Associate Professor
Email: hll@ou.edu
Office: Sarkeys Energy Center, T-219
Education
Ph. D. Chemical Engineering (2012)
North Carolina State University Raleigh, NC
M.S. Chemical Engineering (2007)
Nanjing University of Technology Nanjing, China
B.S. Chemical Engineering (2003)
Nanjing University of Technology Nanjing, China
Research Focus
About
Molecular simulation is an important research tool that gives us an ever-increasing ability to predict the physical and chemical properties of matter, as well as to design and engineer novel materials and efficient processes. The importance of molecular simulation is evidenced by several recent reports from funding agencies in the U.S., which emphasize the rapidly growing value of simulation in the fields of chemistry, chemical engineering, material science, physics, medical and bio-related disciplines. We have had dramatic increases in the power and availability of high- performance computers; in parallel with these developments, increasingly robust and efficient algorithms and simulation methods have been developed, with the ability to integrate quantum mechanical calculations, atomistic Monte Carlo and molecular dynamics simulations, mesoscale and continuum approaches. The combination of multi-scale modeling techniques gives us an unprecedented ability to accurately estimate the properties of complex materials and systems, as well as to aid in the interpretation of experimental results. Our group will use theory and multi-scale molecular modeling methods and collaborate with experimental groups for two main goals:
Achieving such general objectives would have a positive impact on society, giving us new ways to treat diseases such as cancer and diabetes, to improve the accuracy and sensitivity of biosensors, to design materials for the removal of pollutants in the environment, or detect and capture potential chemical or biological warfare agents, and to reduce the production costs of catalytic processes and of chemicals and pharmaceutical products, among others
Current Research Interest(s):
Biofunctionalization of Graphene Oxide Surface for Drug Delivery
Graphene oxide (GO) exhibits unique 2-D structure and exceptional physical, chemical and optical properties that lead to many potential biomedical applications. In the last few years, GO has attracted increasing interest as a molecular carrier for in vitro and in vivo drug delivery. It is also accepted that functionalization of GO sheets must be conducted to attain high biocompatibility. Results have shown that well-functionalized GO sheets are stable and safe for in vitro drug delivery, and that they can be readily excreted through the renal route and are non- toxic in vivo to mice.From the molecular point of view, the carbonyl, epoxy, hydroxyl and other oxygen functional groups on the basal planes and edges of GO sheets significantly alter their van der Waals and electrostatic interactions compared to those on pristine graphene. This explains why GO can immobilize a large number of substances, including metals, drugs, biomolecules and fluorescent molecules. However, there is still no systematic study on GO functionalization and we do not know the fundamental mechanisms that underlie the design of the GO surface to achieve simultaneously high loading capacity, high sensitivity and high biocompatibility for drug delivery purposes.To aid the integration of GO into clinical drug delivery and other biomedical applications, We are interested in applying and improving multi-scale modeling techniques to address the following challenges:
The study of heterogeneous catalysis has bred four Nobel Prizes in Chemistry, Fritz Haber in 1918, Carl Bosch and Friedrich Bergius in 1931, Irving Langmuir in 1932, and Gerhard Ertl in 2007. It is of paramount importance in the chemical, biomedical and materials industries, and the field needs a continuous focus and efforts. In the heterogeneous catalysis process, the phase of the catalyst differs from that of the reactants. In general, the reactants diffuse from the bulk to the catalyst surface, adsorb and form new chemical bonds with the catalytic sites, and then desorb and diffuse from the surface after the reactions. We need fundamental understanding of: (1) the diffusion, adsorption, chemical reaction mechanisms and the mass transport phenomena of the reactants; (2) the properties of the catalytic surface and how to select, optimize and design support materials for different catalysts and different applications.
This fundamental understanding is difficult to achieve from experiments alone, since the measurements reflect a sum of many effects – diffusion, selective adsorption of particular reactants or products, chemical kinetic limitations, activity and stability of catalyst, effects of support material defects and roughness, etc. Theoretical studies can play an important part in determining the role of these many factors, and in achieving both fundamental understanding and fine control of these effects. Titanium dioxide material has been widely studied as a heterogeneous photocatalyst for environmental applications, for example the degradation of organic pollutants and the dye- sensitized solar cell. Due to the in vivo biocompatibility, it also finds application in human osteoblasts and other implant materials. Recently, Crossland and the co-workers reported an enhanced mobility and optoelectronic performance on mesoporous anatase TiO2 single crystals. This is because mesoporous anatase TiO2 provides both the desired large surface area and the long-range electronic connectivity and structural coherence. We recently examined the TiO2 surface activity by studying water dissociation on different TiO2 facets, and the ReaxFF molecular dynamics simulation results showed that the TiO2-B (100) is the most active but stable facet for water dissociation, and that the activity difference can be explained by the surface density of unsaturated Ti sites and the geometric surface curvature. For this project, we plan to collaborate with experimental groups on this project, to use mesoporous titanium dioxide material and study the simultaneous adsorption, diffusion and reactions of water (H2O), ammonia (NH3) and acetic acid (CH3COOH) for the following objectives:
