Physical Sciences and Mathematics Commons^™

Superresolution Mapping Of Energy Landscape For Single Charge Carriers In Plastic Semiconductors, Yifei Jiang, Jason Mcneill

Publications

The performance of conjugated polymer devices is largely dictated by charge transport processes. However, it is difficult to obtain a clear relationship between conjugated polymer structures and charge transport properties, due to the complexity of the structure and the dispersive nature of charge transport in conjugated polymers. Here, we develop a method to map the energy landscape for charge transport in conjugated polymers based on simultaneous, correlated charge carrier tracking and single-particle fluorescence spectroscopy. In nanoparticles of the conjugated polymer poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1′-3}-thiadiazole)], two dominant chain conformations were observed, a blue-emitting phase (λmax = 550 nm) and a …

A Convenient Miniature Test Platform For Polyelectrolyte Membrane Fuel-Cell Research, Jamie A. Shetzline, Saheed Bukola, Stephen E. Creager

Publications

A simple and convenient small-scale fuel-cell test platform was created from a commercial compression fitting and graphite rod current collectors and used to conduct diagnostic tests on disk-shaped membrane-electrode assemblies (MEAs) fabricated from Nafion membranes and Nafion-impregnated platinum-on-carbon-cloth anodes and cathodes. A key advantage of this test platform is that it requires very little material, perhaps just a few milligrams, to conduct a fuel-cell test on a supported catalyst. Electrochemically-active surface area (ECSA) values for supported platinum on carbon-cloth electrodes were obtained by in-situ(in the fuel cell) and ex-situ (in liquid electrolyte) cyclic voltammetry on similarly-prepared electrodes, and values …

Correlated Mutation In The Evolution Of Catalysis In Uracil Dna Glycosylase Superfamily, Bo Xia, Yinling Liu, Jose Guevara, Jing Li, Celeste Jilich, Ye Yang, Liangjiang Wang, Brian N. Dominy, Weiguo Cao

Publications

Enzymes in Uracil DNA glycosylase (UDG) superfamily are essential for the removal of uracil. Family 4 UDGa is a robust uracil DNA glycosylase that only acts on double-stranded and single-stranded uracil-containing DNA. Based on mutational, kinetic and modeling analyses, a catalytic mechanism involving leaving group stabilization by H155 in motif 2 and water coordination by N89 in motif 3 is proposed. Mutual Information analysis identifies a complexed correlated mutation network including a strong correlation in the EG doublet in motif 1 of family 4 UDGa and in the QD doublet in motif 1 of family 1 UNG. Conversion of EG …

Understanding The Role Of Nadh In Cellular Fe2+ Generation Of Hydroxyl Radical And The Effects Of Polyphenol Antioxidants, Craig Goodman, Julia L. Brumaghim

Chemistry Annual Research Symposium

Structurally similar polyphenols have opposite effects on rates of Fe3+ reduction by NADH. In future work, we anticipate exploring several avenues:

What is the role of autoxidation? UV-vis kinetic experiments in an air-free atmosphere should reveal if MEGA is increasing the pool of reducible Fe3+.

What occurs in the presence of H2O2 and/or increased levels of NADH? Mimicking the environment of a stressed cell should yield interesting information about antioxidant activity if the rates change significantly.

Surface Functionalized Nylon Capillary-Channeled Polymer (C-Cp) Fibers For Protein Ion-Exchange Separations, Liuwei Jiang, R. Kenneth Marcus

Chemistry Annual Research Symposium

Native nylon C-CP fibers have a very low density (~20 μmol g-1) of carboxylic acid groups that limits its performance on protein separations. To overcome this challenge, surface modification was done on native nylon fibers by grafting monomer ligands (acrylics) via microwave-assisted free radical polymerization.

