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TY  - THES
AU  - Schweizerhof, Sjören
TI  - Selective surface modification of gold nanorods with functional polymers for tunable self-assembly and optical properties
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2020-06286
SP  - 1 Online-Ressource (XV, 236 Seiten) : Illustrationen, Diagramme
PY  - 2020
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, RWTH Aachen University, 2020
AB  - The beautiful optical appearance of colloidal gold inspired not only alchemists and glass makers centuries ago to design unique decorative art, but particularly impelled renowned scientists to extensively explore and reveal the physicochemical nature of these imposing materials. The progressively gained knowledge and the potential and diversity of colloidal gold lead to a remarkably fast-growing and multidisciplinary research field that is basically built on these plasmonic nanoparticles - better known as ‘Nanotechnology’. The precise control over the gold nanoparticles (AuNPs) size, shape, composition and the relative orientation of adjacent AuNPs decisively determines their opto-thermal properties, which display the key attributes that are utilized within this research area. Recent advances allowed for developing sophisticated AuNPs-based systems that already find application in eminent fields like (bio)medicine and cancer therapy, as well as for building smart optothermally-driven devices and plasmonic sensors.In this work, I will present how anisometric AuNPs, i.e. gold nanorods (AuNRs), are reversibly guided into ordered aggregates, either by light or heat, for substantially tuning their opto-thermal properties in dispersion. The approach to enable such a thermoreversible association behavior is to combine AuNRs with thermosensitive polymeric ligands based on poly(N-isopropylacrylamide) (PNIPAm) which respond to minor local temperature changes. The temperature-dependent phase transition of the anchored PNIPAm is supposed to control the interparticle distance in aqueous medium by switching between hydrophobic attraction at high temperatures and steric stabilization at low temperatures. Therefore, the main focus of my work comprises the selective surface modification of AuNRs with PNIPAm to realize their (photo)thermally and reversible self-assembly into predictable plasmonic structures. The assembly modes are programmable either by tethering the PNIPAm (1) uniformly to the AuNR surface or (2) selectively at the AuNR tips or (3) at the AuNR side. I will particularly focus on the first two concepts and additionally investigate the profound impact of the dispersion composition and how the herein used PNIPAm types affect the AuNR aggregation behavior. In this context, I am going to highlight the accompanied and pronounced spectral shifts of the absorption maximum of the aggregated AuNRs with respect to their single plasmon resonance maximum. Especially the aggregation-induced spectral changes during photothermal treatment were observed to have a self-limiting effect on the heat generation of the dispersion. This phenomenon depicts an important step towards the realization of an opto-thermal feedback mechanism that might facilitate the fabrication of light-driven and self-sustaining mesoscopic oscillators. Beyond the main focus of this work, I will investigate how AuNRs can be precisely and covalently linked into plasmonic structures and how this affects their optical properties. For this purpose, novel photoactivatable ligands are synthesized, combined with AuNRs, and their reversibly adjustable end-to-end assembly is demonstrated. The herein synthesized photoactivatable ligands can contribute to new reaction pathways for the design of functional AuNRs, which might find application in diverse nanoscopic systems. Among the investigations of reversible AuNR self-assembly, a straightforward method for producing near infrared active polysulfone (PSU) plastics is demonstrated. Inspired by the famous Lycurgus Cup, commercial PSU was equipped with various synthesized plasmonic nanoparticles. It is shown that the obtained composite materials have exceptional but easy to verify overt (coloring) and covert (photothermal) features. In particular, the herein developed dichroic PSU-AuNP composite is rather unique and the optical effect hardly imitable. Hence, such composites might in the future enable advanced forgery-proof strategies for the safety-encoding of bank notes, plastics and consumer goods.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2020-06286
UR  - https://publications.rwth-aachen.de/record/792661
ER  -