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Developing low-cost and efficient flexible supercapacitors is an important step towards the production of new energy storage systems for efficient wearable electronic devices. In this work, we report a simple and cost-effective approach to produce flexible electrodes for supercapacitors. The system consists of a complex ternary structure of hierarchical polyaniline (PAn) assembled on a polypyrrole (PPy) layer deposited on graphite pencil traces (Grt) in sandpaper. The proposed ternary composite PAn-PPy-Grt-Sp assembled in a device offered a maximal areal capacitance of 55.35 mF cm-2 at 0.3 mA cm−2, a higher value when compared to its counterparts of PAn-Grt-Sp (31.8 mF cm−2) and PPy-Grt-Sp (19.75 mF cm−2). The ternary composite also exhibited a higher energy (4.92 μWh cm−2) and power density (87.09 μW cm−2) at a current density of 0.3 mA cm−2 producing a more equilibrated supercapacitor device. The response to mechanical efforts returned negligible variation in electrochemical properties while cyclability remains as 80% of initial value after 3000 cycles.

Polymer electrospun fibers are potential candidates for use as ionic dye adsorbents, due to its low cost and massive production provided by a simple nanofabrication method. The optimization in the processing variables for development of more efficient adsorbents revealed a strong dependence between the fiber diameter and the adsorption capacity of fibers, which was measured as a function of dye concentration, pH, adsorbent amount and contact time. The available active sites on electrospun fibers favor the efficient dye removal and easy desorption, allowing the successive reuse of electrospun fibers, preserving typical adsorption capacity of 135.37 mg·g-1 in association with fast desorption at acidic condition, allowing successive reuses of adsorbents.

The kinetics of ripening of fruits, followed by subsequent degradation process represent important biochemical mechanisms with high aggregate value for agribusiness sector. In contrast to the destructive assays for identification of ripening degree of fruits, the development of non-invasive techniques introduces potential advantages concerning to the development of new methods for fruit production control. In this direction, the electrical impedance spectroscopy was used for the identification of the maturation degree of fruits based on variation of bulk resistance dependence with maturation of fruits, due to the variation in the liquid content in fruit fibers. The results revealed the strong correlation between mechanical assays and electrical parameters, characterizing an important advantage in terms of a non-invasive and non-destructive method for ripening identification degree.

The quest to develop flexible membrane-like supercapacitors to be applied in advanced electronic devices with a flexible structure is important for the modern world. In this study, we developed biomass-based supercapacitors by depositing activated carbon on an eggshell membrane and subsequently coating these with polypyrrole in a two-step procedure. The competition between the electrical double layer capacitance (EDLC) from activated carbon and the pseudocapacitance (PC) for the hybrid device is controlled by varying the amount of polypyrrole (PC component) in a time-dependent polymerization process. An areal capacitance of 172.5 mF cm−2, a corresponding energy density of 4.73 W h kg−1, and power density of 320.8 W kg−1, with a 60% retention even after 1000 cycles were obtained for samples prepared with the polymerization of polypyrrole on the activated carbon (incorporation of an active layer of 3.18 mg cm−2).

Electrically conductive and antibacterial material was prepared via in situ chemical polymerization of polypyrrole on electrospun fibers of Eudragit L-100 and Eudragit L-100/polyethylene oxide, providing an “all-polymer” template for adsorption and removal of Staphylococcus aureus from surfaces. The optimization in the bactericidal activity of resulting wipes depends on type and concentration of oxidizing agent which affects the morphology and electrical properties of resulting material. We report the optimization provided by ferric chloride (oxidant) on bactericidal activity of wipes of Eudragit L-100/polypyrrole electrospun fibers. Promising results for S. aureus removal confirm the potential application of this polymeric material.

Background: The development of alternatives for insulin secretion control in vivo or in vitro represents an important aspect to be investigated. In this direction, natural products have been progressively explored with this aim. In particular, flavonoids are potential candidates to act as insulin secretagogue. Objective: To study the influence of flavonoid on overall modulation mechanisms of insulin secretion. Methods: The research was conducted in the following databases and platforms: PubMed, Scopus, ISI Web of Knowledge, SciELO, LILACS, and ScienceDirect, and the MeSH terms used for the search were flavonoids, flavones, islets of Langerhans, and insulin-secreting cells. Results: Twelve articles were included and represent the basis of discussion on mechanisms of insulin secretion of flavonoids. Papers in ISI Web of Knowledge were in number of 1, Scopus 44, PubMed 264, ScienceDirect 511, and no papers from LILACS and SciELO databases. Conclusion: According to the literature, the majority of flavonoid subclasses can modulate insulin secretion through several pathways, in an indication that corresponding molecule is a potential candidate for active materials to be applied in the treatment of diabetes. SUMMARY The action of natural products on insulin secretion represents an important investigation topic due to their importance in the diabetes controlIn addition to their typical antioxidant properties, flavonoids contribute to the insulin secretionThe modulation of insulin secretion is induced by flavonoids according to different mechanisms. Abbreviations used: KATP channels: ATP-sensitive K+ channels, GLUT4: Glucose transporter 4, ERK1/2: Extracellular signal-regulated protein kinases 1 and 2, L-VDCCs: L-type voltage-dependent Ca+2 channels, GLUT1: Glucose transporter 1, AMPK: Adenosine monophosphate-activated protein kinase, PTP1B: Protein tyrosine phosphatase 1B, GLUT2: Glucose transporter 2, cAMP: Cyclic adenosine monophosphate, PKA: Protein kinase A, PTK: Protein tyrosine kinase, CaMK II: Ca2+/calmodulin-dependent protein kinase II, GSIS: Glucose-stimulated insulin secretion, Insig-1: Insulin-induced gene 1, IRS-2: Insulin receptor substrate 2, PDX-1: Pancreatic and duodenal homeobox 1, SREBP-1c: Sterol regulatory element binding protein-1c, DMC: Dihydroxy-6’-methoxy-3’,5’-dimethylchalcone, GLP-1: Glucagon-like peptide-1, GLP-1R: Glucagon-like peptide 1 receptor.

