coherent light and x-ray scattering studies of the dynamics of colloids in confinement
Post on 14-Jan-2016
34 Views
Preview:
DESCRIPTION
TRANSCRIPT
Coherent light and x-ray scattering studies of the dynamics of colloids in confinement
Jeroen Bongaerts
Thesis defense 16 April 2003, 14.00 hrs
COHERENT LIGHT AND X-RAY SCATTERING STUDIES OF THE DYNAMICS OF COLLOIDS IN CONFINEMENT
University of Amsterdam, Van der Waals-Zeeman InstituteJeroen BongaertsDr. Michel ZwanenburgJ.F. PetersDr. Gerard Wegdam
ETH-Zürich/PSI-SLS, SwitzerlandProf. Dr. Friso van der VeenDr. Thomas LacknerHeilke Keymeulen
• Why study confined fluids?
• How to study them?
• Technical improvements
• Bulk colloidal dynamics
• Confined colloidal dynamics
OUTLINE TALK
WHY STUDY CONFINED FLUIDS?
Examples confined fluids
• Lubricants
• Blood in narrow vessels
• Glue
• Liquids in porous materials
• Emulsions used for cold steel rolling
• Lubricants
• Blood in narrow vessels
• Glue
• Liquids in porous materials
• Emulsions used for cold steel rolling
From: ‘Intermolecular & Surface Forces’ by Jacob Israelachvili
Confined fluid under shear stress
HOW TO STUDY ULTRATHIN CONFINED FLUIDS?
Visible light? No
X rays? Yes
q
q
q
q
ii e
X-ray waveguideX-ray waveguide
i e
visible light : n > 1hard x rays : n < 1 n =1- δ
δ ~10-6
visible light : n > 1hard x rays : n < 1 n =1- δ
δ ~10-6
Silica disk
X-ray waveguideX-ray waveguide
Silica disk
Advantage: large sigal-to-noise ratio
Waveguides modesWaveguides modes
x 10
Typical waveguide dimensions 500 nm x 5 mm
Empty waveguide W = 650 nm
Experiment Calculation
PRL 82 (1999)
Filled x-ray waveguideFilled x-ray waveguide
CONFINED COLLOIDS (STATIC)CONFINED COLLOIDS (STATIC)
Charged colloidal silica spheres
r = 54.9 nm, r = 115 nm
Solvents: water, water/glucerol, ethanol, DMF
Charged colloidal silica spheres
r = 54.9 nm, r = 115 nm
Solvents: water, water/glucerol, ethanol, DMF
Confined complex fluids
• Blood• Colloidal and granular (dry) lubricants
Confined complex fluids
• Blood• Colloidal and granular (dry) lubricants
W = 655 nm W = 310 nm
Layering of confined colloids (r = 54.9 nm)
PRL 85 (2000)
TECHNICAL IMPROVEMENTS
1. Smaller x-ray waveguide gap widths
2. Coherent flux enhancement within the guiding layer
Multi-step-index waveguide geometryMulti-step-index waveguide geometry
Minimum gap: 20 nm (was ca 250 nm)Minimum gap: 20 nm (was ca 250 nm)
Enhancing the fluxEnhancing the flux
TE
Stand ing w ave
i
FZP lens2
Waveguide entrance
DYNAMIC LIGHT SCATTERING (BULK)
Dynamic light scatteringDynamic light scattering
The dynamic structure factorThe dynamic structure factor
SpeckleSpeckle
Courtesy of J.F. Peters, UvA
Short-time and long-time dynamics (BULK)Short-time and long-time dynamics (BULK)
Dilute bulk suspensionDilute bulk suspensionDense bulk suspensionDense bulk suspension
Caging of colloidal particlesCaging of colloidal particles
DYNAMIC X-RAY SCATTERING STUDIES OFCONFINED COLLOIDS
Confinement-induced friction?Confinement-induced friction?
Waveguide dynamic x-ray scatteringWaveguide dynamic x-ray scattering
Silica spheres r =115 nm dissolved in water/Glycerol.Volume fraction 7% (‘dilute’).Negligible particle-particle interaction
Silica spheres r =115 nm dissolved in water/Glycerol.Volume fraction 7% (‘dilute’).Negligible particle-particle interaction
Top viewTop view
Side viewSide view
Short-time confined dynamicsShort-time confined dynamics
Silica spheres r =115 nmIn water /Glycerol
W3 = 1.2 micronW4 = 0.8 micron
Long-time confinement-induced slowing-down of dynamics
Long-time confinement-induced slowing-down of dynamics
Silica spheres r =115 nmIn water /Glycerol
Long-time sub-diffusive behaviorLong-time sub-diffusive behavior
Silica spheres r =115 nmIn water /Glycerol
Inhomogeneous particle-wall interactionsInhomogeneous particle-wall interactions
Investigate inhomogeneous particle-wall interactions
Investigate inhomogeneous particle-wall interactions
OutlookOutlook
• Smaller waveguide gaps (10 nm)
Confined fluids Confined fluids
TE
Stand ing w ave
i
FZP lens2
Waveguide entrance
• Prefocused x-ray beam (higher flux) J. Synchrotron Rad.
9, 383---393 (2002) • Study particle-wall interactions
• Surface force measurements combined with static and dynamic x-ray scattering
SummarySummary
• Confined fluids studied by use of an x-ray waveguide
• Waveguide technique works
• Dynamic x-ray scattering in waveguide geometry
• Confinement affects short and long-time diffusion.
COHERENT LIGHT AND X-RAY SCATTERING STUDIES OF THE DYNAMICS OF COLLOIDS IN CONFINEMENT
University of Amsterdam, Van der Waals-Zeeman InstituteJeroen BongaertsDr. Michel ZwanenburgJ.F. PetersDr. Gerard Wegdam
ETH-Zürich/PSI-SLS, SwitzerlandProf. Dr. Friso van der VeenDr. Thomas LacknerHeilke Keymeulen
top related