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The You Group focuses on the synthesis and characterization of novel multifunctional materials for a variety of applications, predominately in electronics and photonics. Challenges to be addressed include, for example, can a 10% solar cell be made through organic materials? Can single molecules serve as the fundamental unit for electronics and spintronics? Group members are working tirelessly to answer these questions by applying interdisciplinary approaches, including organic and polymer synthesis, surface chemistry, nano-patterning, device fabrication, and physical properties characterization using state-of-the-art instrumentation.
Dark-field microscopy, DFM, is widely used to optically image and spectroscopically analyze nanoscale objects. In a typical DFM configuration, a sample is illuminated at oblique angles and an objective lens collects light scattered by the sample at a range of lower angles. As demonstrated in an article published as the cover of ACS Photonics, researchers in the Cahoon Group have developed waveguide scattering microscopy, WSM, as an alternative technique to image and analyze photonic nanostructures. WSM uses an incoherent white-light source coupled to a dielectric slab waveguide to generate an evanescent field that illuminates objects located within several hundred nanometers of the waveguide surface.
Using standard microscope slides or coverslips as the waveguide, the group demonstrate high-contrast dark-field imaging of nanophotonic and plasmonic structures such as Si nanowires, Au nanorods, and Ag nanoholes. Scattering spectra collected in the WSM configuration show excellent signal-to-noise with minimal background signal compared to conventional DFM. In addition, the polarization of the incident field is controlled by the direction of the propagating wave, providing a straightforward route to excite specific optical modes in anisotropic nanostructures by selecting the appropriate input wavevector. Considering the facile integration of WSM with standard microscopy equipment, the Cahoon Group scientists anticipate it will become a versatile tool for characterizing photonic nanostructures.
Typically, diesel fuel is made from crude oil, but scientists can make high-grade diesel from coal, natural gas, plants or even agricultural waste, using a process called Fischer-Tropsch, or FT. Just about any carbon source is an option. FT Diesel is the ideal liquid transportation fuel for automobiles, trucks and jets. It's much cleaner burning than conventional diesel, and much more energy efficient than gasoline. But, FT Diesel is expensive to make and generates lots of waste.
With support from the National Science Foundation, NSF, and its Center for Enabling New Technologies Through Catalysis, CENTC, chemists from around the United States, including professor Maurice Brookhart from Carolina, are working together to improve the cost and energy efficiency of alternative fuels. CENTC scientists have invented and patented, and are bringing toward commercialization, catalysts that will convert light hydrocarbons into FT Diesel, improving the process, whether it's diesel made from traditional sources, such as oil, or alternative sources, such as biomass.
NSF: Miles O'Brien, Science Nation Correspondent; Ann Kellan, Science Nation Producer
Primary patient samples are the gold standard for molecular investigations of tumor biology yet are difficult to acquire, heterogeneous in nature and variable in size. Patient-derived xenografts, PDXs, comprised of primary tumor tissue cultured in host organisms such as nude mice permit the propagation of human tumor samples in an in vivo environment and closely mimic the phenotype and gene expression profile of the primary tumor. Although PDX models reduce the cost and complexity of acquiring sample tissue and permit repeated sampling of the primary tumor, these samples are typically contaminated by immune, blood, and vascular tissues from the host organism while also being limited in size.
For very small tissue samples, on the order of 103 cells, purification by fluorescence-activated cell sorting, FACS, is not feasible while magnetic activated cell sorting, MACS, of small samples results in very low purity, low yield, and poor viability. Researchers in the Allbritton Group have now developed a platform for imaging cytometry integrated with micropallet array technology to perform automated cell sorting on very small samples obtained from PDX models of pancreatic and colorectal cancer using antibody staining of EpCAM, CD326, as a selection criteria. Published in Cytometry Part A, the data collected demonstrate the ability to automate and efficiently separate samples with very low number of cells.
