http://en.wikipedia.org/wiki/Dynamic_light_scattering
Dynamic
light scattering (also known as Photon Correlation Spectroscopy or
Quasi-Elastic Light Scattering) is a technique, which is used
to study solutions of macromolecules.
For instancE, it can be used to determine the size distribution
profile of small particles in suspension or polymers in solution. It
can also be used to probe the behavior of complex fluids such as
concentrated polymer solutions.
In the experiment the
intensity autocorrelation function
g(q,t) = <I(q,t0) I(q,t0 +t)>/<I(q,t0)2>
is determined.
Simplest approach to obtain hydrodynamic radius from the data: The correlation function is assumed to have a shape of single exponential decay
g(q,t) = exp(-Gt),
where t is decay rate.
Here G is related to the diffusion coefficient D as
G = q2 D.
The length of the
scattering vector may be written as
q = 4π/λ sin(θ) no,
where no is the refractive index of the
sample.
The diffusion coefficient D is used to
determine the hudrodynamic radius by means of Stokes equation
assuming that the particles in the solution are spherical.
http://en.wikipedia.org/wiki/Static_light_scattering
For static light scattering experiments, monochromatic laser light is launched in a solution containing the macromolecules. One or many detectors are used to measure the scattering intensity at one or many angles.
Static light scattering is used e.g. to determine the weight average molecular weight Mw of a macromolecule like a polymer or a protein from intensity I(0).
Measurement of the scattering intensity at many angles allows e.g. calculation of the radius of gyration Rg for a dilute solution of macromolecules. Data is analysed like in small angle x-ray scattering.
In order to measure the average molecular weight directly, without calibration, from the light scattering intensity, the laser intensity, the quantum efficiency of the detector and the full scattering volume and solid angle of the detector needs to be know. Another method is to use a calibration sample (a strong, known scatterer like toluene).
Static light-scattering (SLS) and dynamic light-scattering (DLS) measurements
Brookhaven Instruments BI-200SM goniometer and a BI-9000AT digital correlator.
A helium/neon laser (Spectra Physics SP127-35, 35 mW) operating at a 632.8 nm
The shortest sample times from 1 to 10 μs, and the last delay was varied from 100 ms to 1 s.
An argon laser (λ = 488 nm) could also be used.
Commercial
apparatus
http://www.bic.com/Light_Scattering_overview.html?submenuheader=4
There is also x-rays based method X-ray Photon Correlation Spectroscopy XPCS.
A few references: http://sinhagroup.ucsd.edu/Research_XPCS.htm),
Beam lines:
http://www.esrf.eu/UsersAndScience/Experiments/SoftMatter/ID10A
http://8id.xor.aps.anl.gov/UserInfo/Analysis/
Neutrons (http://www.ill.eu/?id=11552, http://dirac.cnrs-orleans.fr/~kneller/HERCULES/hercules2004.pdf)
Pouzot et al. Structure Factor and Elasticity of a Heat-Set
Globular Protein Gel. Macromolecules, 2004, 37 (2), pp
614–620
http://pubs.acs.org/doi/abs/10.1021/ma035117x
LAUGER
J, GRONSKI . A MELT RHEOMETER WITH INTEGRATED SMALL-ANGLE
LIGHT-SCATTERING.
RHEOLOGICA ACTA Volume: 34
Issue: 1 Pages: 70-79 Published: JAN-FEB 1995
LAUGER J, GRONSKI W. A MELT RHEOMETER WITH INTEGRATED SMALL-ANGLE
LIGHT-SCATTERING.
RHEOLOGICA ACTA Volume: 34
Issue: 1 Pages: 70-79 Published: JAN-FEB 1995
Panine P, Gradzielski M, Narayanan T. Combined rheometry and
small-angle x-ray scattering.
REVIEW OF SCIENTIFIC INSTRUMENTS
Volume: 74 Issue: 4 Pages: 2451-2455
Published: APR 2003
T. Thurn-Albrecht et al. (Phys. Rev. E 68, 031407 (2003)) used also silica particles (glycerol) in their XPCS study.
Busch S, Jensen TH, Chushkin Y, et al. Dynamics in shear flow studied by X-ray Photon Correlation Spectroscopy. EUROPEAN PHYSICAL JOURNAL E 26(1-2), 55-62, MAY 2008
S. Srivastava et al. Complex dynamics in polymer nanocomposites. PHYSICAL REVIEW E 79, 021408, 2009