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Photocatalysis and Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dot-based Heterostructures.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Photocatalysis and Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dot-based Heterostructures./
作者:	Suwandaratne, Nuwanthi Savindrika.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	273 p.
附註:	Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
Contained By:	Dissertations Abstracts International81-09B.
標題:	Inorganic chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27736748
ISBN:	9781658421478

Photocatalysis and Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dot-based Heterostructures.
Suwandaratne, Nuwanthi Savindrika.

Photocatalysis and Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dot-based Heterostructures. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 273 p.

Source: Dissertations Abstracts International, Volume: 81-09, Section: B.

Thesis (Ph.D.)--State University of New York at Buffalo, 2020.

This item must not be sold to any third party vendors.

Quantum dot (QD)-based heterostructures are intriguing material architectures for light harvesting, excited-state charge transfer, and solar energy conversion. The design of such architectures for photocatalysis requires careful consideration of both thermodynamic offsets and interfacial charge-transfer kinetics. This dissertation explores the photocatalysis and charge transfer dynamics in cadmium chalcogenide QD-based heterostructures. Chapters 2-5 of this dissertation focus on heterostructures comprising MxV2O5 (M = intercalated metal cation, Pb2+ or Sn2+) or α-V2O5 nanowires (NWs) interfaced with CdE (E=S/Se/Te) QDs with programmable energetic offsets to promote light-induced charge separation and photocatalytic proton reduction. Chapter 6 reports on dynamics of electron transfer (ET) from photoexcited CdSe QDs and adsorbed fullerene derivatives, as well as redox photocatalysis at these nanocomposites.CdSe/β-Pb0.33V2O5 was fabricated and characterized as a robust photocathode that promotes the photoinduced reduction of protons to H2 under illumination by visible light. The results were consistent with a mechanism in which excited-state interfacial hole transfer facilitates charge separation and photocatalysis, suggesting that the CdSe/β-Pb0.33V2O5 heterostructures are indeed promising architectures for light harvesting and photoelectrochemical (PEC) water-splitting. To further improve the performance of the CdE QD/β-Pb0.33V2O5 NW heterostructure photocathodes, we incorporated Pt as a proton reduction cocatalyst and prepared a ternary heterostructure system which promotes H2 evolution. Both transient absorption (TA) and PEC experiments revealed that the addition of Pt to the CdS/β-Pb0.33V2O5 O5 binary heterostructures promoted faster ET to Pt and resulted in improved proton reduction. Moreover, we increased the distance between QDs and NWs by changing the capping ligand of the QDs from cysteine to homocysteine. The ultrafast TA measurements revealed that deleterious QD-to-NW ET can be slowed down by increasing the distance between NWs and QDs.The topochemical synthesis yielded a metastable β-Sn0.23V2O5 compound exhibiting Sn 5s-derived midgap states ideally positioned to extract photogenerated holes from interfaced CdSe QDs. The existence of these midgap states near the upper edge of the valence band has been confirmed, and β-Sn0.23V2O5/CdSe heterostructures have been shown to exhibit a 0 eV midgap state-VB offset, which underpins ultrafast subpicosecond hole transfer. The β-Sn0.23V2O5/CdSe heterostructures are further shown to be viable photocatalytic architectures capable of efficacious hydrogen evolution.α-V2O5 NWs were interfaced with CdE QDs using successive ionic layer adsorption and reaction (SILAR) and linker assisted assembly (LAA). Soft and hard x-ray photoelectron spectroscopy in conjunction with density functional theory calculations revealed that all QD/α-V2O5 heterostructures exhibited Type-II band offset energetics. TA measurements revealed that the Type-II energetic offsets promoted the ultrafast (10-12 to 10-11 s) separation of photogenerated electrons and holes across the QD/NW interface to yield long-lived (10-6 s) charge-separated states. The separation of photoexcited electrons and holes across the QD/NW interface could be exploited in photocatalytic reduction of protons.We assembled covalently-linked donor-acceptor light-harvesting nanocomposites consisting of the fullerene-derivative (C60SAM) adsorbed to CdSe QDs at a range of surface coverages. The ligand-exchange reactions to produce these assemblies were characterized using UV/vis spectroscopy, steady-state emission, time-resolved emission, and 1H NMR. The results revealed that the influence of surface coverage is greater than the effect of driving force for ET dynamics. Thus, larger QDs promote better ET efficiencies than smaller QDs due to their higher possible surface coverages. Moreover, the better charge separation in CdSe-C60SAM assemblies could be exploited in methanol oxidation.