Human Insulin Adsorption To Monolayer Graphene. A Molecular Dynamics Study., Richard Overstreet, Brian Dominy

Chemistry Annual Research Symposium

Molecular dynamics simulations were conducted using the CHARMM22 potential and TIP3P solvent to model human insulin adsorption to graphene. TIP3P explicit solvent was used to capture the hydrophobic effect, the mechanism responsible for the adsorption of proteins to hydrophobic surfaces. This water model was originally parameterized for the CHARMM22 potential and amino acid residues thus it was required to develop Lennard-Jones graphene carbon parameters to reproduce the empirical water graphite contact angle of 86 degrees. Adsorption was modeled with three different orientations about the graphene monolayer. Insulin shows varying degrees of adsorption surface area and correlated binding affinity due to …

Short F···F And F(Cl)···O Contacts In Fluoroorganic Crystals, And Short Ag···Ag And Ag···O Contacts In Silver Polyfluoroacetate Salts, Xiaolin Liu, Andrej V. Matsnev, Steven P. Belina, Colin D. Mcmillen, Joseph S. Thrasher

Chemistry Annual Research Symposium

The compound 2,2,5,5-tetrafluoro-2,5-dihydrofuran (1) [1] has been synthesized as a candidate monomer for synthesizing amorphous fluoropolymers in our research laboratory. Meanwhile, several crystal structures of products resulting from either new or existing chemistry of this cyclic ether have been solved and will be reported herein. The structures of the tricyclic ether 4 [2], resulting from the photodimerization of 1 in the presence of dry air, as well as perfluorooxodiacetic acid, resulting from the ring-opening oxidation of 1 [3], show a variety of short H···F, F···F, and O···F interactions. The crystal structure of 1,1,2,2,3,3,4,4-octafluorobutane-1,4-disulfonyl dichloride (ODD) reveals not only short F···F …

Stability Of Copper(Ii) Complexes Of Sulfur And Selenium Antioxidants, Jaime M. Murphy, Brian A. Powell, Julia Brumaghim

Chemistry Annual Research Symposium

We focused on determining the stability constants for Cu(II) binding of sulfur and selenium antioxidants in aqueous conditions by potentiometric or spectrophotometric determination. Correlations of stability constant and antioxidant capability, as previously determined by gel electrophoresis, are examined, as well as the likelihood of each complex forming in vivo.

Development And Application Of Cu-Modified Carbon Electrodes From Pyrolyzed Paper Strips, Gema M. Durán, Tomás E. Benavidez, Jason Giuliani, Ángel Ríos, Carlos D. Garcia

Chemistry Annual Research Symposium

A one-step approach for the synthesis and integration of copper nanoparticles (CuNPs) onto paper-based carbon electrodes is herein reported. The method is based on the pyrolysis (1000 ºC under a mixture of 95% Ar / 5% H2 for 1 hour) of paper strips modified with a saturated solution of CuSO4 and yields to the formation of abundant CuNPs on the surface of carbonized cellulose fibers. The resulting substrates were characterized by a combination of scanning electron microscopy, EDX, Raman spectroscopy as well as electrical and electrochemical techniques. Their potential application, as working electrodes for non-enzymatic amperometric determination of glucose, was …

Investigation Of Ionic And Electronic Conductivities In Modified Carbon/Zirconia Composites, Jamie A. Shetzline, Jung-Min Oh, Stephen E. Creager

Chemistry Annual Research Symposium

Ionic and electronic conductivities were recently shown to be able to be independently probed utilizing a near-DC based method for free standing thin films containing mixtures of nafion and carbon black. Recently the mixed conductivity methodology was extended to packed powders in order to study ionic and electronic conductivities of carbon/zirconia nano composite materials for which molecular and polymer electrolytes were covalently grafted onto the carbon/zirconia particle surfaces. The method relies upon careful control of the nature of the contact between the sample and the current-carry-ing electrodes, as well as the geometry of the sample configuration.

Insights Into The Effect Of Metal Ions And Conformational Change On Binding Between Protective Antigen And Tumor Endothelial Marker 8, Zhe Jia, Christine Ackroyd, Kenneth Christensen, Brian Dominy

Chemistry Annual Research Symposium

No abstract provided.

