Research in biosensing currently occupies an important role among biomolecular detection techniques, especially with respect to medical diagnoses. Is this sense, the development of biosensors based on the localized surface plasmon resonance (an optical transducer) or electrochemical transductions have been highlighted. However, optical and electrochemical detection working together enable more versatile detections in biosensing. Thus, we propose a dual sensor, which incorporates these two mechanisms on the same platform. The sensor shared the same transducer that was based on a glass-indium thin oxide (ITO) surface covered with gold nanoparticles. The transducer was prepared by the immobilization of gold nanoparticles on (3-aminopropyl)triethoxysilane-activated glass-ITO. The substrate ability to respond to physical surface variations was assessed. For this, measurements of the gold nanoparticles band redshift (plasmonic transduction) and charge transfer resistance from impedance spectra (electrochemical transduction) were performed. The platform was able to detect streptavidin immobilized on the surface by both mechanisms demonstrating its applicability as a device for biodetection in dual detection mode.

RESUMO Esse trabalho mostra uma rota sintética mediada por tetraetilenoglicol (P. E. 325°C) em que utiliza o ácido túngstico, como material de partida. A formação de uma suspensão estável de cor azul foi observada durante o curso da reação. O tamanho das partículas depende do tempo de síntese, sendo que partículas de tamanho em torno de 400 nm foram obtidas após 15 minutos de reação em tetraetilenoglicol. Os materiais particulados foram então recozidos em diferentes temperaturas: 150°, 350°C, 500°C e 800°C, e caracterizados por TGA / DSC, DRX, FT-RAMAN, MEV, Espectroscopia óptica UV-VIS e adsorção de N2 a 77K. Observou-se que a síntese proporcionou WO3 sob fase ortorrômbica que evoluiu para monoclínica após tratamento térmico na temperatura igual ou superior a 350°C. A caracterização morfológica indicou a formação de partículas ovoides quando tratadas em temperaturas em torno de 500°C, temperatura a partir da qual a área superficial diminui drasticamente. A atividade fotocatalítica para a degradação de rodamina B (rhB, 10 mg.L-1) foi avaliada sob irradiação ultravioleta (6 Watts). Maior atividade foi encontrada para o material tratado a 500°C, sendo que descoramento foi total após 180 minutos na presença de 10 mg desse catalisador.

ABSTRACT This work shows a synthetic route mediated by tetraethylene glycol (P. E. 325 ° C) in which tungstic acid is used as the starting material. The formation of a stable blue suspension was observed during the course of the reaction. The size of the particles depends on the synthesis time, and particles of size around 400 nm were obtained after 15 minutes of reaction in tetraethylene glycol. The particulate materials were then annealed at different temperatures: 150 °, 350 ° C, 500 ° C and 800 ° C, and characterized by TGA / DSC, DRX, FT-RAMAN, MEV, UV-VIS optical spectroscopy and N2 adsorption at 77K. It was observed that the synthesis provided WO3 under orthorhombic phase that evolved to monoclinic after heat treatment at a temperature equal to or greater than 350 ° C. The morphological characterization indicated the formation of ovoids particles when treated at temperatures around 500 ° C, a temperature from which the surface area decreases dramatically. The photocatalytic activity for the degradation of rhodamine B (rhB, 10 mg.L-1) was evaluated under ultraviolet irradiation (6 Watts). Greater activity was found for the material treated at 500 ° C, with total discoloration after 180 minutes in the presence of 10 mg of this catalyst.

Localized surface plasmon resonance (LSPR) is a collective oscillation of free electrons induced by the incident light in nanometric surfaces of conductive materials. Gold nanorods (AuNRs) have been studied for plasmonic devices due to their anisotropic properties. Herein, we report the construction of a specific biosensor using polyacrylamide (PAAm) as the gold nanorods support and test its efficiency with specific streptavidin interaction using biotinylated substrates. First, the hydrogels were synthesized by electropolymerization using cyclic voltammetry on ITO/glass substrates and swallowed with AuNRs. The AuNRs were characterized by visible absorption spectroscopy and transmission electron microscopy. The substrates were characterized by scanning electron microscopy and their plasmonic sensitivities were evaluated using sucrose solutions with different concentrations. The results showed a sensitivity of ca. 226.4 nm RIU-1 with linear correlation of 0.9974. Furthermore, this composite presented reliable detection of the streptavidin biomolecule in the gold surface with good signal-to-noise ratio (SNR).

