Posts tagged: Chemistry

Corbin Livingston, ’16

Dominguez, C., Metz, K. M., Hoque, M. K., Browne, M. P., Esteban-Tejeda, L., Livingston, C. K., et al. (2018). Continuous Flow Synthesis of Platinum Nanoparticles in Porous Carbon as Durable and Methanol-Tolerant Electrocatalysts for the Oxygen Reduction Reaction. Chemelectrochem, 5(1), 62-70.

Abstract: The development and commercialization of direct methanol fuel cells (DMFCs) as energy conversion devices remains a challenge despite their advantages in terms of energy density and energy-conversion efficiency. The bottleneck for the development of DMFCs is mainly caused by the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode of fuel cells, and the effect of the so-called methanol crossover in state-of-the-art Pt/C electrocatalysts. Herein, we report for the first time an easily scalable continuous flow method based on ultraspray pyrolysis (USP) for the preparation of Pt nanoparticles directly embedded on highly porous carbon spheres. A study on the effect that post-synthesis treatment procedures have on the level of graphitization and catalytic properties is described. Use of USP results in a substantial reduction of the final Pt content with respect to typical Pt/C electrocatalysts, while yielding also excellent durability and tolerance to methanol crossover under acidic conditions. These results demonstrate that the USP method reported herein is a good candidate for its use in the preparation of ORR catalysts in commercial applications.

Michael Dix, ’14, Joshua Pender, ’15 and Stephanie Sanders, ’15

Metz, K. M., Sanders, S. E., Pender, J. P., Dix, M. R., Hinds, D. T., Quinn, S. J., et al. (2015). Green Synthesis of Metal Nanoparticles via Natural Extracts: The Biogenic Nanoparticle Corona and Its Effects on Reactivity. ACS Sustainable Chemistry & Engineering.

Abstract: The optical and catalytic properties of metal nanoparticles have attracted significant attention for applications in a wide variety of fields, thus prompting interest in developing sustainable synthetic strategies that leverage the redox properties of natural compounds or extracts. Here, we investigate the surface chemistry of nanoparticles synthesized using coffee as a biogenic reductant. Building on our previously developed synthetic protocols for the preparation of silver and palladium nanoparticle/carbon composite microspheres, a combination of thermogravimetric and spectroscopic methods was used to characterize the carbon microsphere and nanoparticle surfaces. Infrared reflectance spectroscopy and single particle surface enhanced Raman spectroscopy were used to characterize Pd and Ag metal surfaces, respectively, following synthesis. Strongly adsorbed organic layers were found to be present at metal nanoparticle surfaces after synthesis. The catalytic activity of Pd nanoparticles in hydrogenation reactions was leveraged to study the availability of surface sites, and coffee-synthesized nanomaterials were compared to commercial Pd-based hydrogenation catalysts. Our results demonstrate that biogenic adsorbates block catalytic surface sites and affect nanoparticle functionality. These findings highlight the need for careful analysis of surface chemistry as it relates to the specific applications of nanomaterials produced using greener or more sustainable methods.

 

Cassandra Waun, ’13, Erica Bennett, ’13, Erica Earl, ’14

McCaffrey, V. P., Zellner, N. E. B., Waun, C. M., Bennett, E. R., & Earl, E. K. (2014). Reactivity and Survivability of Glycolaldehyde in Simulated Meteorite Impact Experiments. Origins of Life and Evolution of Biospheres, 1-14.

Abstract: Sugars of extraterrestrial origin have been observed in the interstellar medium (ISM), in at least one comet spectrum, and in several carbonaceous chondritic meteorites that have been recovered from the surface of the Earth. The origins of these sugars within the meteorites have been debated. To explore the possibility that sugars could be generated during shock events, this paper reports on the results of the first laboratory impact experiments wherein glycolaldehyde, found in the ISM, as well as glycolaldehyde mixed with montmorillonite clay, have been subjected to reverberated shocks from ~5 to >25 GPa. New biologically relevant molecules, including threose, erythrose and ethylene glycol, were identified in the resulting samples. These results show that sugar molecules can not only survive but also become more complex during impact delivery to planetary bodies.

 

Stephanie Sanders, ’15, Anna Miller, ’13

Metz, K. M., Sanders, S. E., Miller, A. K., & French, K. R. (2014). Uptake and Impact of Silver Nanoparticles on Brassica rapa: An Environmental Nanoscience Laboratory Sequence for a Nonmajors Course. Journal of Chemical Education, 91(2), 264-268.

