Quasi-Elastic Light Scattering QELS

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). 

The technique is alternatively called photon correlation spectroscopy (PCS) or quasi-elastic light scattering (QELS). 

Effect of Radiation Dose on Micellar Properties. Figure 1 shows the concentration dependence of the micellar diffusion coefficient at 40° as determined by quasi-elastic light scattering (QELS) for solutions subjected to radiation doses of up to 4.56 Mrad. Limiting diffusion coefficients, D0>were obtained by extrapolation of data for dilute solutions (<0.05%) to zero concentration, the critical micelle concentration (CMC) being negligibly low for this poloxamer ( 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. 

Quasi-elastic light scattering (QELS) techniques... 

FIGURE 12.14 Effect of functional monomer on hydrodynamic particle diameter measured by quasi-elastic light scattering (QELS) at 20°C. (Erom Duracher, D. ta.., Macromol. Symp., 150, 297, 2000. With permission.)... 

Quasi-elastic light scattering (QELS) experiments were conducted on both neutralized and unneutralized sols, in a Brookhaven model BI-90 particle sizer. This instrument measured the autocorrelation function, C(t), and fit this function to... 

This is also known as photon correlation spectroscopy (PCS) or quasi-elastic light scattering (QELS). It uses scattered light to measure the rate of diffusion of protein particles in a sample. The data on molecular motion are digitally processed to yield a size distribution of particles in the sample, where the size is given by the mean Stokes radius or hydrodynamic radius of the protein particles this is the effective radius of a particle in its hydrated state. Clearly, the hydrodynamic radius depends on both mass and shape. 

The problem of particle nucleation was first addressed in the 1980s by Candau and coworkers [14,104] for the case of water-in-oil microemulsions. Their studies concerned the polymerization of acrylamide inside water-swollen micelles stabilized by AOT and dispersed in toluene. A thorough investigation of the structures prior to and after polymerization by elastic and quasi-elastic light scattering (QELS), viscomelry, and ultracentrifugation experiments yielded two key experimental results ... 

In recent years, the quasi-elastic light scattering (QELS) method has become increasingly routine in experimental studies of polymer dynamics in both dilute and concentrated solutions. It allows us to obtain information about the possible modes of Brownian motion of a polymer molecule either isolated or entangled with others. Leaving its technical details and various practical applications to reference books [38], we here give a brief account of its important aspects which are closely related to the current theory of dilute polymer solutions. 

Dynamic light scattering (DLS) DLS, also known as PCS or quasi-elastic light scattering (QELS), records the variation in the intensity of scattered light on the microsecond timescale used to calculate particle size... 

Calorimetry (DSC), Atomic Force Microscopy (AFM) and Quasi-Elastic Light Scattering (QELS). 

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