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As técnicas de microscopia de varredura por força tem promovido um grande impacto em ciência dos materiais devido a possibilidade de obtenção de imagens em escala que pode chegar no nível atômico. Neste trabalho serão apresentados o princípio básico de funcionamento da microscopia de varredura por força, os vários modos de operação e as forças envolvidas e medidas. O potencial de aplicação destas técnicas no estudo de materiais, e em particular de polímeros, serão discutidos. Uma comparação da microscopia de força atômica com outras técnicas de microscopia será apresentada, assim como exemplos da utilização da técnica de microscopia de força atômica para o estudo de polímeros.The scanning force microscopy techniques are promoting a great impact on materials science due to the possibility to obtain images down to the atomic scale. This work reports on the basic principles of the scanning force microscopes, their operation modes and the forces involved and measured. The potential application of these techniques on the study of materials, particularly on polymers, is discussed. A comparison of atomic force microscopy - AFM - with other techniques is presented, as well as some examples of the use of AFM on the study of polymers.

We review the recent progress that have led to the development of porous materials based on cellulose nanostructures found in plants and other resources. In light of the properties that emerge from the chemistry, shape and structural control, we discuss some of the most promising uses of a plant-based material, nanocellulose, in regenerative medicine. Following a brief discussion about the fundamental aspects of self-assembly of nanocellulose precursors, we review the key strategies needed for material synthesis and to adjust the architecture of the materials (using three-dimensional printing, freeze-casted porous materials, and electrospinning) according to their uses in tissue engineering, artificial organs, controlled drug delivery and wound healing systems, among others. For this purpose, we map the structure–property–function relationships of nanocellulose-based porous materials and examine the course of actions that are required to translate innovation from the laboratory to industry. Such efforts require attention to regulatory aspects and market pull. Finally, the key challenges and opportunities in this nascent field are critically reviewed.

Detection of mycotoxins in food is essential due to their potential harm to human and animal health. However, developing affordable and rapid methods for their detection, particularly with the necessary selectivity to differentiate between various mycotoxins, remains a challenge. Herein, we present low-cost paper-based sensing platforms modified with curcumin, a natural polyphenolic compound, for the electrochemical and optical detection of ochratoxin A (OTA). By exploiting the fluorescence quenching effect of OTA on curcumin through Förster energy transfer, we successfully conducted optical detection with LODs of 0.09 ng mL−1 and a linear range of 0.5 to 15 ng mL−1. Additionally, by using electrochemical impedance spectroscopy and a portable instrument, we detected OTA with a limit of detection (LOD) as low as 0.045 ng mL−1. These sensitivity levels meet the requirements established by food regulatory agencies for monitoring food quality in relation to OTA contamination. Our curcumin-modified paper-based sensors offer a compelling combination of simplicity in manufacturing and cost-effectiveness, underscoring their potential for routine food quality monitoring, especially concerning ochratoxin A.

The identification and quantification of plant pathogens in the early stages of infection play an important role to ensure food security and decrease crop loss. Over the past years, advances in nanomaterials research have allowed the development of novel plant disease (bio)sensors with high sensitivity and specificity. In this review, we address the use of different 0D, 1D, 2D and 3D nanomaterials for designing varied plant disease (bio)sensors. Specifically, the appealing features of nanomaterials, including high surface area/volume ratio, tunable physical-chemical properties and capability to incorporate biomolecules, are discussed, while illustrative examples on how they can be applied to improve the performance of electrical, electrochemical, optical, gravimetric and thermal sensors are presented. Finally, future trends, challenges and opportunities on the use of such nanomaterial-based (bio)sensors for on-site and expedite plant pathogen detection are also presented.

A potentiometric E-tongue system based on low-selective polymeric membrane and chalcogenide-glass electrodes is employed to monitor the taste-and-odor-causing pollutants, geosmin (GE) and 2-methyl-isoborneol (MIB), in drinkable water. The developed approach may permit a low-cost monitoring of these compounds in concentrations near the odor threshold concentrations (OTCs) of 20 ng/L. The experiments demonstrate the success of the E-tongue in combination with partial least squares (PLS) regression technique for the GE/MIB concentration prediction, showing also the possibility to discriminate tap water samples containing these compounds at two concentration levels: the same OTC order from 20 to 100 ng/L and at higher concentrations from 0.25 to 10 mg/L by means of PLS-discriminant analysis (DA) method. Based on the results, developed multisensory system can be considered a promising easy-to-handle tool for express evaluation of GE/MIB species and to provide a timely detection of alarm situations in case of extreme pollution before the drinkable water is delivered to end users.

Neste estudo, fibras de coco verde foram incorporadas em uma matriz composta de glúten de milho (GM) e poli(hidroxibutirato-co-valerato) (PHBV). As composições foram processadas por extrusão, onde o teor máximo de glúten adicionado à matriz para obter misturas com viscosidade suficientemente baixa para o processamento foi de 50% (em peso) em relação ao teor de PHBV. O teor de fibras nos compósitos variou de 5 a 20% por peso em relação ao peso total dos polímeros. Os plastificantes usados foram acetil tributil citrato (ATBC) e glicerol. Os materiais extrudados foram moldados por compressão a quente para obtenção de corpos de prova para a caracterização das propriedades de absorção de água, solubilidade em água, resistência mecânica, além de propriedades termo-dinâmico-mecânicas (DMTA) e morfológicas. Foi observado que as matrizes apresentaram duas transições vítreas (Tg's) uma para cada componente, indicando que as mesmas são compostas de duas fases (GM) e PHBV. A adição do PHBV ao glúten favoreceu ao aumento da rigidez e houve diminuições significativas na absorção de água e na solubilidade em água, enquanto a presença das fibras provocou, em algumas composições, um aumento no módulo de elasticidade e na resistência à tração.

