In this paper, the optical properties of viburnum extract flavonoids in the visible region of the spectrum were investigated and their use as a potential photosensitizer of singlet oxygen for photodynamic therapy was evaluated. The presence of long-lived excited states in the extract molecules was established by spectral methods and time-resolved spectroscopy methods and the dependences of the absorption capacity and luminescence intensity of the extract molecules on the concentrations of oxygen and ablative nanoparticles of the gold in the reverse micelles of AOT (sodium dioctyl sulfosuccinate) were established. The plasmonic enhancement of the luminescence of the extract molecules and the processes of their complexation with oxygen were also established. Furthermore, the rate constants of the processes of conversion of exciting energy in complexes were determined.

Subject of study. This study investigates the luminescence spectral and kinetic features of singlet oxygen generation in chitosan microfilms (10 µm thick) embedded with an extract of viburnum fruit (Viburnum opulus L.). These films were deposited on both glass and gold film (80 µm thick), with the gold film electrochemically deposited on a rough, modified titanium surface. Aim of study. The aim was to determine the primary photophysical patterns of singlet oxygen dynamics in chitosan films containing viburnum fruit extract, following pulsed monochromatic photoexcitation by a structured titanium surface coated with electrochemically deposited gold. Method. The films were investigated in the visible and near-infrared regions using fluorescence techniques. The luminescence lifetime of Viburnum opulus L. flavonoids in the nanosecond range was measured using multichannel photon counting with a picosecond diode. The lifetime of the flavonoid triplet states and singlet oxygen phosphorescence in the studied extract in the microsecond range under excitation by a pulsed xenon lamp were also recorded. Main results. Long-lived delayed annihilation fluorescence of Viburnum opulus L. flavonoid molecules in the 590 nm spectral region, along with luminescence at 1272 nm attributable to singlet molecular oxygen, were observed. A comprehensive kinetic analysis was performed, considering the rate constants of photophysical processes involving singlet oxygen in films with viburnum fruit extract on rough gold surfaces under conditions of sample saturation with molecular oxygen. Stable generation of singlet oxygen was achieved in the chitosan microfilms containing viburnum fruit extract. Practical significance. The findings of this study can be applied to biological methods for cancer treatment.

The presented work shows the study of energy transitions in the NIR and visible regions in the system of Bi₂O₃ and Tm₂O₃ powders. Mechanisms of upconversion luminescence and NIR luminescence between two Bi³⁺ and Tm³⁺ ions at T = 80 K accompanied with nonradiative energy transfer through the vibrational levels were investigated under IR photoexcitation. The absorption bands of the samples on the reflection spectra were examined in the visible region. The values of the emission cross-section parameters were calculated for the Bi₂O₃/Tm₂O₃ complexes.

В работе представлены результаты исследования спектров отражения по-рошков оксида висмута Bi2O3 и смеси оксидов висмута и иттербия Bi2O3/ Yb2O3. Описана методика приготовления образцов порошков оксидов из металлов, а также результаты спектральных эллипсометрических и люминесцентных измерений. Установлена зависимость изменения коэффициента отражения в среде Bi2O3 в присутствии Yb2O3. Получены значения оптических характеристик коэффициентов отражения p- и s-поляризованного света для Bi2O3 и Bi2O3/ Yb2O3. На длине волны λ = 590 нм образец, содержащий оксид иттербия, имеет коэффициенты отражения Rp = 0,321 и Rs = 0,331. Коэффициенты отражения для образца оксида висмута без добавления оксида иттербия Rp = 0,223 и Rs = 0,220. Спектры стоксовой ИК и антистоксовой апконверсионной красной люминесценции образцов получены при возбуждении в ИК-диапазоне. Зарегистрировано увеличение интенсивности люминесценции ионов висмута, распределенных в кристаллической решетке оксида в присутствии ионов иттербия, на длине волны 640 нм, что объясняется переносом энергии между энергетическими уровнями ионов. Интенсивность апконверсионной люминесценции нелинейно зависит от мощности возбуждающего ИК-излучения полупроводникового лазера. Проведено численное моделирование этой зависимости в рамках экспоненциальной и квадратичной моделей.

