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  • Chemistry
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  • 1
    Language: English
    In: Journal of The Electrochemical Society, 2015, Vol.162(9), pp.H681-H685
    Description: A remarkable new supported metal catalyst structure on Mo2C substrates, ‘rafts’ of platinum consisting of less than 6 atoms, was synthesized and found to be catalytically active electrocatalyst for oxygen reduction. A novel catalytic synthesis method: Reduction-Expansion-Synthesis of Catalysts (RES-C), from rapid heating of dry mixture of solid precursors of molybdenum, platinum and urea in an inert gas environment, led to the creation of unique platinum Nanorafts on Mo2C. The Pt Nanorafts offer a complete utilization of the Pt atoms for electrocatalysis with no “hidden” atoms. This structure is strongly affected by its interaction with the substrate as was observed by XPS. In this work, we show for the first time, evidence of electrocatalytic activity with such small clusters of non-crystalline Pt atoms as catalysts for oxygen reduction. Electrochemical half-cell characterization shows that this structure permit more efficient utilization of platinum, with mass activity conservatively measured to be 50% that of platinum particles generated using traditional approaches. These novel material may dramatically enhance stability relative to the commercial Pt/carbon catalysts.
    Keywords: Engineering ; Chemistry;
    ISSN: 0013-4651
    E-ISSN: 1945-7111
    Source: Electrochemical Society (ECS) (via CrossRef)
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  • 2
    Language: English
    In: Carbon, 2011, Vol.49(4), pp.1058-1066
    Description: Dramatic increases in solid carbon deposition rates using palladium and cobalt are achievable at 550 °C while flowing ethylene and hydrogen by simple mixing of the powders of the two otherwise inactive metals. The synergistic mechanism is attributed to a favorable change in gas chemistry coupled with close proximity. ► Palladium and cobalt mixtures catalyze carbon deposition readily. ► When separate, neither metal is effective at carbon deposition. ► No extensive alloying was observed under normal reaction conditions. ► The synergism is attributed to favorable gaseous species being created. ► Close proximity is necessary for utilization of radicals by the other metal. The rate of catalytic carbon nanofiber formation from a mixture of ethylene and hydrogen at 550 °C was found to be dramatically faster over physical mixtures of palladium and cobalt micron scale particles than over either metal independently. The rate correlated with the metal fraction nearly identically for either Pd or Co rich mixtures. The highest rate increase over either pure metal was observed for a 1:1 mass ratio (∼150 times faster), although significant increases were found even at metal ratios of 11:1 (∼45 times faster). There was no direct evidence of extensive alloy formation from the mixed powders which suggests that a synergistic mechanism driven by proximity only may be responsible for the observed rate increases. It is thought a species (e.g. hydrogen atoms) formed at one metal (e.g. palladium) diffuses to the other where it accelerates carbon deposition by affecting the other catalyst material directly, or by generating favorable radical species. Kinetic synergism was also observed for Pd–Co alloys, although it was clearly less dramatic than that found for mixtures. Still, the fundamental similarity in behavior suggests that on the alloy surface two site types exist: one primarily Pd and one primarily Co.
    Keywords: Chemistry
    ISSN: 0008-6223
    E-ISSN: 1873-3891
    Source: ScienceDirect Journals (Elsevier)
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  • 3
    Language: English
    In: Carbon, June 2013, Vol.57, pp.363-370
    Description: A unique type of nonwoven carbon material has been developed which is flexible, resilient, and produced at modest temperature and near ambient pressure using catalytic deposition. This material is comprised entirely of nanoscale carbon fibers, which are extensively interlaced to create a coherent, bulk material. The structure and basic mechanical and electrical properties of this material were investigated through cyclic compression and resistance measurement. The material was highly elastic and capable of being repeatedly compressed without disintegration. The mechanical response varied with density, and the density was controlled by the amount of catalyst used. The material exhibited a high electrical resistivity, which varied nonlinearly with compression.
