This Thesis aims at gaining a deeper knowledge of the photophysical properties of hybrid plexcitonic nanosystems. Plexcitons are hybrid states originating from the mixing of the plasmon resonances of metal nanostructures with molecular excitons. Here, colloidal plexciton systems are considered, where the plasmonic component is a colloidal nanoparticle. The exploration of the dynamical properties of these nanohybrids is still in its infancy, with just a handful of papers devoted to their ultrafast characterization. Nonetheless, there are high expectations for effectively using the strong coupling to modify rates of chemically relevant molecular processes. The emerging interest in these materials affects several application fields (like sensing, photonics, plasmonic switching and lasing, quantum information processing and artificial light-harvesting) for the chance to obtain useful devices exploiting the peculiar properties of these nanosystems, including their possible capability of sustaining coherent energy transfer. The research activity has focused first on the synthesis of plexcitonic hybrids, performed by supramolecular coupling of gold nanorods with J-aggregates of the pseudoisocyanine (PIC) molecule. Once fine-tuned and optimized the synthesis procedures, the photophysical properties of the hybrid systems have been characterized and studied with the pump-probe spectroscopy: their ultrafast dynamics are analyzed in different coupling regimes and with different pump fluences. Overall, the obtained findings suggest that in the first few picoseconds, the hybrid system behaves like the plasmonic moiety. At longer timescales, instead, unique dynamics are found, strongly dependent on the coupling regime. Signatures of coherent dynamics between the states have also been found. The obtained results allow drawing essential guidelines to learn how to tune the photophysical and dynamic behavior of these nanomaterials by modifying the experimental parameters involved in their preparation. The results reported in this Thesis represent an essential step toward developing functional supramolecular materials for quantum-nano-photonic applications.

Colloidal plexcitonic nanosystems based on gold nanorods: design, synthesis and photophysical characterization

BOCCHIO, CATERINA
2020/2021

Abstract

This Thesis aims at gaining a deeper knowledge of the photophysical properties of hybrid plexcitonic nanosystems. Plexcitons are hybrid states originating from the mixing of the plasmon resonances of metal nanostructures with molecular excitons. Here, colloidal plexciton systems are considered, where the plasmonic component is a colloidal nanoparticle. The exploration of the dynamical properties of these nanohybrids is still in its infancy, with just a handful of papers devoted to their ultrafast characterization. Nonetheless, there are high expectations for effectively using the strong coupling to modify rates of chemically relevant molecular processes. The emerging interest in these materials affects several application fields (like sensing, photonics, plasmonic switching and lasing, quantum information processing and artificial light-harvesting) for the chance to obtain useful devices exploiting the peculiar properties of these nanosystems, including their possible capability of sustaining coherent energy transfer. The research activity has focused first on the synthesis of plexcitonic hybrids, performed by supramolecular coupling of gold nanorods with J-aggregates of the pseudoisocyanine (PIC) molecule. Once fine-tuned and optimized the synthesis procedures, the photophysical properties of the hybrid systems have been characterized and studied with the pump-probe spectroscopy: their ultrafast dynamics are analyzed in different coupling regimes and with different pump fluences. Overall, the obtained findings suggest that in the first few picoseconds, the hybrid system behaves like the plasmonic moiety. At longer timescales, instead, unique dynamics are found, strongly dependent on the coupling regime. Signatures of coherent dynamics between the states have also been found. The obtained results allow drawing essential guidelines to learn how to tune the photophysical and dynamic behavior of these nanomaterials by modifying the experimental parameters involved in their preparation. The results reported in this Thesis represent an essential step toward developing functional supramolecular materials for quantum-nano-photonic applications.
2020
Colloidal plexcitonic nanosystems based on gold nanorods: design, synthesis and photophysical characterization
plexciton
gold nanorods
pump and probe
cyanine
optical properties
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12608/30047