RESUMO: Este trabalho teve como objetivo analisar o potencial das soluções de óxido de zinco e de nitrato de prata como alternativa para antissepsia de tetos de bovinos (in situ), considerando a escassez de literatura a respeito do uso destes compostos na profilaxia de mastites. Primeiramente foram realizados ensaios de microdiluição e CBM (Concentração Bactericida Mínima) a fim de verificar a atividade antimicrobiana das soluções de óxido de zinco e de nitrato de prata sobre 30 isolados de Staphylococcus spp., obtidos de casos de mastite. Todos os isolados apresentaram sensibilidade às duas soluções testadas, mas a solução de nitrato de prata apresentou menores valores de CBMs (3,05 a 97,65 μg/mL), quando comparada as CBMs da solução de óxido de zinco (97,65 a 6.250μg/mL). Posteriormente, foram conduzidos os ensaios de antissepsia dos tetos (in situ) através da imersão dos mesmos nas soluções antimicrobianas testadas. Para isso, foram utilizados 40 tetos (n=40) oriundos de vacas abatidas, os quais foram divididos em 4 grupos de 10 tetos, destinados ao teste das solução de óxido de zinco a 3% (30mg/mL), de nitrato e prata 1% (10mg/mL) e seus respectivos controles. Os tetos foram submetidos à contagem de microrganismos mesófilos na superfície dos tetos (UFC/cm2) antes e após a imersão nas soluções testadas. Como resultado, todas as soluções (de óxido de zinco e de nitrato de prata) apresentaram significativa redução de UFC/cm2 até aos 60 minutos após a imersão (M 0’ a M 60’). A solução de nitrato de prata apresentou redução de UFC/cm2 significativamente maior, quando comparado ao grupo testado com solução de óxido de zinco. Tais resultados validam o potencial das soluções de óxido de zinco e nitrato de prata para utilização no pré e pós-dipping em vacas leiteiras. ABSTRACT: This study aimed to analyze the zinc oxide and silver nitrate solutions as an alternative antiseptic for cow teats (in situ), considering the lack in the literature about these compounds uses in mastitis prophylaxis. First microdilution tests med and MBC (Minimal Bactericidal Concentration were perfor in order to determine the antimicrobial activity of zinc oxide and silver nitrate solutions over 30 Staphylococcus spp. isolates, obtained from cows with mastitis. All strains tested showed sensitivity to both solutions, but the silver nitrate solution had lower MBC values (3,05 to 97,65ug/ml) compared with zinc oxide solution MBCs (97,65 to 6,250 ug/ml). Subsequently, the antiseptic teat tests were conducted (in situ) by immersing the teats in same antimicrobial solutions tested in the first experiment. Therefore, 40 teats were used (n = 40) originating from slaughtered cows were divided into 4 groups of 10 teats, to test test zinc oxide 3% (30mg/mL) and silver nitrate 1% (10mg/mL) solutions and their respective controls. The teats were submitted to mesophilic count on the teat surface (CFU/cm2) before and after immersion in tested solutions. As a result, all the solutions (zinc oxide and silver nitrate) had a significant reduction in CFU/cm2 until 60 minutes after immersion (M 0’ to 60 M’). Silver nitrate solution showed a reduction of CFU/cm2 significantly higher compared to the group treated with zinc oxide solution. These results validate the potential use of zinc oxide and silver nitrate solutions in dairy cows as a pre- and post-dipping antiseptic.

The performance of metal oxide-based devices for humidity impedimetric sensors depends on different conduction mechanisms during water molecules adsorption. As consequence, new strategies for development of hierarchical and doped structures of mixed metal oxides play a critical role in the production of more efficient humidity sensors. It is reported an alternative method for synthesis of hexagonal ZnO nanocrystals on TiO2-decorated electrospun fibers, allowing the production of ordered arrays of hierarchical TiO2/ZnO nanostructures. Polymeric matrix supporting fibers were removed after annealing (500 °C), providing nanostructures with promising application as low-cost humidity sensors. The structure of resulting materials was explored in addition to the influence of relative humidity (RH) (measured in the range 400 Hz–40 MHz) on complex impedance spectra.

Flexible batteries and supercapacitors (SCs) are expected to play a crucial role in energy storage and management in portable electronic devices. In addition, use of materials based on renewable resources would allow for more affordable and sustainable gadgets. In this context, eggshell membranes (ESMs) represent a promising functional platform for production of high-performance electronic components. In this work, we use ESMs for preparing flexible SCs through the incorporation of carbon nanotubes and subsequent in situ polymerization of polypyrrole, producing a highly conductive nanostructure characterized by a porous surface that exhibits both faradic and nonfaradic mechanisms for charge storage. We have found that by controlling the conducting polymer/carbon derivative relative concentration, one can maximize the corresponding capacitance to attain values up to the order 564.5 mF/cm2 (areal capacitance), 24.8 F/cm3 (volumetric capacitance), and 357.9 F/g (gravimetric capacitance). These bioinspired flexible devices exhibit a capacitance retention of 60% after 4000 cycles of charge/discharge and present negligible aging even after 500 bending repetitions (at a density of current 5 mA/cm2). The successful use of ESM-based electrodes in association with carbon derivatives/conducting polymers confirm that the exploit of biological materials offers a promising perspective for the development of new ecofriendly electronic devices.

