Browsing by Author "Brinson, Bruce E."
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Item Diatoms at >5000 Meters in the Quelccaya Summit Dome Glacier, Peru(BioOne, 2015) Fritz, Sherilyn C.; Brinson, Bruce E.; Billups, W.E.; Thompson, Lonnie G.; Richard E. Smalley Institute for Nanoscale Science and TechnologyDiatoms were found in late Holocene age ice-core samples recovered from the Quelccaya Summit Dome in the tropical Andes of Peru and were imaged by environmental scanning electron microscopy and identified. Freshwater diatoms in the genera Hantzschia, Pinnularia, and Aulacoseira were the most common taxa in the samples and indicate a freshwater source for the material, which also is suggested by the presence of the freshwater alga Volvox. The overall species composition of the diatoms suggests that the majority of taxa originated from a high-elevation lake or wetland in the cordillera surrounding the ice cap. The abundant diatom valves, up to 70 µm in size, likely were transported to the ice via wind.Item Identification by laser desorption ionization mass spectroscopy of large fullerenes formed during the growth of single-walled carbon nanotubes in the HiPco process(2004) Brinson, Bruce E.; Johnson, Marie PontierIron catalyzed gas-phased disproportionation of carbon monoxide under high pressure is known to produce carbon Single Walled Nano-Tubes (SWNT). Non-tubular carbon by products and iron encapsulated-graphitic shelled nano-particles are produced concomitantly under conditions optimized for SWNT production, are undesirable bi-products. Differences in oxidation thresholds of the constituents and acid leaching of iron particles have been exploited in the co-development of Laser Desorption Ionization Mass Spectroscopy (LDI) evaluation and SWNT purification. LDI threshold conditions have been established for the analysis of non-SWNT carbon species. It has been shown that neither photochemical decomposition nor photo assisted molecular self-assembly contribute to the mass spectra. Raw, processed materials and molecular specific extractions are evaluated. Laser Desorption Ionization mass spectroscopy, Transmission Electron Microscopy, Raman and TGA results are reported.Item Nonresonant surface enhanced Raman optical activity(2009) Brinson, Bruce E.; Halas, Naomi J.Nanoshells (NS) and nanoparticles (NP) are tunable plasmonic particles that can be precisely engineered for specific applications including surface enhanced spectroscopies. A new, general method for the synthesis of core-shell and solid nanoparticles has been developed and is presented. Based on the CO reduction of Au3+, this new process yields the highest quality gold nanoshells synthesized to date. The constraints on precursor lifetime have been relaxed and post-synthesis purification has been eliminated. Nonresonant surface enhanced Raman optical activity (SEROA) has been investigated using biomolecular analytes deposited on Au nanoshell or nanoparticle substrates. The first, and currently the only, near-infrared (780 nm) excited scattered circular polarization Raman optical activity spectrometer (NIROAS) has been constructed. Surface enhanced Raman optical activity spectroscopy has been validated by the collection of symmetrical, surface enhanced, signed circular polarization intensity difference spectra from several test molecules including, (S)- and (R)-tryptophan, and (SS)- and (RR)-phenylalanine-cysteine.Item Ring-locking enables selective anhydrosugar synthesis from carbohydrate pyrolysis(Royal Society of Chemistry, 2016) Chen, Li; Zhao, Jinmo; Pradhan, Sivaram; Brinson, Bruce E.; Scuseria, Gustavo E.; Zhang, Z. Conrad; Wong, Michael S.The selective production of platform chemicals from thermal conversion of biomass-derived carbohydrates is challenging. As precursors to natural products and drug molecules, anhydrosugars are difficult to synthesize from simple carbohydrates in large quantities without side products, due to various competing pathways during pyrolysis. Here we demonstrate that the nonselective chemistry of carbohydrate pyrolysis is substantially improved by alkoxy or phenoxy substitution at the anomeric carbon of glucose prior to thermal treatment. Through this ring-locking step, we found that the selectivity to 1,6-anhydro-β-D-glucopyranose (levoglucosan, LGA) increased from 2% to greater than 90% after fast pyrolysis of the resulting sugar at 600 °C. DFT analysis indicated that LGA formation becomes the dominant reaction pathway when the substituent group inhibits the pyranose ring from opening and fragmenting into non-anhydrosugar products. LGA forms selectively when the activation barrier for ring-opening is significantly increased over that for 1,6-elimination, with both barriers affected by the substituent type and anomeric position. These findings introduce the ring-locking concept to sugar pyrolysis chemistry and suggest a chemical-thermal treatment approach for upgrading simple and complex carbohydrates.Item Teslaphoresis of Carbon Nanotubes(American Chemical Society, 2016) Bornhoeft, Lindsey R.; Castillo, Aida C.; Smalley, Preston R.; Kittrell, Carter; James, Dustin K.; Brinson, Bruce E.; Rybolt, Thomas R.; Johnson, Bruce R.; Cherukuri, Tonya K.; Cherukuri, PaulThis paper introduces Teslaphoresis, the directed motion and self-assembly of matter by a Tesla coil, and studies this electrokinetic phenomenon using single-walled carbon nanotubes (CNTs). Conventional directed self-assembly of matter using electric fields has been restricted to small scale structures, but with Teslaphoresis, we exceed this limitation by using the Tesla coil’s antenna to create a gradient high-voltage force field that projects into free space. CNTs placed within the Teslaphoretic (TEP) field polarize and self-assemble into wires that span from the nanoscale to the macroscale, the longest thus far being 15 cm. We show that the TEP field not only directs the self-assembly of long nanotube wires at remote distances (>30 cm) but can also wirelessly power nanotube-based LED circuits. Furthermore, individualized CNTs self-organize to form long parallel arrays with high fidelity alignment to the TEP field. Thus, Teslaphoresis is effective for directed self-assembly from the bottom-up to the macroscale.