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Nonlinear Processes in Plasmonic Catalysis
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Nonlinear Processes in Plasmonic Catalysis. |
| 개인저자 | Nelson, Darby Adam. |
| 단체저자명 | The Ohio State University. Chemistry. |
| 발행사항 | [S.l.]: The Ohio State University., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 110 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-06B. Dissertation Abstract International |
| ISBN | 9781392380833 |
| 학위논문주기 | Thesis (Ph.D.)--The Ohio State University, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-06, Section: B.
Advisor: Schultz, Zachary. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | Optical excitation of plasmon resonances has been shown to drive catalytic processes on the surfaces of nanostructured materials. Plasmon resonances have the ability to be tuned across the solar spectrum, sparking interest in their use for plasmonic catalysis in varying applications. Previous research indicates that nanostructures with tight junctions can generate direct current (DC) electric fields, arising from a second order nonlinear phenomenon known as optical rectification (OR). The impact that OR generated DC electric fields have on plasmonic catalysis is not known. Through the utilization of Stark spectroscopy, spectro-electrochemical methods, and a home-built SHG/AFM system this research sets out to understand the impact nonlinear phenomena have on plasmonic catalytic activity.Chapter 1 provides a brief introduction to the field of plasmonic catalysis and the main catalytic mechanism in the literature of `hot' electron generation. It also describes second order nonlinear processes, those being second harmonic generation and optical rectification, and the reasons behind the hypothesis of this thesis that optically rectified fields can act as a complimentary mechanism to `hot' electrons.In Chapter 2, a mixed monolayer of p-mercaptobenzonitrile (MBN) and either 4-nitrothiophenol (NTP) or 4-aminothiophenol (ATP) is used to correlate the OR field with surface catalytic activity. The DC electric field strength is measured using a vibrational Stark reporter (MBN). The catalytic activity is assessed by monitoring the formation of 4,4-dimercaptoazobenzene (DMAB) and loss of NTP/ATP using changes in the observed surface-enhanced Raman spectrum. The results show that, at relatively low laser powers, optical rectification modulates the plasmonic catalysis.Further light is shed on the impact optically rectified fields in Chapter 3, where spectro-electrochemical measurements show an effect on catalytic reactions. Cyclic voltammetry shows that the electrochemical reduction and oxidation potentials of a 2 mM CuSO4 solution occur at ~100 mV lower overpotential on an optically excited Ag nanodendrite electrode. Stark spectroscopy of nitriles absorbed to these surfaces indicates photo-associated changes in surface potential across the Ag nanodendrites. Localized areas evince photo-induced changes in surface potential upwards of 300 mV. These results provide evidence of optically rectified fields altering electrochemical reactivity on plasmonic surfaces and suggest optimizing this nonlinear phenomenon may improve plasmonic photocatalysts.Chapter 4 utilizes Stark spectroscopy and second harmonic signals to understand the impact optically rectified fields have on other second order nonlinear phenomena as well as elucidate the temporal differences that have been shown between quantum regime electron tunneling events and optically rectified surface charge buildup. It is shown that surface potentials averaging -400 mV are only generated upon continuous illumination of a gold nanoisland plasmonic surface with a widefield LED source. Negligible changes in SHG signals are seen from surface excitation with the femtosecond laser alone, showing the importance of continuous plasmon excitation for sustained surface potentials. It isalso shown, through Stark spectroscopy and spectro-electrochemical measurements, that optically rectified fields impact SHG signals in a similar fashion to an externally applied bias on pristine plasmonic surfaces. This result shows the potential for utilizing SHG signals to better understand the impact surface heterogeneity has on the optically rectified DC field and enables the optimization of plasmonic surfaces for future use as photocatalysts.Chapter 5 discusses the main conclusions of this thesis and how I believe the results shown in this document fit into the advancement of the field of plasmonic catalysis. It also briefly touches on how important I believe the plasmonic catalysis field is and the potential it has to have a positive impact on the world.Overall, this research shows the impact plasmon generated nonlinear phenomena have on plasmonic catalysis and the potential to utilize OR generated DC fields to advance our understanding of plasmonic materials in photocatalysis. Specifically, surface optimization promoting nonlinear phenomena can be used to improve catalytic efficiencies of plasmonic surfaces. |
| 일반주제명 | Chemistry. Analytical chemistry. Optics. |
| 언어 | 영어 |
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