Lapachol is a natural naphthoquinone with important activity due to its chemical and structural properties. Nine semisynthetic derivatives of this substance were tested against strains of Staphylococcus spp. to identify the antimicrobial activity of these compounds. Only β-lapachone and oxime of lapachol showed good activity against the strains studied. The minimum bactericidal concentration values ranged from 62.5 to 15.62 μg/mL. The antimicrobial activity of these substances may be related to functional groups characteristics by technique Fourier transform infrared spectroscopy. There is great antimicrobial potential mainly related to β-lapachone and to oxime of lapachol, instigating further studies on the mechanisms of action. Key words: β-Lapachone, lapachol oxime, spectroscopic analyses.

The adequate functionalization of magnetic/organic nanocomposites with β-galactosidase provides adequate nanoenvironment for reaction media and improved production of galacto-oligosaccharide from lactose with additional advantage related with magnetic removal of enzyme derivative and reuse (our results indicated retention level of 76% after 10 cycles of application). In this work, we have explored different combination of parameters for enzyme action in order to improve the action of magnetic nanoparticles/polypyrrole/enzyme in the galacto-oligosaccharide production.

Antimicrobial resistance in bacteria, such as Staphylococcus aureus, has been the subject of many assistance studies of alternatives for the treatment of infections. These studies aim to solve this problem for bacteria, such as biofilm formation. Aiming to control the emergence of the problem or enhance antibiotic activity, the data sources are inserted into new therapeutic alternatives for the treatment of infections. β-Lapachone and Lapachol Oxime are semi-synthetic derivatives of Lapachol with antimicrobial potential. Clinical isolates from human blood cultures were used in this study. Scanning electron microscopy (SEM) was performed following the glutaraldehyde fixation protocol. The presence of β-Lapachone and Lapachol Oxima interfered in the biofilm formation state. In the MEV, the effect was observed in the reduction of the population of biofilm-forming cells. Therefore, it was possible to conclude the promising potential of the anti-biofilm of substances, justifying the nature of the natural products as agents of inspiration for the detection of new compounds with the biological function.

We report an alternative random laser (RL) architecture based on a flexible and ZnO-enriched cellulose acetate (CA) fiber matrix prepared by electrospinning. The electrospun fibers, mechanically reinforced by polyethylene oxide and impregnated with zinc oxide powder, were applied as an adsorbent surface to incorporate plasmonic centers (silver nanoprisms). The resulting structures – prepared in the absence (CA-ZnO) and in the presence of silver nanoparticles (CA-ZnO-Ag) - were developed to support light excitation, guiding and scattering prototypes of a RL. Both materials were excited by a pulsed (5 Hz, 5 ns) source at 355 nm and their fluorescence emission monitored at 387 nm. The results suggest that the addition of silver nanoprisms to the ZnO- enriched fiber matrix allows large improvement of the RL performance due to the plasmon resonance of the silver nanoprisms, with ~80% reduction in threshold energy. Besides the intensity and spectral analysis, the RL characterization included its spectral and intensity angular dependences. Bending the flexible RL did not affect the spectral characteristics of the device. No degradation was observed in the random laser emission for more than 10,000 shots of the pump laser.

The search for light sources with targeted characteristics motivates the work of a large part of the photonics community. One topical subject in this area is the study of Random Lasers (RLs), which use as feedback mechanism the light scattering in a random medium instead of a Fabry-Perot cavity [1]. A large variety of RLs and a diversity of applications have already been demonstrated, as reviewed in [1]. Of interest in many applications are RLs based on flexible hosts-which act not only as mechanical support-but also as scattering agent. Such host can be obtained, for example, by electrospinning fibers made by environment-friendly materials [3].

The detection of traces of substances by surface-sensitive techniques such as surface enhanced Raman spectroscopy (SERS) explores the interaction of adsorbed molecules on plasmonic surfaces to improve the limit of detection of analytes. This article is an overview about recent development in SERS substrates applied in the detection of organophosphorus pesticides on plasmonic surfaces (arrays of metal nanoparticles). The morphology, roughness, chemical functionalization degree, and aggregation level of plasmonic centers are some of the critical parameters to be controlled in the optimization of SERS signal from specific analytes.

The development of highly conductive, flexible, mechanical reinforced and chemically modified cotton yarns for electrodes of supercapacitors represents an important advance in the energy storage devices applied in wearable electronics. The production of carbon-based conductive layers as supports for chemical polymerization of active polymeric materials (such as polypyrrole) is an important strategy that associates the high electrical double-layer capacitance of the carbon derivatives (carbon nanotubes and graphene nanoplatelets) and the pseudocapacitance of the polypyrrole in truly flexible devices with improved electrochemical response—high capacitance. These properties are affected by relative concentration of graphene nanoplatelets in carbon complexes due to the variation in overall conductivity of electrodes (in consequence of low aggregation degree and available surface area) and the electrochemical properties of the resulting devices that reaches capacitance in order of 45.5 F g−1 with a capacitive retention of 70% after 2000 cycles of use. These promising results open possibilities for new systems in wearable electronics.

