The research in the Rubinstein Group is in the field of polymer theory and computer simulations. The unique properties of polymeric systems are due to the size, topology and interactions of the molecules they are made of. Our goal is to understand the properties of various polymeric systems and to design new systems with even more interesting and useful properties. Our approach is based upon building and solving simple molecular models of different polymeric systems. The models we develop are simple enough to be solved either analytically or numerically, but contain the main features leading to unique properties of real polymers. Computer simulations of our models serve as an important bridge between analytical calculations and experiments.
Research in the Alexanian Group focuses on the general areas of reaction development and chemical synthesis. Our studies are ultimately driven by the discovery of new and useful forms of chemical reactivity. A theme of these studies is an emphasis on catalytic transformations employing easily accessed substrates and common molecular functionality. We also use the wide array of unique architectures found in nature to challenge and inspire ourselves to develop creative solutions to current problems in complex molecule synthesis.
One current area of investigation is the utilization of simple hydroxamic acids to develop general, radical-mediated approaches to the metal-free difunctionalization of alkenes. We are also exploring novel approaches to the catalytic activation of alkyl electrophiles for the development of new carbon-carbon bond-forming processes, and the development of new complexity-generating multi-component cycloadditions for synthesis. Ultimately, we strive to apply these new processes to the efficient syntheses of bioactive natural and un-natural products.
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.
John P. Barker Distinguished Professor Michael Rubinstein, an expert on polymer theory, has been selected as the new Chair of the editorial board for the journal Soft Matter.
Soft Matter publishes 48 issues per year, has a global circulation and an interdisciplinary audience with a particular focus on the interface between physics, biology, chemical engineering, materials science and chemistry.
Catalytic transformations of C1 feedstocks are a key foundation of the chemical industry. Formic acid is a C1 species that is especially difficult to convert to more valuable products. Formic acid is also readily produced from renewable resources such as CO2 or biomass. New transformations of formic acid are therefore needed to promote development of renewable C1 chemistry; conversion to methanol would represent a renewable route to a major commodity chemical and high energy density fuel. In 1911, Sabatier and Mailhe reported that some dimethoxymethane was produced upon thermolysis of formic acid over thorium oxide, thereby providing indirect evidence of methanol production. Given the great interest in the facile interconversion of various C1 chemicals, it is remarkable that one hundred years have passed without further reports on this matter.
A team of investigators, including the Miller Group, has set out to uncover new routes to methanol as part of the NSF Center for Enabling New Technologies Through Catalysis (CENTC). Published in Angewandte Chemie, that team now reports that a molecular iridium species catalyzes the disproportionation of formic acid to methanol, water, and CO2. This study represents the first well-defined example of such a reaction mode of formic acid. Methanol is produced under mild, aqueous conditions, without the use of any organic solvents or hydrogen gas.
Femtosecond pump–probe microscopy is used by researchers in the Papanikolas Group to investigate the charge recombination dynamics at different points within a single needle-shaped ZnO rod. As described in The Journal of Physical Chemistry B, recombination in the tips of the rod occurs through an excitonic or electron–hole plasma state, taking place on a picosecond time scale. Photoexcitation in the larger diameter sections of the interior exhibit dramatically slower recombination that occurs primarily through defects sites, i.e., trap mediated recombination.
Transient absorption imaging shows that the spatial variation in the dynamics is also influenced by the cavity resonances supported within the hexagonal cross section of the rod. Finite element simulations suggest that these optical resonator modes produce qualitatively different intensity patterns in the two different locations. Near the end of the rod, the intensity pattern has significant standing-wave character, which leads to the creation of photoexcited carriers in the core of the structure. The larger diameter regions, on the other hand, exhibit intensity distributions in which the whispering gallery (WG) mode character dominates. At these locations, the photoexcited carriers are produced in subsurface depletion zone, where the internal fields separate the electrons and holes and lead to a greater degree of trap recombination on longer time scales.
Each year, The Graduate School at UNC-Chapel Hill presents Graduate Education Advancement Board Impact Awards to graduate students whose research is of exceptional benefit to North Carolina. This year, Andy Lavender and Christine Hajdin, both in the Weeks Group, were among the distinguished recipients.
Follow the link below to read about research projects that are truly making an impact in North Carolina and beyond. Christine's research is already being applied to the hepatitis C virus, the primary cause of liver cancer in the United States. Andy's multifaceted approach to developing RNA structure models represents an important early step in developing new therapies that would benefit thousands of North Carolinians.
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.