Photoinduced Charge Transfer at Quantum Dot-Molecule-Semiconductor Interfaces
David Watson Principal Investigator
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David Watson at the University at Buffalo (UB) is supported by an award from the Macromolecular, Supramolecular and Nanochemistry program to study photoinduced charge-transfer processes at quantum dot (QD)-molecule-semiconductor interfaces. The research involves basic science to tether QDs to semiconductor substrates or to each other via small molecules, and to characterize charge transfer at the resulting interfaces using time-resolved spectroscopy and photoelectrochemistry. One research initiative involves elucidating the influence of interfacial chemistry and properties on the mechanisms, dynamics, and yields of charge transfer at QD-molecule-TiO2 interfaces. Specific aims are to increase the stability and inertness of interfaces while maintaining high charge-transfer yields and promoting long-lived charge separation, to measure charge-transfer dynamics at complex interfaces, and to engineer interfacial properties to promote long-distance charge-transfer between QDs and TiO2. A second research initiative involves covalently tethering QDs to each other via carbodiimide chemistry and exploring the photoinduced charge-transfer reactivity of the resulting assemblies. Goals are to establish synthetic methods and to synthesize Type-II interfaces that promote the separation of photogenerated charges. A third research initiative involves tethering QD-molecule-QD assemblies to electron- or hole-accepting semiconductor substrates, towards the goal of promoting photoinduced vectorial charge transfer.<br/><br/>Semiconductor QDs have unique size-dependent electronic and optical properties, which make them intriguing harvesters of light and donors of energetic electrons and holes for solar energy conversion. QD-based solar cells and photocatalysts require (1) the controlled placement of QDs on nanostructured surfaces and (2) the existence of mechanisms through which photogenerated electrons or holes can be extracted from QDs before recombining. This research project involves basic science to establish syntheses of stable and inert QD-containing interfaces and to discover how the structure and properties of such interfaces govern the rates and efficiencies of charge-transfer reactions. The research addresses two basic challenges in materials chemistry: (1) to assemble materials interfaces precisely and (2) to establish structure-property-reactivity relationships involving charge transfer at complex interfaces. This award supports outreach programs involving collaboration between researchers at UB and students and teachers at Buffalo Public Schools. Outreach activities involve mentoring high school students and teachers in hands-on research projects. Goals are to introduce participants to the nature of scientific research, to increase teacher content knowledge, and to develop expanded mentoring networks. Research and educational initiatives are intended to benefit society by yielding new fundamental knowledge pertaining to solar energy conversion while broadening the participation of underrepresented groups and advancing discovery and understanding.