Metal nanoparticles prepared by excimer and solid state laser irradiation in silicate glass: dependence of atomic structure, strength of interaction with matrix and properties of nanoparticles upon their sizes, spatial configurations and the preparation p

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The basic relations between preparation conditions, atomic structure and optical properties should be revealed for Ag and Ag/Au nanoparticles and specific arrays as prepared by UV laser irradiation in glasses. Especially, ArF laser irradiation should allow the generation of high-resolution patterns of nanoparticles immediately below the surface of glasses, which are of specific interest because of their high potential for manifold applications of nanoplasmonics. The starting point are pure and Au containing glasses, which will be doped with silver ions by means of Ag/Na ion exchange processes. ArF excimer (193nm) and for comparison solid state laser irradiation (405nm) using fluences below the ablation threshold should provide the generation of stabilized nanoparticles based on detailed investigations of elementary processes of reduction of metal ions and the growth of particles under UV irradiation. The formation of UV defects, metal atoms and nanoparticles will be detected by optical spectroscopy and further methods.The precise sizes of particles and their distribution should be determined by means of SAXS, XRD and transmission electron microscopy experiments for some selected samples. The existence of homogeneous or of core-shell Ag/Au particles has to be clarified by anomalous small angle X-ray scattering (ASAXS) experiments at the Ag K-edge and the Au-L3-edge core and shell will be calculated separately by this method for such species. The X-ray absorption spectroscopy (XAS) at Ag K-edge and Au L3-edge will be applied to determine the inhomogeneous atomic structure of nanoparticles that is to be expected for all nanostructures. The structural information are to be obtained by two complementary approaches for the processing of experimental EXAFS spectra, which enables to determine local structure parameters of Ag and Au atoms existing in various species or local orders inside the particles. Furthermore, 3D models of very small (< 2-5 nm) Ag and Ag/Au nanoparticles will be constructed using the density functional theory (DFT) method using plane waves and pseudopotential formalisms and by the method of Langevin molecular dynamics. The simulation of optical spectra of surface plasmon resonances by means of Mie-Theory should reveal a direct correlation with the detailed structural results of metal nanostructures. This is to allow a defined generation of plasmonic spectra due to UV laser irradiation.