Dynamic light scattering particles

Figure 4 shows the impact of the number of primary particles per aggregate and the coefficient of penetration on the result of a dynamic light-scattering particle sizing of those aggregates. The impact of /is very low. Therefore, it is now very easy to give the number of primary patticles as a result of a PSD measurement rather than the equivalent spherical diameter 2 n,yd. 

Kops-Werkhoven, et al. measured tracer diffusion of dilute 38 nm radius silica spheres diffusing through suspensions of 33 nm silica spheres, all in cyclo-heptane(12). The experimental method was dynamic light scattering particle motions were observed over distances large compared to their radius. They found ku =-2.7 0.3. 

Ansari, R. R., Suh, K., Dynamic Light Scattering Particle Size Measurements in Turbid Media, Proc. SPIE-Int. Soc. Opt. Eng. 1998, 3251, 146-156. 

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). 

FIGURE 1 Effect of (sequential) extrusion of MLV dispersions through polycarbonate membrane filters (Unipore) with pore sizes of 1.0, 0.6, 0.4, 0.2, and 0.1 ym on the mean liposome diameter. DXR-containing MLV (phosphatidylcholine/phosphatidylserine/ cholesterol 10 1 4) mean diameter of nonextruded dispersion about 2 ym pH 4. Mean particle size determined by dynamic Light scattering (Nanosizer, Coulter Electronics). (From Crommelin and Storm, 1987.)... 

An alternative approach is the use of pH-sensitive fluorophores (Lichtenberg and Barenholz, lOSS). These probes are located at the lipid-water interface and their fluorescence behavior reflects the local surface pH, which is a function of the surface potential at the interface. This indirect approach allows the use of vesicles independent of their particle size. Recently, techniques to measure the C potential of Liposome dispersions on the basis of dynamic light scattering became commercially available (Muller et al., 1986). 

Additional evidence for silica nucleation on biopolymer macromolecules was furnished by experiments in which solutions of proteins were studied by dynamic light scattering. As an illustration, Figure 3.6 shows the relative intensity of light scattering versus the diameter of the scattering particles in solution with 1 wt.% of bovine serum albumin. Curve 1 presents the initial state where the protein was not yet treated with silica precursor. The measured... 

Fig. 3.6 The relative intensity of dynamic light scattering vs. the diameter of scattering particles for a solution with 1 wt.% bovine serum albumin (1) and the same solution after addition of 3 wt.% of THEOS (2). Before the measurements, the solutions were left at ambient temperature for a week. The drawings are a schematic representation of a protein macromolecule before and after the treatment by silica precursor.

Fig. 4 PIC dye nanoparticles prepared by the ion-association method. (1) Particle size distributions (determined by the dynamic light scattering technique) and the corresponding electron micrographs of the dye nanoparticles. The average diameter can be controlled by tuning the molar ratio of TPB- to PIC+ (=[TPB-]/[PIC+]. With an increase in the molar ratio, the average diameter decreased. (2) Absorption spectra of PIC nanoparticles in aqueous solution with different sizes (125 and 64 nm in diameter), exhibiting size-dependent peak shift of the 0-0 band. The spectrum of the aqueous PIC-Br monomer solution is also shown...

Particles of a size of less than 2 turn are of particular interest in Process Engineering because of their large specific surface and colloidal properties, as discussed in Section 5.2. The diffusive velocities of such particles are significant in comparison with their settling velocities. Provided that the particles scatter light, dynamic light scattering techniques, such as photon correlation spectroscopy (PCS), may be used to provide information about particle diffusion. 

Instrumentation and data processing techniques for systems employing dynamic light scattering for the examination of fine particle motion are currently under development. 

P. N. Pusey and R. J. A. Tough, Particle interactions, in Dynamic Light Scattering Applications cfPhoton Correlation Spectroscopy (R. Pecora, ed.), pp. 85-179, Plenum Press, New York (1985). 

Methods for analysis of the particle size distribution in the aerosol cloud include techniques such as time of flight measurement (TOE), inertial impaction and laser diffraction. Dynamic light scattering (photon correlation spectroscopy) is confined to particles (in suspension) in the submicron range. In addition to the size distribution, the particle velocity distribution can be measured with the Phase Doppler technique. 

Thomas J.C., The determination of log normal particle size distributions by dynamic light scattering, J. Colloid Interface Sci., 117, 187, 1987. 

The enzyme-containing nanosize silica particles prepared by Jain et al. (33) were characterized for their particle size (dynamic light scattering and TEM), entrapment efficiency, in vitro leaching capacity, and enzyme activity. For all three biomolecules, the entrapment efficiency was 80-90% and the entrapped molecules were found to be stable towards leaching (up to 45 days). The enzymatic activity of the entrapped molecules was lower than that of the corresponding free molecules, a result that was attributed to diffusional constraints. 

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