A interação entre células e nanoestruturas poliméricas vem sendo considerado um importante tema para a biotecnologia. As fibras eletrofiadas apresentam estruturas porosas na ordem de submícrons com características que mimetizam os componentes fibrilares da matriz extracelular natural, favorecendo a atuação local efetiva de sistemas bioativos. A complexação de ácidos nucleicos com essas fibras e sua utilização em terapias de recuperação funcional e regeneração tecidual podem ser alternativas ao transplante celular e aos sistemas de entrega de proteínas indutivas. Na customização do perfil de interação entre essas matrizes e o material genético, é relevante manter a disponibilidade de seus tipos moleculares em concentrações efetivas no microambiente, com maior expressão gênica e maior tempo de ação terapêutica. Ao se buscar equilíbrio entre eficiência de transfecção e a viabilidade celular, diferentes estratégias são seguidas, como a incorporação de polinucleotídeos em soluções poliméricas ou em emulsões antes do processo de eletrofiação, ou mesmo a funcionalização de nanofibras pela modificação de sua superfície. Diante disso, esta revisão tem por finalidade apresentar os diferentes métodos de produção de nanofibras eletrofiadas funcionalizadas com ácidos nucleicos e suas aplicações na área da saúde.

O dissulfeto de molibdênio é um material amplamente utilizado para remediação ambiental tendo em vista sua excelente capacidade de adsorção, que é atribuída principalmente aos sítios ativos de enxofre na superfície do MoS2. Além disso, este material possui vantagens quando comparado com outros fotocatalisadores, como por exemplo por alta atividade fotocatalítica, baixa toxicidade e boa capacidade de remoção de contaminantes orgânicos e inorgânicos. Nesta revisão apresentaremos os diferentes métodos de preparação do dissulfeto de molibdênio a partir da esfoliação mecânica, química, eletroquímica e os métodos hidrotérmico, solvotérmico e de deposição de vapor químico. Abordaremos ainda suas propriedades tais como as capacidades de adsorção para diferentes tipos de metais pesados em solução, os tipos de degradação fotocatalítica a partir da comparação dos adsorventes a base de MoS2 com outros adsorventes, os mecanismos de adsorção e os fatores que afetam esse processo, como o pH e temperatura da solução, tempo de contato, tipos de contaminantes e a influência de outros íons presentes em solução que podem atrapalhar o processo de adsorção. Outro processo a ser reportado se refere à associação entre o MoS2 e outros compostos, como óxido de grafeno e compostos derivados do nitrogênio, óxido de titânio e associações com bismuto e prata, tendo como principal vantagem o aumento da capacidade de adsorção do material. Como conclusão, será tratado sobre a eficiência de remoção das diferentes associações do dissulfeto de molibdênio frente aos diferentes tipos de contaminantes assim como os diversos fatores que influenciam nesta eficiência.

Background: Usnic acid has been progressively reported in the literature as one of the most important lichen metabolites characterized by a rich diversity of applications such as antifungal, antimicrobial, antiprotozoal and antiviral agent. Particularly, antimicrobial activity of usnic acid can be improved by encapsulation of active molecules in enteric electrospun fibers, allowing the controlled release of active molecule at specific pH. Few relevant patents to the topic have been reviewed and cited. Methods: Bactericidal activity of usnic acid-loaded electrospun fibers of Eudragit L-100 and polyvinylpyrrolidone was examined against Staphylococcus aureus using inhibition hales methodology. Results: The controlled release of active material at high pH is established after 10 minutes of interaction with media and results in reasonable activity against S. aureus, as detected by inhibition hales. Conclusion: The strong biological activity of usnic acid-loaded electrospun fibers provides a promising application for corresponding material as a bactericidal agent for wound healing treatment.

TiO2/ZnO hierarchical heteronanostructures were produced following a two-step procedure in which the hydrothermal growth of nanorods takes place on the surface of decorated electrospun fibers. The reaction product was a 3D-nanorod arrangement of a single-phase hexagonal wurtzite deposited onto the surface of a TiO2-decorated 1D-polymer nanoporous structure. The resulting composite was characterized as a potential candidate for photocatalytic applications, due to the available surface area and the high concentration of charge carriers, which minimizes the recombination of electrons and holes during photocatalytic processes. Photodegradation tests using rhodamine B (under visible-light irradiation) were performed to explore the photocatalytic activity of the nanostructures. Dye photodegradation ratio was determined to be 90% after 70 min, which indicates that TiO2/ZnO hierarchical heteronanostructures are potential photocatalysts.

We have applied electrical impedance spectroscopy (EIS) to investigate how the dielectric characteristics of protein aqueous solutions respond to varying amounts of a co-dissolved surfactant. Using bovine serum albumin (BSA) as our model system, we followed the conformational changes of the protein molecules that result from the progressive increment in the concentration of either ionic (sodium dodecyl sulfate – SDS, and dodecyltrimethylammonium bromide – DTAB) or non-ionic (Triton X-100) surfactants, and modeled the corresponding electrical response through a modified Randles circuit. From the dielectric data, we selected the behavior of the passive layer resistance (RPL) as a convenient parameter to map the conformational changes in the BSA molecules. The profile of the dielectric response of the BSA–surfactant solutions as a function of the amount of the added surfactant allows the identification of different ranges of the detergent relative concentration that can be associated to each one of the successive regimes of the surfactant–protein interaction. These results were similar to those obtained from a standard Stern–Volmer analysis of the fluorescence emission of the protein chain, with a better agreement occurring in the case of the non-ionic surfactant. We propose this novel EIS approach as a convenient alternative methodology to follow conformational changes of weakly fluorescent proteins.

