Zeta-potential measurement particles, charge

Surface polarity can also be independently evaluated by physical means. deMayo and coworkers have assigned surface polarity of silica gel particles by observing shifts in the absorption spectra of absorbed spiropyrans which are sensitive to solvent polarity . Darwent and coworkers have shown that kinetic salt effects follow surface charge on colloidal titanium dioxide and, with zeta potential measurements, that surface area and charge could be separately evaluated... 

Recent advances made in measuring particle charge and mobility in nonaqueous suspensions are reviewed. Microelectrophoretic techniques have been used to determine zeta potential and the measurements related to particle stability. 

Interactions between the ceria abrasives and the oxide surface have been investigated using both the chemical and the instrumental approaches. Suphantharida and Osseo-Asare [27] used zeta-potential measurements, silicate adsorption, and polishing experiment to investigate the role of ceria abrasives-Si02 surface interaction. T o determine the effect of pH on the surface charges, the zeta potentials of abrasive particles were measured (Fig. 13.21). The points of zero charge (pzc) or isoelectric point is at pH 6.0 for ceria and pH 1.5 for silica. These values are consistent with those reported by others [28,29]. 

The original Acoustosizer used a single frequency whereas a later development has a range of 13 frequencies between 0.3 and 13 MHz. This allows the measurement of the dynamic mobility spectrum and the determination of the zeta potential and particle size. In order to invert the mobility spectrum into a size distribution a log-normal distribution of particle size is assumed. A comparison with photon correlation spectroscopy for determining particle size and laser Doppler anemometry for particle charge eonfirmed the results using ACS [266]. These and additional sedimentation measurements confirmed that changes in particle size and zeta potential due to dilution effects are likely to occur in aqueous and non-stabilized systems. 

Physical techniques for evaluating surface polarity led deMayo and coworkers to assign relative rates of reaction on silica gel particles from shifts in the absorption spectra of absorbed spiropyrans [76, 77]. Similarly, Darwent and coworkers demonstrated that kinetic salt effects correlate with surface charge and with zeta potential measurements on colloidal titanium dioxide [80]. 

Another important consideration is solids concentration, since this affects the type of separator to be used. In applications with low solids concentration (e.g., less than 50 ppm), sand filters or cartridge filters may be suitable. If the solids concentration is high, then cake filters are used. Electrical charges on particles affect the agglomeration of particles. Zeta potential measurements may be made but the results are unreliable and have not been used industrially. 

The particle size of complexes was measured by dynamic light scattering, and the overall charge by zeta potential measurements, using a particle analyzer (Zetamaster, Malvern Instrnments, Spain). 

Colloid vibration potentials offer a means of measuring the zeta-potential, and hence charge, on colloid particles. Values of-KT4 Vein s at frequencies of a few hundred kilohertz seem to be typical of this effect, and a range of colloids were examined, including silver, silver iodide, and arsenic trisulfide. 

Also useful are the measurements of zeta potential. Particles in suspensions typically acquire a surface charge by the adsorption of ions on the surface, dissolution of the material, chemical reaction, or preferential adsorption of a specific additive or impurity ions from the solution. Surface charge of colloidal particles can be inferred through the measurement of the zeta potential (the particle... 

Kunzelmann, U., Jacobasch, H.J., and Reinhard. G., Investigations of the influence of vapour phase inhibitors on the surface charge of iron oxide particles by zeta-potential measurements, Werkstoffe Korrosion. 40, 723, 1989. 

Zeta potential measurements show that particles coated with NOM have the greatest negative charge (results not shown). This supports the hypothesis that salts present in the NOM allow the colloids to... 

If the loose or diffuse double layer is removed, for example, by shearing, charge measurement becomes possible. However, the charge is slightly reduced by the dense layer surrounding the particle. This weakened and measurable particle charge is termed Zeta Potential. 

Scheme V, silica particles are brought into contact with a cation-exchange resin, and if necessary, with an anion-exchange resin, to obtain an acidic silica sols of pH 2-4. This acidic sol is stable because it is negatively charged even at pH 2-4, according to zeta-potential measurements. Starting from such acidic silica sol, surface-modified silica sols are manufactured.

It has been demonstrated by zeta potential measurements that when powdered human dental enamel is dispersed in the aqueous media that contains salts of the polymeric sulfonates, a substantially negative surface charge is built up on the enamel particles. ... 

Particle charge plays a major role on the stabilization of colloidal systems. Especially when nanoparticles are stabilized by an adsorption layer of polyelectrolytes, zeta potential measurements are very useful. The stabilization of the nanoparticles results from a combination of ionic and steric contributions. The zeta potential can be detected by means of electro-osmosis, electrophoresis, streaming potential, and sedimentation potential measmements. The potential drop across the mobile part of electric donble layer can be determined experimentally, whenever one phase is made... 

Figure 12.5 Particle with surface charge (consisting of an intrinsic particle charge and charge of specifically adsorbed ions), Helmholtz layer HL, part of the diffuse double layer and the shear plane SP of the zeta-potential measurement (schematic representation).

This expression is fairly accurate for values of down to 0.1. These expressions can be used, provided the validity conditions are met, to find the particle zeta potential and net charge from mobility measurements. Other approximate expressions have been proposed, but we will not go further here (see Makino and Ohshima 2010 and references therein). 

The ability of these cationic polyrotaxanes to condense pDNA into particulate structures was evaluated by agarose gel electrophoresis, particle size analysis, and zeta-potential measurements. All the cationic polyrotaxanes could completely complex the pDNA at N/P ratios of 2 and above, which displayed a similar or slightly better DNA condensation ability than PEI (25K). The particle size of the polyrotaxane/DNA complex decreased with the increase of N/P ratio, and when the N/P ratio reached 6, the particle size remained in the 150-250-nm range. Similarly, the surface net charge of the complexes increased from negative to positive as the N/P ratio increased from 0 to 4 and reached a plateau at N/P ratio of 4 and above. The transfection efficiency of the cationic polyrotaxane was also... 

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