Associate Professor of Chemistry
The Owen Group is an inorganic chemistry group that specializes in the synthesis and surface modification of semiconductor nanocrystals. We are developing methods to exchange nanocrystal surface ligands and characterize the influence of surface structure on electronic properties. Small molecule model systems that can be characterized with X-ray crystallography and NMR spectroscopy are helping us develop a molecular picture of nanocrystal structure and reactivity. Ultimately these fundamental studies will lead us to integrate these extraordinary chromophores in device and biological detection applications.
Our research group is developing an atomically precise description of colloidal nanocrystal structure and reactivity. To address this challenge we apply the synthetic methods and experimental techniques of organometallic chemistry to nanocrystals. By studying the kinetics and mechanisms of crystal growth, we seek to prepare nanocrystals with unambiguous composition. With this approach we are pursuing three research goals: 1) To control the interplay between surface structure and charge trapping in semiconductor nanocrystals in solution and in thin solid films. 2) To resolve the microscopic steps that lead to the nucleation and growth of colloidal crystals. 3) To develop practical synthetic methods that afford novel nanomaterials of unambiguous composition including colloidal quantum wells and soluble diamond nanocrystals with nitrogen vacancy and silicon vacancy color centers
Nanocrystal Surface Chemistry: The goal of our research is to characterize and manipulate the structure of interfaces and so-called “defects” in colloidal semiconductor nanocrystals. At the nanoscale, the interaction of charges with surface atoms dominates electronic properties like photoluminescence quantum yield, fluorescence blinking, vibrational cooling of excited carriers, and trapping of charges during electrical transport. A deeper understanding of surface structure and its interaction with excited electrons and holes is necessary to understand these phenomena and to apply these tunable solution processable materials in optoelectronic devices (Hendricks, Campos et al Science 2015; Wolcott, Schiros et al 2014).
Our research distinguishes between dative ligands that are adsorbed to nanocrystal surfaces and ligands that balance their charge with the crystal lattice. These findings contrast strongly with the prevailing description of nanocrystal surface structure, particularly of CdSe quantum dots, where the dative ligand binding model is widely accepted. We are building upon this distinction to obtain predictive control over electronic states within the nanocrystals band gap and to design surface modification strategies for thin-film fabrication.