Abstract: Nanoscience is one of the fast growing fields in science and engineering. Curricular materials ranging from laboratory experiments to entire courses have been developed for undergraduate science majors. However, little material has been developed for the nonmajor students. Here we present a semester-long laboratory sequence developed for a nonmajors course, where students investigate the potential environmental impacts of nanoscience. Students synthesize and characterize silver nanoparticles using green synthetic methods. They then use the suspension of silver nanoparticles to “water” Wisconsin Fast Plants, Brassica rapa, over a three to four week period to simulate environmental exposure. Possible impacts are examined throughout the growth period, and silver uptake by the plants is quantified at the end of the growth period. This lab requires design input from the student, making it an open-ended experiment. Although designed for nonmajors, this lab could easily be adapted for an environmental chemistry or chemical nanoscience course.

Lyndsey Reynolds, ’12, Stephanie Sanders, ’15

Duffy, P., Reynolds, L. A., Sanders, S. E., Metz, K. M., & Colavita, P. E. (2013). Natural reducing agents for electroless nanoparticle deposition: Mild synthesis of metal/carbon nanostructured microspheres. Materials Chemistry and Physics, 140(1), 343-349.

Abstract: Composite materials are of interest because they can potentially combine the properties of their respective components in a manner that is useful for specific applications. Here, we report on the use of coffee as a low-cost, green reductant for the room temperature formation of catalytically active, supported metal nanoparticles. Specifically, we have leveraged the reduction potential of coffee in order to grow Pd and Ag nanoparticles at the surface of porous carbon microspheres synthesized via ultraspray pyrolysis. The metal nanoparticle-on-carbon microsphere composites were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). To demonstrate the catalytic activity of Pd/C and Ag/C materials, Suzuki coupling reactions and nitroaromatic reduction reactions were employed, respectively.

Nicholas Herrman, ’12

Bindman, N., Merkx, R., Koehler, R., Herrman, N., & van der Donk, W. A. (2010). Photochemical cleavage of leader peptides. Chemical Communications, 46(47), 8935-8937.

Abstract: We report a photolabile linker compatible with Fmoc solid phase peptide synthesis and Cu(I)-catalyzed alkyne-azide cycloaddition that allows photochemical cleavage to afford a C-terminal peptide fragment with a native amino terminus. (Journal abstract)

Shauna Paradine, ’08

Altermann, S. M., Richardson, R. D., Paradine, S. M., French, A. N., Page, T. K., Schmidt, R. K., et al. (2008). Catalytic Enantioselective Alpha-Oxysulfonylation of Ketones Mediated by Iodoarenes. European Journal of Organic Chemistry(31), 5315-5328.

Abstract: The alpha-oxysulfonylation of ketones catalysed by enantio enriched iodoarenes using mCPBA as stoichiometric oxidant is reported to give useful synthetic intermediates in good yield and modest enantioselectivity. We believe this to be the first report of an enantioselective organocatalytic reaction involving hypervalent iodine reagents which should open up a new field for enantioselective organocatalysis of oxidation reactions. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Shauna Paradine, ’08

Richardson, R. D., Page, T. K., Altermann, S., Paradine, S. M., French, A. N., & Wirth, T. (2007). Enantioselective Alpha-Oxytosylation of Ketones Catalysed by Iodoarenes. Synlett(4), 538-542.

Abstract: The alpha-oxytosylation of ketones catalysed by enantioenriched iodoarenes using mCPBA as stoichiometric oxidant is reported to give useful synthetic intermediates in good yield and modest enantioselectivity. We believe this to be the first report of an enantioselective catalytic reaction involving hypervalent iodine reagents which should open up a new field for enantioselective organocatalysis of oxidation reactions.

Amanda Boye and Crystal Ingison

Boye, A. C., Meyer, D., Ingison, C. K., French, A. N., & Wirth, T. (2003).  Novel lactonization with phenonium ion participation induced by hypervalent iodine reagentsOrganic Letters, 5, 2157-2159.

Abstract: A novel lactonization of 4-aryl-4-pentenoic acids is described using aryl-λ3-iodanes as reagents for this transformation. The hypervalent iodine species acts as a hypernucleofuge, generating intermediate phenonium ions, which react to aryl-migrated lactones.

Michael Blankinship

Chrisman, W., Blankenship, M. J., Taylor, B., & Harris, C. E. (2001).  Selective deoximation using alumina supported potassium permanganateTetrahedron Letters, 42, 4775-4777.

Abstract: Ketoximes are converted to the parent ketones in good yields when treated with potassium permanganate supported on neutral alumina (ASPP). An optimized procedure has been developed, the simple work-up minimizes loss of product and oximes have been selectively oxidized in the presence of alkenes.

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