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

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

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

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  1. Nano-Liquids, Nano-Particles, Nano-Wetting: X-ray Scattering Studies 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?

  2. •Particle rotation by optical traps Pump •3m Silica in 6m Channel Nano Particle Structures Sawitowski, T., Y. Miquel, et al. (2001). "Optical properties of quasi one-dimensional chains of gold nanoparticles." Advanced Functional Materials 11(6): 435-440. A. Terray, J. Oakey, and D. W. M. Marr, Science 296, 1841 (2002). Applications of Nano-Liquids/Nano-Particles

  3. Co Workers Harvard Students and Post Docs K Alvine Graduate Student PhD Expected Jan/Feb 06 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.

  4. Contact Angle Ellipsometry Quartz Microbalance Macroscopic Non-Linear Optics •Length Scale: m •Interpretation: Theory Absorption Liquid SurfacesTraditional Tools and/or Techniques AFM Imaging 

  5. A DA nnR n nR = 270 kHz Q=500 Aset<10nm Noncontact AFM imaging of liquidsA. Checco, O. Gang and B. Ocko (Brookhaven National Laboratory) sine-wave generator AFM piezo-scanner A lock-in f Deflection sensor dither piezo A Adsorbed Liquid van der Waals forces Chemical Pattern Powerful: surface topology

  6. DT>>0 DT~0 DT<0 AFM Visualization of Condensation of ethanol onto COOH nanostripes 1 2 3 COOH AFM topography across the stripes 3 2 1 Limited by size of probes.

  7. Macroscopic Meniscus Macroscopic Liquid/Solid: Contact Angle  Wetting Non-wetting Nano Thin Films Vapor Pressure Thickness P Van der Waals Wetting & Nano Thin Films

  8. Control of  Outer cell: 0.03C Inner cell: 0.001C Wetting film on Si(100) at T = Trsv+DTm. z Saturated vapor Bulk liquid reservoir: atT = Trsv. • Chemical potentialDmwas controlled by offset DTm between substrate and liquid reservoir. • Dominant contribution to Dmis from latent heats of pure materials: Dm [n(s°v – s°l)] DTm.

  9. z r Reflectivity Density Profile z log R r el q z log R el q q z c System I: Structure normal to the surface : X-Ray Reflectivity

  10. Comparisons • Via gravity • For h < 100 mm, • Dm < 10-5J/cm3 • L > ~500 Å •  small Dm, large L • Via pressure under-saturation • For DP/Psat > 1%, • Dm > 0.2 J/cm3 • L < 20 Å •  large Dm, small L Example of 1/3 Power Law Methyl cyclohexane (MC) on Si at 46 °C • Via temperature offset L (2Weff /Dm)1/3 (DTm)-1/3 Thickness L [Å] DTm [K] Dm [J/cm3]

  11. Capillary Filling: or T Transition Surface  Min: DR0 Volume  Min: D0 System II: Capillary Filling of Nano-Pores (Alumina) Energy Cost of Liquid

  12. Anodized Alumina (UMA) Top Fig. 1: AFM image (courtesy UMA) of anodized alumina sample. The ~15nm pores are arranged in a hcp array with inter-pore distance ~66nm Fig 2: SEM (courtesy of UMA) showing hcp ordering of pores and cross-section showing large aspect ratio and very parallel pores. ~90 microns thick ~ 15nm Side

  13. <10> Short Range Hexagonal Packing <11> <20> ∆T decreasing Thin films Condensation SAXS Data Pore fills with liquid Contrast Decreases

  14. Wall film thickness [nm] ~ 2/D Capillary filling—film thickness Transition

  15. ∞ Adsorbed Liquid Long Channels Variety of Shapes ( Adsorpton vs Shape: Phase Diagram 1/ System III: Sculpted Surfaces Theory:Rascon & Parry, Nature (2000) Crossover Geometry to Planar Planar Geometry Dominated

  16. Self Alignment on Si PMMA removal by UV degradation & Chemical Rinse Reactive Ion Etching C. Black (IBM) Parabolic Pits: Tom Russell (UMA) Diblock Copolymer in Solvent ~40 nm Spacing ~20 nm Depth/Diameter

  17. Diffraction Pattern of Dry PitsHexagonal Packing Cross over to other filling! Thickness D~ X-ray Grazing Incidence Diffraction (GID)]In-plane surface structure Liquid Fills Pore: Scattering Decreases:

  18. Filling GID Reflectivity Electron Density vs T Filling X-ray Measurement of Filling

  19. R-P Predictionc~3.4 Sculpted Crossover to Flat Results for Sculpted Surface Sculpted is Thinner than Flat Flat Sample c Observed c

  20. Conventional Approach:Dry Bulk Solution  Imaging of Dry Sample Controlled Wetting:Dry Monolayer  Adsorption Formation LangmuirIsotherms Gold Nanoparticles & Controlled Solvation Liftoff Area Of Monolayer

  21. TEMbi-modal distribution Stellacci et al OT: MPA (2:1)OT=CH3(CH2)7SHMPA=HOOC(CH2)2SH Au Particles: Coating Size Segregation

  22. Adsorption GID Qz Qxy Qxy Qxy GID: X-ray vs Liquid Adsorption(small particles) Return to Dry

  23. Three FeaturesThat Can Be Understood! 1-Minimum at low qz 2-Principal Peak Reduces and Shifts Solid lines are just guides for the eye! 3-2nd Minima Moves to Lower qz Temperature Dependence of Reflectivity:

