Department of Chemistry
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The Forbes Group

The Forbes Group

The Forbes Group seeks to understand the structure, reactivity and dynamics of free radicals in a variety of media. We are especially interested in how radicals behave in confined environments such as micelles, nanocrystals polymers, and host-guest complexes. Using time–resolved and steady-state magnetic resonance spectroscopies (EPR and NMR), our current projects include investigation of the role of spin in proton-coupled electron transfer reactions, the spectroscopic signatures of free radicals trapped in organic nanocrystals, the degradation of novel polymers in solution, the location of singlet oxygen in photodynamic therapy for cancer treatment, and the adhesion of polymers to each other via grafting reactions. Previous projects have included the elucidation of the mechanism of formation of "skunky" beer by sunlight, and the formation of free radicals upon UV exposure to commercial sunless tanning lotions.

 

The Ashby Group

The Ashby Group

Members of the Ashby Group focus on the synthesis of functionalized materials with applications ranging from biology to alternative energy. We synthesize degradable polyester based material to take advantage of their enhanced biocompatibility and high degree of physical and chemical control. The materials we have synthesized range in applications from cell scaffolds to degradable shape memory devices.

A need in current biomaterials is the integration of functional groups into degradable polymers to impart properties for specialized applications. Two methods we employ utilize cyclization chemistry through "click" type reactions and Diels-Alder chemistry to integrate polar groups into a polyester backbone. Group members are also investigating functionalization chemistry based on aminooxy coupling reactions.

 

Improved Diesel Process

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.

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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

 

Chemical Vapor Deposition

Researchers in the Ramsey Group, published in Analytical Chemistry, describe a chemical vapor deposition, CVD, method for the surface modification of glass microfluidic devices designed to perform electrophoretic separations of cationic species. The microfluidic channel surfaces were modified using aminopropyl silane reagents. Coating homogeneity was inferred by precise measurement of the separation efficiency and electroosmotic mobility for multiple microfluidic devices.

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Microfluidic devices with a 23 cm long, serpentine electrophoretic separation channel and integrated nanoelectrospray ionization emitter were CVD coated with (3-aminopropyl)di-isopropylethoxysilane, APDIPES, and used for capillary electrophoresis (CE)-electrospray ionization (ESI)-mass spectrometry (MS) of peptides and proteins. Peptide separations were fast and highly efficient, yielding theoretical plate counts over 600,000 and a peak capacity of 64 in less than 90 s. Intact protein separations using these devices yielded Gaussian peak profiles with separation efficiencies between 100,000 and 400,000 theoretical plates.

 

Prize-Winning Scientific Art

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.

Snowflake Robe

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.

 

Small Sample Sorting

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.

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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.

 

Dual Action Antibacterial Agents

Published in Bioconjugate Chemistry, researchers in the Schoenfisch Group describe the synthesis of nitric oxide, NO, releasing quaternary ammonium, QA, functionalized generation 1, G1, and generation 4, G4, poly(amidoamine), PAMAM, dendrimers. Dendrimers were modified with QA moieties of different alkyl chain lengths, such as methyl, butyl, octyl, dodecyl, via a ring-opening reaction. The resultant secondary amines were then modified with N-diazeniumdiolate NO donors to yield NO-releasing QA-modified PAMAM dendrimers capable of spontaneous NO release.

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The bactericidal efficacy of individual, non-NO-releasing, and dual action, NO-releasing, QA-modified PAMAM dendrimers was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria. Bactericidal activity was found to be dependent on dendrimer generation, QA alkyl chain length, and bacterial Gram class for both systems. Shorter alkyl chains, such as methylQA and butylQA, demonstrated increased bactericidal activity against P. aeruginosa versus S. aureus for both generations, with NO release markedly enhancing overall killing.

 

Electrocatalytic Carbon Dioxide Reduction

Accumulation of carbon dioxide in the atmosphere is considered a major contributor to climate change. Once captured, CO2 is a potentially useful feedstock if it can be converted into formate/formic acid, carbon monoxide, or more highly reduced hydrocarbon products. Electrochemical and photoelectrochemical CO2 reduction could become an integral part of an energy storage strategy with solar- or wind-generated electricity used to store energy in the chemical bonds of carbon-based fuels.

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The Meyer Group, in collaboration with the Department of Electrical and Computer Engineering at Duke University, published in JACS, reports on how Nitrogen-doped carbon nanotubes are selective and robust electrocatalysts for CO2 reduction to formate in aqueous media without the use of a metal catalyst. An overlayer of polyethylenimine (PEI) functions as a cocatalyst by significantly reducing catalytic overpotential and increasing current density and efficiency.

 

 

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."