Wu, Mingyan
(2011)
Spectroscopic Investigations of Nanoscale Aggregates and Their Electron Transfer Properties in Solution.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
In part I, the changes in the absorption and fluorescence properties of poly-(p-phenylene-ethynylene) (PPE)-based conjugated polyelectrolytes were investigated as a function of the solution conditions such as concentration, temperature, solvent, surfactant, and the ionic strength. The equilibrium between unaggregated and aggregated forms of the polymer was described and quantified. The fluorescence quenching of polymers by positively charged and neutral macromolecules were also investigated and showed that the quenching depends on electrostatic, hydrophobic, and energy transfer interactions with the quencher. A detailed study using fluorescence correlation spectroscopy was performed and allowed us to probe the templating of a surfactant OTAB on the polyelectrolytes well below its critical micelle concentration. Furthermore, it was found that the optical and aggregation properties of these conjugated polyeletrolytes can be manipulated by changing the charge density along the polymer backbone. In part II, assemblies of CdSe and CdTe NPs were controlled by the electrostatic attraction of the charged functionalities placed on the NP surface coating. Electron transfer (ET) in assemblies of these NPs was studied in aqueous solution by fluorescence quenching. Three factors were found to determine how the ET depends on the nature of the NP assemblies by both steady-state and time-resolved fluorescence measurements: the interparticle distance, the energetic alignment of the NP bands (hence the size of the NPs), and the direction of the electric field between the NPs, created by their surface charges. In addition, the assemblies of CdSe NPs on a dithiol coated Au electrode were created and their electronic energetics were quantified. The energy level alignment of the filled and unfilled electronic states of CdSe NPs with respect to the Au Fermi level was investigated by both cyclic voltammetry and photoemission spectroscopy separately. These two measurements showed that the CdSe filled states become ‘pinned' to the Fermi level of the Au electrode. Furthermore, the preliminary electrochemical studies at the interface were carried out in order to investigate the organization and reactivity of nanoparticles/dyads at ITIES.
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| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
30 September 2011 |
| Date Type: |
Completion |
| Defense Date: |
3 June 2011 |
| Approval Date: |
30 September 2011 |
| Submission Date: |
22 July 2011 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
aggregates; conjugated polymer; electron transfer; nanoparticle; polyelectrolyte; solar cell.; spectroscopy |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-07222011-101340/, etd-07222011-101340 |
| Date Deposited: |
10 Nov 2011 19:53 |
| Last Modified: |
15 Nov 2016 13:46 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8529 |
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