ChE Seminar – “The Importance of Interfaces: Using Ionic Liquids and Nanodiamonds to Explore New Concepts in Materials Design” by Dr. Matthew Gebbie

ABSTRACT:  

Interfaces are critical to many pressing societal challenges, particularly in the areas of clean energy, water, and catalysis. This talk will present two examples of using systematic molecular engineering to investigate foundational theories in interface science.

The first portion of the talk will discuss new insights into ionic liquids. Ionic liquids are composed entirely of ions and show promise as stable, nontoxic electrolytes, but higher conductivities are needed for most applications. Ionic liquids were initially hypothesized to have extremely high ‘free ion’ densities. We utilized nanoscale molecular force measurements to reveal that greater than 99.99% of the ions in ionic liquids behave as neutral ‘bound’ pairs. From these results, we propose a new way of envisioning concentrated electrolyte solutions to guide the design of high performance ionic liquids and next-generation energy storage electrolytes.

The second portion of the talk will present an approach for directly measuring the nucleation energy landscape of diamond. Nanodiamond exhibits potential as a material for biological imaging and quantum sensing, since diamond lattices can host stable fluorescent ‘color center’ defects. However, inconsistencies surround prior models of diamond nucleation, hindering the synthesis of high quality diamond for molecular sensing. By measuring relative nucleation probabilities from atomically-defined diamond templates, called ‘diamondoids’, we find that 26 carbon atom clusters composed solely of surface atoms are post-critical nuclei. Further, we measured the nucleation barrier to be three orders of magnitude smaller than classical estimates. Our results answer key questions regarding diamond synthesis and support both classical and non-classical concepts for nucleation and growth through multi-step intermediates.

BIOGRAPHY:

Matthew Gebbie received his Ph.D. in Materials from UC Santa Barbara in 2016, where he was a 2011 – 2015 Science and Engineering Fellow in the NSF Center for Nanotechnology in Society. Working with Prof. Jacob Israelachvili, Matt led research that bridged colloid science and electrochemistry to substantially progress a molecular-level understanding of how electrostatic correlations govern the properties of ionic liquids and underwater peptide-based adhesives. Currently, Matt is a 2016 – 2018 GLAM Postdoctoral Fellow at Stanford University, where he works with Prof. Nicholas Melosh to tackle fundamental questions surrounding nanoscale nucleation and growth, create fluorescent diamond nanomaterials for molecular sensing, and design diamond-based materials to enhance energy interfaces.