Bulavinets T. Photodynamic properties of nanostructures under plasmon resonance conditions for biomedical applications

The object of research is interaction of electromagnetic radiation with metal and metal-semiconductor nanostructures. Research methods. Simulation of the interaction of electromagnetic radiation with plasmon nanostructures was performed using the methods of dipole equivalence and discrete dipole approximation (DDA). Characterization of synthesized silver nanostructures, Ag/TiO2 nanosystems and their properties was carried out using modern research methods: spectrophotometry; transmission (TEM) and scanning (SEM) electron microscopy; dynamic light scattering (DLS); electrophoretic light scattering (ELS); thermography; as well as a set of biochemical methods according to standard research procedures. Scientific novelty of the obtained results. Scientific ideas and knowledge about the dependence of optical parameters of metal and metal-semiconductor nanostructures on their morphology, shape and geometric dimensions are expanded. It is shown that the optical response of Ag-based nanostructures is the most sensitive to changes in morphology and parameters of the environment. This allows one to control its optical parameters and adjust the plasmon resonance to the desired spectral range. For the first time, the geometric parameters of nanostructures for efficient use for selected practical applications are determined. The method of obtaining a stable biocompatible silver colloid with photoinduced reduction of silver ions from an aqueous solution of AgNO3 at room temperature under laser irradiation with a wavelength of 445 nm was improved, and sodium citrate was used as a stabilizer of nanoparticles. This synthesis method allows to obtain silver nanoparticles both in the colloidal solution and on the surface of semiconductor nanostructures as a silver shell with controlled thickness. For the first time, an original radial irradiation device was developed and manufactured to modify the spatial and optical parameters of silver nanoparticles under the influence of light fluxes of high-power LEDs. The device equipped with the heat dissipation system and three isolated chambers for irradiating colloidal solutions of nanoparticles with blue, green and red radiation. It is shown that long-term irradiation of silver colloids leads to modification of the geometric shape and size of nanoparticles and displacement of its plasmon absorption peaks on the spectral scale to the NIR range. The influence of geometric shape and concentration on the efficiency of heat generation by silver nanostructures under the action of laser radiation with wavelengths of 445 and 880 nm is specified. It is shown that the synthesized triangular nanoprisms with shifted optical absorption in the NIR region, in comparison with spherical silver nanoparticles, have the highest efficiency of heat generation both in air and in biological media. It is established that Ag/TiO2:C,S nanosystems intensively absorb radiation of the whole visible range, show high photocatalytic action and significantly reduce the duration of photodegradation reaction of organic compounds under the action of visible light. The practical significance of the thesis. The results obtained in this work are important for a number of applications in technologies and tools of micro- and nanosystem technology. The method of obtaining silver colloid with the visible range laser radiation (445 nm) from an aqueous solution of silver salt and sodium citrate as a stabilizing agent has been improved. The obtained nanostructures are characterized by high stability and purity. The novelty of the used technology is confirmed by the declaratory patent of Ukraine for the utility model № 131184 "Method of obtaining a solution of colloidal silver". A device for simple modification of the morphology of plasmon nanostructures based on LEDs with different wavelengths has been developed. The device allows to modify the spatial parameters of silver nanoparticles and shift the plasmon absorption peaks to the NIR region. Silver nanostructures with modified optical parameters can be actively used in some fields of biomedicine as bactericidal and fungicidal agents. The effectiveness of the use of modified silver nanostructures in endodontics is confirmed by the relevant act of implementation. The obtained research results can be used in the improvement and manufacture of elements and devices of micro- and nanosystem technology, in particular sensor electronics and microactuators. Some results of dissertation research are used in the research work "Nanostructured interfaces based on non-toxic materials for practical applications" (DB / INTERFACE № 0120U100675); in the educational process for the preparation of students in 153 "Micro- and nanosystem technology" and in performing student's bachelor and master theses of the Department of Photonics of the National University "Lviv Polytechnic", which is confirmed by relevant acts.