Synthesis of high surface area TiO2 nanoparticles by mild acid treatment with HCl or HI for photocatalytic propene oxidation

Nanostructured TiO2 photocatalysts with small crystalline sizes have been synthesized by sol-gel using the amphiphilic triblock copolymer Pluronic P123 as template. A new synthesis route, based on the treatment of TiO2 xerogels with acid-ethanol mixtures in two different steps, synthesis and extraction-crystallization, has been investigated, analyzing two acids, hydrochloric and hydriodic acid. As reference, samples have also been prepared by extraction-crystallization in ethanol, being these TiO2 materials amorphous and presenting higher porosities. The prepared materials present different degrees of crystallinity depending on the experimental conditions used. In general, these materials exhibit high surface areas, with an important contribution of microporosity and mesoporosity, and with very small size anatase crystals, ranging from 5 to 7 nm. The activity of the obtained photocatalysts has been assessed in the oxidation of propene in gas phase at low concentration (100 ppmv) under a UVA lamp with 365 nm wavelength. In the conditions studied, these photocatalysts show different activities in the oxidation of propene which do not depend on their surface areas, but on their crystallinity and band gap energies, being sample prepared with HCl both during synthesis and in extraction-crystallizations steps, the most active one, with superior performance than Evonik P25.

Surface, Thermal and Antimicrobial Release Properties of Plasma-Treated Zein Films

The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an active ingredient were evaluated. The plasma discharge was optically characterized to identify the reactive species. A significant increase in the film roughness (p < 0.05) was observed due to the etching effect of DBD plasma, which was correlated with the increase in the diffusion rate of thymol in the food simulant. The diffusion of thymol from the zein film was measured in aqueous solution. The kinetics of thymol release followed the Fick’s law of diffusion as shown by the high correlation coefficients between experimental and theoretical data. No significant change (p > 0.05) was observed for the thermal properties of the antimicrobial films after DBD plasma treatment.

Characterization of polylactic acid films for food packaging as affected by dielectric barrier discharge atmospheric plasma

Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltages and treatment times to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the initial degradation temperature and maximum degradation temperature was observed. DBD plasma treatment did not adversely affect the oxygen and water vapor permeability of PLA. A very limited overall migration was observed in different food simulants and was much below the regulatory limits. Industrial relevance: In-package DBD plasma is a novel and innovative approach for the decontamination of foods with potential industrial application. This paper assesses the suitability of PLA as food packaging material for cold plasma treatment. It characterizes the effect of DBD plasma on the packaging material when used for in-package decontamination of food. The work described in this research offers a promising alternative to classical methods used in fruit and vegetable industries where in-package DBD plasma can serve as an effective decontamination process and avoids any post-process recontamination or hazards from the package itself.

Spectrally tunable light source based on light-emitting diodes for custom lighting solutions

This study describes a novel spectral LED-based tunable light source used for customized lighting solutions, especially for the reconstruction of CIE (Commission Internationale de l’Éclairage) standard illuminants. The light source comprises 31 spectral bands ranging from 400 to 700 nm, an integrating cube and a control board with a 16-bit resolution. A minimization algorithm to calculate the weighting values for each channel was applied to reproduce illuminants with precision. The differences in spectral fitting and colorimetric parameters showed that the reconstructed spectra were comparable to the standard, especially for the D65, D50, A and E illuminants. Accurate results were also obtained for illuminants with narrow peaks such as fluorescents (F2 and F11) and a high-pressure sodium lamp (HP1). In conclusion, the developed spectral LED-based light source and the minimization algorithm are able to reproduce any CIE standard illuminants with a high spectral and colorimetric accuracy able to advance available custom lighting systems useful in the industry and other fields such as museum lighting.