Core-Satellite Metallic Nanoclusters in Silica Obtained by Multiple Ion Beam Processing
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1020-GG06-09
Core-Satellite Metallic Nanoclusters in Silica Obtained by Multiple Ion Beam Processing Giovanni Mattei1, Valentina Bello1, Paolo Mazzoldi1, Giovanni Pellegrini1, Chiara Maurizio2, and Giancarlo Battaglin3 1 Department of Physics, University of Padova, via Marzolo 8, Padova, I-35131, Italy 2 ESRF, GILDA-CRG, CNR-INFM, Rue Horowitz 6, B.P. 220, Grenoble, 38043, France 3 Department of Physical Chemistry, University of Venice, Dorsoduro 2137, Venice, I-30123, Italy ABSTRACT Ion irradiation has been used to transform spherical bimetallic AuAg nanocluster embedded in silica in a more complex structure made of a central cluster surrounded by a halo of smaller satellite nanoclusters, whose composition, size and distance from the central cluster can be tailored by controlling the irradiation parameters. This peculiar topology produces a red-shift of the surface plasma resonance of the composite through the electromagnetic coupling between the central cluster and the satellites. A calculation of the local field properties of the investigated systems within the fully-interacting generalized Mie theory showed that the satellite topology produces large local field enhancements around the central cluster.
INTRODUCTION Monoelemental or metal alloy nanoclusters embedded in SiO2-based matrices exhibit peculiar nonlinear optical properties which are function of the cluster size and composition [1-5]. Among different synthesis techniques, sequential ion implantation in glass has demonstrated to be a very effective technique to obtain such nanocomposites [6]. In this work, we used an ion beam-based multi-step approach for synthesizing embedded nanoclusters and for modifying in particular their near-field and far-field properties, through an ion-beam controlled tuning of the dielectric environment around them, therefore obtaining the plasmon tuning of the composite. In the first step noble metal nanoclusters are synthesized in silica by ion implantation followed by thermal treatments. The second step is ion irradiation which allows to create a peculiar nanostructure made of a halo of small satellite nanoclusters around the original ones [7,8]. For instance, in the Au-Cu system we found that irradiation with Ne+ ions promotes a preferential extraction of Au from the alloy, resulting in the formation of Au-enriched "satellite" nanoparticles around the original AuxCu1-x clusters [7]. Despite the experimental demonstration of this core-satellite formation in ion irradiated mono- and bi-elemental systems, the microscopic mechanisms triggering the process are still not thoroughly understood. Therefore, we performed a systematic investigation of the role played by the irradiation parameters (i.e., fluence, flux, energy of the implanted ions) on controlling the satellite nanostructure. In the present work, we used this ion beam based technique to promote a controlled redshift of the plasma resonance absorption (i.e., plasmon tuning) of bimetallic AuxAg1-x clusters exploiting the coupling of the satellite nanoclusters with the or
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