PHAR2823 Lecture Notes - Lecture 5: Nanopore, Tunable Resistive Pulse Sensing, Dynamic Light Scattering
Measurement can be done in
liquid
Yes, majority is done in liquid
– mostly want to know how
particles react in liquid – big
adv
Dynamic light scattering
When macromolecules are struck by the solvent
molecules it leads to a random motion of the
molecules called Brownian motion.
Each particle is constantly moving, and its motion is
uncorrelated with the other particles but is correlated
with its size.
When light scatters from the moving
macromolecules, this motion imparts a randomness
to the phase of the scattered light.
Analysis of these fluctuations yields the velocity of
the Brownian motion and the particle size can be
calculated using the Stokes-Einstein relationship.
Big particles vibrate less and can sediment. Smaller particles vibrate more.
Advantages
Disadvantages
Size (any limitations?)
Can’t measure dry powder,
you have to suspend it in a
solution
Size distribution
Can measure down to 1nm –
10 microns
Distinct peaks for small and
large particles
Larger particles will sediment
and diminish signal
Document Summary
Mostly want to know how particles react in liquid big adv. When macromolecules are struck by the solvent molecules it leads to a random motion of the molecules called brownian motion. Each particle is constantly moving, and its motion is uncorrelated with the other particles but is correlated with its size. When light scatters from the moving macromolecules, this motion imparts a randomness to the phase of the scattered light. Analysis of these fluctuations yields the velocity of the brownian motion and the particle size can be calculated using the stokes-einstein relationship. Can"t measure dry powder, you have to suspend it in a solution. Yes can calculate concentration of particles in solution. Trps measures nanoparticles suspended in electrolytes on a particle-by-particle basis as they pass through a nanopore. If a particle passes thru a pore, the current drops magnitude of drop of current is proportional to size of particle passing through. How much we can stretch the pore to accommodate.