RESUMO Filmes constituídos por amido de mandioca, álcool polivinílico (PVA) e argila Bentonita (BNT) e glicerol como plastificante foram obtidos utilizando o método casting. A fim de aumentar a compatibilidade dos polímeros ao mineral e sua hidrofobicidade, estes foram posteriormente modificados quimicamente utilizando metacrilato de glicidila (GMA) para a substituição dos grupamentos hidroxilas por vinílicos. Este procedimento gerou filmes com excelente estabilidade a sorção de água e permeabilidade ao vapor de água 15% menor quando comparados coms os filmes sem modificação química. Adicionalmente, esta estratégia também resultou na melhora de 25% na resistência a tração, mantendo o mesmo módulo de Young mas, com uma leve diminuição na estabilidade térmica (início de degradação 14ºC menor). A adição da argila BNT gera filmes compósitos com propriedades, mecânicas, térmicas e físicas diferenciadas, contudo há uma dependência entre a quantidade de reforço e a distribuição estrutural das lamelas de argila na matriz. As modificações químicas foram comprovadas por RMN H1, FTIR, DRX e os filmes foram caracterizados por DRX, sorção e permeabilidade a água, ensaios mecânicos (tração, alongamento e módulo de Young) e TGA. A utilização de 1% m/m deste reforço gera compósitos com BNT estruturalmente esfoliado, independentemente da prévia modificação com metacrilato de glicidila. Já a formulação com 5% m/m gerou filmes compósitos intercalados. Qualquer outro teor de reforço exibe estruturas lamelares aglomeradas (empacotadas). Destaca-se que nas formulações reforçadas com 1% de argila, houve melhora em cerca 30% na resistência a tração com permeabilidade a água 60% menor, para cargas maiores de argila. Estes fatos apontam que as modificações propostas neste trabalho geraram propriedades promissoras para a produção de materiais de embalagem biodegradáveis.

ABSTRACT Films constituted by cassava starch, polyvinyl alcohol (PVA) and Bentonite clay (BNT) and glycerol as plasticizer were obtained using the casting method. In order to increase the compatibility of the polymers with the mineral and its hydrophobicity, they were subsequently chemically modified by replacing the hydroxyl groups with vinyls using glycidyl methacrylate (GMA). This procedure generated films with excellent water sorption stability and 15% lower water vapor permeability. This strategy also resulted in a 25% improvement in tensile strength, maintaining the same Young’s modulus and slight decrease in thermal stability (onset of degradation 14 ° C lower). The addition of BNT clay generates composite films with different mechanical, thermal and physical properties, however, there is a dependence between the amount of reinforcement and the structural distribution of the clay lamellae in the matrix. The chemical modifications were confirmed by H 1 NMR, FTIR, XRD and the films were characterized by XRD, sorption and water permeability, mechanical tests (traction, stretching and Young’s modulus) and TGA. The use of 1% w / w of this reinforcement generates composites with structurally exfoliated BNT, independently of the previous modification with glycidyl methacrylate. The formulation with 5% m / m generated intercalated composite films. Any other reinforcing content exhibits agglomerated (packaged) lamellar structures. It is noteworthy that in the formulations reinforced with 1% clay, there was an improvement of about 30% in tensile strength with 60% lower water permeability, for higher clayey loads. These facts indicate that the modifications proposed in this work have generated promising properties for the production of biodegradable packaging materials.