Fast Production Of Microfluidic Devices By Co2 Laser Engraving Of Wax-Coated Glass Slides, Eric T. Da Costa, Mauro F.S. Santos, Hong Jiao, Claudimir L. Do Lago, Ivano G.R. Gutz, Carlos D. Garcia

Chemistry Annual Research Symposium

Glass is one of the most convenient materials for the development of microfluidic devices. However, most of the fabrication protocols, require long processing times and expensive facilities. Polymeric materials have been extensively used due to the fast and low-cost production methods. Ablation by CO2 laser has been used to prototype on polymeric materials, but is difficult to extend to glass devices, because the local heating causes surface cracking. We herein describe a simple procedure to produce microfluidic devices for capillary electrophoresis from microscope glass slides.

A Smart Polymer Hydrogel As A Chemical Sensor On Biomedical Implant, Md Arifuzzaman, Caleb Behrend, John Desjardins, Jeffrey N. Anker

Chemistry Annual Research Symposium

Orthopedic implants are manufactured to support on healing fractured bones. In United States, over 2 million fracture fixation devices, including intra-medullary nails, external fixation pins, plates, and screws, and over 600 thousands joint prostheses, are implanted in patients annually. While fairly common, these fixation surgeries (5%) sometimes lead to unavoidable infection, which only amplifies health care costs accumulated from the initial procedures. In most cases, bacterial biofilms acutely causes infection which is a major reason of medical device failure. In order to obtain proper infections detection around biomedical implants a non-invasive chemical sensor is required. In vivo detection of low …

Hydrothermal Single Crystal Growth And Characterization Of Novel Rare Earth Niobates And Tantalates: Lnnbo4 (Ln = La-Lu , Y), La2tao5(Oh) And Ln3ta2o9(Oh), Liurukara D. Sanjeewa, Kyle Fulle, Colin D. Mcmillen, Joseph W. Kolis

Chemistry Annual Research Symposium

Rare-earth niobates and tantalates are refractory materials that have been exploited in applications involving ion conductivity, photo-catalysis, and luminescence, both in doped and un-doped forms.

In general, refractory oxides have high melting points therefore synthesis of single crystals are more challenging. For example LnNbO4 can be grown readily by melt techniques such as Czochralski pulling ~1300 ˚C. However during the cooling crystal quality degraded resulting low quality crystals therefore high temperature melting techniques are not suitable for bulk single crystals growth.

Electrochemically-Preadsorbed Collagen Promotes Adult Human Mesenchymal Stem Cell Adhesion On Carbon Nanostructured Substrates, Tomás E. Benavidez, Marissa E. Wechsler, Madeleine M. Farrer, Rena Bizios, Carlos D. Garcia

Chemistry Annual Research Symposium

The effect of electric potential on the adsorption of collagen type I onto optically transparent carbon electrodes (OTCE) and its mediation on subsequent adhesion of adult, human, mesenchymal stem cells (hMSCs) is described. Adsorption was investigated as a function of the protein concentration and applied potential. The resulting substrate surfaces were characterized using spectroscopic ellipsometry (SE), atomic force microscopy (AFM), and cyclic voltammetry (CV). While the higher applied potential and protein concentration, the higher the adsorbed amount, the application of potential values higher than +800 mV resulted in the oxidation of the adsorbed protein. Subsequent adhesion of hMSCs on the …

A Ph Sensor For Non-Invasive In Vivo Detection And Imaging Of Implant Associated Infection, Unaiza Uzair, Donald Benza, Fenglin Wang, Yash Raval, Tzuen-Rong J. Tzeng, Jeffrey N. Anker