In the last decade, exploration in high temperature and pressure wells has motivated the improvement of drilling fluids with the application of nanoparticles. In this context, nanoclay, the most available of nanoparticles, has been applied in the development of nanofluids, mainly associated with polymers. In parallel, among the polymers used, xanthan gum has been little explored for this purpose. In this work, the interaction between xanthan gum, hydrophobic nanoclay, sodium and calcium chloride and their influence on the rheological parameters of the mixture was evaluated in solution. The influence of temperature and hydration time on the rheological parameters of the mixture was also evaluated. For this purpose, nanoclay was first characterized with XRF, XRD and TGA. Then, a complete factorial design 24 was adopted, varying the concentrations of nanoclay, xanthan, sodium and calcium chlorides. Third, a Doehlert Matrix of the 7x5x3 type was adopted, varying the concentrations of nanoclay, xanthan and temperature, with the concentrations of the constant salts. In the fourth, select the effect of the hydration time on the color rheological parameters. Finally, Conductivity and Potential Zetas of sizes were verified, varying the concentration of the components and the hydration time of the mixtures. It was concluded that the interactions between the components of the mixture do not stabilize; the temperature, the salts have no significant influence on the rheology of the mixture; nanoclay in concentrations not exceeding 5% (m/v) interacts with the Minimum Shear Stress; the rheological parameters stabilize after 96h of hydration. En la última década, la exploración en pozos de alta temperatura y presión ha motivado la mejora de los fluidos de perforación con la aplicación de nanopartículas. En este contexto, la nanoarcilla, la más disponible de nanopartículas, se ha aplicado en el desarrollo de nanofluidos, principalmente asociados con polímeros. Al mismo tiempo, de los polímeros utilizados, la goma de xantano ha sido poco explorada para este propósito. En este trabajo, se evaluó en solución la interacción entre la goma de xantano, la nanoarcilla hidrófoba, el cloruro de sodio y calcio y su influencia en los parámetros reológicos de la mezcla. También se evaluó la influencia de la temperatura y el tiempo de hidratación en los parámetros reológicos de la mezcla. Para este propósito, la nanoarcilla se caracterizó por primera vez con FRX, DRX y TGA. Luego, se adoptó un diseño factorial completo 24, variando las concentraciones de cloruros de nanoarcilla, xantano, sodio y calcio. En tercer lugar, se adoptó una matriz Doehlert del tipo 7x5x3, variando las concentraciones de nanoarcilla, xantano y temperatura, con las concentraciones de las sales constantes. Cuarto, se evaluó el efecto del tiempo de hidratación sobre los parámetros reológicos de las muestras. Finalmente, se verificaron los potenciales de conductividad y Zeta de las muestras, variando la concentración de los componentes y el tiempo de hidratación de las mezclas. Se concluyó que las interacciones entre los componentes de la mezcla no se estabilizan; la temperatura, las sales no tienen influencia significativa en la reología de la mezcla; nano arcilla en concentraciones que no exceden el 5% (m / v) interactúa con el esfuerzo de corte mínimo; Los parámetros reológicos se estabilizan después de 96 h de hidratación. Na última década, a exploração em poços de altas temperatura e pressão tem motivado o aperfeiçoamento dos fluidos de perfuração com a aplicação de nanopartículas. Nesse contexto, as nanoargilas, as mais disponíveis das nanopartículas, tem sido aplicada no desenvolvimento de nanofluidos, principalmente associada a polímeros. Paralelamente, dos polímeros utilizados, a goma xantana tem sido pouco explorada para essa finalidade. Nesse trabalho foi avaliada, em solução, a interação entre a goma xantana, nanoargila hidrofóbica, cloreto de sódio e de cálcio e a influência destes sobre os parâmetros reológicos da mistura. Também foi avaliada a influência da temperatura e do tempo de hidratação sobre os parâmetros reológicos da mistura. Para tanto, primeiramente caracterirou-se a nanoargila com FRX, DRX e TGA. Em seguida, adotou-se um planejamento fatorial completo 24 variando as concentrações da nanoargila, xantana, cloretos de sódio e de cálcio. Em terceiro, adotou-se uma Matriz de Doehlert do tipo 7x5x3 variando as concentrações de nanoargila, xantana e temperatura, com as concentrações dos sais constantes. Em quarto, avaliou-se o efeito do tempo de hidratação sobre os parâmetros reológicos de amostras. Por fim, verificou-se Condutividade e Potenciais Zeta das amostras, variando a concentração dos componentes e o tempo de hidratação das misturas. Concluiu-se que as interações entre os componentes da mistura não estabilizam; a temperatura, os sais não exercem influência significativa sobre a reologia da mistura;a nanoargila em concentrações não superior a 5% (m/v) interage na Tensão de Cisalhamento Mínima; os parâmetros reológicos estabilizam após 96h de hidratação.

The improvement in the electrochemical performance of flexible electrodes for supercapacitors depends on adequate doping level of pseudocapacitive prototypes incorporated into truly flexible devices. The interaction of graphene nanoplatelets, carbon dots and polypyrrole on flexible supports of eggshell membranes offers an adequate combination in which redox reactions and fast charge separation contribute to the reversible storage of energy. The mutual incorporation of carbon dots and graphene nanoplatelets in overall structure of PPy-based electrodes returned a capacitive retention of 96.3% (after 2000 cycles of use) and areal capacitance of 173.81 mF cm−2. Superior mechanical resistance and good performance at different bending conditions are additional advantages related to the chemical modification of eggshell membranes as supports for electrodes of supercapacitors.

The development of electrospun polymer fiber networks embedded with metal oxide nanoparticles in organic dye media favors the photons waveguiding and multiple scattering, providing the adequate environment for random laser action. The use of water-soluble polymer solution as support for electrospun matrix introduces relevant application in biomedical applications. Herein, it is explored the use of block copolymers (Eudragit L100) as support for electrospinning of polymer fiber doped with titanium dioxide (scatter centers) and rhodamine B (gain media). The resulting fiber net presented random laser behavior that depends on aggregation degree of gain media (rhodamine B) due to the combination of reabsorption/reemission processes with tunable response (emission peak position). These results open new possibilities for use of low-cost and water soluble electrospun-based random lasers based on organic dyes and random network of polymer matrix.

