Postdoctoral Research Associate in Chemistry
Michael Enright
Michael Enright
I am an Assistant Professor of Chemistry and Biochemistry at San Francisco State University. Previously, I studied as a postdoctoral research assistant in materials chemistry in the research lab of Professor Ralph Nuzzo and the Photonics at Thermodynamic Limits (PTL) EFRC. My studies focus on the synthesis of luminophores for luminescent solar concentrators. I am devising synthetic and post-synthetic methodologies for obtaining bright, near-infrared infrared emissive heterostructure quantum dots with tunable emission with a specific interest to incorporate them in LSCs integrated with micro solar cells. I completed my graduate studies at the University of Washington in Brandi Cossairt's research group where I investigated synthetic strategies for anisotropic semiconductor nanomaterials and their use in biomass valorization.
MRS Spring/Fall Meeting
November 27 - December 4
UPCOMING EVENTS
Photonics at Thermodynamic Limits Seminar Series
October 14
MY LATEST RESEARCH
Abstract: Quantum dots are used as photoredox catalysts to drive bond cleavage in lignin model substrates. Cadmium selenide quantum dots selectively cleave C–O bonds with yields comparable to the best transition-metal-based molecular photocatalysts, thereby emulating depolymerization of the β-O-4 linkages that account for 45–60% of all linkers in native lignin. Compared to their molecular catalyst counterparts, the quantum dots demonstrate higher turnover frequencies, higher surface tunability for solvent versatility, and lower catalyst loading under mild, ambient temperature reaction conditions. The robust nature and solvent versatility of these quantum dot photoredox catalysts enable a direct, single-vessel route to convert benzylic alcohols (a majority of species in native and processed lignin) into high-value guaiacols and acetophenones without any prerequisite filtration, purification, or solvent change.
Abstract: While it is well understood that controlling anisotropic nanostructure growth can be accomplished by establishing kinetic growth conditions, the practical translation of this knowledge to access nanorods with a specific aspect ratio has not been realized. In this study we empirically determine the precursor consumption rates for growing nanorods and use this data to customize the size and shape of anisotropic nanostructures. The purpose of this work is to go beyond simply creating a set of growth conditions to obtain rods, dots, rice, and tetrapods by describing how to synthesize a nanomaterial of desired dimensions and aspect ratio in a pre-meditated fashion. Measured growth rates for model systems of CdSe (3.5 monomers rod−1 s−1 at 250 °C) and CdS nanorods (36 monomers rod−1 s−1 at 340 °C) were used to design elongated nanorods with enhanced aspect ratios and synthesize dot in rod CdS/CdSe and CdSe/CdS heterostructures. These model systems enable us to establish a rubric for the synthesis of customizable nanostructures and serve as a test case for understanding heterostructure assembly in colloidal systems.
Abstract: The kinetic parameters governing cation exchange between molecular Cd2+ precursors and ZnTe nanorods is mapped out in detail to provide an all-inclusive rubric for tuning the rate and extent of cation exchange in this system—allowing for band gap tunability over a 1 eV range. Evaluation of cation exchange as a function of concentration, temperature, and time supports a mechanism involving initial, rapid Cd2+ adsorption followed by a rate determining cation exchange step with a measured activation energy of 24 kJ/mol. Provided there is sufficient cadmium to occupy the available surface sites, the solution concentration of cadmium has little influence on the rate of cation exchange, allowing the system to be modeled using pseudo-first-order kinetics, with observed rates ranging from 0.03 × 10–3 s–1 at 20 °C to 2.8 × 10–3 s–1 at 240 °C. It is also demonstrated that, due to the ease of cation exchange in these systems, previous claims of ZnTe/CdSe heterostructures are more accurately described as alloys.