Coherent light and x-ray scattering studies of the dynamics of colloids in confinement Jeroen...

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

qq

q

qq

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