Active plasmonics in soft matter doped with gold nanoparticles plasmonica attiva in materia soffice drogata con nanoparticelle d'oro

Abstract

The main objective of this study is active plasmonics. The work has been focussed on the design, characterization and theoretical interpretation of novel systems. Top-down and bottom-up, self-assembling, approaches have been utilized to realize devices where spherical gold nanoparticles have been periodically and randomly arranged. Two main paths have been followed to achieve this goal. In the first one, by utilizing a rigid periodic structure as a host platform for soft-matter (cholesteric liquid crystals) mixed with plasmonic nano-entities, was possible to obtain a chirally-organized tuneable plasmonic system. The tunability of the obtained device has been induced by applying temperature changes or external electric fields. In the second one, the surface of an elastomeric platform has been randomly covered by gold-nanoparticles. Controlled nano-chemistry processes have been successively applied to the nanoparticles (immobilized on the surface) to locally increase their size. The elastic properties of the template together with the increased size of particles have allowed a systematic study of the coupling between near-fields of the spherical nanostructures. Colloidal nano-chemistry technics have been utilized both to synthetize spherical gold nano-particles and to increase their sizes. Spectroscopic analysis has been used to analyse the response of obtained structures under electrical, thermodynamical and mechanical stimuli. SEM and TEM imaging have been exploited to study the morphology of devices, the shape of nano-structures and to measure their sizes. Moreover, from SEM images, through the use of a MatLab code written to the purpose, it has been possible to extract fundamental parameters used to perform a theoretical analysis of experimental results