Quasi-elastic light scattering particles

Photon Correlation Spectroscopy. Photon correlation spectroscopy (pcs), also commonly referred to as quasi-elastic light scattering (qels) or dynamic light scattering (dls), is a technique in which the size of submicrometer particles dispersed in a Hquid medium is deduced from the random movement caused by Brownian diffusion motion. This technique has been used for a wide variety of materials (60—62). 

Finsey R., Particle sizing by quasi-elastic light scattering, Adv. Colloid Interface Set, 52, 79, 1994. 

Ford NC (1983) In Dahneke B (ed) Measurement of suspended particles by quasi-elastic light scattering. Wiley, New York... 

B.E. Dahneke (Ed.), Measurement of Suspended Particles by Quasi-Elastic Light Scattering, Wiley, New York, 1983, 570 pp. 

Recently, a four-laboratory cooperative study has led to a comparison of the determination of particle size distribution by electron microscopy, quasi-elastic light scattering and wide angle light scattering (20). 

Using Quasi-Elastic Light Scattering To Study Particle Size Distributions in Submicrometer Emulsion Systems... 

Quasi-elastic light scattering is an excellent technique for studying the formation and stability of submicrometer emulsions. Improvements in the methods of quasi-elastic light scattering data acquisition and analysis that enable full particle-size distribution studies of sub-micrometer emulsion systems are discussed. Using several oil/water emulsion systems as examples, we demonstrate the ability of these techniques to determine the effect of emulsifier concentration on the particle-size distribution produced by an inversion method of emulsification. Some of the benefits of obtaining the full distribution are also discussed. 

Many excellent introductions to quasi-elastic light scattering can be found in the literature describing the theory and experimental technique (e.g. 3-6). The use of QELS to determine particle size is based on the measurement, via the autocorrelation of the time dependence of the scattered light, of the diffusion coefficients of suspended particles undergoing Brownian motion. The measured autocorrelation function, G<2>(t), is given by... 

Pecora, R. In "Measurement of Suspended Particles by Quasi-Elastic Light Scattering" Dahneke, B. E., Ed. Wiley New York, 1983 Chap. 1. 

An alternate approach for determining particle density involves fraction collection followed by the application of quasi-elastic light scattering (QEL) to the fraction (19). The QEL technique is particularly effective in providing a mean particle diameter d for narrow particle distributions. With this d and the X obtained from V (the volume at which the fraction was collected), Ap can be calculated directly from Equation 3. 

A powerful, versatile tool for particle sizing is quasi-elastic light scattering. 

Mazumder, M.K., Ware, R.E., Yokoyama, T., Rubin, B. and Kamp, D. (1982), Measurement of suspended particles by quasi-elastic light scattering, ed. B. Dahneke, publ. John Wiley Sons Inc. New York, pp 328-341, 506... 

Dynamic (quasi-elastic) light scattering that is usually referred as photon correlation spectroscopy this is a rapid technique that is especially suited to measuring submicron particles (nanosize range). 

Schematic models for the expanded structure of bile acid-phosphatidylcholine mixed micelles are shown in Fig. 2B. The original model was proposed by Small in 1967 (S36). In this model the mixed micelle consisted of a phospholipid bilayer disk surrounded on its perimeter by bile acid molecules, which were oriented with their hydrophilic surhices in contact with aqueous solvent and their hydrophobic sur ces interacting with the hydrocarbon chains of the phosphohpid molecules. This model has recently been revised, based on further studies of mixed micelles using quasi-elastic light scattering spectroscopy (M20). In a new model for the molecular structure of bile acid-phospholipid mixed micelles. Mazer et al. (M20) propose a mixed disk, in which bile acids are found not only on the perimeter of phospholipid bilayers, but also incorporated within their interior in high concentrations (Fig. 2B). The size of these mixed micelles was estimated to be as high as 200 to 400 A in radius in some solutions, and disk-shaped particles in this size range were observed by transmission electron microscopy (M20). Micellar aggregates similar in size and structure to those found in model bile solutions have been demonstrated in dog bile (M22).

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