NER: Modulation doped colloidal quantum dots and solution-based semiconductor nanowires

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The objective of this research is to develop a generic doping strategy for solution-based colloidal quantum dots and semiconductor nanowires. The approach is based on the concept of modulation doping, first developed for bulk semiconductors. Within the context of the proposed work, this study specifically entails passivating colloidal quantum dots and nanowires with another semiconductor in a core/shell or coaxial configuration. Dopant atoms will simultaneously be incorporated into the outer semiconductor cladding, enabling the spatially indirect doping of the targeted material because of favorable band offsets at the interface. This approach bypasses longstanding problems associated with the direct substitutional doping of nanostructured materials. The intellectual merit of the proposed work includes the development of an alternative, yet generic, doping strategy for nanoscale materials. It also addresses the doping of solution-based semiconductor nanowires, which has yet to be accomplished. The broader impact of the work includes the possible development of nanowire-based devices involving branched nanowire morphologies such as those with tripod, v-, and y-shapes. More immediate applications include the possible development of dual contrast agents for biological tagging applications. This is achieved by preserving the high fluorescence quantum yields of native nanostructures while simultaneously incorporating spin active impurities into an outer cladding layer. Such nanostructures can then be imaged via divergent techniques such as fluorescence resonance energy transfer and/or magnetic resonance imaging. Broader Impact:All proposed studies are tied into educational initiatives by the PI and Co-PI to expose undergraduates and local area high school teachers to the emerging field of nanoscience.