Materials Research
Welcome to materials chemistry research at Portland State University. Professors Woods, Goforth, Yan, Rananavare, and Strongin are pursuing materials chemistry extensively in their research programs. We create functional molecular structures and elucidate the fundamental principles guiding their properties and behavior. Our mission includes the invention of unique materials at the forefront of biomedical, environmental, sensor and microelectronics research. The active incorporation of research discoveries into teaching programs and academic and industrial collaborations is a distinctive feature of the PSU materials chemistry community.
Current specializations include targeted contrast media for magnetic resonance imaging, nanometer sized inorganic imaging agents, dye-sensitized solar cells, surface and interface chemistry, environmental sensors and biomedical diagnostics, as well as unique white light and near infra-red emitting materials. Strong collaborations in these latter and related areas with local researchers affiliated with OHSU, PNL, ONAMI, PSU Physics, and Mechanical Engineering, are ongoing, affording students working on these projects a world-class interdisciplinary education. Facilities on the PSU campus for materials chemistry research include a state-of the-art microscopy laboratory, lithography and clean-room facilities.
Nanoporous films of tin oxide doped with antimony:
(Left) -0.1% Sb-doped SnO2 and (Right) - 1.0% Sb-doped SnO2
Professor Shankar Rananavare has discovered that nanoporous films of tin oxide (SnO2) doped with antimony (Sb)can detect chlorine in as little as 60 seconds at room temperature. Chlorine is useful in a number of industrial processes, but can be harmful when released into the environment. levels of 15 ppm cause throat irritation in humans and exposure to concentrations of 1000 ppm can be fatal. Reference: A. Chaparadza, S.B. Rananavare "Room temperature Cl2 sensing using thick nanoporous films of Sb-doped SnO2", Nanotechnology, 19 245501 (2008), This work has been featured at the IOP (Institute of Physics) web site.
SEM and TEM images illustrating such a junction
Dr. Rananavare has also been able to fabricate metallurgical junction between Si Nanowires. Such SiNW junctions are cornerstones for the next generation of grid-architecture contemplated in nanoelectronics. Below are some SEM and TEM images illustrating such a junction:
Nanofibers of Conductive Porphyrin Polymers for Solar Cells (Artificial Photosynthesis
Schematic of natural (top) and artificial (bottom) photosynthesis.
The Wamser research group has been investigating novel conductive polymers made by electropolymerization of amino-substituted porphyrins. The polymer is generated as a thin film on a transparent electrode with a nanostructure of interconnected, electronically conductive fibers. These are being integrated into solar cells by bonding a secondary dye on the nanofiber surfaces to promote the growth of adherent films of semiconductor nanoparticles (e.g., TiO2). References: (1) Synthesis and Characterization of Electropolymerized Porphyrin Nanofibers, M. G. Walter and C. C. Wamser, Matl. Res. Soc. Symp. Proc,2007, 1013, Z04-07. (2) Syntheses and Optoelectronic Properties of Amino/carboxyphenylporphyrins for Potential use in Dye-Sensitized Solar Cells, M. G. Walter, C. C. Wamser, J. Ruwitch, Y. Zhao, D. Braden, M. Stevens, A. Denman, R. Pi, A. Rudine, and P. J. Pessiki, J. Porph. Phthalo., 2007, 11(8), 601-612.
A chemomechanical Polymer that shrinks in response to changing blood plasma glucose levels with high glucose selectivity
A chemomechanical Polymer that shrinks in response to changing blood plasma glucose levels with high glucose selectivity
Professor Robert Strongin has also invented a functional polymer that shrinks and expands selectively and reversibly in response to blood glucose concentration changes, a material serving to guide the design of nanovalves and self-regulated insulin or related drug-delivery devices ("Samoei, G. K.; Wang, W.; Escobedo, J. O.;, Xu, X.; Schneider, H.-J.; Cook, R. L.. and Strongin, R. M. "A Chemomechanical Polymer that Functions in Blood Plasma with High Glucose Selectivity" Angew. Chem. Int. Ed. 2006, 45, 1 – 5).
An Organic White Light-Emitting Fluorophore
Top view of a quartz cuvette showing fluorescent white light upon excitation at 310 nm for a solution of a seminaphtofluorone (see reference above) dye in MeOH.
The Strongin group has synthesized a seminaphtofluorone dye with unique properties, including white light emission as well as excitation over a 400 nm range. Additionally, this compound shows promise for use in cellular imaging studies (Yang, Y.; Lowry, M.; Schowalter, C. M.; Fakayode, S. O.; Escobedo, J. O.; Xiangyang, X.; Zhang, H.; Jensen, T. J.; Fronczek, F. R.; Warner, I. M.; Strongin, R. M. "An Organic White Light-Emitting Fluorophore" J. Am. Chem. Soc., 2006, 128 (43), 14081-14092).
Soft Surfaces and Interfaces (Dr. Yan Group)
Covalently immobilized polymer single molecule (Liu, L.; Yan, M. Angew. Chem. Int. Ed. 2006, 45, 6207)
Self-assembled polymer nanostructures (Chada, S.; Yan, M. Soft Matter 2008, 4, 2164)
Polymer nanostructure by direct writing with nanoprobes (Maedler, C.; Chada, S.; Cui, X.; Taylor, M.; Yan, M.; La Rosa, A. J. Appl. Phys. 2008, 104, 014311-1)
Single-layer graphene (Liu, L.-H.; Yan, M. Nano Lett. 2009, 9, 3375)
Magnetic nanoparticles capturing bacteria (Liu, L.-H.; Dietsch, H.; Schurtenberger, P.; Yan, M. Bioconjugate Chem. 2009, 20, 1349)
Research in Professor Yan’s group centers around functional surfaces and interfaces. It lies at the interface of organic chemistry, materials, and nanotechnology. The modification of surfaces of materials to impact specific physical, chemical, or biological properties is important in a wide range of settings from bioanalytical and medical devices to nanomaterials and nanoelectronics. Surfaces as the outmost boundary of a material or device serve as the interface communicating with the physical phase surrounding the material, and play a critical role in the functions of materials and devices. The need of surface engineering for nanomaterials and nanodevices is both inherent, i.e., high surface energy at the nanoscale, and application driven where ligands presented on the surface act as points of contact communicating with external receptors. An intricate balance must be achieved in order to provide the multifaceted functions of the surface ligands in preventing nanomaterials from agglomerating, presenting the necessary molecular recognition functions, and at the same time preserving the physical properties of the nanomaterials needed for translating the molecular recognition events into reliable readouts.
Current research activities in Professor Yan’s laboratory include developing effective surface coupling chemistry that is general, efficient, can accommodate ligand diversity, maintain ligand bioaffinity, and give bioactive and stable interfaces. For more information, visit the Yan group website at http://www.chem.pdx.edu/~yanm.
