOD molecules preserved their catalytic activity towards glucose oxidation. Using electrochemical measurements, we showed that chitosan/GOD LbL films can be used to detect glucose with a limit of detection of 0.2 mmol l−1 and an activity of 40.5 μA mmol−1 L μg−1, which is highly sensitive when compared to other sensors in previous reports in the literature. The highest sensitivity of the LbL film was achieved when only the top layer contained GOD, thus indicating that GOD in inner layers did not contribute to glucose oxidation, probably because it hampers analyte diffusion and electron transport through the deposited layers. This may be explained by the dense packing of GOD molecules in the LbL films with chitosan, as inferred from estimates of the amount of GOD adsorbed per layer using a quartz crystal microbalance.

Amperometric biosensors were fabricated based on a crude enzymatic extract of avocado as a source of polyphenol oxidase (PPO) immobilized on polypyrrole (PPY) films electrodeposited on fluorine-tin-oxide glass (FTO) electrodes. These enzymatic electrodes can be applied for determination of phenolic compounds from pesticides. The working electrode, FTO, was initially modified with a thin PPY film electrodeposited in a non-aqueous medium solution. The pre-deposited FTO/PPY films allowed us to obtain thicker and homogeneous PPY-PPO films by cyclic voltammetry in an aqueous medium solution. The enzyme, PPO, was immobilized onto FTO/PPY films by electropolymerization of pyrrole in the presence of crude PPO extract at a fixed amount. The PPY-PPO films exhibited a high sensitivity for catechol in solution and a highly selective response at very low concentrations of catechol. A detection limit of around 10 nmol L/sup -1/ for catechol was estimated for PPY-PPO films.