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Tuning structure to optimise charge transport: nanoparticle composites, microcrystals and metallopolymers

Keane, Lorraine (2003) Tuning structure to optimise charge transport: nanoparticle composites, microcrystals and metallopolymers. PhD thesis, Dublin City University.

Abstract
Enhancing charge transport is important for the development of materials in devices including sensors, electronics and catalysts The focus of the work presented here is the investigation of factors that enhance charge transport in redox active materials including solid deposits, metallopolymers and metallopolymer nanoparticle composites Deposits of the osmium polypyndyl complex, [Os(OMe-bpy)3]2+ have been mechanically attached to a microelectrode surface Due to close packing of the material particles the internal free volume is low and solvent/counterion uptake occurs slowly Electrochemical cycling in HCIO4 causes changes in the deposit morphology with evidence of nucleation and crystal growth. This process appears to be promoted by the protonation of the methoxy groups that encourages hydrogen bonding between adjacent complexes The rate of charge transport increases from 1 5±0 1 x 10 9 cm2s 1 for 0 1 < [HCIO4] < 0 6 M to 13±1 x 1 0 9 cm2s 1 in 1 0 M HCIO4. For the osmium polypyndyl polymer, [Os(bpy)2 (PVP)io Cl]+ ‘break in’ and physical effects from the electrolyte perchlorate ion or protons were not evident. Polymeric materials are rigid and rapidly swollen in electrolyte with the result of possible fast uptake of solvent/counterions Introducing gold nanoparticles forming metallopolymer nanoparticle composites increases the charge transport by approximately an order of magnitude from 5 3±2 x l0 10t o 5 8 x l 0 9 cm2s 1 corresponding to electron transfer rates between the redox centres o f 1 9 x 106 and 1 7 x 107 M ]s 1 Enhanced charge and electron transport values may indicate the formation of an interconnected network where the osmium centres mediate electron transfer between the gold nanoparticles To demonstrate the possible application of these solid state and polymeric osmium polypyndyl complexes as optical devices, it is necessary to understand their photophysical properties As a first step in elucidating these properties, the quenching of excited state Os2+ species by Os3+ has been explored using [Os(bpy)3](PF6)2 as a model.
Metadata
Item Type:Thesis (PhD)
Date of Award:2003
Refereed:No
Supervisor(s):Forster, Robert J.
Uncontrolled Keywords:Charge transfer; Enhanced charge transport; Oxidation-reduction reaction
Subjects:Physical Sciences > Chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:17948
Deposited On:24 Apr 2013 13:31 by Celine Campbell . Last Modified 23 Aug 2013 13:57
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