The feasibility of wearable electronics depends on the development of reliable energy storage devices that could combine high energy density to mechanical flexibility. A significant step towards this goal would be the preparation of supercapacitors prepared on truly flexible supports, which could present an adequate balance of Faradaic and non-Faradaic charge-discharge mechanisms. In this work, we have examined the performance of supercapacitors made by the incorporation of PEDOT, a conducting polymer, and carbon nanostructures (graphene nanoplatelets and two types of carbon nanotubes) on electrodes based on eggshell membranes. These biological substrates, which are flexible and present resilient mechanical properties, have a characteristically high porosity that favors the in situ polymerization of PEDOT. The final devices exhibit a very good electrochemical performance (such as a low IR drop, a good cyclability and a high capacitive retention, which after 2000 uses suffers a reduction of only 10% on its value), and an areal capacitance of the order of 39.6 mF cm–2.

Electrospun fiber-based random lasers are environment-friendly flexible systems in which waveguiding/scattering processes provided by their structure with a broad distribution of diameters are essential elements to generate a suitable lasing mechanism. In this work, we prepared electrospun fibers with dual-size diameter distribution (above and below the critical value for waveguiding), allowing that both optical processes can be established in the polymer network. As a result, random laser emission was observed for the electrospun fibers presenting dual-size diameters with rhodamine 6G as the gain medium, characterizing the combination of waveguiding/scattering as an adequate condition for development of organic nanofibrous random lasers. Degradation assays were also performed in order to evaluate the prolonged use of such random laser systems.

The production of more efficient yeast-based fuel cells (YFCs) depends on a combination of effective proton exchange membranes, electron mediators and current collectors. The adhesion of organisms on electrode surface plays a key role in the electron transfer process optimizing the generated power density. In this work, it is reported the preparation of a new YFC prototype using membranes of polyvinyl alcohol/ phosphoric acid and anodes of carbon nanotubes/polyurethane. The high surface area for yeast adhesion and the strong interaction established between cells/carbon nanotubes favor the energy generation in fuel cell. To evaluate the influence of external mediators and the consumption of feed solution (glucose) on performance of YFC, the kinetics of current generation of resulting fuel cells was analyzed. Results reveal that increases in the impedance of electrodes on generated power can be minimized by periodical infusion of feed fuel, preserving 70% of maximum power, representing an important condition for prolonged activity of fuel cell.

Multifunctional wearable electronic textiles based on interfacial polymerization of polypyrrole on carbon nanotubes/cotton fibers offer advantages of simple and low-cost materials that incorporate bactericidal, good electrochemical performance, and electrical heating properties. The high conductivity of doped polypyrrole/CNT composite provides textiles that reaches temperature on order of 70 °C with field of 5 V/cm, superior electrochemical performance applied as electrodes of supercapacitor prototypes, reaching capacitance in order of 30 F g–1 and strong bactericidal activity against Staphylococcus aureus. The combination of these properties can be explored in smart devices for heat and microbial treatment on different parts of body, with incorporated storage of energy on textiles.

Aims This study aimed to verify the formation of biofilms by Moraxella bovis, Moraxella ovis and Moraxella bovoculi isolates from ruminants. In addition, the lysozyme activity against the isolates of M. bovis, M. ovis and M. bovoculi in free form and in biofilms was determined. Methods and results In this study, 54 isolates of Moraxella sp. obtained from bovine and ovine clinical samples were evaluated in vitro for capacity of biofilm formation and lysozyme susceptibility in planktonic and sessile cells. In addition, biofilms produced by four Moraxella sp. isolates were visualized under scanning electron microscope (SEM). It was possible to demonstrate, for the first time, the ability to form biofilms by M. ovis and M. bovoculi. The isolates of Moraxella sp. have the capacity to form biofilms in different intensities, varying among weak, moderate and strong. It was verified that the lysozyme shows activity on Moraxella sp. in planktonic form. However, on biofilms there was a reduction in the production, but without impairing its formation, and on consolidated biofilms the lysozyme did not have the capacity to eradicate the preformed biofilms. Conclusions This work shows the capacity of biofilm formation by Moraxella sp. of veterinary importance. The lysozyme susceptibility of Moraxella sp. in planktonic form shows that this enzyme has bacteriostatic activity on this micro-organism and it reduced the production of biofilms. Significance and impact of the study Based on the results, it is possible to infer that the biofilm formation capacity by Moraxella sp. and the resistance to lysozyme concentrations equal to or greater than the physiological levels of the ruminant tear may be linked not only to the capacity to colonize the conjunctiva, but also to remain in this place even after healing of the lesions, being a reservoir of Moraxella sp. in a herd.

The development of nanostructures based on interaction of organic matrix and metal oxide particles (such as polypyrrole/zinc oxide composites) introduces interesting advantages due to synergistic/complementary photocatalytic activity of resulting material. Particularly, the available high surface area of resulting composite contributes with minimal aggregation of metal oxide nanoparticles and reduces the electron/hole pair recombination rate (if applied as a photocatalyst). Results indicate that superior performance is detected for composite of polypyrrole/zinc oxide applied in the photodegradation of rhodamine B and rhodamine 6G in comparison with degradation established by colloidal photocatalyst (surfactant/zinc oxide/dye). Progressive cleavage of organic dye molecule takes place in substitution to typical N-deethylation process.

Polymer composites synthesized by fractal growth of polypyrrole in the presence of titanium dioxide nanoparticles were investigated as potential photocatalysts. These branched structures are characterized by high surface area and improved action as photocatalyst in the degradation of rhodamine B. The resulting absorption of photons in the visible region and low rate of electron–hole recombination with adequate generation of radicals for subsequent N-deethylation of rhodamine B represent important aspects which corroborate potential application of new composite as efficient photocatalyst.

