Time: 10:00 am, Monday, 2016-12-26
Place: Room 318, No. 11 Teaching Bld
Coordinator: Prof. Chuanhong Jin
Pre-equilibrium in-situ solvated ion/molecular adsorption processes and events on solid substrates via liquid phase TEM: adsorption discretization, surface adsorption waves and repulsive forces
Mario A. Gomez1, Dongsheng Li2, Scott Lea2, Jim J. DeYoreo3, Shaofeng Wang4 and Yongfeng Jia1,4
1Institute of Environmental Protection, Shenyang University of Chemical Technology, Shenyang, 110142, China
2Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, 99354, USA
3Physical Science Division, Pacific Northwest National Laboratory, Richland, 93352, USA
4Key Laboratory of Pollution Ecology and Environmental Engineering, Chinese Academy of Sciences, Shenyang 110016, China
After initial classical description by Volmer and Weber 1, Becker and Doring 2 during the 1920-30’s, the last decade of the 20th century has focused abundant research global efforts on Non-Classical Crystallization Theory to further understand natures secrets of crystal formation and phase transformation. Studies using state of the art high resolution (HR) TEM have revealed the discovery of oriented-attachment formation mechanism as first reported by Penn and Banfield in 1998. 3 A decade later in 2012, the first real-time observation of this oriented-attachment formation mechanism was observed for two distinct crystal systems (Pt3Fe and Fe(III)-oxyhydroxide) via liquid phase (LP) HR-TEM. 4-5 Since then more work has been published on the formation of facet/shape evolution and electron beam effects on nano particle growth. 6-8 However, to date, no such work exists to detect real time surface adsorption phenomena via in-situ LP TEM measurements. The adsorption of ions/molecules in solution onto solid substrates is a common process that controls many natural and man-made processes in the environment, electronics, medicine, city infrastructure, automotive manufacturing, and mining.9-21 Here we show the real-time in-situ adsorption, chemical zoning and surface energy behavior of Fe(II)(aq) ions on the surface of a Fe(III) hydroxide crystal via LP TEM analysis. The adsorption behavior of Fe(II)(aq) ions onto semi-crystalline and crystalline Fe(III) hydroxide-oxide solids has been extensively reported in the literature but to date, only indirect equilibrium snap shots of the sorbed Fe(II)(aq) ions species have been observed via techniques such as XAS, AFM, STM, XRD, and IR/Raman. Furthermore, once adsorbed, the pre-equilibrium behavior of the sorbed Fe(II)(aq) ions on the surface of Fe(III) hydroxide-oxide solids is unknown to date. Our work reveals how the Fe(II)(aq) ions distribute themselves once on the surface (“chemical zoning”) of a non-perfectly crystalline Fe(III) hydroxide substrate and how the surface of the Fe(III) hydroxide substrate affects the path that the sorbed Fe(II)(aq) ions species follow. Our results show the experimental feasibility of observing surface ion behavior on crystal surfaces through the real-time in-situ adsorption behavior of Fe(II)(aq) ions on the surface of a non-perfectly crystalline Fe(III) hydroxide substrate via LP TEM analysis. Furthermore, our work shows how solvated ion pre-equilibrium adsorption events on the surface of solid substrates are not static but a fluid process and is followed by a series of events where the sorbed ions redistribute themselves on the surface of the solid substrate. We anticipate our work to be the starting point for more sophisticated real time in-situ LP TEM adsorption experiments of inorganic and organic solvated ions onto surfaces of semi-crystalline and crystalline substrates in various interdisciplinary research fields across the spectrum from environment, electronics, synthesis-catalysis, medicine, mining and manufacturing industries.
Introduction of presenter:
Dr. Gomez completed undegraduate degrees in Mathematics and Chemistry (with honors) at the University of Saskatchewan. After this Dr. Gomez moved to McGill University to complete a Ph.D. in Mining and Materials Engineering with Prof. George Demopoulos. He was then recruited back to the University of Saskatchewan to work as a Post-Doctoral and Professional Research Associate fellow with Prof. Jim Hendry. Now he is a staff member at the Shenyang University of Chemical Technology with Prof. Yongfeng Jia.
He holds awards from the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), McGill University and Chinese Academy of Sciences (CAS). Thus far Dr. Gomez has authored and co-authored 23 international journal publications, 1book chapter, 13 international refereed conference publications, 8 international consultation industrial reports and is a peer reviewer for 14 different types of intenational journals in the fields of environmental chemistry, engineering and energy.
The primary research interest of Dr. Gomez over the last 10 years has mainly focused in the areas of industrial aqueous processing, the production of materials and minerals, the environmental stability evaluation (reactivity-geochemistry) and characterization (lab and synchrotron based) of these products often presented in industrial mills and tailings disposal sites during production or after decommissioning (e.g. Cu, Au, Zn, U).
