Speaker
Ayman Karim, Ph.D.
Speaker's Institution
Virginia Polytechnic Institute and State University
Date
9/6/19
Time
4:00 pm
Location
Chemistry A101
Mixer Time
3:45 pm
Mixer Location
Chemistry B101E
Additional Information

About the Seminar:

Nanoparticles are becoming the enabling building blocks of materials for many applications including fuel cells, biosensors, batteries, photovoltaics, and catalysts. The nanoparticles’ size/shape and their distributions are often key to their specific, desired properties. Colloidal synthesis is one of the most tunable methods (using a variety of ligands and reaction conditions) to control the nanoparticle size and shape. However, a priori design of nanoparticles of desired sizes and shapes remains a grand challenge and a trial-and-error approach is still often employed. Therefore, understanding how ligands affect nucleation and growth is crucial in controlling the nanoparticles size, shape and their distributions. In this seminar, I will present my group’s recent efforts on integration of thermodynamics, kinetic modeling and advanced in situ characterization measurements to develop a methodology for enabling a priori design of metal colloidal nanoparticles with specific sizes.
The first part of the seminar will cover the importance of using multiple in-situ experimental observables to extract the nucleation and growth rates and determine how ligands directly and indirectly affect them for a model Pd system. Using the in-situ measured rates, a kinetic model was developed, and the accurate predictions of both size evolution and final size under different conditions will be presented. In the second part of the talk, the effect of metal-ligand binding thermodynamics on the nucleation and growth kinetics, and evolution of size distribution will be presented. We show that the metal precursor-ligand and nanoparticle-ligand binding energies are correlated with the nucleation and growth rates, respectively. Lastly, building on those findings, I will describe a new modeling approach for predicting the evolution of nanoparticle size distribution and designing mono-disperse nanoparticles.

About the Speaker

Dr. Karim joined the Department of Chemical Engineering at Virginia Tech as an Associate Professor in the Fall of 2014. His research is focused on the synthesis and characterization of nanomaterials, and the design of heterogeneous catalysts for energy and environmental applications. He is a co-principal investigator for the Synchrotron Catalysis Consortium (SCC) and his group uses a combination of advanced in-situ and in-operando characterization techniques (SAXS, XAFS, FTIR) to study the synthesis mechanisms of colloidal nanoparticles and catalysts and to study the reaction mechanisms on heterogeneous catalysts. He recently received the 3M Non-Tenured Faculty Award, Virginia Tech Institute for Critical Technology and Applied Science (ICTAS) Junior Faculty Award and is a member of the Young Editorial board for Journal of Energy Chemistry. He has co-authored 50 peer reviewed publications, one patent and delivered over 20 invited lectures and presentations. Prior to Virginia Tech, he worked as a senior research scientist (2008-2014) at the Pacific Northwest National Laboratory (PNNL), one among 10 U.S. Department of Energy (DOE) national laboratories managed by DOE’s Office of Science. Dr. Karim earned his BSc in Biomedical Engineering from Cairo University in Egypt (2000) then moved to the U.S. and received his PhD in Chemical Engineering from the University of New Mexico working with Prof. Abhaya Datye (2001-2006) followed by a postdoctoral fellowship at the University of Delaware in the Chemical Engineering Department with Prof. Dionisios Vlachos (2007-2008).

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