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The particle mobility in a dispersion can, in contrast to dynamic light scattering (DLS), where an average value of the mobility is determined for a large number of particles, can also be determined for single particles by using methods ranging from a sophisticated computer-controlled 3D autotracking confocal microscope (for example, Schätzel et al (1992) to observations of a 2D projection of the 3D motion of a particle with an optical microscope (for example, Nakroshis et al 2003 - who used it to determine the Boltzmann constant, Greczylo and Debowska 2005 - who used it to determine the dispersion fluid viscosity).
The particle mobility, as represented by the translational diffusion coefficient (see Dynamic light scattering), is related to the hydrodynamic particle size, i.e. the equivalent hydrodynamic diameter (EHD). Thus, particle tracking can be used to measure the particle size. Garbow et al 1997, who measured one-dimensional Brownian motion of single particle in a potential well created by a laser beam focus, evaluated the uncertainty of particle size based on the tracking data to be on the order of 10%. However, when single particle tracking was combined with measurement of the intensity of light backscattered by the particle, the particle size error for homogeneous spheres was reduced to about 2%. An imaging-based, many-particle tracking technique has been used to determine the particle size distribution as well (see PSD by particle tracking).
Note that dynamic light scattering microscopy (DLSM) enables one to determine average mobilities of particles within a small volume, such as the interior of a cell.
| CITATION: Jonasz M. 2006. Particle mobility and size by single particle tracking (SPT) (www.tpdsci.com/Tpc/SngPtTrk.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 17-Jan-2006 Modified: 05-Jul-2006 Reviewed: PENDING |
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