  24. Construction of Model: Dry Sample Model Fit: Based on Particle Size Distribution Vertical electron density profile Core size distribution

  25. 3-Second Minima Moves to Lower qz 2-Principal Peak Reduces and Shifts 1-Minimum at low qz Fits of Physical Model

  26. Thick wetting film regime Beginning of bilayer transition Thin wetting film regime Evolution of Model with Adsorption

  27. Summary of Nano-particle experiments 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

  28. Empty SEM of empty pores, diameter~30nm 50 nm Fill with Particles ~2nm dia. Filled TEM of nanoparticles in pores. NanoParticle Assembly in Nanopores: Tubes

  29. Scattered x-rays Alumina membrane With nano-particles Incident x-ray's Top T Toluene 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

  30. With nanoparticles Heating/Cooling, w/ nanoparticles Hex. Packing Note: Shift in Capillary Condensation Below: w/o nanoparticles • Capillary transition shifts from ~2K for pores w/o nanoparticlesto about ~8K w/ nanoparticles • Strong hysteresis T~ /R Small Q peaks pore filling hysteresis <01> <11> <02> • Decrease/Increase in contrast indicates pores filling/emptying.

  31. Images Thin film Slices Intensity 1 q radial (spherical coord.) Intensity 2 q radial 3 Intensity Filled pore q radial Larger Q Data / WAXS (Particle-Particle Scattering)

  32. Modeling WAXS with Shell/Tile Model  2) Powder average over all tiles of a given orientation. • Break shell up into ~flat tiles no correlation between tiles. • Scattering from 2) is same from flat monolayer • S(q) is 2D lorentzian ring • F(q) is form factor for distribution of polydisperse spheres (Shulz) • 4) Add up scattering from all tile orientations 

  33. Fitted Data High T • Shell model fits for thin films: • fit slices simultaneously with 3 global parameters plus backgnd. • Nanoparticle radius, polydispersivity from bulk meas. • Fits in good agreement with data.

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

  35. Summary nanoparticle self-assembly • Strong dependence upon solvent: • Subtle confinement effect for aggregation in “poor” solvent • Most systems reversible upon adding/removing solvent • Able to probe different geometries: • Flat  sheets • Pores  tubes • Some similarity, interesting differences • Thermal offset method gives us precise control of self-assembly process while doing in-situ measurements.

  36. 47.7 °C MC rich PFMC rich Temperature [C] 46.2 °C 45.6 °C x (PFMC mole fraction) Critical Casimir Effect in Nano-Thick LiquidsBinary Liquid Methylcyclohexane (MC) Perfluoro- methylcyclohexane (PFMC) [Heady & Cahn, J. Chem. Phys. 58, 896 (1973)] Tc = 46.13  0.01 °C, xc = 0.361  0.002

  37. Experimental Paths T=(T-Tc)/Tc wetting film on Si(100) T = Trsv+DTm. Liquid Phase Vapor Phase Outer cell: 0.03C Inner cell: 0.001C Film-TRes 2 Phase Coexistence Bulk MC + PFMC reservoir: (x ~ xc = 0.36) atT = Trsv. Thermodynamic Casimir effect in critical fluid filmsFisher & de Gennes (1978): Confinement of critical fluctuations in a fluid produces “force” between bounding interfaces Same Experiment: Thickness of Absorbed Film Critical Point

  38. x = 0.36 ~ xc R/RF DTm 0.020 K Tc = 46.2 °C Film thickness L [Å] qz [Å-1] 0.10 K 0.50 K Tfilm [°C] X-ray reflectivity  Film thickness L Paths

  39. d = 2 Ising (exact) [R. Evans & J. Stecki, PRB 1994] d = 4 Ising (mean field) [M. Krech, PRE 1997] Excess free energy/area of a wetting film:  Casimir term “Force” or “pressure” balance: (+,-) (+,-) +,(y) / +,-(0) +,(y) (+, +) (+, +) y = (L/x+)1/n = t (L/x0+)1/n y = (L/x+)1/n = t (L/x0+)1/n Theory

  40. d = 4 (MFT) Q+,-(y) Q+,-(0) DTm 0.020 K 0.10 K d = 2 (exact) y = (L/x+)1/n = t (L/x0+)1/n Experiment vs Theory There is prediction for for 3D. Theory for d=3 does not exist!

  41. Universal “Casimir amplitudes” • At bulk Tc (t = 0), scaling functions reduce to: D q(0) = Q(0)/(d – 1) For recent experiments with superfluid He (XY systems), see: R. Garcia & M.H.W. Chan, PRL 1999, 2002; T. Ueno et al., PRL 2003

  42. Summary Delicate Control of Thickness of Thin Liquid Layers (~T) • Flat Surfaces: van der Waals1/3 power law • Porous Alumina: Capillary filling • Sculpted Surfaces: Cross over behavior • Nano Particles: Flat Surface Self Assembly & Solvent Effects. Size Segregation. • Nano Particles: Porous Alumina- Reversible self assembly, dissolution within the pore. Capillary filling changed be presence of the particles • Casimir Effect. Future • Monodisperse Particle • Vary force/solvent effects (Casimir effects) • Variation in Self Assembly • Test Casimir effect for symmetric bc.

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