When positively charged conjugated polymer chains are jointly dispersed with (single-stranded or double stranded) DNA chains in solvents of low polarity, complex hybrid structures can result. Interpolymer complexes (IC) can be formed due to the mutual Coulomb interactions between the positive charges in the doped conjugated polymer and the negatively charged phosphate groups along the external ridge of the nucleotide chains. In fact, some of these IC have been reported as potential candidates for several biotechnological applications as, for instance, the development of reliable methods for determining the precise concentration of DNA, a still acute necessity for a number of applications. In this work, we measure the dielectric response of polyaniline/DNA complexes as a convenient procedure to investigate the dominating mechanisms involved in their process of aggregation when dispersed in chloroform. As the ratio of concentrations [PANI]/[DNA] is progressively increased, the corresponding charge transfer resistance varies in a characteristic way, according to the nature of the microscopic reactions taking place in the solution. In fact, the patterns of variation of the charge transfer resistance and optical absorbance of the solution corresponding to the polaron band transition are quite similar, but exhibiting opposite trends. We take this as strong evidence that the electrical characterization of such IC systems represents an alternative method to conventional spectroscopic techniques for investigating the dominant interaction mechanisms DNA and PANI chains in solutions.

The production of electrospun fibers of enteric polymer for controlled delivery of drugs represents a simple and low cost procedure with promising advantages relative to the longer therapeutic window provided by cylindrical geometry in association with intrinsic properties of pH-dependent drug carriers. In this work, we have explored the incorporation of additives (block copolymers of poly(ethylene)-b-poly(ethylene oxide)) into matrix of Eudragit L-100 and the effective action of hybrid composites on delivery of nifedipine, providing improvement in the overall process of controlled release of loaded drug.

Hybrid ZnO/TiO2nanoparticles were applied as potential photocatalyst agents incorporated into electrospun fibers of enteric block copolymers. The resistance of fibers avoids aggregation and contributes to prolonged action of semiconductor nanoparticles under continuous light irradiation. Such behavior is attributed to the minimal aggregation degree and elevated efficiency of photodegradation of modified nanoparticles in comparison with pristine ones. Hybrid ZnO/TiO2in nanofibers contributes to the association of different mechanisms such as N-deethylation and cleavage of dye molecules applied in the overall process of photodegradation.

BASIC PHYSICS TEACHING FOR ENGINEERING: THE CASE OF UNIVASF The retention and consequent avoidance of first year’s engineering students are historically related with difficult of physical concepts in the previous formation and new tools of differential and integral calculus. In this work, we have explored an alternative methodology implemented at Univasf, since 2004, in which introductory Classical Mechanics was separated in two different disciplines. At first level, the study of movement and Newton’s laws are explored with focus on the graphical interpretation and concepts of slope. In the second semester, the complementary content is explored. As a result, we observed a progressive increase in the performance of students and a reduction in the index of retention and dropout.

The development of new materials for hybrid supercapacitors requires the adequate combination of pseudocapacitance and electrical double layer capacitance, morphology, high surface area and low mass density of electrodes. In this work, we have explored a simple and low cost composite based on incorporation of titanium dioxide/single walled carbon nanotube complex during polymerization of hollow nanotubes of polypyrrole. The resulting composite is characterized by superior electrical properties (high conductivity) and improved electrochemical response. The optimization in the relative concentration of components of ternary composite results in a capacitance of 282 Fg−1 and specific energy density in order of 1.0 Wh kg−1 which is a result of synergistic interaction of components during polymerization of polymeric hollow nanotubes and core/shell structures of SWCNTs/polypyrrole decorated with titanium dioxide nanoparticles.

The improved bactericidal activity of new composites for wound dressing prototypes represents an important strategy for development of more efficient devices that make use of synergistic interaction between components. The doping level of polyaniline represents a critical parameter for its corresponding biologic activity. In this work, it is explored the doping effect of usnic acid on undoped polyaniline, that introduces important advantages namely, improved bactericidal activity of polyaniline and the anti-biofilm properties of lichen derivative. The deposition of the resulting material on polyurethane foam potentializes its applicability as wound dressing, characterizing a new platform for application against Escherichia coli and Staphylococcus aureus.

Electrical impedance spectroscopy (EIS) appears a promising label-free methodology for the investigation of processes related to the aggregation of macromolecules in solution. Here, we explore the EIS technique as a convenient tool for studying the irreversible aggregation of human insulin and describing its corresponding fibrillation kinetics. The in situ measurement of the electrical response of pure insulin solutions at 60°C allows for the real-time monitoring of the protein fibrillation as a function of the incubation time. The fitting of the EIS data through an equivalent circuit based on a constant phase element provides a simple set of electric parameters whose abrupt changes can be associated to transitions occurring in the organization of the macromolecules. For establishing the reliability of the method proposed, we have compared the protein aggregation profile collected from the EIS data to that obtained from a conventional fluorescence methodology where Thioflavin T (ThT) is used as a dye probe. The description of the fibrillation process is quite similar in both cases, since characteristic times of the same order were found for the consecutive processes associated to the initial lag phase of insulin fibrillation, to the rapid growth of amyloidal aggregates and to the final saturation step. Our results suggest that in situ EIS can be considered as a promising approach for the real-time label-free monitoring of protein fibril formation.

