Search

A ceramic-metal composite was produced by using the sol–gel method and the electrospinning technique as a potential enhancement substrate for infrared spectroscopy. The precursor solution of tetraethyl orthosilicate, aluminum nitrate, and zirconium butoxide was mixed with polyvinylpyrrolidone and then electrospun into nonwoven fibrous membranes. The membranes were sintered, decorated with silver nanoparticles, and characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The ceramic membranes were composed of cylindrical fibers with an average diameter of ∼190 nm with a smooth surface and spherical particles with an average diameter of ∼9 nm embedded evenly on top. The enhancement capacity of the substrates was tested using pyridine at different concentrations with infrared spectroscopy. An enhancement factor of approximately 1 × 106 times for the signal of pyridine 1 nM was achievable, showing the material is a promising alternative to a low-cost nanostructured surface enhancement substrate for infrared spectroscopy. [ABSTRACT FROM AUTHOR]

In this work, nanoparticles of the chitosan-poly((α,β)-DL-aspartic acid) polyelectrolyte complex (PEC) were synthesized. The purpose is to develop a biodegradable, biocompatible, and non-toxic polymeric platform as a vehicle for the encapsulation of hydrophilic drugs. The ionotropic gelation method, using solutions of chitosan and poly((α,β)-DL-aspartic acid sodium salt), allowed synthesizing particles with diameters of 142.1 ± 2.9 nm determined by DLS, while by FESEM particle diameters in the 60–200 nm range were observed. A preliminary trial showed that encapsulation of isoniazid, a hydrophilic drug to treat tuberculosis, is possible with encapsulation efficiency in the range of 5.3–5.8%. [ABSTRACT FROM AUTHOR]

The application of a hyperelastic approach to simulate the tensile mechanical behavior of wood fiber/polymer composites is proposed. This research was conducted with the purpose of selecting the theoretical model that best fits the experimental data for use in the finite element model. The analyses by the four strain energy density functions (Polynomial, Ogden, Yeoh, and Marlow models) and the Cauchy-Green tensor invariants were used as the theoretical models. The experimental mechanical behavior of three wood fiber/polymer composites formulated with high-density polyethylene as the polymer matrix, and pine, cherry, and walnut sawdust as the fillers, at a concentration of 40 wt%, was evaluated. Experimental data showed that with filler addition, the tensile modulus of the high-density polyethylene matrix increased almost 131% regarding the neat high-density polyethylene; however, no significant differences were found respecting the kind of sawdust. Nevertheless, it was found that the elongation (%) at break was higher when walnut sawdust was employed. As for the strain energy density function analyses, the best approximation to the experimental data was achieved by the Marlow model, because this model only demands the sum of the principal extension ratios for a polymer-based material, I1. The numerical results showed that the proposed finite element model predicts the response with less than 1% error, regarding the experimental data, and consequently the use of the finite element models was simplified for the prediction of the tensile mechanical behavior of this kind of composites. [ABSTRACT FROM AUTHOR]

Chemical sensing based on semiconducting metal oxides has been largely proposed for acetone sensing, although some major technical challenges such as high operating temperature still remain unsolved. This work presents the development of an electrochemical sensor based on nanostructured PANI/cellulose/WO3 composite for acetone detection at room temperature. The synthesized materials for sensor preparation were polyaniline (PANI) with a conductivity of 13.9 S/cm and tungsten trioxide (WO3) in monoclinic phase doped with cellulose as carbon source. The synthesized materials were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and Raman spectroscopy. The composite was applied for acetone detection in the range of 0 to 100 ppmv at room temperature with electrochemical impedance spectroscopy (EIS) for monitoring resistance changes proportional to acetone concentration. The developed sensor achieved a calculated limit of detection of 10 ppm and R2 of 0.99415 with a RSD of 5% (n=3) at room temperature. According to these results, the developed sensor is suitable for acetone sensing at room temperatures without the major shortcomings of larger systems required by high operating temperatures. [ABSTRACT FROM AUTHOR]