This work presents the dependences of the absorption intensity of the acid-soluble chitosan biopolymer films in the infrared (IR) region of the spectrum on the concentrations of silver and gold nanoparticles (NPs) of different morphologies. The interaction mechanisms in the vibrational spectra overlapping area of the silver NPs and chitosan molecules (2500–3500 cm⁻¹) were observed. The influence of the metal NPs on the dipole moments of the OH-, NH₃ ⁺- and CH-chitosan molecule group oscillations was established. This interaction leads to a linear increase of the IR absorption intensity with an increase of the silver nanoparticle concentration, synthesized by the citrate and borohydride methods. The presence of silver and gold ablative NPs in the chitosan films demonstrates the IR absorption intensity exponential decrease with the metal NPs’ concentrations.

Medicinal plants contain various biologically active substances. This study aimed to investigate properties of plant extracts and component composition of plant raw materials from the continental part Kaliningrad region (Guards district). For this, we used column chromatography and IR spectroscopy. The objects of the study were samples of plant extracts of Eryngium maritimum, Hedysarum neglectum, Melilotus officinalis, and Aesculus hippocastanum. To produce medicinal plant extracts, we prepared methanol extraction by the Soxhlet method for 8 h (15 cycles). The antioxidant activity of the studied samples was determined by their ability to reduce the radical 2,2-diphenyl-1-picrylhydrazyl. The disk-diffusion method was used to evaluate the antimicrobial activity of the plant extracts against such test strains as Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. In the extracts, 3,4-dihydroxybenzoic acid, astragalin, luteolin-7-glucoside, rosmarinic acid, and chlorogenic acid were identified. However, more research is needed to determine which of the individual phenolic compounds in E. maritimum, H. neglectum, M. officinalis, and A. hippocastanum are involved in exhibiting antioxidant activity. It was found that the plant extract of H. neglectum had activity against the bacterium B. subtilis and the mold fungus C. albicans, while the plant extract of E. maritimum was detrimental to the growth and development of both Gram-positive and Gram-negative bacteria. Infrared spectroscopy can help in further studies to determine properties of medicinal plants to ensure the safety and efficacy of plant-based products.

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 optical processes of plasmonic quenching of rhodamine 6G (R6G) molecules fluorescence in polyvinyl alcohol dielectric films formed on rough silver (Ag) surfaces were researched. The depth of penetration of the surface plasmon field into the dielectric film with R6G molecules is calculated. The angular and spectral-kinetic characteristics of dye molecules fluorescence decay on rough Ag surfaces are determined.