introduction to dynamic light scattering dls l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Introduction to DYNAMIC LIGHT SCATTERING (DLS) PowerPoint Presentation
Download Presentation
Introduction to DYNAMIC LIGHT SCATTERING (DLS)

Loading in 2 Seconds...

play fullscreen
1 / 31

Introduction to DYNAMIC LIGHT SCATTERING (DLS) - PowerPoint PPT Presentation


  • 406 Views
  • Uploaded on

Introduction to DYNAMIC LIGHT SCATTERING (DLS). or PHOTON CORRELATION SPECTROSCOPY (PCS). Christer Svanberg. Outline. Basic of DLS Experimental set-up Accessible time- and length-scales Applications Size and shape of sub-micron objects Research Glass transition Polymer dynamics.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Introduction to DYNAMIC LIGHT SCATTERING (DLS)' - libitha


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
introduction to dynamic light scattering dls
Introduction toDYNAMIC LIGHT SCATTERING (DLS)

or

PHOTON CORRELATION SPECTROSCOPY

(PCS)

Christer Svanberg

outline
Outline

Basic of DLS

  • Experimental set-up
  • Accessible time- and length-scales

Applications

  • Size and shape of sub-micron objects

Research

  • Glass transition
  • Polymer dynamics
scattered electric field
Scattered Electric Field
  • DLS probes
    • density fluctuations
    • concentration fluctuations
slide5

Time range of DLS

DLS

QENS

NMR

Raman

Brillouin

Dielectric

-14

-10

-6

-2

2

LOG(TIME (s))

DLS covers a very large time range!

Typically: 10-7 - 103 s! => 10 decades in time!

slide6

Experimentally accessible wave vectors

Q-range: typically 0.6 – 2×10-3 Å-1

DLS is therefore suitable for diffusional studies of macromolecules, such as polymers and large biomolecules!

advantages and disadvantages
Wide time range

Cheap

Simple experimental set-up

Advantages and Disadvantages
  • Only transparent samples
  • Very clean samples needed
  • Sensitive for mechanical disturbances

+ -

scientific instruments
Scientific instruments
  • More laser power!
  • Specially designed cryo-furnaces
  • Polarization options
  • Vibration isolation table
brownian motion
Brownian Motion
  • First observed in 1827 by the botanist Robert Brown. He was looking at pollen grains under a microscope. The force of life?
  • Desaulx in 1877: "In my way of thinking the phenomenon is a result of thermal molecular motion in the liquid environment (of the particles).”
  • The mathematical theory of Brownian motion was developed by Einstein in 1905.
  • Jean-Baptiste Perrin verified Einstein's analysis (Nobel Prize 1926).
brownian motion12

Stoke-Einstein relation:

Brownian Motion

Explanation:

A suspended particle is constantly and randomly bombarded from all sides by molecules of the liquid. If the particle is very small, the number of hits it takes from one side at a given time will be stronger than the bumps from other side. This make the particle jump. These small random jumps are what make up Brownian motion.

applications of dls
Applications of DLS

Size:

Using Stoke-Einstein equation DLS can be used to easy, fast and accurate determination of the hydrodynamic radius of particles.

Typically range: 1 nm – 1μm.

Shape:

Ellipsodial particles results in a small fraction depolarized scattered light. Can be used for estimation of ellipticity of the particles. Difficult!

examples
Examples

Some examples of sub-micron systems:

  • Micro-emulsions
  • peptides
  • micelles
  • macromolecules
  • polymers
  • paint pigments
  • bacteria, viruses
estimation of ellipsodial objects

Calculated ellipitic shape

Lysozome

Hydrodynamic size

Calculated hard sphere

Estimation of Ellipsodial objects
size distribution of insulin
Size Distribution of Insulin

Intensity

Diameter (nm)

the influence of ph on insulin
The influence of pH on Insulin

Amplitude

Diameter (nm)

research using dls
Research using DLS
  • Determination of size on complex systems:
    • “water-in-oil”
    • bio-molecules
    • cellulose
  • Glass transition dynamics
  • Polymer dynamics
glass transition dynamics

1.0

0.8

0.6

correlation

0.4

t

0.2

0.0

-2

-1

0

1

2

log[t/t (s)]

Glass transition dynamics

log 

glass

liquid

-relaxation

  • cooperative intermolecular motion
  • stretched exponential decay
  • non-Arrhenius temp. dep.
  • freezes at Tg

-relaxation

  • local motion
  • broad response
  • Arrhenius temp. dep.

fast

1/T

1/Tg

poly propylene glycol

1

0,8

0,6

192 K

0,4

Temp.

0,2

221 K

0

-6

-4

-2

0

2

4

10

10

10

10

10

10

Time (s)

Poly(propylene glycol)
arrhenius plot

Arrhenius Plot

4

Polymer

Dimer

(n=69)

(n=2)

0

Oligomer

(n=7)

Monomer

-4

log[ Relaxation time (s)]

(n=1)

-8

-12

2

2.5

3

3.5

4

4.5

5

5.5

6

1000/T (1/K)

Arrhenius Plot

Conclusion:

Shorter polymer chains relax

faster than long chains.

glass transition dynamics in free standing polymer films

200 - 500 Å

Glass Transition dynamics in Free-standing Polymer Films

Polystyrene

Tg=369 K

DLS can be used to probe the dynamics of thin free-standing polymer films

glass to glass transitions
Glass-to-glass transitions

copolymer micellar system

SCIENCE 300, 619 (2003)

multiple glassy states in a simple model system
Multiple Glassy States in a Simple Model System

Sterically stabilized PMMA-particles in cis-decalin.

SCIENCE 296 104 ( 2002)

polymer dynamics

Dilute solutions

Semi-dilute solutions

f*

2xh

Entangled dynamics

2Rg

Brownian motion

Polymer Dynamics
polymer gel electrolytes
Polymer Gel Electrolytes

Poly(methyl methacrylate)

+

Propylene Carbonate / Ethylene Carbonate

+

Lithium Perchlorate (LiClO4)

relaxations and conductivity in polymer gel electrolytes
Relaxations and Conductivity in Polymer Gel Electrolytes

Nernst-Einstein equation

…there is a close connection between the fast diffusive process and the ionic conductivity!

outlook x ray pcs
Outlook: X-ray PCS

Exemplary correlation functions of colloidal silica suspension measured at q ~ 7.6 × 10-4 Å-1 using three different X-ray energies as indicated.

summary dls technique
Summary: DLS technique

Probes density and/or concentration fluctuations.

Time scales: ~10-6 - 103 s

Wave vectors: ~10-3 Å-1

Standard characterisation techniques for particles

  • Determination of size 1 nm - 1 mm
  • Estimation of ellipticity and/or swelling

Research

  • Polymer dynamics
  • Glass transition dynamics