Nano-Liquids, Nano-Particles, Nano-Wetting: X-ray Scattering Studies

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Nano-Liquids, Nano-Particles, Nano-Wetting
X-ray Scattering Studies
P.S. Pershan Physics DEAS, Harvard Univ.
Physics of Confined Liquids with/without
Nanoparticles

• Confinement ?Phase transitions are suppressed
  and/or shifted.
• When do Liquids fill nano-pores? (i.e. wetting
  and capillary filling).
• Contact Angles vary with surface structure. (i.e.
  roughness wetting)
• Attraction/repulsion between surfaces. (i.e.
  dispersions or aggregation)
• Important for formation of Nanoparticle arrays
  (i.e. electronic/optical properties, potential
  use for sensors, catalysis, nanowires)

How will these affect nano-scale liquid
devices? How will these affect processes that are
essential fornano-scale liquid technology?
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Co Workers
Harvard Students and Post Docs K Alvine Graduate
Student PhD March 06, Current NIST D.
Pontoni Post Doc. O. Gang Former Post
Doc. Current Brookhaven National Lab. O.
Shpykro Former Grad. Student Post Doc. Current
Argonne National Lab M. Fukuto Former Grad.
Student Post Doc. Current Brookhaven National
Lab Y. Yano Former Guest. Current Gakushuin
Univ., Japan Others B. Ocko Brookhaven National
Lab. D. Cookson Argonne National Lab. A.
Checco Brookhaven National Lab. F.
Stellacci MIT K. Shin U. Mass. Amherst T.
Russell U. Mass. Amherst C. Black I.B.M.
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Experiments Thin to Thick Liquids
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Control of Liquid Thickness
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Van der Waals 1/3 Power Law
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X-Ray Reflectivity Film Thickness
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Example of 1/3 Power Law
Methyl cyclohexane (MC) on Si at 46 C
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Capillary Filling of Nano-Pores (Alumina)
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Anodized Alumina (UMA)
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SAXS Data
Pore fills with liquid ?Contrast Decreases
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Capillary fillingfilm thickness
Transition Liquid Layer 1nm Pore Diameter15nm
What is the filling process?
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Geometry Theoretical BackgroundC. Rascon and A.
O. Parry, "Geometry-dominated fluid adsorption on
sculpted solid substrates",Nature 407, 986 (2000).
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Parabolic Pits (?2) Tom Russell (UMA)
Diblock Copolymer in Solvent
40 nm Spacing 20 nm Depth/Diameter
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X-ray Grazing Incidence Diffraction (GID)
In-plane surface structure
Liquid Fills Pore Scattering Decreases
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X-ray Measurement of Filling
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Results for Sculpted Surface
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Gold Nanoparticles Controlled Solvation
Liftoff Area Of Monolayer
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Thiol Coated Au Particles
Stellacci et al OT MPA (21)OTCH3(CH2)7SHMP
AHOOC(CH2)2SH
Size Segregation
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GID X-ray vs Liquid Adsorption(small particles)
Return to Dry
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Reversible Self Assembly Annealing
Bimodal/polydisperse Au nanocrystals in
equilibrium with undersaturated vapor
Poor vs Good Solvent
Good Solvent
Aggregation in Poor Solvent
Reversible
Dissolution in Good Solvent
Self Assembly
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NanoParticle SelfAssembly in Nanopores Tubes

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SAXS Experimental Setup

• Brief experiment overview
• Study in-situ SAXS/WAXS of particle self assembly
  as function of added solvent.
• Solvent added/removed in controlled way via
  thermal offset as in flat case.

Small Qx Pore-Pore Distances Large Qx, Qy.Qz
Particle-Particle Distances
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Small Q peaks pore filling hysteresis
lt01gt
lt11gt
lt02gt

• Decrease/Increase in contrast indicates pores
  filling/emptying.

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Summary of Au-Au Scattering(Drying)
Real space model
Images
Slices
Cylind. Shell
Intensity
q radial
Shell Isotropic clusters
Intensity
Heating
q radial
Shell Isotropic solution
Intensity
q radial
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Summary

• Control Thickness ?T??
• X-ray Non-destructive probe
• Capillary Filling pores structures
• Thin Liquid Solvation