Abstract In this paper was investigated the chemical, physical, thermal, mechanical and morphological characteristics of the recyclable materials obtained of the NESCAFÉ® DOLCE GUSTO® branded beverage capsules, characterizing different resulting compositions. The characterization was made by following techniques: Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Water Absorption and techniques for the analysis of mechanical properties (tensile and impact test). The results showed that the body of the capsule and the inner filter, both made of polypropylene, are the most interesting materials to be reused, having good properties, while the materials resulting from the mixtures of all the constituents in the beverage capsules presented decreased mechanical properties.

Abstract The thermoplastic starch (TPS) is regarded as a promising material for manufacturing packaging and products with biodegradable properties. This study aimed at obtaining hydrophobic starch using silanized silica nanoparticles (nSS) with hexamethyldisilazane. A factorial design 22 with central point was developed to evaluate the influence of glycerol (plasticizer) and nSS addition on the properties of water absorption, solubility and TPS contact angle. The materials morphology was also evaluated by means of scanning electron microscopy. The amount of glycerol and nSS influenced on starch hydrophobic character, for the increase of the glycerol dosage contributed to the increase of absorption and solubility of TPS in water. On the other hand, nSS has greater influence on the characteristics related to the TPS surface, favoring an increase of up to 27% in the contact angle values. Therefore, the sample with the greatest hydrophobic character was obtained by using lowest amounts of glycerol (30%) and highest amounts of nSS (5%).

Abstract In this study, an alternative method for recycling residues of labels and stickers (parings) containing biaxically oriented polypropylene (BOPP) and polyurethane-based glue was discussed. The recycling of this type of material is complicated, once the separation and the milling processes are difficult to be accomplished, due to the presence of a large amount of glue. In this study, sugarcane bagasse ash was used to enable the milling process of stickers residues. Composites were prepared with post-consumer polypropylene extrusion with different polypropylene/parings ash ratio. These materials were analyzed by tensile, three point flexural, hardness, density, water absorption, Izod impact tests, thermogravimetric analysis, environmental exposure and scanning electron microscopy. Addition of sticker residues/ash to the polypropylene matrix makes the material more rigid and does not affect significantly thermal and degradation properties. Thus, the recycling process proposed in this paper is environmentally and economically viable.

Resumo Foi discutida neste estudo a influência de nanopartículas de sílica na compatibilidade entre fibras de sisal e polietileno de alta densidade, utilizados na preparação de compósitos. As fibras de sisal foram tratadas quimicamente e recobertas com nanopartículas de sílica por moagem mecânica. Os compósitos foram preparados por extrusão do polietileno com diferentes quantidades de fibras. Utilizou-se diferentes técnicas de caracterização para se obter as propriedades térmicas e a morfologia das fibras de sisal e dos compósitos, a influência das fibras de sisal e da sílica na cristalinidade do polietileno e o comportamento mecânico e a absorção de água do polietileno e dos compósitos. Foi observado que a as propriedades térmicas do polietileno não são afetadas pela presença das fibras e nanopartículas. Os diferentes tratamentos químicos e a presença de sílica nas fibras de sisal resultaram em propriedades mecânicas melhoradas e foram preponderantes para a diminuição da absorção de água nos compósitos, comparados ao polietileno.

Abstract In this study, the influence of silanized silica nanoparticles on the compatibility of composites prepared with sisal fibers and high density polyethylene is discussed. The sisal fibers were chemically treated and covered with silica nanoparticles by mechanical milling. The composites were prepared by extrusion of HDPE and different amount of fibers. The morphology and thermal properties of the sisal fibers and composites, the influence of sisal fibers and silica nanoparticles on crystallinity of HDPE, the mechanical behavior and water uptake of composites were evaluated by different techniques. It was observed that thermal properties of HDPE on composites were not changed by the presence of sisal fibers and silica nanoparticles. The different chemical treatments in sisal fibers and the presence of silica nanoparticles resulted in improved mechanical properties and were preponderant to the water uptake decrease in the composites, comparing with HDPE.