Em artigo de revisão anterior[1], o processo de eletrofiação foi discutido, incluindo suas bases teóricas e experimentais, e a obtenção de diferentes nanofibras de materiais poliméricos. Neste segundo artigo de revisão, são abordados os aspectos relacionados à aplicação de materiais eletrofiados em diferentes áreas, como médica, agrícola, sensores, processamento de outros materiais, entre outras. São também discutidas as técnicas de caracterização utilizadas mais frequentemente nestes materiais, e suas potencialidades. Esta segunda revisão é complementar à anterior e segue, em seus aspectos gerais, a mesma terminologia.In our previous review[1], the process of electrospinning was discussed on the basis of theoretical and experimental aspects toward preparation of different polymeric nanofibers. In this second review, we focus on the aspects related to the application of electrospun materials in various fields such as medicine, agriculture, sensors, and processing of other materials. We discuss the most often characterization techniques used for these materials and their potential. This review complements the previous one and uses the same terminology.

Fibras de sisal com quatro tratamentos, a saber: fibra lavada com água, lavada com cicloexano/etanol, tratamento alcalino (NaOH) e tratamento com peróxido alcalino (branqueamento), foram incorporadas na blenda amido termoplástico/policaprolactona 80/20 (TPS/PCL). As propriedades morfológicas, mecânicas e térmicas dos biocompósitos TPS/PCL/Sisal foram analisadas. Os compósitos com a fibra branqueada apresentaram os melhores resultados de resistência à tração e estabilidade térmica. Verificou-se também melhora da adesão fibra-matriz no compósito com a fibra branqueada, com aumento de 145% na resistência à tração.Sisal fibers treated with four methods, namely washing with water, washing with cyclohexane/ethanol, alkali treatment (NaOH) and bleaching (alkaline peroxide treatment), were incorporated in thermoplastic starch/polycaprolactone 80/20 (TPS/PCL) samples. Morphological, mechanical and thermal properties of TPS/PCL/Sisal biocomposites were analysed. The best results were obtained with the composite using the bleached fiber, which had improved tensile strength and thermal stability. An increased adhesion between the fiber and matrix was also observed with the bleached fiber, with 145% increase in the tensile strength

Neste trabalho foram desenvolvidos compósitos condutores elétricos de borracha natural contendo negro de fumo e compostos condutivos baseados em polímeros condutores (Eenomer®). Os compósitos foram processados a quente num reômetro de torque HAAKE e moldados por prensagem. Foram obtidas placas homogêneas, flexíveis e com ótimo acabamento superficial. Os compósitos foram analisados pelas medidas de torque no processamento, medidas de condutividade elétrica, análise termogravimétrica (TGA), calorimetria diferencial de varredura (DSC) e ensaios de tração. Estes compósitos apresentaram valores de condutividade elétrica entre 10-7 a 10-1 S/cm, dependendo do tipo de negro de fumo ou composto condutivo utilizado e da quantidade destes no compósito. A análise térmica demonstrou que os compósitos são termicamente estáveis até cerca de 300°C. Os compostos condutivos atuam como reforço para a borracha natural melhorando suas propriedades mecânicas sem perder significativamente sua flexibilidade.In this work, electrically conducting composites of natural rubber with carbon black and natural rubber with conductive compounds containing electrically conducting polymers (Eenomer®) were developed. The composites were processed in a torque reometer HAAKE and then hot pressed. Homogeneous and flexible plates were obtained with excellent surface finish. The composites were analysed by the torque measurement during processing, electrical conductivity, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and mechanical analysis. Conductivity in the order of 10-7 to 10-1 S/cm were achieved, depending on the type of carbon black or conductive compound used and their content in the composite. Thermal analysis demonstrated that the compounds are thermally stable until 300°C. The conductive compounds act as reinforcements in the natural rubber matrix, improving its mechanical properties without significant loss on its flexibility.

A pectinbased hydrogel was used as a remover of Cu2and Pb2ions from water and wastewater and in the release of phosphate, potassium, and urea. The swelling studies in either aqueous or saline solutions were analyzed at different pressures, and the prediction of profile of water and solute transports was further analyzed on basis of transport process by diffusion in swellable polymer networks. The hydrogel composed of 0.10 g mL−1final polymer concentration showed an excellent absorption capacity for removal of Cu2and Pb2from the solution: 120 mg Cu2and 130 mg Pb2per g hydrogel, both at pH 5.5. The hydrogel help to conserve water in a pressure range in which a variety of horticultural plants can absorb it. The release process of urea, phosphate, and potassium from the hydrogels is controlled by nonFickian mechanism with a tendency to macromolecular relaxation. This type of hydrogel is an interesting system for applications in which the efficient use of water is required and release of fertilizers for agriculture. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]