Roman Golovchak

The optical properties of Dy³⁺- and Pr³⁺-doped (B₂O₃)₆₀(ZnO)₁₀(SrO)₁₀(CaO)₁₀(MgO)₁₀ borate glasses were investigated using transmission, photoluminescence (PL), and three-dimensional excitation–emission matrix (EEM) spectroscopy. The transmission spectra revealed characteristic 4f–4f absorption bands of the rare-earth ions used. Dy³⁺-doped glasses exhibited prominent blue and yellow luminescence with the highest emission intensity observed for the 1.0 mol% Dy₂O₃ composition, which also exhibited near-white chromaticity. Pr³⁺-doped glasses showed weaker visible luminescence, with a dominant band in the orange region of the spectrum. In Dy³⁺/Pr³⁺ co-doped glasses, the visible Dy³⁺ emission was reduced, while the EEM maps revealed broadened excitation and additional near-infrared emission features.

Photochromic dihydroazulene/vinylheptafulvene systems have been extensively investigated in solution, whereas their behavior in solid polymer matrices remains much less understood despite their relevance for photonic and optically responsive devices. Here, a phenyl-substituted dihydroazulene derivative (Ph-DHA) was embedded in nine optically transparent polymer matrices that differ in polarity, chemical functionality, rigidity, and segmental mobility. The resulting films were examined by in situ optical transmission measurements under continuous 365 nm irradiation and during subsequent thermal recovery. UV exposure induced pronounced coloration of all films, accompanied by a red shift of the optical absorption edge from approximately 2.7–2.9 eV to 1.8–1.9 eV, indicating formation of the photoinduced vinylheptafulvene form in the solid state. The initial photoinduced changes in absorbance followed a stretched exponential time dependence with the stretch exponent β approaching unity (pure exponential). The minimal time constants (fastest responses) were observed in the 460–500 nm spectral region. Thermal recovery at elevated temperatures was also adequately described by a stretched exponential function but with greater β variation (0.6–1.0). The characteristic relaxation times showed weaker spectral dependence and generally decreased upon heating. No simple correlation between the kinetic parameters and any single polymer property, such as polarity, molecular weight, or chemical functionality, was observed. Instead, the results suggest that a broad distribution of local microenvironments and relaxation pathways within the polymer host governs the rate of photochromic response of Ph-DHA in solid films. This systematic comparison demonstrates that Ph-DHA retains robust and thermally reversible photochromism across chemically diverse solid polymer matrices and provides a phenomenological basis for designing polymer-based photoresponsive films.

Mixed Se–Te glasses are unique materials for infrared optical applications due to their exceptional IR transparency, molding and fiber-drawing capability, environmental stability, and tailored physical properties. In this work, the effect of the gradual substitution of Sb with P in bulk P_xGa₅Ge₂₀Sb_10−xSe₄₅Te₂₀ glasses is studied with structural methods, optical spectroscopy, and differential scanning calorimetry (DSC). Non-isothermal and isothermal DSC studies reveal crystallization of several phases, some of them following the non-conventional anti-Arrhenius behavior of crystallization kinetics. The thermal stability of the glass is shown to increase with P concentration, and the glasses with x = 7, 9, 10 do not fully crystallize during the regular DSC heating scans. Their time–temperature-transformation curves reveal a known “nose”-like shape, suggesting crystallization at close proximity to the melting points of corresponding crystalline phases. It is found that the substitution of Sb with P in glass composition leads to a slight decrease in the optical gap and shift of the main Raman signal at ~ 150 cm⁻¹ to higher wavenumbers.

The emergence of antibiotic-resistant strains caused by the extensive use of antibiotics in the world requires a preventive approach to stop the infection spread, especially in a hospital setting. So, there is a growing demand for materials that can inhibit bacteria growth or have bactericidal effects. In this paper, an inexpensive and durable Cu-containing strontium-modified phosphate glass with a considerable antimicrobial effect is proposed. The basic physical properties of the material are studied, and its antimicrobial effect is evaluated on Staphylococcus aureus bacteria, known to be the most common problem in hospital environments because of healthcare-associated infections. The glass powders demonstrate strong antibacterial efficacy with a concentration of only a few mg/mL, sufficient to eradicate the entire bacterial colonies within 24 h. Bulk surfaces of these glasses inhibit bacterial growth and release low, non-toxic levels of their constituent elements into simulated body fluid. On the basis of the obtained results, it is shown that the proposed glass can be used as a structural material for various medical equipment and/or components of antimicrobial coating/paint not only in medicine but also for high touch point articles in public places like schools, gyms, public offices and similar.

Phase-change materials, demonstrating a rapid switching between two distinct states with a sharp contrast in electrical, optical or magnetic properties, are vital for modern photonic and electronic devices. To date, this effect is observed in chalcogenide compounds based on Se, Te or both, and most recently in stoichiometric Sb₂S₃ composition. Yet, to achieve best integrability into modern photonics and electronics, the mixed S/Se/Te phase change medium is needed, which would allow a wide tuning range for such important physical properties as vitreous phase stability, radiation and photo-sensitivity, optical gap, electrical and thermal conductivity, non-linear optical effects, as well as the possibility of structural modification at nanoscale. In this work, a thermally-induced high-to-low resistivity switching below 200 °C is demonstrated in Sb-rich equichalcogenides (containing S, Se and Te in equal proportions). The nanoscale mechanism is associated with interchange between tetrahedral and octahedral coordination of Ge and Sb atoms, substitution of Te in the nearest Ge environment by S or Se, and Sb–Ge/Sb bonds formation upon further annealing. The material can be integrated into chalcogenide-based multifunctional platforms, neuromorphic computational systems, photonic devices and sensors.