Noira Rakhimovna Vokhidova

With the advancement of 6G technology, the development of broadband absorbing materials that are effective in both the terahertz (THz) and gigahertz (GHz) bands is crucial for modern electronic packaging and electromagnetic protection. This paper proposes an innovative method for the first time, where organic dyes containing multi-polar functional groups and copper powder are co-doped into an epoxy resin matrix to fabricate insulating composite thin films with excellent terahertz absorption properties. With a thickness of 1 mm, the EP-25%Acid Black-Cu film achieves an average reflection loss (RL) of -15.6 dB and an effective absorption bandwidth of 2.5 THz, representing a 145% improvement in absorption performance compared to pristine epoxy. Simultaneously, its electromagnetic interference (EMI) shielding effectiveness reaches 50 dB, enabling the integration of wave absorption and shielding functionalities. Furthermore, in the GHz band, the EP-25%Acid Black-Cu film with a thickness of 5.0 mm demonstrates a decent absorption effect of -28.1 dB around 15 GHz. This allows for holistic electromagnetic wave absorption across different bands in complex electromagnetic environments, effectively mitigating stray electromagnetic interference. This composite absorbing film holds significant potential for application in high-frequency, highly integrated electronic devices in the future 6G field.

This study aimed to engineer Bombyx mori chitosan–caffeine nanocapsules via a self-assembly approach and to comprehensively characterize their structural architecture, physicochemical properties, and release kinetics under precisely controlled pH conditions. Chitosan–caffeine nanocapsules were synthesized in aqueous medium at low temperature under controlled acidic conditions (pH 3.2 and 4.5), achieving yields of 91–94 %. Their physicochemical properties were analyzed using UV and FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that hydrogen bonding and electrostatic interactions between the protonated amino groups of chitosan and the carbonyl groups of caffeine promoted the formation of spherical and oval nanostructures with diameters in the range of 100–400 nm. Spectroscopic analysis confirmed the intermolecular interactions responsible for encapsulation, while X-ray diffraction indicated a decrease in caffeine crystallinity after incorporation into the polymer matrix. SEM and TEM micrographs demonstrated efficient encapsulation of caffeine within the chitosan matrix and confirmed the formation of stable core–shell nanostructures. Release profile analysis showed that approximately 20 % of the total caffeine content was released from the chitosan nanocapsules over the monitored period, confirming their controlled release behavior. These chitosan-caffeine nanocapsules hold potential for future use in the development of drugs with prolonged release properties.

Manganese nanoparticles are highly reactive and tend to aggregate and oxidize, which limits their practical application. Therefore, the aim of this study was to synthesize and stabilize Mn nanoparticles using Bombyx mori chitosan as a natural biopolymer matrix under controlled in situ conditions and to investigate their structural and physicochemical properties. Samples containing Mn nanoparticles stabilized with chitosan in the presence of reducing agents, with hydrodynamic dimensions of 118 nm (97 %) and 144 nm (96 %), were synthesized under in situ conditions. The structural and morphological characteristics were studied using IR spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and electron microscopy. IR spectroscopic studies revealed local rearrangements within the repeating units of the chitosan polymer chain and interactions between the –NH and –C=O functional groups and manganese-containing nanoparticles. XRD analysis confirmed the reduction of Mn2+ ions. Morphological studies of chitosan–manganese films showed the formation of 50 nm tetragonal and 90 nm spherical metal nanoparticles under the selected synthesis conditions. The results confirm the stabilization of Mn nanoparticles with Bombyx mori chitosan by the chemisorption method and demonstrate effective control of particle size and morphology. Further research should focus on evaluating long-term stability, functional properties, and potential biomedical applications of the synthesized nanocomposites.

Silver nanoparticles were obtained in the presence of 2-propanol under both in situ and ex situ conditions. It was established that the hydrodynamic radius and polydispersity of the particles increase with rising pH (6.0–11.0) due to the accelerated reduction of Ag⁺ ions. Variation of the chitosan molecular-weight parameters and the chitosan/Ag⁺ molar ratio (5–30) enabled controlled formation of stabilized nanoparticles ranging from 20 to 140 nm. The chitosan–silver nanoparticle dispersions in 0.2–0.5% aqueous acetic solutions demonstrated pronounced fungicidal activity against Fusarium solani 169, Fusarium oxysporum 280, and Verticillium dahliae 57, producing sterile zones of 31–34 mm.