Maria Ina and Aleksandr Zhushma in the Sheiko Group, won second place in the sixth annual CHANL Scientific Art Competition with their “Snowflake Robe,” a fractal-like spot captured with an electron microscope. "Initially, I was imaging some particles, when I came across this interesting pattern on the surface," says Aleksandr. Maria and Aleksandr realized that it could be art-worthy, so they took a high resolution image of the feature. They believe this is some soapy material that came off the particles and dried on the surface.
The original SEM image is black and white, so they colorized the image using ImageJ. Lightroom was then used for post processing to fine-tune color and contrast. In naming the image, the snowflake pattern was obvious, but the background waviness was open for interpretation. "So I imagined that it is a flowing robe, with the snowflake pattern on it," says Aleksandr.
The Chapel Hill Analytical and Nanofabrication Laboratory (CHANL) was established in 2006 as part of the Institute for Advanced Materials, Nanoscience and Technology, but has since moved into the Department of Applied Physical Sciences. CHANL operates as a shared instrumentation laboratory open to UNC researchers from all departments as well as to researchers from other universities, government labs, and industry.
In vivo glucose biosensors have the potential to greatly improve the way diabetics manage their disease. Unfortunately, such devices do not function as intended, that is, reliably, after implantation due to inflammation and encapsulation due to the "foreign body response.” The Schoenfisch Group has for the last decade researched the benefits of materials that release nitric oxide, NO, to mitigate the foreign body response. In an article published in Analytical Chemistry, they describe the analytical performance benefits of a NO-releasing glucose biosensor percutaneously implanted in a swine model.
Needle-type glucose biosensors were modified with NO-releasing polyurethane coatings designed to release similar total amounts of NO for either rapid or slower durations, and remain functional as outer glucose sensor membranes. Relative to controls, NO-releasing sensors were characterized with improved numerical accuracy on days one and three.
The clinical accuracy and sensitivity of rapid NO-releasing sensors were superior to control and slower NO-releasing sensors at both one and three days after implantation. In contrast, the slower/extended NO-releasing sensors were characterized by shorter sensor lag times in response to intravenous glucose tolerance tests versus burst NO-releasing and control sensors. Collectively, these results highlight the great potential for NO release to enhance the analytical utility of in vivo glucose biosensors. Initial results also suggest that this analytical performance benefit is dependent on the NO-release duration.
Wnt/β-catenin signaling is of significant interest due to the roles it plays in regulating development, tissue regeneration and disease. Transcriptional reporters have been widely employed to study Wnt/β-catenin signal transduction in live cells and whole organisms and have been applied to understanding embryonic development, exploring oncogenesis and developing therapeutics. Polyclonal heterogeneity in reporter cell lines has historically been seen as a challenge to be overcome in the development of novel cell lines and reporter-based assays, and monoclonal reporter cell lines are commonly employed to reduce this variability.
Published in Integrative Biology, researchers in the Allbritton Group describe how A375 cell lines infected with a reporter for Wnt/β-catenin signaling were screened over short (<6) and long (>25) generational timescales. To characterize phenotypic divergence over these time-scales, a microfabricated cell array-based screen was developed enabling characterization of 1119 clonal colonies in parallel. This screen revealed phenotypic divergence after <6 generations at a similar scale to that observed in monoclonal cell lines cultured for >25 generations. Not only were reporter dynamics observed to diverge widely, but monoclonal cell lines were observed with seemingly opposite signaling phenotypes. Additionally, these observations revealed a generational-dependent trend in Wnt signaling in A375 cells that provides insight into the pathway's mechanisms of positive feedback and self-inhibition.
At the Department of Chemistry, we feel strongly that diversity is crucial to our pursuit of academic excellence, and we are deeply committed to creating a diverse and inclusive community. We support UNC's policy, which states that "the University of North Carolina at Chapel Hill is committed to equality of opportunity and pledges that it will not practice or permit discrimination in employment on the basis of race, color, gender, national origin, age, religion, creed, disability, veteran's status, sexual orientation, gender identity or gender expression."