Using mixed metal clusters in the reductive synthesis of doped ZnO nanocrystals

University Of Washington, Seattle WA

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Abstract

DESCRIPTION (provided by applicant): The development of new tools for early disease detection and diagnosis is essential to improving public health and lowering healthcare costs. Semiconductor nanocrystals, also known as quantum dots, display optical properties that give them enormous potential in the fields of fluorescence imaging, biosensing, and diagnostics. To advance the effectiveness of nanocrystals in these applications, however, the range of their physical properties must be broadened to include: 1) tuning of fluorescence emission and increased lifetimes 2) sensitivity to electric or magnetic fields and 3) suppression of blinking. One current approach has been the incorporation of metal impurities in the crystal lattice, or doping. Doped nanocrystals comprise a relatively unexplored field, although in recent years nanocrystals with Mn2+, Cu2+, and lanthanide dopants have been studied for their unique optical and magnetic properties. Controlling the amount and location of dopant incorporation within the nanocrystal is important for controlling these new physical properties. Unfortunately, this level o synthetic control has been challenging to achieve, and the mechanisms of dopant incorporation in nanocrystals are still not completely understood. The overall objective of the proposed research is to develop new synthetic methods for doped zinc oxide (ZnO) nanocrystals with improved control over dopant density and distribution. Specifically, this proposal describes the design and synthesis of mixed metal carboxylate-supported multinuclear zinc clusters with coordinated oxometallate ligands as soluble single-source precursors of doped ZnO nanocrystals. The synthesis of these clusters affords the opportunity to study solution-state cluster degradation and aggregation of multinuclear zinc complexes that may serve as intermediates for nucleation clusters. A second aspect of this research plan is to develop a novel approach for the synthesis of doped nanocrystals based upon in situ reduction of oxometallate anions during ZnO lattice growth. With this approach, different nucleation and growth dynamics will be observed that may afford novel and spectroscopically unique nanostructures. These results will allow the design of different types of doped nanocrystals that target specific optical and magnetic properties. The broad, long-term goal of the proposed project is to provide access to these materials to expand the chemical toolkit available for biomedical applications.