Synthesis of colloidal semiconductor heterostructures for photocatalysis

Abstract

The development of colloidal nanoscale semiconductors for next-generation technologies is attractive due to their size-dependent optoelectronic properties and compatibility with solution-based manufacturing methods. This versatile class of nanomaterials holds great promise for light absorption, emission, and energy conversion. However, while the synthesis of single component, isotropic nanocrystals is well developed, the true promise of these materials is in their customization within heterostructure motifs where significant synthetic challenges remain. In particular, colloidal semiconductor nanomaterial heterostructures hold great potential as photocatalysts. Efficient electron-hole recombination is promoted by quantum confinement making traditional quantum dots non-ideal for photocatalytic applications. However, charge carriers can be thermodynamically separated across a nanoheterostructure interface. This prolongs the lifetime of photogenerated charge carriers, paving the way for efficient photoredox chemistry. This thesis uncovers the underlying, generalizable principles for accessing tailor-made heterostructures to provide a roadmap for accessing desirable colloidal semiconductor nanoheterostructures. The generalized rubrics describe strategies and identify potential pitfalls for the synthesis of desirable nanostructures, even if explicit examples of the target structure have not been previously reported. Beyond developing anisotropic heterostructures with rod and tetrapod morphologies, this work demonstrates a new application for nanomaterial photocatalysis by using quantum dots to cleave C-O bonds in biomass model substrates. In all, this thesis makes strides in developing our understanding of how to design and synthesize colloidal semiconductor nanoheterostructures, and of the use of nanomaterials in photolytic applications.