Date/Time
Date(s) - 09/14/2020
9:35 am - 10:30 am
Categories
Taylor J. Woehl, Ph.D.
Assistant Professor
Department of Chemical and Biomolecular Engineering
University of Maryland
Assembly and crystallization of colloids and nanoparticles mediated by interfacial chemistry
Abstract: In this talk, Dr. Woehl will describe his lab’s work investigating how interfacial chemistry and interfacial chemical reactions mediate and can be used to control the assembly and crystallization of colloids and nanoparticles. In the first part of the talk, he will describe work investigating surface chemistry-mediated nucleation of metal nanocrystals at solid-liquid interfaces. Liquid phase transmission electron microscopy is used to directly visualize nucleation of silver nanocrystals at a planar solid-liquid interface. Advanced image analysis of nanoscale videos of nucleation measures nucleation kinetics and identifies preferential nucleation sites. Nucleation is observed to occur preferentially within ~100 nm hydrophilic domains containing high concentrations of silanol and silamine surface groups. A model based on classical nucleation theory is developed to explain the dependence of nucleation kinetics on interfacial chemistry and supersaturation ratio. In the second part of the talk, Dr. Woehl will describe recent work investigating the electrokinetcs of micron sized colloids in pH gradients and low frequency (< 1 kHz) oscillatory electric fields. He will discuss how dynamic changes in colloid surface charge modify various electrokinetic phenomena, including electrophoresis and induced charge electrophoresis. Colloids exhibit an entirely new set of behaviors due to dynamic changes in surface charge and polarizability in the pH gradient, including levitation and explosive disassembly, which can be used to separate particles based on surface chemistry and density or to form bilayer colloidal crystals.
Biography: Prof. Taylor J. Woehl obtained his Ph.D. in Chemical Engineering from University of California, Davis in 2013 under Prof. Bill Ristenpart and Prof. Nigel Browning. He was an Assistant Research Scientist at Ames Laboratory from 2013-2014 in the Prozorov lab, followed by an NRC postdoctoral fellowship from 2014-2016 in the Material Measurement Lab at the National Institute of Standards and Technology. Prof. Woehl joined the Department of Chemical and Biomolecular Engineering at University of Maryland, College Park in 2016 as an assistant professor with an affiliate appoint in the Department of Materials Science, where he leads the Nanoscale Assembly and Electron Microscopy Lab, which focuses on topics including nanochemistry of multicomponent nanocrystal formation, fuel driven dissipative assembly of colloids, colloidal electrokinetics, and protein aggregation.
