Surface Studies of Molecular Films and Materials Chemistry

Contact: John Z. Larese (UTK) jzl@utk.edu  


A representative selection of the concentration profiles,
C(z) at nominal bilayer coverage in the z-direction for
cyclopentane molecules on MgO. The subfigures
in B and C are the MD snapshots from molecular
trajectories at 270K and 40K respectively.

Understanding the adsorption and wetting properties of molecules on solid surfaces is central to many scientific and technological challenges. Fundamental studies of the interaction between molecular films and surfaces are extremely valuable for developing synthetic methods to produce novel materials with specific functionality in such areas as gas separation, energy conversion, lubrication, catalysis and environmental remediation. One aspect of our research efforts is focussed on how molecular and surface symmetry effects the physicochemical properties of adsorbed molecular films. Recently, our studies are aimed at establishing a detailed understanding of the behavior of the first ten linear alkanes (methane-decane) and cyclic alkanes (cyclopropane-cyclodecane) on the surfaces of MgO (100), hexagonal BN(hBN) and the graphite basal plane(GBP). The investigation is a comprehensive one that includes thermodynamics, molecular modeling and characterization of the microscopic structure and dynamics using neutron scattering techniques. Our ultimate goal is to produce accurate, robust descriptions of the intermolecular potentials and potential energy surfaces. Our materials synthetic efforts focus on chemically and size selective metal oxide nanoparticles and using in situ neutron imaging to study gamma and neutron detector materials.


Neutron radiograph, snapshots at 5 min intervals,
of thesolidification of a CLYC (CeLiYtCl) sample.
The upper portion of each frame is the melted
portion of the sample. Note the CONCAVE shape
of the interface. This sample was grown and
imaged in a 1ft x 1 ft x 3ft furnace.

Challenges we are working on

Surface Wetting Modification of molecular adsorption at interfaces presents significant opportunities and challenges in the areas of catalysis and agriculture. Here we are investigating how the wetting properties of certain waxy molecules can be employed to reduce the quantity of pesticides needed to protect crops or improve surface mediated chemical reactions. In nanomaterial synthesis we are investigating a new route for decorating nanoparticle metal oxide materials with nanometer scale transition and noble metals using physical vapor deposition techniques to investigate how these new materials

can be employed in surface plasmon driven hydrogenation catalysis and as novel optoelectronic devices. Furthermore, using pulsed neutron imaging, we have developed a new, in situ method for investigating Bridgeman growth of materials at the industrial scale for use as gamma and neutron detectors for both national security and medical applications. We seek to identify the conditions needed to control/manipulate the shape of the solid-liquid interface during the growth process using both radiographic and neutron resonant imaging techniques.

Collaborations

ORNL; University of Cambridge (UK); Diamond Light Source (UK); European Spallation Source (Lund, Sweden); Los Alamos