Events: NanoSEC Seminars

• Overview of biorefinery technologies---biomass production and conversion to value added products, KC Das, Jim Kastner, Sudhagar Mani

  Friday, February 12, 2010 1:30 pm - 2:30 pm
  Location: Auditorium, Riverbend Research Laboratory South

  iCal

  Professors KC Das, Jim Kastner, and Sudhagar Mani of the Department of Biological and Agricultural Engineering will be presenting their talk entitled "Overview of biorefinery technologies---biomass production and conversion to value added products," this week.

  Seminar will cover selected existing and up coming technologies for converting biomass to fuels and chemicals. Focus will be on Biorefinery and Carbon Cycling Program activities in biomass production, pre-treatment, conversion and utilization, with the intent to identify opportunities for application of nano-science and engineering capabilities.

• Phase Distribution of Solubilized Multiwall Carbon Nanotubes in Aqueous Systems Containing Solid Organic Matter, Qingguo (Jack) Huang

  Friday, February 5, 2010 3:00 pm - 4:00 pm
  Location: Auditorium, Riverbend Research Laboratory South

  iCal

  Dr. Jack Huang of the University of Georgia Department of Crop and Soil Sciences, Griffin Campus, will be presenting his talk entitled "Phase Distribution of Solubilized Multiwall Carbon Nanotubes in Aqueous Systems Containing Solid Organic Matter" this week.

  We are conducting research to investigate the environmental and ecological behavior of water-dispersed carbon nanotubes, including water-sediment phase distribution, possible degradation and food chain transport, thereby providing useful information for environmental risk assessment and potential waste treatment. To unambiguously identify and quantify carbon nanotubes from various natural materials including water, sediments and organisms, we use C14-labeled carbon nanotubes in our study. Previous studies indicate carbon nanotube uptake by organisms from soil/sediment media and from aqueous phase exhibited different behaviors. Thus, information on phase distribution between different environmental compartments is essential to risk assessment. We conducted experiments to examine phase distribution of C14 labeled multiwall carbon nanotubes (MWCNTs) in aqueous systems containing peat as a model organic solid phase under a series of varying pH and ionic strength conditions. Our results suggest that the solid phase distribution of water-dispersed MWCNTs tends to be governed by three interactive processes: i) dissolved cations tend to promote CNT aggregation via double layer compression; ii) dissolved organic matter released from the solid phase tends to stabilize CNTs dispersion via steric hindrance; and iii) CNTs sorb onto the solid phase. All processes are variously influenced by aqueous conditions (e.g. pH, electrolytes, dissolved organic matter) and their interplay governs the phase distribution of MWCNTs. We also characterized MWCNT length distribution by SEM before and after phase distribution. The results suggest that the shorter nanotubes (<300 nm) tend to be more readily removable from aqueous phase, likely because their higher specific surface areas promote aggregation and sorptive interactions on solid phase.

• Advanced Nanofabrication by Dynamic Shadowing Growth, Yiping Zhao

  Friday, January 22, 2010 3:00 pm - 4:00 pm
  Location: Auditorium, Riverbend Research Laboratory South

  iCal

  Dr. Yiping Zhao of the University of Georgia Department of Physics and Astronomy will be presenting his talk entitled "Advanced Nanofabrication by Dynamic Shadowing Growth" this week.

  Dynamic shadowing growth (DSG) or Glancing Angle Deposition (GLAD) is a simple nanofabrication technique that combines oblique angle deposition (OAD) with substrate manipulations and source controls in a physical vapor deposition system. The geometry shadowing effect is the dominant growth mechanism resulting in the formation of various nanostructure arrays by programming the substrate rotation in polar and/or azimuthal direction. With recent advance in a multilayer deposition procedure, one can design complex and multifunctional heterogeneous nanostructures. In addition, with a codeposition system of two or more sources, novel nanocomposites or doped nanostructure arrays can be produced, which results in nanostructures with different morphology. In this talk, I will give a general overview on the art of designing different nanostructures by DSG, and highlight our recent progress in multi-component nanorod array fabrication. Those multicomponent nanorods can be used as a high sensitive virus and bacteria sensor base on florescence enhancement, and novel energy related applications, especially for designing new photocatalytic materials for hydrogen generation.

• Electrochemical Atomic Layer Deposition (ALD), John Stickney

  Friday, January 15, 2010 3:00 pm - 4:00 pm
  Location: Auditorium, Riverbend Research Laboratory South

  iCal

  Dr. John Stickney of the University of Georgia Department of Chemistry will presenting his talk "Electrochemical Atomic Layer Deposition (ALD)" this week.

  Recent results in studies of the formation of compound and metal nanofilms by electrochemical atomic layer deposition (ALD) will be discussed. ALD is the deposition of materials an atomic layer at a time using surface limited reactions. Electrochemical surface limited reactions are generally referred to as underpotential deposition or UPD. By combining UPD and ALD, electrochemical ALD is created. Historically most electrochemical ALD has been performed in the creation of compound semiconductor thin films. More recently a number of elemental deposits have been formed by electrochemical ALD, and a surface limited reaction referred to here as a surface limited redox replacement or SLRR. Recent work on the formation of compound for photovoltaics, thermoelectrics, and for phase change memory may be discussed. In addition, recent work on the growth of Pt and Ru nanofilms for fuel cell electrodes may be described. Deposit characterization involves electron beam microprobe analysis (EPMA) for deposit stoichiometry. Glancing angle X-ray diffraction for structural characterization, while scanning tunneling microscopy (STM) was used to characterize the surface morphology. Optical characterization involves reflection absorption studies as well as photoelectrochemical studies. Optimization studies involve systematic investigation of the conditions which result in the formation of one compound or elemental monolayer with each deposition cycle. In general, deposits formed at a rate of one monolayer per cycle or less show the best structure, stoichiometry and morphology. Nano templates can be used to form nanoclusters, rods or wires, depending on the number of cycles performed. Superlattices can be formed by alternating some finite number of cycles for the growth of one compound with a similar number of cycles of another. X-ray diffraction can then be used to characterize the period of the superlattice.

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