ISBN: 9781658421478Subjects--Topical Terms:

3173556
Inorganic chemistry.
Subjects--Index Terms:

Photocatalysis

Photocatalysis and Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dot-based Heterostructures.
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500 $a Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
500 $a Advisor: Watson, David F.
502 $a Thesis (Ph.D.)--State University of New York at Buffalo, 2020.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be sold to any third party vendors.
520 $a Quantum dot (QD)-based heterostructures are intriguing material architectures for light harvesting, excited-state charge transfer, and solar energy conversion. The design of such architectures for photocatalysis requires careful consideration of both thermodynamic offsets and interfacial charge-transfer kinetics. This dissertation explores the photocatalysis and charge transfer dynamics in cadmium chalcogenide QD-based heterostructures. Chapters 2-5 of this dissertation focus on heterostructures comprising MxV2O5 (M = intercalated metal cation, Pb2+ or Sn2+) or α-V2O5 nanowires (NWs) interfaced with CdE (E=S/Se/Te) QDs with programmable energetic offsets to promote light-induced charge separation and photocatalytic proton reduction. Chapter 6 reports on dynamics of electron transfer (ET) from photoexcited CdSe QDs and adsorbed fullerene derivatives, as well as redox photocatalysis at these nanocomposites.CdSe/β-Pb0.33V2O5 was fabricated and characterized as a robust photocathode that promotes the photoinduced reduction of protons to H2 under illumination by visible light. The results were consistent with a mechanism in which excited-state interfacial hole transfer facilitates charge separation and photocatalysis, suggesting that the CdSe/β-Pb0.33V2O5 heterostructures are indeed promising architectures for light harvesting and photoelectrochemical (PEC) water-splitting. To further improve the performance of the CdE QD/β-Pb0.33V2O5 NW heterostructure photocathodes, we incorporated Pt as a proton reduction cocatalyst and prepared a ternary heterostructure system which promotes H2 evolution. Both transient absorption (TA) and PEC experiments revealed that the addition of Pt to the CdS/β-Pb0.33V2O5 O5 binary heterostructures promoted faster ET to Pt and resulted in improved proton reduction. Moreover, we increased the distance between QDs and NWs by changing the capping ligand of the QDs from cysteine to homocysteine. The ultrafast TA measurements revealed that deleterious QD-to-NW ET can be slowed down by increasing the distance between NWs and QDs.The topochemical synthesis yielded a metastable β-Sn0.23V2O5 compound exhibiting Sn 5s-derived midgap states ideally positioned to extract photogenerated holes from interfaced CdSe QDs. The existence of these midgap states near the upper edge of the valence band has been confirmed, and β-Sn0.23V2O5/CdSe heterostructures have been shown to exhibit a 0 eV midgap state-VB offset, which underpins ultrafast subpicosecond hole transfer. The β-Sn0.23V2O5/CdSe heterostructures are further shown to be viable photocatalytic architectures capable of efficacious hydrogen evolution.α-V2O5 NWs were interfaced with CdE QDs using successive ionic layer adsorption and reaction (SILAR) and linker assisted assembly (LAA). Soft and hard x-ray photoelectron spectroscopy in conjunction with density functional theory calculations revealed that all QD/α-V2O5 heterostructures exhibited Type-II band offset energetics. TA measurements revealed that the Type-II energetic offsets promoted the ultrafast (10-12 to 10-11 s) separation of photogenerated electrons and holes across the QD/NW interface to yield long-lived (10-6 s) charge-separated states. The separation of photoexcited electrons and holes across the QD/NW interface could be exploited in photocatalytic reduction of protons.We assembled covalently-linked donor-acceptor light-harvesting nanocomposites consisting of the fullerene-derivative (C60SAM) adsorbed to CdSe QDs at a range of surface coverages. The ligand-exchange reactions to produce these assemblies were characterized using UV/vis spectroscopy, steady-state emission, time-resolved emission, and 1H NMR. The results revealed that the influence of surface coverage is greater than the effect of driving force for ET dynamics. Thus, larger QDs promote better ET efficiencies than smaller QDs due to their higher possible surface coverages. Moreover, the better charge separation in CdSe-C60SAM assemblies could be exploited in methanol oxidation.
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650 4 $a Physical chemistry. $3 1981412
650 4 $a Materials science. $3 543314
653 $a Photocatalysis
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710 2 $a State University of New York at Buffalo. $b Chemistry. $3 1035962
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