    Keywords: Chemistry
    ISSN: 0008-6223
    E-ISSN: 1873-3891
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  • 4
    Language: English
    In: Carbon, 2010, Vol.48(7), pp.1932-1938
    Description: Carbon nanofiber growth on palladium particles from ethylene–oxygen mixtures was investigated with respect to thermal history. Electron microscopy, combined with focused ion beam cross-sectioning show particles sinter quickly, but can be stabilized by the addition of a short carbon deposition step at a temperature below the general reaction temperature. This step generates a thin layer of carbon on the catalyst which reduces sintering once the temperature is raised to the optimal reaction temperature. For example, high temperature (e.g. 500 °C) catalyst pre-treatment leads to catalyst particle sintering, and subsequent fiber growth produces large diameter fibers. In contrast, small diameter fibers form on catalyst particles pretreated at low temperature (ca. 350 °C), even if the fibers are grown at a temperature at which deposition rates are faster (e.g. 550 °C). These results led to the development of unique multiple temperature fiber growth protocols that produce smaller diameter fibers while improving the deposition rate.
    Keywords: Chemistry
    ISSN: 0008-6223
    E-ISSN: 1873-3891
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  • 5
    Language: English
    In: The Journal of Physical Chemistry C, 04/08/2010, Vol.114(13), pp.5804-5810
    Description: The nature of observed growth of solid carbon on palladium from ethylene−hydrogen mixtures is consistent with the supposition that the primary source of carbon for growth is homogeneously generated radicals. Evidence includes the lack of growth in the absence of a reacting mixture, sharp maxima as a function of temperature, and dramatic differences in temperature of growth as a function of mixture composition. The finding that the structure of the support strongly influenced the morphology of the solid carbon, and the temperature regime for deposition, is also consistent with this model. Carbon nanofibers were found to form on sputtered palladium films and palladium nanopowder (ca. 700 °C), whereas planar carbon structures deposited on palladium micrometer powder and foil (ca. 600 °C). A radical species growth mechanism is consistent not only with observations made herein but also with data presented in earlier studies.
    Keywords: Chemistry;
    ISSN: 1932-7447
    E-ISSN: 1932-7455
    Source: American Chemical Society (via CrossRef)
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  • 6
    Language: English
    In: Angewandte Chemie International Edition, 07 December 2015, Vol.54(50), pp.15156-15159
    Description: Immunoglobulin G (IgG) monoclonal antibodies (mAbs) are a major class of medicines, with high specificity and affinity towards targets spanning many disease areas. The antibody Fc (fragment crystallizable) region is a vital component of existing antibody therapeutics, as well as many next generation biologic medicines. Thermodynamic stability is a critical property for the development of stable and effective therapeutic proteins. Herein, a combination of ion‐mobility mass spectrometry (IM‐MS) and hydrogen/deuterium exchange mass spectrometry (HDX‐MS) approaches have been used to inform on the global and local conformation and dynamics of engineered IgG Fc variants with reduced thermodynamic stability. The changes in conformation and dynamics have been correlated with their thermodynamic stability to better understand the destabilising effect of functional IgG Fc mutations and to inform engineering of future therapeutic proteins. (IM‐MS) and hydrogen/deuterium exchange mass spectrometry (HDX‐MS) approaches were used to elucidate the global and local conformation and dynamics of engineered IgG Fc variants with reduced thermodynamic stability.
    Keywords: Antibodies ; Hydrogen Exchange ; Immunoglobulin ; Ion Mobility ; Mass Spectrometry
    ISSN: 1433-7851
    E-ISSN: 1521-3773
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  • 7
    Language: English
    In: Carbon, June 2018, Vol.132, pp.411-419
    Description: This study shows high stability Sn (10 wt %)/carbon Li-ion battery anodes can be made via the Reduction Expansion Synthesis (RES) process. Hybrid Sn/C anodes had an initial capacity of 425 mAh g-1 which stabilized to ∼340 mAh g-1 after less than 10 cycles. Unlike earlier Sn/C anodes, capacity remained virtually constant for more than 180 additional cycles. Neat carbon independently tested for Li capacity had a steady specific capacity of 280 mAh g-1. The difference detected between the pure carbon and Sn/C cases are consistent with Sn having the theoretical capacity of ∼1000 mAh g-1. The high stability of the RES derived anodes, relative to earlier Sn based electrodes, is postulated to exist because RES synthesis enables the formation of direct, strong bond between Sn and carbon substrate atoms, hence reducing the rate of Sn electrode disintegration and capacity fade due to expansion upon lithiation. X-ray diffraction and transmission electron microscopy are consistent with this postulate as both show an initial Sn particles size of only a few nanometers and minimal growth after cycling. Reduced interface resistance is also indicative of unique Sn-carbon bond.