In recent years, laser-structured titanium dioxide (TiO ₂ ) surfaces have attracted considerable attention due to their combination of high specific surface area, biocompatibility, and unique optical properties, offering promising opportunities for photonics, sensing, and energy applications. Of particular interest is the study of the optical manifestations of porous Ti/TiO ₂ films fabricated via laser structuring, with potential evidence of plasmonic resonances and anomalous dispersion. The samples were prepared from titanium foil subjected to anodization in potassium hydroxide solution, followed by nanosecond laser structuring at the wavelength of 1064 nm and an energy density of (3.2 ± 0.2)∙10 ³ J/cm ² . Surface morphology was analyzed using scanning electron microscopy and optical profilometry, while optical characteristics were investigated by spectrophotometry and ellipsometry. To interpret the spectral data, a modified Adachi-Forouhi model within the dipole approximation was applied, enabling quantitative description of the contributions of interband transitions and plasmonic modes. The surfaces produced by laser structuring exhibited pronounced porosity (pore sizes of 300–1100 nm, depth ~200 nm), submicron cracks, and nanoparticles of the laser-structured material. Reflection spectra revealed minima corresponding to the excitation of surface plasmons and interference modes. Dielectric permittivity spectra displayed a region of anomalous dispersion and field localization at a wavelength of 625 nm. Calculated parameters included the skin layer thickness, Purcell factor for a nanopore, damping length of plasmon oscillations on the surface, propagation length of surface plasmons, and the critical value of polarizability enhancement in the plasmon resonance localization region. Modeling indicated a narrowing of the bandgap to 1.016 eV. Contributions to the dielectric permittivity of the semiconductor component from interband absorption saturation, changes in band structure, and free carriers were determined. While the bandgap narrowing played a decisive role, the dominant contribution to the experimentally observed dielectric behavior arose from the generation of resonant plasmonic modes. It was established that the key mechanism of the optical response is the resonant localization of the electromagnetic field within the nanopores, confirming the manifestation of hyperbolic metamaterial behavior. The material obtained exhibited significant bandgap narrowing due to the nanosecond laser treatment. The results highlight the potential of porous laser-structured anodized titanium surfaces for photonic and sensing devices, as well as for use in waveguiding structures.

The results of a study of the luminescent dynamics of combined aqueous-alcoholic solutions of extracts of red viburnum (Viburnum opulus L.) fruits with chitosan and gold nanoparticles at different oxygen concentrations were presented. The search for natural sources of photosensitizers is an urgent task. The sensitive analytical methods, in particular luminescence, with amplification of the analytical signal as a result of the generation of plasmons in nanoparticles of noble metals, have been used in this work. An additional studies under the conditions of plasmon energy generation showed a significant changes in the dynamics of optical spectra with variations in oxygen concentration in solutions. The spectral-temporal dynamics was investigated with complete oxidation of vitamin C in the studied system. The main method for recording the dynamics of interaction of Viburnum opulus L. flavonoids with oxygen molecules is the luminescent method. Luminescence spectra were measured by means of Fluorolog-3 optical system (Horiba, Japan). Methods of absorption analysis (Shimadzu spectrophotometer, Japan) were also used in the work. The nanosecond luminescence lifetimes of the extracts were measured in the multichannel photon counting mode using a picosecond NanoLED-405L nanoled by means of Fluorolog-3 spectral setup. Microsecond lifetimes were recorded when excited by a pulsed Xe lamp. For the synthesis of gold nanoparticles, the method of laser ablation of a metal plate of gold in distilled water was used. Laser ablation was performed at the LQ929 installation of Solar Laser System (Belarus). A plasmonic effect of amplification of the optical absorption density and luminescence intensity was detected. The kinetics of luminescence quenching of Viburnum opulus L. extract with chitosan under the influence of gold nanoparticles, close to diffusion, was studied. The oxygen concentration at which the flavonoids of the extract are oxidized was spectrally determined. Under the oxygen concentration changing, the dependences of changes in the luminescence intensity of the extract with chitosan at the wavelengths of registration of luminescence spectra were established. When oxygen was doped into all solutions, the spectral and kinetic features of luminescence attenuation with maxima at wavelengths of 480 and 580 nm were detected and investigated. It was established that the lifetime of luminescence at a registration wavelength of λ = 480 nm varies depending on the concentration of gold nanoparticles and the concentration of oxygen molecules and it is the nanosecond spectral region (3–4 ns). It was shown that luminescence at a wavelength of 580 nm is due to the oxidized form of quercetin which is a part of the Viburnum opulus L. flavonoids, appeared at a high oxygen concentrations. Long-lived chemiluminescence at a wavelength of 580 nm with time decay of 15 μs as a result of radical processes involving molecular oxygen and extract molecules was recorded. The spectral methods presented in this paper, as well as a method for determining of quercetin as a result of oxygen oxidation of flavonoids of red viburnum fruits, can be used in the field of biophysics, biotechnology and chemical analysis.