Chemistry Annual Research Symposium

We develop a pH sensor based on use of X-ray Excited Luminescence Chemical Imaging (XELCI) to non-invasively detect and image changes in pH of a surface with high spatial and pH resolution while minimizing tissue scattering effects. Diagnosis and treatment of infections associated with implanted medical devices is a challenge, as clinical symptoms of implant associated infection are often delayed and can sometimes be completely absent till infection reaches a later stage. Early diagnosis of implant associated infection and non-invasive continuous monitoring of infection to evaluate eradication and success of treatment has not been established yet. Treatment of implant infection …

In Silico Model For Naatm1 Type Atp Binding Cassette Exporter Conformational Transitions, Yinling Liu, Brian N. Dominy

Chemistry Annual Research Symposium

No abstract provided.

Liquid Sampling-Atmospheric Pressure Glow Discharge Ion Source For Nonproliferation Of Nuclear Material, Edward Hoegg, R. Kenneth Marcus, Charles Barinaga, George Hager, David Koppenaal, Garret Hart

Chemistry Annual Research Symposium

An area of continuing intense interest has been the development of portable or fieldable (man-portable, luggable, or transportable) analytical instrumentation. One specific driver for portable or fieldable analytical instrumentation are the needs of the nuclear safeguards community for versatile, easy-to-use, in-field mass spectrometer systems for determining the 235U/238U isotope ratios in UF6 at enrichment facilities. In order to meet this demand the authors propose using a liquid sampling-atmospheric pressure glow discharge (LS-APGD) ion source, Fig 1.1-3 The LS-APGD was optimized for isotope ratio analysis to have a liquid flow rate of 30 uL min-1 a gas flow rate of 0.5 …

Recent Advances In The Synthesis And Application Of Sf5-Containing Organic Compounds, Andrej V. Matsnev, Steven P. Belina, Si-Yan Qing, Kyle A. Berger, Anthony R. Scavuzzo, Piotr Dudzinski, Anna-Lena Dreier, Günter Haufe, Joseph S. Thrasher

Chemistry Annual Research Symposium

It is well known that fluorinated molecules play an important role in daily life. For example, organic molecules bearing either a fluorine atom itself or a short polyfluorinated substituent such as mono-, difluoro-, and trifluoromethyl groups, or pentafluoroethyl and perfluoropropyl groups are already widely used in medicinal and agricultural chemistry. In contrast, molecules with long perfluorinated chains have found vast application in materials science. Among the fluorine-containing moieties, the pentafluorosulfanyl (SF5) substituent occupies a special place.1 The pentafluorosulfanyl group brings unique properties to organic compounds and often improves their biological activities due to the group’s high chemical and metabolic stability, …

Ratiometric Single-Nanoparticle Oxygen Sensors For Biological Imaging, Changfeng Wu, Barbara Bull, Kenneth Christensen, Jason Mcneill

Publications

It makes sense: Conjugated polymer nanoparticles doped with a platinum porphyrin dye exhibit bright phosphorescence that is highly sensitive to the concentration of molecular oxygen. The small size, extraordinary brightness, excellent sensitivity, and ratiometric emission, together with the demonstration of single-particle sensing and cellular uptake, indicate the potential of the nanoparticle sensors for quantitative mapping of local molecular oxygen concentration.

Multicolor Conjugated Polymer Dots For Biological Fluorescence Imaging, Changfeng Wu, Barbara Bull, Craig Szymanski, Kenneth Christensen, Jason Mcneill

Publications

Highly fluorescent conjugated polymer dots were developed for demanding applications such as fluorescence imaging in live cells. These nanoparticles exhibit small particle diameters, extraordinary fluorescence brightness, and excellent photostability. Single particle fluorescence imaging and kinetic studies indicate much higher emission rates (∼10⁸ s⁻¹) and little or no blinking of the nanoparticles as compared to typical results for single dye molecules and quantum dots. Analysis of single particle photobleaching trajectories reveals excellent photostability—as many as 10⁹ or more photons emitted per nanoparticle prior to irreversible photobleaching. The superior figures of merit of these new fluorescent probes, together …