N-succinylchitosan (N-SCS) was obtained by the reaction of chitosan derived from Bombyx mori with succinic anhydride mixed at a 1:1 molar ratio in dimethyl sulfoxide for 24 hours at 22°C and pH 7. In order to increase the effectiveness of insecticidal properties, N-succinylchitosan complexes with Co2+ ions (N-CSC/Co2+) were further obtained. The structural studies show that Co2+ ions interact with the carboxyl groups of N-succinylchitosan. The IR spectra of chitosan, N-SCS, and N-SCS/Co2+ show characteristic absorption bands at 1388, 1578, and 473 cm-1, respectively. Absorption bands characteristic of –NH–CO groups were also noticed at 1674 cm-1. The concentration dependence of the insecticidal activity of N-SCS/Co2+ solutions was studied, and it was found that a 1.0% solution exhibits 86.7% biological effectiveness against termites. The presented results are helpful for the development of eco-friendly insecticides based on natural polysaccharides.

The review article presents current research on obtaining chitosan nanoparticles (NPs). It highlights their key properties and potential applications in agriculture. Various methods of chitosan nanoparticle formation were considered: emulsion method in the presence of special agents, drying method, crosslinking of molecules through covalent bonds, self-organisation processes and obtaining interpolyelectrolyte complexes, and ionotropic gelation. Some examples of the chitosan NPs application have also been reviewed.

This review provides a comprehensive summary of the results of research, published from 2002 to 2023, on the synthesis, physicochemical properties and medical applications of binary and ternary interpolyelectrolyte complexes (IPECs) based on chitosan, carboxymethylcellulose and collagen. The application of IPECs in the medical field mainly refers to their use in medical therapy and bone regeneration. In addition, we describe our original studies on IPECs based on chitosan and collagen.

We obtained binary polyelectrolyte complexes containing chitosan from Bombyx mori and collagen with a mass ratio of 10:1; 10:2, and 10:3. During the interaction between the macromolecules, due to the compensation of the positive charges of chitosan with the negative charges of collagen, the zeta potential of the solutions of polyelectrolyte complexes changed from +15.2 to +5.67 mV. We revealed the dependence of the size characteristics of the particles of polyelectrolyte complexes on time and the ratio of macromolecules. An examination of the morphology of the films of polyelectrolyte complexes demonstrated that in the evaluated chitosan/collagen mass ratios, non-spherical nanosized particles up to ≤ 60 nm form on the surface of the films. We evaluated the mechanism of formation of complexes by using Fourier-transform infrared spectroscopy and confirmed the findings with density functional theory and molecular dynamics. We found that the particle diameter is inversely proportional to the diffusion coefficient. The results show that the particles are almost uniformly distributed over the surface of the polymer matrix and have a unimodal character. We obtained reproducible results when using a chitosan/collagen mass ratio of 10:2 to dye natural silk. We found that the complexes contribute to increase the intensity and stability of colour relative to soap and friction.

The current study aimed to obtain a calcium-containing, biocompatible drug based on chitosan Bombyx mori. Composites of Chitosan (CS) Bombyx mori with hydroxyapatite (HA) in the ratio of CS/HA = 50:50 mass percentage were synthesized in situ conditions at Ca/P = 1.67 mol% with intensive stirring for one hour at a speed of 1400 rpm and a temperature of 40 ± 2ºС. It was revealed that the components form an intermediate complex through –N-Ca, O-Ca, O (glycosidic bond)–Ca, H–O-bonds interacted by electrostatic forces. Atomic force microscopy studies indicated particles in the 100-50 nm size range on the polymer matrix surface. The polymer matrix prevented the growth of HA crystals and particle agglomeration. It was also determined that the CS/HA composite was non-toxic, and the LD50 was more than 5000 mg/kg. The composites were introduced into the chickens’ diet in groups for 30 days at 25 to 40 mg/kg doses. The findings indicated an increased survival rate of chickens by 100%, improved the morphological parameters of the blood, and enhanced the contents of calcium, phosphorus, and hemoglobin. The addition of CS/HA=50:50 mass percentage contributed to an increase in the number of erythrocytes in the blood of broilers and hemoglobin by 11-12%. It should be noted that CS/HA did not adversely affect other morphological parameters of chicken blood. Therefore, CS/HA is recommended for the prevention of osteoporosis and osteomalacia in broiler chickens.