Yuriy Khalavka

Inorganic halide perovskites, particularly CsPbBr ₃ , have emerged in recent years as promising materials for optoelectronic applications due to their easily tunable bandgap, high charge carrier mobility, and radiation sensing capabilities.

Caffeine is one of the most well-known biologically active compounds in coffee beans, and its content largely determines the taste and stimulating properties of the drink. However, the amount of caffeine in beans can vary significantly depending on growing conditions, even within the same coffee variety. The growing global demand for coffee and the current market dynamics emphasize the necessity to investigate how the origin of coffee beans influences beverage quality. Arabica beans, particularly the Red Bourbon variety, are known to exhibit variations in chemical composition, sensory characteristics, and technological behavior depending on their cultivation environment. The study aimed to evaluate the physicochemical and sensory properties of Arabica Red Bourbon beans sourced from distinct geographic regions, considering factors such as altitude and local environmental conditions. The sensory characteristics of the resulting beverages were evaluated using the capping method, and water activity, density, moisture content, color, pH, extractivity and caffeine content were determined. Roasted bean color ranged from 61.4 to 62.5, while ground coffee color was 72.5–75.4. Moisture content was highest in Col and R (3.4%) and lowest in Con (3.1%). The greatest moisture loss during roasting occurred in S and R (13.4%). Water activity decreased from 0.50–0.56 in green beans to 0.18–0.30 post-roasting. Extraction yield ranged from 20.03 to 21.21%, and total dissolved solids (TDS) varied at 1.23–1.30%. The least acidic sample was S (pH 5.04). Colombian beans contained unusually high caffeine. The conducted research confirmed that the geographical origin of Arabica Red Bourbon beans significantly impacts their physicochemical and sensory attributes. Variations in moisture, acidity, and caffeine content were observed among the samples, despite a consistent roasting profile.

In this study, the dielectric and electrical properties of a solution-grown CsPbBr ₃ single crystal were investigated in an Au/CsPbBr ₃ /Au device configuration using broadband impedance spectroscopy (0.1 Hz–1 MHz, in the dark at room temperature).

У даній роботі представлено концепцію інструмента мультимодальної системи комп'ютерного зору та машинного навчання для встановлення кореляцій між мікроструктурою поверхні екструдованих термоелектричних матеріалів на основі Bi-Te та їхніми термоелектричними властивостями. Платформа поєднує дані атомно-силової мікроскопії (АСМ), металографічної мікроскопії, хімічного складу, термоелектричних властивостей та технологічних режимів синтезу у єдину базу для подальшого глибокого навчання. Описано розроблений інструмент для створення анотованої бази даних, архітектуру нейронної мережі для автоматизованої сегментації дефектів, а також мультимодальну модель поєднання даних для прогнозування термоелектричних властивостей.

In this work, the luminescence properties of AgInS ₂ colloid nanoparticles in solution and in films were investigated and compared. Decay time of fast and slow relaxation processes differ by about an order of magnitude. Both components are significantly reduced in films compared to the corresponding contributions in colloids that hint towards charge carrier transfer between AgInS ₂ particles enhanced in the films.

This review covers major aspects of nanochemistry in Ukraine. It describes current state of the field, lists main contributors and discuss the trends and limitations of its development. Ukraine's nanotechnology can be traced back to the country's rich scientific heritage, which includes a long tradition of excellence in materials science, chemistry, and physics. Despite limited and sporadic financial support, nanochemistry has occupied decent plase in the country scientific agenda. Related courses in the education institution contributed to the formation of the generation of skilled chemists who build their successful career internationally.