Beinyk T. SERS substrates based on ensembles of gold nanoparticles of branched morphology

Thesis is devoted to the development of the methods for the formation of ensembles of gold nanoparticles, which correspond to the basic requirements for developed materials using as substrates for surface-enhanced Raman spectroscopy (SERS-substrates), in two ways (self-assembly method and template synthesis). Stable homogeneous ensembles of non-agglomerated branched gold nanoparticles of controlled size and shape with different layer thickness (500?800 nm) on the surface of glass substrates were obtained by self-assembly method. It is shown that the obtained materials are characterized by a frame (arc) structure. Using of nanoparticle ensembles as SERS substrates showed high efficiency in Raman signal enhancing of the molecules under investigation (Rhodamine 6G and Crystal Violet): enhanced factor is EF = 105. In this case, the thickness of the ensembles does not affect the enhancement efficiency due to the plasmon excitation only of the surface layer of ensembles. New method of forming the ensemble of branched gold nanoparticles of controlled size and morphology directly on the surface of glass substrates with surface filling degree up to 80% (the method of template synthesis) has been developed. Investigation of the ensemble's surface has shown that gold nanoparticles form a monolayer on the substrate surface. It was established that the developed ensembles of isolated gold nanoparticles (average size 80 nm, the filling degree of the substrate surface 25%) is a new type of effective SERS-substrates, enhanced factor of the Raman signal of Crystal Violet molecules is 106 and is higher by order of magnitude than this value when using assemblies obtained by self-assembly method, which is due to the nanoparticle isolation in monolayer ensemble and the possibility of creating "hot spots" on each nanoparticle sharp branch. Keywords: branched gold nanoparticle, ensemble of nanoparticles, monolayer, optical properties, SERS-substrate.