Our focus in the Ashby Group is the synthesis of functional shape memory materials for biomedical applications. We have recently reported the topological control of mesenchymal stem cells by responsive poly(ε-caprolactone) surfaces in which we engineered a biocompatible shape memory surface to mechanically alter stem cell topology.
Group members are also developing scaffolds for nitric oxide release in collaboration with the Schoenfisch Group, and are working towards the synthesis of new iodinated polyesters for use in X-ray computed tomography.
Biological assays have dramatically improved in recent years due to the increasing use of living cells as "test tubes" for research studies. These cell-based assays have demanded that new technologies be developed for the life sciences in order to fully exploit the potential of designer drugs, stem cell engineering, and genetic medicine. The Allbritton Group is at the forefront of this technology development for biomedical and pharmaceutical research.
Micropallet Technology
In the area of cloning for cancer and stem cell studies, the Allbritton group demonstrated a novel and effective approach for the isolation of specific, single cells from a population of cells. Using principles borrowed from the electronics industry, microengineered arrays of extremely small structures (30 – 50 microns) termed micropallets are fabricated on the surface of a microscope slide. A laser is used to detach an individual micropallet and its attached cell from the slide whereupon it is collected. This strategy has been demonstrated for single-cell isolation with unprecedented survival and colony forming ability of single cells (>85%), thus dramatically improving the cloning process. This tool is now under development in an NIH-funded project with Mike Ramsey in the Department of Chemistry and colleagues in the Lineberger Cancer Center's Animal Models Facility to improve the process for creating genetically modified mice for medical research.
Margaret Radack, an undergraduate chemistry major in the You Group, has been selected to receive the Gertrude Elion Undergraduate Scholarship Award by the North Carolina section of the American Chemical Society. The award is in memory of Gertrude B. Elion, 1988 Nobel Laureate in Medicine, and honors her interest in fostering the research careers of students, and particularly women.
Margaret, who will begin her senior year this fall, is currently doing her summer research program in the You Group, focusing on the development of new strategies to increase the light absorption width of conjugated polymers. Such polymers can more effectively harvest the solar spectrum, with a great potential to increase the current of these polymers based solar cells. Congratulations, Maggie!
Work entirely designed, implemented, and interpreted by UNC undergraduates has been published in Biochemistry and is highlighted on the journal web page. Many viruses encode their genetic information in RNA molecules and these RNAs can have complex structures that are essential for efficient replication. The all-undergraduate team developed a model for the genome of the satellite tobacco mosaic virus, which is roughly the "hydrogen atom" of RNA viruses.
The UNC undergraduates discovered that the RNA genome has a complex higher-order structure with three domains, each of which corresponds to an essential viral function. This work is likely to broadly inform our understanding of the role of genome structure in the infectivity and pathogenesis of many RNA viruses, including those that infect humans.
The work was carried out as part of the UNC Undergraduate Transcriptome Project, an NSF-funded program developed in the Weeks Laboratory, designed to help undergraduates explore their potential for independent creativity, to fuel their passion for science, and to be a model for engaging undergraduates in a research university.
The sun provides about 10,000 times our current daily energy needs and is the ultimate solution to the world's need for renewable, environmentally friendly energy. However, to be practical, utilization of solar energy requires energy storage on massive scales, far greater than any existing technology. Photosynthesis provides a role model in this regard, with the only practical approach consisting of an "Artifical Photosynthesis" strategy with "solar fuels" as the product. Solar fuels are high-energy molecules like carbohydrates or hydrogen with the energy of the sun stored in chemical bonds. Target reactions are water splitting into hydrogen and oxygen and light-driven reduction of CO2 to CO or other reduced forms of carbon.
At the U.S. DOE-funded Energy Frontier Research Center here at the Department of Chemistry, the goal is to generate solar fuels using dye-sensitized photoelectrosynthesis cells, DSPEC. Molecules do most of the work in this approach, absorbing light, transferring electrons, and catalyzing reactions. The DSPEC design also benefits from a modular approach, allowing the separate parts to be synthesized, evaluated, and improved in an iterative manner. Using an integrated team-based structure, we are making real progress in translating our concept of the DSPEC into a viable prototype. Many challenges lie ahead but there is light shining at the end of a very long tunnel.
Undergraduate proficiency exams will be given on
Monday, August 19, 2013
Follow this link for more information about the exam, beginning at 08:30 am in Venable/Murray Hall G202.
Organic solar cells typically employ only two organic semiconductors: a p-type Donor and a n-type Acceptor. Due to the intrinsic narrow absorption width of organic Donors, the binary solar cells exhibit a noticeably poor light-harvesting capability, which limits their highest efficiency achieved today to ~ 10 %. Ternary solar cells that mix two or more Donors of different absorption features, on the other hand, enjoy both an increased light absorption width, and an easy fabrication process associated with their simple structures. However, their fundamental working principles are still under investigation
In a Perspective, published in the Journal of Physical Chemistry Letters, investigators in the You Group offer their insights on the major governing mechanisms in these intriguing ternary solar cells. Through careful analyses of exemplary cases, they summarize the advantages and limitations of the three major mechanisms: charge transfer, energy transfer, and parallel-linkage. Further, they identify a few worthy future directions for these ternary solar cells. For example, incorporating singlet fission or upconversion materials into the energy transfer dominant ternary solar cells can theoretically breach the S-Q limit of single junction solar cells. This Perspective assures researchers working in this area that the feedback loop between fundamental understanding of mechanisms and materials selection will accelerate the efficiency improvement of these ternary solar cells.
Researchers in the Meyer Group, in collaboration with colleagues from UNC's Department of Physics and Astronomy, RTI International, and Rutgers University, used orthorhombic Nb2O5 nanocrystalline films functionalized with [Ru(bpy)2(4,4′-(PO3H2)2bpy)]2+ as the photoanode in dye-sensitized photoelectrosynthesis cells (DSPEC) for hydrogen generation. As published in the journal Chemistry of Materials, they undertook a set of experiments to establish key properties—conduction band, trap state distribution, interfacial electron transfer dynamics, and DSPEC efficiency, to develop a general protocol for future semiconductor evaluation and for comparison with other wide-band-gap semiconductors.
The investigators found that, for a T-phase orthorhombic Nb2O5 nanocrystalline film, the conduction band potential is slightly positive (<0.1 eV), relative to that for anatase TiO2. Anatase TiO2 has a wide distribution of trap states including deep trap and band-tail trap states. Orthorhombic Nb2O5 is dominated by shallow band-tail trap states. Trap state distributions, conduction band energies, and interfacial barriers appear to contribute to a slower back electron transfer rate, lower injection yield on the nanosecond time scale, and a lower open-circuit voltage (Voc) for orthorhombic Nb2O5, compared to anatase TiO2. In an operating DSPEC, with the ethylenediaminetetraacetic tetra-anion (EDTA4–) added as a reductive scavenger, H2 quantum yield and photostability measurements show that Nb2O5 is comparable, but not superior, to TiO2.