Filmes ultrafinos de poli(o-etoxianilina)-POEA foram depositados sobre lâminas de quartzo pela técnica de automontagem a partir de soluções aquosas desse polímero em pH 3 e 5. A influência das condições de preparação sobre a quantidade de POEA adsorvida foi avaliada por meio de espectroscopia UV-Vis, microscopia de força atômica e voltametria cíclica. Verificou-se que em pH 5 a quantidade de POEA adsorvida é sempre maior que em pH 3, independentemente do tempo de imersão do substrato na solução polimérica. Imersões sucessivas do substrato na solução de POEA contribuíram para um aumento significativo da quantidade de polímero adsorvido. Quando as imersões foram realizadas em tempos longos o processo de adsorção atingiu um equilíbrio em cerca de 3 min. Por outro lado, se imersões sucessivas são feitas em curtos períodos de tempo, a quantidade de POEA nos filmes pode ser aumentada indefinidamente o que indica a existência de um processo de não-equilíbrio.Ultra-thin films of poly(o-ethoxyaniline)-POEA were deposited onto quartz slides by the selfassembly technique from aqueous solutions of this polymer in pH 3 and 5. The influence of the experimental conditions on the amount of POEA adsorbed was evaluated by UV-Vis spectroscopy, atomic force microscopy and cyclic voltammetry. It was observed that in pH 5 the amount of POEA adsorbed is always greater than that in pH 3, regardless the time of substrate immersion into the polymeric solution. Repeatedly immersions of quartz substrate into the POEA solutions contributed to an increase on the amount of polymer adsorbed. When long time immersions were made the adsorption process reached a maximum around 3 minutes. However, if repeatedly short time immersions were adopted the amount of POEA adsorbed could be increased indefinitely indicating the existence of a non-equilibrium process.Keywords: conducting polymers, poly(o-ethoxyaniline), self-assembled films, thin films IntroductionThe fabrication of ultra-thin films of conducting polymers using the self-assembly technique (SA) has become very popular in the last years.1 This technique is based on the spontaneous adsorption of molecules from solutions onto a solid substrate and it has been used for the deposition of mono and multilayer films from different classes of materials, including polyelectrolytes, conducting polymers, proteins, fullerenes, etc.2,3 Among the advantages offered by using SA technique on the preparation of ultra-thin films we can include the low cost of experimental apparatus, short-time intervals for film fabrication and the control over the film properties by manipulating the experimental conditions. 2,3 The films obtained present very low thickness (around tens to hundreds of angstrons), smoothness and exhibit structural organization at the molecular level.2,3 Prototypes of molecular electronic devices such as light emitting diodes, 4 gas and taste sensors 5,6 and biosensors 7 have already been produced by using the SA technique.After the first work proposing the use of SA technique for the fabricatio...
Neste trabalho, foi investigada a interação entre substâncias húmicas e um polímero condutor (poli-(o-etoxianilina) -POEA), ambos em solução e filmes automontados. Os resultados mostram que as substâncias húmicas dopam a POEA por protonação, isto é evidenciado por espectroscopia UV-Vis e Raman. Os estudos de microscopia de força atômica (AFM) em filmes automontados mostram haver um aumento na rugosidade do filme polimérico quando este é exposto a substâncias húmicas (ácidos húmico e fúlvico), o que evidencia a existência de interação entre a POEA e as substâncias húmicas. Esta mudança na morfologia é reversível com a lavagem dos filmes com água, em concordância com as medidas elétricas, possibilitando a aplicação em sensores. Um sistema sensor formado por um arranjo de diferentes unidades sensoriais foi capaz de distinguir substâncias húmicas em solução aquosa, como é mostrado pela análise multivariada (análise da componente principal), o que é importante para controle da qualidade de água e solo.The interaction between humic substances and poly(o-ethoxyaniline) (POEA), a conducting polymer, was investigated for both solution and self-assembled films. The results have shown that the humic substances induce a doping of POEA by protonation, as indicated by UV-Vis and Raman spectroscopies. The atomic force microscopy (AFM) studies on the self-assembled films have shown that the average roughness of the polymer film has increased after exposing it to humic substances (fulvic and humic acids), consistent with the interaction between POEA and humic substances. However, this change in morphology is reversible by washing the films with water in agreement with the electrical data allowing using this system in sensor applications. Here, the sensor formed by an array of different sensing units was able to detect and distinguish humic substances in aqueous solution, as shown by multivariate analysis (principal component analysis). The motivation to detect humic substance comes due to its importance in terms of quality control of water or soil.
A fitorremediação é uma técnica de descontaminação de solos em que utiliza-se o potencial de espécies vegetais para extrair metais e outros contaminantes do ambiente. Neste trabalho foram utilizadas as espécies Brassica juncea (L.) Czern (Mostarda), Helianthus annus L. (Girassol) e Mimosa bimucronata (DC.) O. Kuntze (Maricá) para fitoextrair chumbo e níquel de solos. Para a realização do procedimento, foi feito o acompanhamento ao longo de 11 semanas de dois experimentos simultâneos em que o solo utilizado foi Latossolo Vermelho coletado dentro dos limites da Universidade Tecnológica federal do Paraná. No experimento 1, utilizaram-se 2 kg (massa seca) em potes de polipropileno contaminados com acetato de chumbo e sulfato de níquel em concentrações de 0,5, 1,0, 2,0 e 5,0 g/kg de chumbo e níquel, para identificar o potencial fitorremediador de Brassica juncea (L.) Czern e Helianthus annus L. Para o segundo experimento, foi utilizado 1 kg (massa seca) de solo contaminado com acetato de chumbo em concentrações de 0,25, 0,5 e 1,0 g/kg para verificar se a Mimosa bimucronata (DC.) e O. Kuntze possuem potencial fitorremediador.
Sensory quality is very important to determine the acceptance of food by consumers, and it is essential to identify the sensory attributes that contribute to food acceptability. This paper aimed to identify the attributes that contribute to the sensory acceptance of cookies containing rice, sorghum, and teff flour. The formulations were subjected to sensory descriptive analysis (Flash Profile) to describe the cookie samples. The substitution of wheat flour for sorghum and teff flour did not affect the acceptance of the products. The optimized formulation proved to be a good alternative as a new food for people with celiac disease due to its sensory, nutritional, and technological characteristics, such as the good amount of iron, proteins, and zinc and the crunchiness inherent in the biscuit. Novelty impact statement The use of unconventional gluten‐free flour is an alternative to improve the nutritional quality of gluten‐free foods. Teff and sorghum flours can be used as a substitute for rice flour, traditionally used in this type of product. The sensory description of cookies made with these flours, using the flash profile method, demonstrates that the use of these flours, or mixtures of them, makes the products different from cookies made only with rice flour, but with pleasant sensory characteristics. In addition, ComDim is a good alternative to statistical analysis for the flash profile.
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