Engineering plasmonic nanomaterials for SERS applications

Identifier:  TDX:4126

Handle: https://hdl.handle.net/20.500.11797/TDX4126

Authors:  Turino, Mariacristina

Abstract:
Due to their exceptional properties, gold and silver nanoparticles have been used in a variety of applications, including those related to surface-enhanced Raman scattering (SERS) spectroscopy. In this regard, the increasing employment of this spectroscopic technique as an ultrasensitive analytical tool in a wide range of application fields, encouraged research in further improvements in the SERS substrates engineering. With these considerations in mind, the proposed dissertation aims to examine approaches for the design of novelty nanomaterials and expands the molecular library surface ligands that can decorate the plasmonic platforms with a special focus on SERS application. First, the formation of a smooth silver layer onto gold cores with different geometrical features through a cold nanowelding process was proposed as a new synthetical approach that overcomes the issues identified in the conventional chemical reductions of metal salts in solution. In particular, the conducted research has demonstrated the strong implication of some experimental parameters in the generation of bimetallic Au/Ag structures that retain the original gold substrate morphology. Secondly, a novel azobenzene derivative was synthesized as an efficient low-cost chemoreceptor for the SERS detection of clinically relevant low molecular weight thiols. More concretely, colloidally stable silver nanoparticle clusters were equipped with the obtained mercapto-azobenzene probe that, in the presence of biothiols, displays dramatic SERS spectral alterations quantitatively correlated to the small thiolated molecules-mediated breakage of the diazo bond. The dissertation finally reports a study conducted on the production of a metallic metamaterial. The resulting hybrid graded-index (GRIN) lens was obtained through the hierarchical assembly of gold nanoparticles onto a micrometric core of silica with the aim to examine the exotic optical properties to concentrate the light at the center of the microsphere deriving from the complex architecture.