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Title: Dynamic plasmonic systems with actuating nanotransducers
Author: Cormier, Sean
ISNI:       0000 0004 8501 382X
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2020
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The development of programmable nanomachines that deliver therapeutic drugs to specific target sites, assemble objects, or work together to apply coherent forces on-demand has been long sought after in the field of nanotechnology. A major hurdle in this endeavour is the lack of a reliable source of power for driving these machines. In this work, plasmonic nanoparticles coated with thin thermoresponsive polymeric shells actuate in response to light to give rapid, dynamic optical and mechanical responses. They are called actuating nanotransducers (ANTs). Their fast, reversible response and small size suggests they are good candidates for powering nanomachines. ANTs consist of gold nanoparticles coated with the poly(N-isopropylacrylamide) (PNIPAM). Gold nanoparticles have renowned tunable plasmonic properties, while PNIPAM is a well-known polymer that expands and contracts in response to temperature in aqueous media. The particular combination of these materials enables fast local actuation of the PNIPAM shell in response to light via plasmonic heating. These simple nanoparticle actuators exhibit optical and self-assembly behaviours that vary greatly depending on their environment. In this thesis, various ANT systems are studied. The crucial role of local surface charge on the reversible self-assembly of gold colloids is examined. The mechanical responses of individual ANTs are characterised in Nanoparticle on Mirror plasmonic structures. The dynamic behaviours of ANTs in thin-films and microdroplets are also investigated. It is observed that the thin-films undergo a reversible insulator-to-metal transition that is well captured with an effective medium model. In addition, the microdroplets are shown to mimic the optical response of chromatophores, giving rise to substantial changes in colour. This work demonstrates that the optical and physical properties of individual ANTs can be switched with light, and particle ensembles can effectuate significant responses at much larger scales.
Supervisor: Baumberg, Jeremy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Plasmonic ; Nano-actuators ; Dynamic Nanosystems