This paper presents a factorial design (mixture design) used to analyze the hardness and degree of monomer conversion into composites containing conventional monomers and an organic-inorganic hybrid polymer-based methacryloyloxypropyl trimethoxysilane (MEMO). For this purpose, resins (composites with SiO2) were formulated with the hybrid polymer (polycondensed, pMEMO), and two conventional monomers used in dentistry, bisphenol-A dimethacrylate (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA). The resins were characterized through the degree of monomer conversion and Vickers hardness, and the pMEMO by means of FTIR and ¹H NMR. The results showed an increase in hardness for resins containing the hybrid material relative to the resins containing only conventional monomers. The mathematical model adjusted to the experimental data yielded an optimized formulation, which presented a higher hardness value (48.88 HV).

Este trabalho descreve a síntese e a caracterização de BiFeO3 obtido a partir da rota Pechini, utilizando-se nitrato de bismuto e nitrato de ferro como precursores. Os pós foram calcinados a 800 °C em ar durante 2 h. Os difratogramas de raios X mostraram que o material apresenta duas fases, BiFeO3 (95%) e α-Bi2O3 (5%). A transição de fase ferroelétrica da amostra em 821 °C foi detectada por análise térmica diferencial. Os resultados das análises por microscopia eletrônica de varredura (SEM), espectroscopia de energia dispersiva (EDS) e fluorescência de raios X por dispersão de energia (EDX) mostraram que a amostra é quimicamente homogênea. As imagens de microscopia eletrônica de transmissão revelaram que a amostra é uniforme e apresenta partículas com formato esférico e tamanho médio de 30 nm.

This work describes the synthesis and characterization of BiFeO3 obtained by the Pechini route using bismuth nitrate and iron nitrate as precursors. The powders were annealed at 800 °C in air for 2 h. X-ray diffraction patterns showed that the material presents two phases, BiFeO3 (95%) and α-Bi2O3 (5%). The ferroelectric transition of the sample at 821 °C was detected by differential thermal analysis. Results of analyses by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and energy dispersive X-ray fluorescence (EDX) showed that the sample is chemically homogeneous. Transmission electron microscopy images revealed that the sample is uniform and contains spherical particles with an average size of 30 nm.

CO2 supercrítico foi utilizado para preparar compósitos poliméricos com prata, prata/poli álcool vinílico e prata/ poli álcool vinílico/ poli (tereftalato de etileno) sulfonado, pela impregnação de um precursor de prata nas matrizes poliméricas no estado sólido seguida da redução térmica do precursor. Difração de raio X, microscopia eletrônica de varredura, espectroscopia de energia dispersiva, microscopia de força atômica, análise termogravimétrica e espectroscopia no UV/vis dos compósitos indicaram que as condições de preparação e a composição da matriz polimérica influenciam o tamanho e a forma das partículas de prata formadas, assim como, a uniformidade e a distribuição das partículas nas matrizes poliméricas. As partículas de prata nos compósitos ricos em PVA são menores, possuem formas mais uniformes e apresentam distribuição de tamanho mais estreita do que nos compósitos ricos em PETs.

Supercritical CO2 has been used to prepare silver polymer composites, silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/sulfonated poly(ethylene terephthalate) through impregnation of a silver precursor in solid-state polymeric matrices followed by thermal reduction of the silver precursor. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, thermogravimetric analysis and UV/vis spectroscopy indicate that synthesis conditions and polymeric matrix composition affect silver particle size, shape and distribution in polymeric matrices. Silver particles are smaller, have a more uniform shape and present narrower size distribution in PVA-rich than in PETs-rich composites.

Si3N4/SiC nanocomposite powders were obtained from a preceramic polymeric network based on poly(methylsilane) as the in situ quasi-stoichiometric SiC source. These powders were constituted of nanosized SiC particles homogeneously distributed in the Si3N4 particulate matrix. beta-SiC whiskers were grown at 1400 °C in the pores of the matrix. At 1600 °C, the alpha -> beta Si3N4 phase transition took place, but no elemental silicon from Si3N4 decomposition was detected, evidencing the protective effect of the SiC phase.