    Keywords: Chemistry
    ISSN: 0008-6223
    E-ISSN: 1873-3891
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  • 8
    Language: English
    In: Biochemical Society transactions, October 2013, Vol.41(5), pp.1152-8
    Description: There is enormous interest in molecular self-assembly and the development of biological systems to form smart nanostructures for biotechnology (so-called 'bottom-up fabrications'). Repeat proteins are ideal choices for development of such systems as they: (i) possess a relatively simple relationship between sequence, structure and function; (ii) are modular and non-globular in structure; (iii) act as diverse scaffolds for the mediation of a diverse range of protein-protein interactions; and (iv) have been extensively studied and successfully engineered and designed. In the present review, we summarize recent advances in the use of engineered repeat proteins in the self-assembly of novel materials, nanostructures and biosensors. In particular, we show that repeat proteins are excellent monomeric programmable building blocks that can be triggered to associate into a range of morphologies and can readily be engineered as stimuli-responsive biofunctional materials.
    Keywords: Biosensing Techniques ; Protein Engineering ; Nanostructures -- Chemistry ; Proteins -- Chemistry
    ISSN: 03005127
    E-ISSN: 1470-8752
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  • 9
    Language: English
    In: Journal of visualized experiments : JoVE, 06 April 2017(122)
    Description: Obstructive respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD) are currently treated by inhaled anti-inflammatory and bronchodilator drugs. Despite the availability of multiple treatments, both diseases are growing public health concerns. The majority of asthma patients are well controlled on current inhaled therapies but a substantial number of patients with severe asthma are not. Asthma affects an estimated 300 million people worldwide and approximately 20 percent have a severe form of the disease. In contrast to asthma, there are few effective therapies for COPD. An estimated 10% of the population has COPD and the trend in death rates is increasing for COPD while decreasing for other major diseases. Although developing drugs for inhaled delivery is challenging, the nose-only inhalation unit enables direct delivery of novel drugs to the lung of rodents for pre-clinical efficacy and safety/toxicology studies. Inhaled drug delivery has multiple advantages for respiratory diseases, where high concentration in the lung improves efficacy and minimizes systemic side effects. Inhaled corticosteroids and bronchodilators benefit from these advantages and inhaled delivery may also hold potential for future biologic therapies. The inhalation unit described herein can generate, sample for characterization, and uniformly deposit a drug aerosol in the lungs of rodents. This enables the pre-clinical determination of the efficacy and safety of drug doses deposited in the lungs of rodents, key data required before initiating clinical development.
    Keywords: Equipment Design ; Nose ; Bronchodilator Agents -- Administration & Dosage ; Drug Delivery Systems -- Instrumentation
    E-ISSN: 1940-087X
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  • 10
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 17 February 2004, Vol.20(4), pp.1189-93
    Description: Hydrogen spillover over macroscopic distances was demonstrated and exploited in the design of two novel catalytic reactors for 1-butene isomerization. A dual-bed reactor containing separate zones of noble metal and bimetallic catalysts yielded activities up to 2.7 times greater than that of the noble metal alone. The noble metal catalyst contained palladium supported on graphitic carbon. The bimetallic catalyst contained a base metal, either iron or cobalt, and a lanthanide metal, either cerium or praseodymium, also supported on graphitic carbon. The bimetallic catalysts by themselves had no measurable activity at the current experimental conditions. Results from a dual-bed, dual-feed reactor using the same catalysts showed dramatic activity increases relative to controls. In this reactor, the hydrocarbon never contacted the noble metal catalyst, yet substantial hydrocarbon conversion was measured. No hydrocarbon conversion was detected when blank support replaced the bimetallic catalyst or when no material at all was placed above the noble metal catalyst. In both reactors, the activity increase was attributed to hydrogen spillover. That is, molecular hydrogen adsorbed and dissociated on the noble metal catalyst. The adsorbed atomic hydrogen was then transported via surface diffusion to the bimetallic catalyst, activating those sites. The results also demonstrated that a catalytic reaction may occur at distinctly different reactive sites and that catalysts may be selected to promote specific steps within the reaction.
    Keywords: Chemistry;
    ISSN: 0743-7463
    E-ISSN: 15205827
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