Nanopatterns – understanding emergence of properties at scale
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novel pedogogy for understanding the emergence of properties at the nanoscale
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Nanopatterns – understanding emergence of properties at scale
- 1. Nanopatterns – Understanding Emergence of Properties at Scale Robert D. Cormia & Jill N. Johnsen Foothill College
- 6. 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
- 7. 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 - http://www.nanoqed.org/
- 9. Phonon Network http://en.wikipedia.org/wiki/Phonon Images Wikipedia commons
- 12. Graphene Nanostructure Extended sp 2 hybridized carbon and p-p* network
- 13. Graphene as a System
- 14. 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
- 22. 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 http://en.wikipedia.org/wiki/Exosome_(vesicle) http://en.wikipedia.org/wiki/Phospholipid
- 23. Nanosystems
Editor's Notes
- http://www.grin.com/en/doc/231229/size-dependent-magnetic-properties-of-nickel-nanoparticles-embedded-in 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