Nanopatterns – understanding emergence of properties at scale
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Nanopatterns – understanding emergence of properties at scale



novel pedogogy for understanding the emergence of properties at the nanoscale

novel pedogogy for understanding the emergence of properties at the nanoscale



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  • Abstract or Introduction In this dissertation, synthesis, structural and magnetic properties of nickel (Ni) nanoparticles (NPs) embedded in amorphous silica matrix are described in detail. These Ni NPs were prepared using the sol-gel technique. The percent composition of x-Ni/SiO2 was varied from 1, 5 and 15%. Further, the samples were annealed in a furnace at temperatures between 400° to 800°C for the duration of 2 hours in a continuous flow of ultra high pure (UHP) nitrogen in order to obtain different particle sizes ranging from 3.8 to 23 nm for the 15% Ni/SiO 2 composition. Structural characterization of the Ni NPs was done using transmission emission microscopy (TEM) and x-ray diffraction (XRD). Average particle sizes were obtained from the TEM micrographs by fitting them to log-normal distribution giving 3.8, 11.7, 15, 21 and 23 nm. The particle sizes were compared to those calculated from XRD patterns using the Debye-Scherrer equation Magnetic properties of these Ni NPs was studied using the superconducting quantum interference device (SQUID). The variations of the blocking temperature (TB) with measuring frequency (fm) and applied field (H) are reported for Ni NPs with the nominal composition Ni/SiO2 (15/85). Measurements from the variation in magnetization (M) vs. temperature (T) (2 to 350 K) in H enabled us to determine the TB from the peaks in the zero field cooled curves. Measurements from M vs. H data above T B was fit to the modified Langevin function to obtain the magnetic moment per particle (muP). The large value of the moment of the order of (103 muB) characterized these particles as superparamagnetic above TB. Hysteresis measurements on cooling the sample in H were also done as a check for the presence of anti-ferromagnetic/ferromagnetic layer leading to exchange bias. Temperature dependence of AC susceptibility measurements were done for frequencies varying from 0.1 to 997 Hz. The blocking temperatures TB, as determined by peaks in chi'' vs. T data, were fit to the Vogel-Fulcher law to determine the energy barrier and strength of the interparticle interaction The temperature dependence (5 to 300 K) of the electron magnetic resonance (EMR) lines observed at 9.28 GHz in 15% Ni/SiO2 nanocomposites with different particle sizes are also reported. In EMR, three resonance lines are observed: (i) Line 1 with linewidth DeltaH≃50 Oe and g≃2, and Curie-like variation of the line-intensity, with DeltaH and g being temperature and size-independent; (ii) Line 2 with DeltaH≃50 Oe and g≃2.3 for D=3.8 nm at 294 K with both DeltaH and g increasing with decreasing T and DeltaH size-dependent; and (iii) weak line 3 with g∼4 at 300 K, with g also increasing with decreasing T. We argue that the line 1 is due to dangling bonds in SiO2 as a similar line with DeltaH≃9 Oe is also observed in SiO2 without Ni doping. Lines 2 and 3 are attributed to majority Ni NPs and large Ni clusters respectively whose anisotropy is both size and temperature dependent, leading to the observed DeltaH and g values of the lines

Nanopatterns – understanding emergence of properties at scale Nanopatterns – understanding emergence of properties at scale Presentation Transcript

