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Synthesis and Dynamics of Photocatalytic Type-II ZnSe/CdS/Pt Metal-Semiconductor Heteronanostructures

O'Connor, Timothy F., III
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1340038781

Abstract Details

2012, Master of Science (MS), Bowling Green State University, Physics.
The following presents an analysis of the energetics of photocatalytic ZnSe/CdS/Pt metal-semiconductor heteronanorods capable of performing a sustained H2 reduction reaction. The study begins with an investigation of the effects of charge carrier localization on the stability and efficiency of ZnSe/CdS/Pt. By switching the seed material of the dot-in-a-rod structure from ZnSe to ZnTe, the band edge alignment of the linear system can be altered from one that expels positive holes to the surface ligands of the structure to one that localizes holes in the semiconductor core, as is energetically favorable in the ZnTe seeded system. Positive holes that are not removed from the semiconductor domain are then available to oxidize the core, compromising the structure and photocatalyic capacity of the nanocrystal. In contrast, ZnSe seeded heteronanorods capable of removing chemically active holes pass this photodegradation on to the ligand moieties, destroying the inexpensive, organic surfactants rather than the nanostructure. Interestingly, it was found that fresh ligands can be reattached after the desorption of oxidized ligands, allowing for a larger turnover of photocatalytic cycles to be achieved. After studying the effects of band edge energetics, a deeper analysis of the ultrafast charge carrier dynamics was undertaken to determine the time scales at which the three dominant charge transfer processes, namely, electron transfer from CdS to Pt, hole localization within ZnSe, and the subsequent hole transfer to the surface ligand, occur. The photocatalytic reaction rate is theorized to be limited by the slowest charge transfer mechanism, which was determined to be the removal of the hole from the semiconductor core by employing femtosecond transient absorption spectroscopy. These time resolved spectroscopic measurements yield a more complete understanding of the energetic processes at work within the nanostructures and glean insight as to methods of making more efficient photocatalytic nanoreactors.
Dr. Mikhail Zamkov (Advisor)
Dr. Lewis Fulcher (Committee Member)
Dr. Liangfeng Sun (Committee Member)
Chemistry; Energy; Nanoscience; Nanotechnology; Physics
nano; nanotechnology; nanoscience; catalysis; semiconductor; nanocrystal; heterostructure; ZnSe; CdS; Pt; photo; photocatalysis; metal-semiconductor; hybrid; nanostructure; charge carrier dynamics; transient absorption.

Recommended Citations

Citations

  • O'Connor, III, T. F. (2012). Synthesis and Dynamics of Photocatalytic Type-II ZnSe/CdS/Pt Metal-Semiconductor Heteronanostructures [Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1340038781

    APA Style (7th edition)

  • O'Connor, III, Timothy. Synthesis and Dynamics of Photocatalytic Type-II ZnSe/CdS/Pt Metal-Semiconductor Heteronanostructures. 2012. Bowling Green State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1340038781.

    MLA Style (8th edition)

  • O'Connor, III, Timothy. "Synthesis and Dynamics of Photocatalytic Type-II ZnSe/CdS/Pt Metal-Semiconductor Heteronanostructures." Master's thesis, Bowling Green State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1340038781

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.