Enhanced stability of encapsulated lemongrass essential oil in chitosan-gelatin and pectin-gelatin biopolymer matrices containing ZnO nanoparticles.

The use of essential oils is widespread in various fields such as pharmacy, pest control, and active packaging. However, their instability and short-term effects require methods to enhance their durability and effectiveness. Encapsulation in biopolymer matrices appears to be a promising approach due to the environmental safety and cost-effectiveness of such formulations. In this study, different oil-in-water emulsions were prepared by mixing chitosan-gelatin (C-G) or pectin-gelatin (P-G) solutions with lemongrass essential oil (LG). ZnO NPs were used as an additional active component. Encapsulation in biopolymer matrices resulted in stable emulsions with a significantly slower release of LG, and ZnO NPs further suppressed LG release, particularly in the P-G emulsion. They also contributed to the stability of the emulsions and a decrease in the average droplet size of LG. Furthermore, the presence of LG and ZnO NPs improved the smoothness of the films prepared from the emulsions and dispersions using the casting technique. SEM/EDS analysis confirmed the homogeneous distribution of ZnO NPs in both C-G and P-G films. By adjusting the type and content of the biopolymers and NPs, such emulsions could be effectively utilized in various applications where controlled release of active components is required.

Encapsulated Thuja plicata essential oil into biopolymer matrix as a potential pesticide against Phytophthora root pathogens.

A new formulation that gradually released encapsulated Thuja plicata essential oil (TPEO) as an active component from a biopolymer matrix within a given period was obtained. Antimicrobial activity was determined in in-vitro tests where pure TPEO successfully inhibited the development of different Phytophthora species. The TPEO essential oil was encapsulated into the biopolymer matrix and an oil-in-water emulsion was formed. FTIR spectra analysis confirmed the formation of electrostatic interaction between these polymers, and hydrogen interactions between active components of TPEO and polymer chains. The stability of the emulsions was confirmed by zeta potential measurements, with a value of about 30 mV, even after 14 days of aging. UV-Vis spectra analysis revealed that >60 % of TPEO remained in the emulsion after 14 days of exposure to ambient conditions, whereas pure TPEO evaporated faster, and around 20 % remained after 6 days. Encapsulated TPEO almost completely inhibited the growth of Phytophthora species during the ten-day day's exposition being statistically significantly improved compared to fungicide treatment. It was demonstrated that the emulsion exhibited a prolonged antimicrobial effect and successfully suppressed the growth of Phytophthora species, and can be considered as a means of protection in forests and crops.

Microstructural, Thermoelectric and Mechanical Properties of Cu Substituted NaCo2O4.

Polycrystalline samples of NaCo2-xCuxO4 (x = 0, 0.01, 0.03, 0.05) were obtained from powder precursors synthesized by a mechanochemically assisted solid-state reaction method (MASSR) and a citric acid complex method (CAC). Ceramic samples were prepared by pressing into disc-shaped pellets and subsequently sintering at 880 °C in an argon atmosphere. Effects of low concentrations of Cu doping and the above-mentioned synthesis procedures on the thermoelectric and mechanical properties were observed. The electrical resistivity (ρ), the thermal conductivity (κ) and the Seebeck coefficient (S) were measured simultaneously in the temperature gradient (ΔT) between the hot and cold side of the sample, and the figure of merit (ZT) was subsequently calculated. The ZT of the CAC samples was higher compared with the MASSR samples. The highest ZT value of 0.061 at ΔT = 473 K was obtained for the sample with 5 mol% of Cu prepared by the CAC method. The CAC samples showed better mechanical properties compared to the MASSR samples due to the higher hardness of the CAC samples which is a consequence of homogeneous microstructure and higher density obtained during sintering of these samples. The results confirmed that, besides the concentration of Cu, the synthesis procedure considerably affected the thermoelectric and mechanical properties of NaCo2O4 (NCO) ceramics.