Self-Assembly Template Driven 3D Inverse Opal Microspheres Functionalized with Catalyst Nanoparticles Enabling a Highly Efficient Chemical Sensing Platform

The design of semiconductor metal oxides (SMOs) with well-ordered porous structure has attracted tremendous attention owing to their larger specific surface area. Herein, three-dimensional inverse opal In₂O₃ microspheres (3D-IO In₂O₃ MSs) were fabricated through one-step ultrasonic spray pyrolysis (USP) which employed self-assembly sulfonated polystyrene (S-PS) spheres as a sacrificial template. The spherical pores observed in the 3D-IO In₂O₃ MSs had diameters of about 4 and 80 nm. Subsequently, the catalytic palladium oxide nanoparticles (PdO NPs) were loaded on 3D-IO In₂O₃ MSs via a simple impregnation method, and their gas sensing properties were investigated. In a comparison with pristine 3D-IO In₂O₃ MSs, the 3D-IO PdO@In₂O₃ MSs exhibited a 3.9 times higher response (<i>R</i>_air/<i>R</i>_gas = 50.9) to 100 ppm acetone at 250 °C and a good acetone selectivity. The detection limit for acetone could extend down to ppb level. Furthermore, the 3D-IO PdO@In₂O₃ MSs-based sensor also possess good long-term stability. The extraordinary sensing performance can be attributed to the novel 3D periodic porous structure, highly three-dimensional interconnection, larger specific surface area, size-tunable (meso- and macroscale) bimodal pores, and PdO NP catalysts

Determination of sorbic acid diffusivity in edible wheat gluten and lipid based films

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Quantitative water uptake study in thin nylon-6 films with NMR imaging

Nylon-6 is widely used as an engineering plastic. Compared to other synthetic polymers, nylon-6 absorps significant amounts of water. Although the typical sorbed amounts and diffusivity of water are well-known, less is known about the relation between the diffusivity and the water content. Attempts have been made in the past to obtain such relationship from moisture content profiles as measured with NMR imaging. However, these studies were mainly performed at high temperatures and without a proper calibration of the signal. In particular, at room temperature, far below the Tg of dry nylon, plasticizing effects of water will result in a strong contribution of the polymer signal. Therefore, we have studied water uptake in 200 µm nylon-6 films in this temperature range near room temperature with NMR imaging. By calibrating the NMR signal with vapor sorption data, we were able to obtain moisture content profiles. A strongly nonlinear relation between the NMR signal and the moisture was observed at room temperature, which proves that contribution of the polymer to the NMR signal can neither be neglected nor assumed to be constant in time. Furthermore, glass transition temperature measurements combined with the water distribution provide plasticization profiles during water uptake. On the basis of the moisture content profiles, the moisture content dependency of the diffusion coefficient for water uptake is deduced through a Matano-Boltzmann analysis. This relation appeared to be highly nonlinear at room temperature. The self-diffusion coefficient was calculated through combination of the sorption-isotherm and the diffusion coefficient. Exposure of a nylon film to heavy water showed that water affects only a small fraction of the amorphous nylon phase. Water transport most likely occurs in this fraction of the amorphous phase. It is concluded that the heterogeneity of the amorphous phase is an important issue for a profound understanding of water transport in nylon-6 films