hard sphere, globular, dendrimer, chain stiffness, and degree of branching). Hydrodynamic sizes are more easily measured than radii of gyration and can be measured over a wider range of sizes. The conversion from hydrodynamic radius to radius of gyration is a function of chain architecture (including questions of random coil vs. The hydrodynamic radius is not the same as the radius of gyration. Radius calculations are the same except for a factor of two.Īlso, a note to those interested in polymer size. In the scope of DLS, temporal fluctuations are usually analyzed by means of the intensity or photon auto-correlation function (also known as photon correlation spectroscopy or quasi-elastic light scattering). That is, the determined particle size is the size of a sphere that diffuses the way as your particle.įor those who work with protein sizing and other areas where hydrodynamic radius is more commonly used, note that the development here is around diameter. Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. Finally, and most importantly, it reminds the analyst that the particle size determined by dynamic light scattering is the hydrodynamic size. Temperature is even more important due to the viscosity term since viscosity is a stiff function of temperature. The first is that sample temperature is important, at it appears directly in the equation. However, the equation does serve as important reminder about a few points. The calculations are handled by instrument software. T is thermodynamic temperature (we control this) Dynamic Light Scattering instruments can be used to measure size distributions and zeta potentials of particles.k B is Boltzmann’s constant (we know this). D t is the translational diffusion coefficient (we find this by dynamic light scattering).D h is the hydrodynamic diameter (this is the goal: particle size!) Therefore the light scattered down to the earth at a large angle with respect to the direction of the suns light is predominantly in the blue end of the.
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