Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry & Biochemistry

First Advisor

Prashant Nagpal

Second Advisor

Steven George

Third Advisor

Wei Zhang

Fourth Advisor

Jeffrey Cameron

Fifth Advisor

Will Medlin

Abstract

Several strategies are currently being investigated for conversion of incident sunlight into chemical fuels, with readily available chemical feedstocks like air, water, and carbon-dioxide. This thesis focuses on research approach on designing high-efficiency and high-selective photocatalytic materials, ranging from inexpensive and stable inorganic photocatalysts to living nano-biohybrid organisms to achieve solar energy conversion.

This thesis is divided into multiple sections based on the materials and concepts in designing high-efficient and high-selective solar fuel generator. After a brief introduction of photocatalysis in Chapter 1, we describe a novel electrochemical anodization technique for making a wide-variety of doped metal-oxide nanotubes. Using optoelectronic and electrochemical characterizations, we systematically studied dopant (anionic and cationic) effects in photocatalytic water splitting from the aspect of light absorption, charge transport, and charge transfer (Chapter 2 to 4).

In the second part (Chapter 5), we describe a novel low-temperature amine-based synthesis and cation exchange method for synthesizing ultrathin two-dimensional metal chalcogenide nanostructures. We reported their extraordinary optoelectronic characteristics and potential applications in third-generation solar energy conversion devices.

In the third section (Chapter 6), we describe formation of living quantum dot -synthetic bacteria nano-biohybrids, with desired metabolic pathways for selective formation of fuel, designed QD energy states for efficient light-sensitization, suitable alignment, and charge injection to bacterial enzymes for photocatalytic reduction, using cellular uptake, cell viability, and designed site-specific attachment of quantum dots from growth solutions to bacterial enzymes. These engineered nano-biohybrids affect efficient light-driven hydrogen and ammonia production from water and air-water reduction and shows no loss of enzyme function between purified nitrogen and air.

Finally, we demonstrate color tuning of upconversion photoluminescence by modulating the photophysics using surface plasmon polaritons (Chapter 7). Furthermore, by using ultrathin 2D semiconductor nanosheets, we demonstrate the efficacy of color tuning by transforming upconverted light into photocurrent. This can pave the way for designed metal nanostructures for highly-efficient utilization of low-intensity sub-bandgap infrared radiation in optoelectronic devices.

Available for download on Thursday, June 21, 2018

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