Thermo-Oxidative Destruction and Biodegradation of Nanomaterials from Composites of Poly(3-hydroxybutyrate) and Chitosan

A complex of structure-sensitive methods of morphology analysis was applied to study film materials obtained from blends of poly(3-hydroxybutyrate) (PHB) and chitosan (CHT) by pouring from a solution, and nonwoven fibrous materials obtained by the method of electrospinning (ES). It was found that with the addition of CHT to PHB, a heterophase system with a nonequilibrium stressed structure at the interface was formed. This system, if undergone accelerated oxidation and hydrolysis, contributed to the intensification of the growth of microorganisms. On the other hand, the antimicrobial properties of CHT led to inhibition of the biodegradation process. Nonwoven nanofiber materials, since having a large specific surface area of contact with an aggressive agent, demonstrated an increased ability to be thermo-oxidative and for biological degradation in comparison with film materials.

Slowest heating zone migration for heterophase baby food system

В работе приведены результаты исследования миграции зоны наименьшего прогревания (Slowest Heating Zone, далее SHZ) в упаковке при термической стерилизации мелкодисперсной гетерофазной пищевой системы для питания детей раннего возраста. Локализация SHZ является основным параметром, на основе которого производится разработка режимов термической стерилизации для пищевых систем с конвективным теплообменом. В качестве объекта исследования использовали сок яблочный с мякотью для детского питания отечественного производства, который представляет собой гетерофазную систему с жидкой дисперсионной средой и равномерно распределенной в ней высокодисперсной фазой в виде частиц мякоти с плотностью, близкой к плотности жидкой среды. Продукт был расфасован в стеклянные банки III-52-190. Прогрев проводили в термостате при температурах греющей среды 75, 80, 85, 90 и 95 °C, которые поддерживали и регистрировали автоматически, что обеспечивало равномерность температурного поля воды в термостате. Кривые прогрева снимали с помощью термопары, рабочий спай которой размещался по оси банки на высоте 6, 12, 18, 24, 30, 36, 40, 42 и 48 мм от дна. В результате экспериментальных исследований процесса стерилизации установлено, что в подобной пищевой системе локализация SHZ и кинетика ее миграции аналогичны этим параметрам в гомофазных пищевых системах, но различаются важными особенностями, вызванными как наличием дисперсной фазы, так и различиями в теплофизических параметрах продуктов. Отмечено влияние обязательной для питания детей раннего возраста гомогенизации сока с мякотью на вязкость продукта из-за упорядоченности ориентации частиц мякоти, вызывающей миграцию SHZ при изменении температуры сока при нагреве и охлаждении. The paper presents the results of researches of Slowest Heating Zone (SHZ) migration in packaging during thermal sterilization of fine heterophasic food system for feeding young children. Localization of SHZ is the main parameter on the basis of which the development of thermal sterilization modes for food systems with convective heat exchange is made. As the object of the study, we used apple juice with pulp for baby food of domestic production, which is a heterophase system with a liquid dispersion medium and a highly dispersed phase uniformly distributed in it in the form of pulp particles with a density close to the density of the liquid medium. The product was packaged in glass jars III-52-190. Warming up was carried out in a thermostat at temperatures of the heating medium of 75, 80, 85, 90, and 95 °C, which were maintained and recorded automatically, which ensured the uniformity of the temperature field of water in the thermostat. The heating curves were recorded using a thermocouple, the working junction of which was located along the can axis at heights of 6, 12, 18, 24, 30, 36, 40, 42, and 48 mm from the bottom. As a result of experimental studies of the sterilization process, it was found that in such a food system, the localization of SHZ and the kinetics of its migration are similar to these parameters in homophase food systems, but differ in important features caused by both the presence of a dispersed phase and differences in the thermophysical parameters of products. The effect of homogenization of juice with pulp, obligatory for feeding young children, on the viscosity of the product due to the regularity of the orientation of pulp particles, which causes migration of SHZ when the temperature of the juice changes during heating and cooling, has been noted.

Formation Features of Hybrid Nanocomposites Based on Polydiphenylamine-2-Carboxylic Acid and Single-Walled Carbon Nanotubes

Hybrid nanocomposites based on electroactive polydiphenylamine-2-carboxylic acid (PDPAC) and single-walled carbon nanotubes (SWCNTs) were obtained for the first time. Polymer-carbon nanomaterials were synthesized via in situ oxidative polymerization of diphenylamine-2-carboxylic acid (DPAC) in the presence of SWCNTs by two different ways. Hybrid SWCNT/PDPAC nanocomposites were prepared both in an acidic medium and in the heterophase system in an alkaline medium. In the heterophase system, the monomer and the SWCNTs are in the organic phase (chloroform) and the oxidant (ammonium persulfate) is in an aqueous solution of ammonium hydroxide. The chemical structure, as well as the electrical and thermal properties of the developed SWCNT/PDPAC nanocomposite materials were investigated.

Ge Nanoclusters in GeO2: Synthesis and Optical Properties

Ge nanocrystals (NCs) in GeO2 films obtained with the use of two methods were studied. The first method is a film deposition from supersaturated GeO vapor with subsequent dissociation of metastable GeO on heterophase system Ge:GeO2. The second method is growth of anomalous thick native germanium oxide layers with chemical composition GeOx(H2O) during catalytically enhanced Ge oxidation. The obtained films were studied with the use of photoluminescence (PL), Raman scattering spectroscopy, high-resolution electron microscopy (HREM). Strong PL signals were detected in GeO2 films with Ge-NCs at room temperature. “Blue-shift” of PL maximum was observed with reducing of Ge excess in anomalous thick native germanium oxide films. Also a correlation between reducing of the NC sizes (estimated from position of Raman peaks) and PL “blue-shift” was observed. The Ge NCs presence was confirmed by HREM data. The optical gap in Ge-NCs was calculated with taking into account quantum size effects and compared with the position of the experimental PL peaks. It can be concluded that a Ge-NC in GeO2 matrix is a quantum dot of type I.