Lytvyn V. Gold and silver nanostructure arrays for plasmon-controlled fluorescence

The thesis is devoted to the optimization of existing methods of fabrication of gold and silver nanostructure arrays (plasmonic nanochips) with dielectric coatings on the nanostructures for plasmon-controlled fluorescence (PCF). By analytical modeling using the Green's function method for the system "silver nanoparticle on the substrate–coating–dye molecule" the simulations of the coating thickness, size of nanoparticle and exitation wavelength which provide the maximum fluorescence intensity were carried out. It is shown that in the presence of a dielectric substrate on which silver nanostructures with a radius of 20–60 nm are placed, the fluorescence enhancement factor is described by a nonlinear dependence with a maximum at the distance between fluorophore and nanoparticles in the range of 5–15 nm. It is shown that by controlling the parameters of the technological process of fabrication of nanostructure arrays such as thickness of the deposited films and the dielectric coating, annealing time and temperature, type of the dielectric coating it is possible to regulate the localized surface plasmon resonance wavelength in the range from 420 nm to 820 nm. Thus, it becomes possible to obtain a necessary resonant extinction wavelength of the nanostructures, which, depending on the tasks, will enhance or quench the fluorescence signal. The results of the morphological and optical properties of these structures are presented. The influence of the dielectric coatings of silicon dioxide, aluminum oxide and various polyelectrolytes on the spectral properties of such arrays for applications in plasmon-controlled fluorescence was studied. The design of the novel laser-based compact fluorometer "Fluorotest-Nano" is presented. The studies of PCF of organic dyes rhodamine 6G, methylene blue and porphyrin near gold and silver nanostructure arrays with different dielectric coatings have been carried out using presented laser fluorometer. A new heterosystem consisting of a glass substrate, metal nanostructure arrays coated with SiO2 layer and a matrix "polymer-fluorophore" was developed to enhance the fluorescence signal. The design of the fluorometer prototype "Fluorotest-Nano" provides fast (within 10-15 min.) fluorescence analysis and can be applied for biochemical and chemical monitoring, as well as for training specialists in the university and research laboratories