  • Nanopatterns – Understanding Emergence of Properties at Scale Robert D. Cormia & Jill N. Johnsen Foothill College
  • Overview
    • Nanoscience => the big ideas
    • Emergence => the missing idea
    • Nanopatterns => a new rubric
    • Examples => nanopatterns in use
    • Future directions and practice
  • Nanoscience – Big Ideas
    • 2006 workshops
    • NCLT and SRI
    • University of Michigan and Northwestern University
    • Eight big ideas
    • A textbook guide
  • The Big Ideas
    • Size and scale
    • Matter
    • Dominant Forces
    • Properties are size dependent
    • Models
    • Tools
    • Technology and society
    • Self assembly
    The Big Ideas in Nanoscale Science and Engineering Stevens, Sutherland, Schank, & Krajcik, (2007). Collaboration of NCLT, Northwestern University and SRI, in a series of workshops, (culminating in August 2006 in San Luis Obispo)
  • The Missing Idea
    • Emergence of properties at scale
    • We talk about it all the time
    • But no one ever explains it
    • Because……
    Emergence is a very difficult topic to talk about!
  • Emergence Model Archetype Properties Process System Process evolution Archetype Behaviors System process System Archetype System Constituents Actor Interactions Class properties Archetype process System Properties System behaviors Primitive interactions Emergent Properties
  • Size Dependent Properties “ Molecular Dynamics (MD) simulations of heat transfer based on classical statistical mechanics allow the atom to have thermal heat capacity through kT energy. Here k is Boltzmann’s constant and T absolute temperature. The above picture shows melting temperatures applied on the left with the right maintained at freezing. The simulation is discreted and submicron. But lacking periodicity, MD solutions of discrete nanostructures are invalid by QM. Here QM stands for quantum mechanics. Unlike statistical mechanics, QM forbids atoms in discrete submicron nanostructures to have heat capacity, and therefore the nanostructure cannot conserve EM energy by an increase in temperature. Without temperature changes, thermal conduction is precluded at the nanoscale.” Melting point is an emergent property Validity of Heat Transfer by Molecular Dynamics -
  • Size Dependent Properties: Ni nanoparticles => Nanomagnetism
  • Phonon Network Images Wikipedia commons
  • Nanopatterns
    • Network archetypes
    • Memorizing patterns , vs. structures
    • Patterns of atoms in structural networks
    • Atoms as nodes , each with atomic orbitals => focus on bonding networks
    • Network archetypes => nanosystems
      • Smaller motifs, that expand into systems
  • Nanopatterns Rubric
    • Networks of atoms
    • Systems of physics
    • Emergence of properties at scale
    • Draw network of atoms for a structural system
    • Sketch out the chemical bonding / orbital network
    • Look at the extended structure as a system
  • Graphene Nanostructure Extended sp 2 hybridized carbon and p-p* network
  • Graphene as a System
  • Nanostructures and Nanosystems from carbon nano-motifs nanostructure Nano-motif (or structural unit) Nanopattern Nanosystem Graphene/graphite sp 2 moiety bracket graphene hexagon Extended plane Fullerene sp 2 moiety cap hexagon/pentagon Enclosed sphere Nanotube sp 2 moiety mesh zigzag/armchair mesh Enclosed tube Nanoonion sp 2 moiety (ring?) zigzag/armchair swirl? Nanospheres? Boron nitride nanomesh Trigonal BN BN hexagonal ring Planar honeycomb Self Assembled Monolayers alkane (head and tail) 1-2 dimensional SAM 2 dimensional sheet Liposomes phospholipid unit Phospholipid bilayer Spherical bilayers Dendrimers g-0 functional branch Fractal branch (G-x) Spherical/functionalized macro-molecule
  • Allotropes of carbon
    • A - diamond
    • B - graphite
    • C - lonsdaleite
    • D - C 60  Buckminsterfullerene
    • E - Amorphous carbon
    • F - C 70
    • G - C 540
    • H - single-walled carbon nanotube
  • Nano-Onion
    • Nano onion is a proposed structure for graphene which wraps itself into larger spheres and then into chains. The mechanism for forming the spheres is not known, but might be influenced by the chirality of the nanocarbon network, i.e., the armchair/zigzag m/n ratio. This factor can be measured in Raman G band (as G- and G+), and additionally in solid state 13C NMR. Nano-onion is an example of an extended nanostructure becoming a nanosystem, and having levels of unfolding complexity at scales of tens, hundreds, and thousands of Angstroms. The ability to ‘tune’ the chirality of the graphene networks, and alter the unfolding structure at the mesoscale, is one of the goals of combining the nanopatterns rubric with PNPA.
  • Borazine Nanomesh
    • Borazine decomposition
    • Forms ordered surface network
    • One layer thick (like graphene)
    • Extended structure
    • Emergent properties
  • Borazine Nanomesh
  • Networks of atoms in novel nanoscale structures
    • “ Dancing Triangles' are formed by sulfur atoms on a layer of copper, which in turn rests upon a base, or 'substrate' of ruthenium. Scientists at Brookhaven Lab will study this type of configuration to understand how metal behaves on top of another. Layered metals are often used as catalysts, such as those that clean pollutants from automobile exhaust in catalytic converters.”
    Flickr Brookhaven Laboratory Stream /
  • Nanostructures
    • Small networks of atoms
      • Liposomes
      • Dendrimers
      • Carbon nanotubes
      • Self Assembled Monolayers
      • Unit cells of extended nanostructured materials
        • Graphene
        • Nanomesh
  • Each phospholipid is a structural motif, a structure in itself, and a building block in a larger system A system of phospholipids that is an emergent structure itself. Liposomes and cellular vessicles
  • Nanosystems
  • Summary / References
    • Nanopatterns rubric
      • Networks of atoms
      • Systems of physics
      • Emergence of properties at scale
    • Nanostructures => nanosystems
    • The Big Ideas in Nanoscale Science and Engineering Stevens, S. Y., Sutherland, L., Schank, P., & Krajcik, J. (2007).