Archives—October 2009

Nano-Bio-Hybrid Optical Protein for Sensing and Photon Harvesting

Friday, October 23, 2009 3:00 – 4:00 pm
Room 610, M&M Building

Prof. Craig Friedrich
Department of Mechanical Engineering Engineering Mechanics
Michigan Technological University

Abstract

The integration of opto-electrical transduction protein with inorganicnanomaterials, CMOS, and single electron transistors opens up many possibilitiesfor bio-nano-hybrid materials applications in sensing and photon harvesting.  Thetalk will provide results on integrating the protein bacteriorhodopsin with micro andnanoelectronics, quantum dots, and sensing protein to form a bio-nano-hybridsensing platform technology. Additionally, recent work is underway to investigatethe applicability of bacteriorhodopsin coupled with nanostructures of variousmaterials for use as a photon harvester, possibly to power nanosensing systems,and initial results will be shown.

Biography

Prof. Craig Friedrich is Associate Chair and Director of Graduate Studies of theDepartment of Mechanical Engineering- Engineering Mechanics at Michigan TechnologicalUniversity.  He also directs the Multi-Scale Technologies Institute and is the Robbins Professorin Sustainable Design and Manufacturing.  His PhD is from Oklahoma State University.  In theearly 1990s, Dr. Friedrich helped pioneer the field of mechanical micromachining, particularlymicromilling, by creating (at the time) the world’s smallest milling tools and demonstrating themilling process to make micron-scale features with sub-micron tolerances.  He alsodemonstrated mechanically machined x-ray masks and gray-scale x-ray lithography usingmicromilled masks.  Recently, he is working in the area of bio-nano-hybrid materials for a varietyof sensing and energy applications.


Mapping Charge-Mosaic Surfaces in Electrolyte Solutions Using Atomic Force Microscopy

Friday, October 16, 2009 3:00 – 4:00 pm
Room 610, M&M Building

Jaroslaw Drelich
Department of Materials Science and Engineering
Michigan Technological University

Abstract

Colloidal forces dominate stability of particles in aqueous environment and often dictatestrategies in wet processing of minerals and other materials. The most successful approach tothe problem of net interactions between two interfaces in these systems was proposed byDerjaguin, Landau, Verwey and Overbeek and is known as the DLVO theory. This theory treatsthe total interaction force between two surfaces in a liquid medium as an arithmetic sum of twocomponents: van der Waals and electrostatic (electrical double layer) forces. The DLVO theoryhas been used as a mean-field approach, where only one surface potential and one Hamakerconstant are used to describe the colloidal forces. On a contrary, a vast majority of surfaces ofparticles and materials in technological systems are of a heterogeneous (mosaic) naturecomposed of microscopic and sub-microscopic domains of different surface characteristics. Inthese systems, the interactions can be dominated by heterogeneities rather than averagesurface character. Attractions can be stronger, by orders of magnitude, than would be expectedfrom the classical mean-field model when area-averaged surface charge or potential isemployed. To detect heterogeneities in surface charge, analytical tools which provide accurateand spatially resolved information about material surface potential—particularly at microscopicand sub-microscopic resolutions—are needed.

A novel AFM-based technique for mapping surface charge domains on heterogeneous surfaceswas recently introduced by our research team. It relies on recording colloidal force curves overmultiple locations on the substrate surface using small probes. The experiments are conductedin electrolyte solutions with different ionic strengths and pH values. The force-distance curvemeasurements are carried out stepwise across phases of different surface characteristic.Surface charge densities and surface potentials are then calculated by fitting the experimentaldata with a DLVO theoretical model. The surface charge characteristics of the heterogeneoussubstrate are determined from the recorded colloidal force curves, allowing for the surfacecharge variation to be mapped. In this presentation, the AFM technique will be briefly introducedand its use in determination of local surface charges for a multi-phase rock and bitumen will bereviewed.



Effect of Doped Transition Metals on Hydrogen Interaction in Complex Hydrides

Friday, October 2, 2009 3:00 – 4:00 pm
Room 610, M&M Building

Qingfeng Ge
Department of Chemistry and Biochemistry
Southern Illinois University
Carbondale, IL

Abstract

Light-metal complex hydrides have attracted great attention as potential hydrogen-storage materials.Over the past decade, tremendous efforts have been put into improving their storage capacity andadsorption/desorption kinetics. While significant progress has been made in engineering the catalystsand preparing the advanced storage materials over the past few years, hydrogen storage remains amajor obstacle in transition to a hydrogen economy. Developing a practical hydrogen storage materialrequires a detailed understanding of the intrinsic hydrogen-metal bond strength and the effect of localreaction environment. In this talk, I will report the results of our extensive density functional theory studyof the hydrogen storage properties of transition metal (TM)-doped NaAlH4. In particular, we found that thedoped transition metal form a surface interstitial complex structure with three neighboring AlH4- groups.We discovered that this complex played important roles in hydrogen release/uptake from TM-dopedNaAlH4. Our analysis demonstrated that the early TMs are more effective to reduce the hydrogendesorption energy as well as activate the H—H bond than the late TMs. The hydrogen release/uptakeprocess can be viewed as an exchange of σ-bond ligands (H—H for Al—H) by TM on the basis of thecomplex through a metathesis process involving σ-bonds. The balanced ability of accepting electrons inand backdonating electrons from the d orbitals of the early TMs made them ideal candidates as catalystsfor hydrogen release/uptake. We extended the study to Ti-doped LiBH4 and found that both the localcomplex structure and the effect of doped Ti are different from that in NaAlH4.

Biography

Dr. Qingfeng Ge is an Associate Professor in the Department of Chemistry and Biochemistry, SouthernIllinois University Carbondale. He is one of the 70 recipients of the Presidential Hydrogen Fuel Initiative awardsnationwide in 2005. A main thrust of his research is using modeling/simulation to address materials issues relatedto energy and environment. Dr. Ge holds M.Sc and Ph.D degrees in Chemical Engineering from Tianjin University,China. He worked as a Postdoctoral scholar in Copenhagen University, Denmark, Cambridge University, U.K. andUniversity of Virginia before joining SIUC. His experiences ranged from experimental characterization and kineticsmodeling of catalysts to first principles based simulations of various materials. He authored/coauthored more than70 journal papers, including those in Science, the Journal of American Chemical Society, and Physical ReviewLetters.