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Dzakpasu and Axelrod (2004b) describe an experimental implementation of the DLS microscopy (DLSM) based on the use of a progressive-scan CCD in the contiunous scan mode to measure time-variations of the irradiance fluctuations for each pixel of a single line of the CCD pixels imaging a slit of an object in a dark-field microscope with a He-Ne laser as a light source. Position of the line of the He-Ne laser light in the object was advanced mechanically. Thus, the combination of the CCD line scanning and the mechanical motion of the laser light line provided a 2D DLS image of an object.
By experimenting with submicron polystyrene latex particles, Dzakpasu and Axelrod found that the contribution to the irradiance fluctuations due to the fluctuations of the particle concentration are very small for submicron particles in water at ambient temperatures.
Dzakpasu and Axelrod also examined macrophage cells with their technique. They found that an inner zone of the cell contained low-mobility scattering centers and the outer zone contained high-mobility scattering centers. Note that Witkowski et al (1993) used conventional DLS with a suspension of Chlorella cells to examine differences in the mobilities of the cells vs. cell components. However, not being able to localize cell components based on their light scattering measurements that involved many cells, Witkowski et al simply used the knowledge of the cell morphology to interpret their results.
As the particle mobility, at a given temperature, depends on the particle size, this form of microscopy can also be used to map the particle size inside an object containing particles. Note that optical scatter imaging (OSI) is another imaging technique that can map particle size in an object by using a Fourier transform filtering technique.
| CITATION: Jonasz M. 2006. DLSM applications (www.tpdsci.com/Tpc/DLSMApl.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 13-Jan-2006 Modified: 07-Sep-2006 Peer-reviewed: PENDING |