The study of selective metal oxide-based binary/ternary systems has received increasing interest in recent years due to the possibility of producing efficient new ceramic materials for relative humidity (RH) detection, given the superior properties of the mixed compounds in comparison with pristine ones. The aim of this work was focused on preparation and characterization of non-doped and Nb2O5-doped TiO2 : WO3 pair (in the pellet form) and evaluation of corresponding humidity-dependent electrical properties. The microstructure of the samples was analyzed from scanning electron microscopy, X-ray diffraction patterns, Raman spectra, BET surface area analysis, and porosimetry. The electrical characterization was obtained from impedance spectroscopy (100 Hz to 40 MHz) in the 10–100% RH range. The results showed that adequate doping levels of Nb2O5 introduce important advantages due to the atomic substitution of Ti by Nb atoms in highly doped structures with different levels of porosity and grain sizes. These aspects introduced a key role in the excursion (one order of magnitude) in the bulk resistance and grain boundary resistance, which characterizes these composite ceramics as a promising platform for RH identification.

The development of ternary systems composed of conducting polymers, multi-walled carbon nanotubes (MWCNT), and metal oxides represents an important procedure in the optimization of electrical properties of electrodes to be applied as supercapacitors. Superior electrical properties obtained from electrical double-layer capacitance of CNTs and pseudo/redox capacitance of conducting polymer/metal oxides are associated with mechanical properties of CNT, high level of conductivity of polymer, and a reasonable homogeneous dispersion of metal oxide into the bulk of resulting composite. We have explored a low-cost composite of MWCNT/polypyrrole (PPy) and titanium dioxide (TiO2) in this work from which electrodes with a high level of conductivity are obtained as a result of a synergistic interaction between components.

Composites of metal oxide nanoparticles incorporated into poly(vinyl pyrrolidone) electrospun fibers can be considered potential and low cost bactericidal agents. Homogeneous distribution of nanoparticles in the core of fibers and minimal aggregation induced by strong interaction with polymeric template are factors that contribute with diffusion of metal oxide nanoparticles from bulk to the fiber surface and subsequent release of nanoparticles to bacterial culture. Hybrid electrospun fibers were successfully applied against bacteria as a result of reasonable degree of interaction between zinc oxide and fibers as detected from FTIR analysis, DSC curves and SEM images.

This paper describes the adsorption of methylene blue and methyl orange from aqueous solution by eggshell membrane (pristine/modified with silver nanoparticles) which were analyzed by Fourier Transform Infrared/Raman spectroscopy and Scanning Electron Microscopy. The conditions for adsorption were varied in terms of pH, adsorbent mass, dye concentration and time of reaction. The equilibrium condition was evaluated according Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms while the adsorption kinetics was fitted by PSO/PFO and Elovich models. The results indicated that Freundlich model and PSO were better fitted by comparison with other models. In addition, the incorporation of silver nanoparticles favors the detection of dyes traces using the Surface Enhance Raman Spectroscopy (SERS method) in concentration as low as 10−9 M. The good desorption rate observed indicated that membrane has great potential for use as adsorbent and SERS support for dye traces detection.

Interfacial/in situ oxidative polymerization of polypyrrole in the presence of functionalized graphene sheets produces high-quality composites for supercapacitors, as analyzed by electrochemical impedance spectroscopy and cyclic voltammetry analysis. The synergistic interaction induced by the growth of p-type polypyrrole on the surface of negatively charged carboxylate functionalized graphene sheets results in higher storage capacity than graphene-only or polymer-only films. The high conductivity of p-doped polypyrrole and high surface area of graphene promote high charge accumulation in capacitors. We report the optimization of the relative concentrations of carboxylate functionalized graphene in the polypyrrole matrix to maximize the composition’s capacitance to 277.8 F/g.

Submitted by Marcio Luis Ferreira Nascimento (mlfn@ufba.br) on 2016-12-10T19:39:12Z No. of bitstreams: 1 RGI12.pdf: 591799 bytes, checksum: bf8272c17b86b27833e74c20a4832d3e (MD5) Approved for entry into archive by Escola Politécnica Biblioteca (biengproc@ufba.br) on 2017-03-13T16:55:57Z (GMT) No. of bitstreams: 1 RGI12.pdf: 591799 bytes, checksum: bf8272c17b86b27833e74c20a4832d3e (MD5) Made available in DSpace on 2017-03-13T16:55:57Z (GMT). No. of bitstreams: 1 RGI12.pdf: 591799 bytes, checksum: bf8272c17b86b27833e74c20a4832d3e (MD5) Previous issue date: 2016-11-15 A produção de nanofibras a partir da técnica de electrospinning representa uma linha de atuação estratégica nacional tendo em vista os diversos tipos de materiais que podem ser obtidos, assim como um amplo leque de aplicações. Nanocompósitos poliméricos, constituídos geralmente pela junção de um polímero com substâncias inorgânicas torna possível a obtenção de novos materiais com características únicas e otimizadas quando comparadas às substâncias em separado. O uso da técnica de eletrofiação (electrospinning) faz com que a interação entre os dois materiais na formação das fibras ocorra de maneira mais efetiva. Com o objetivo de melhor utilização dessa técnica, nesse trabalho foi analisada financeiramente a viabilidade de compra e instalação de um spin-off acadêmico visando a fabricação de nanofios pela técnica de electrospinning por uma incubadora de inovação de alta base tecnológica, vinculada a um laboratório de pesquisa em materiais brasileiro. A partir da utilização dos métodos de análise econômica de Valor Presente Líquido e Taxa Interna de Retorno foi possível verificar o potencial de lucratividade que a aquisição e operação de uma máquina de electrospinning pode fornecer para uma spin-off, levando em consideração tanto o aparato inicial necessário quanto as particularidades e variações apresentadas pelo mercado em que o produto está inserido Campus Ponta Grossa - Paraná