Characterization zeta potential

An understanding of the complex physico-chemical phenomena associated with the formation and behavior of cementitious compounds is facilitated through the application of many different types of investigative methods. Techniques such as NMR, XRD, neutron activation analysis, atomic absorption spectroscopy, IR/UV spectroscopy, electron microscopy, surface area techniques, pore characterization, zeta potential, vis-cometry, thermal analysis, etc., have been used with some success. Of the thermal analysis techniques the Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), and Conduction Calorimetric methods are more popularly used than others. They are more adaptable, easier to use, and yield important results in a short span of time. In this chapter the application of these techniques will be highlighted and some of the work reported utilizing other related methods will also be mentioned with typical examples. 

For many particles, the diffuse-charge layer can be characterized adequately by the value of the zeta potential. For a spherical particle of radius / o which is large compared with the thickness of the diffuse-charge layer, an electric field uniform at a distance from the particle will produce a tangential electric field which varies with position on the particle. Laplace s equation [Eq. (22-22)] governs the distribution... 

As the particle moves relative to the electrolyte solution, the layer of water mol-ecnles that is directly adjacent to the particle surface is strongly bonnd and will be pnlled along. The thickness of this bonnd layer is approximately one or two diameters of a water molecule. We shall write x, for the x-coordinate of this layer s outer boundary, which is the slip plane. The electrostatic potential at this plane relative to the potential in the bulk solution is designated by the Greek letter and called the zeta potential or electrokinetic potential of the interface discussed. This potential is a very important parameter characterizing the electrokinetic processes in this system. 

The charges present on the insulator surface in contact with the solution give rise to an accumulation of ions of opposite sign in the solution layer next to the surface, and thus formation of an electric double layer. Since straightforward electrochemical measurements are not possible at insulator surfaces, the only way in which this EDL can be characterized quantitatively is by measuring the values of the zeta potential in electrokinetic experiments (see Section 31.2). 

Concerning the SLN produced by hot homogenization as described by Olbrich et al. [19], as lipidic matrix Compritol ATO 888 or paraffin were used, as tenside a mixture of Tween 80 and Span 85 was used, and as charge carrier either EQ1 [N,N-di-(()-s(eaoryI e(liyI)-.V,A -di methylammonium chloride] or cetylpyridinium chloride were used. The resulting particles were characterized by size between 101 and 105 nm and showed zeta potentials around 40 mV at pH 7.4. 

The obtained STPP liposomes were characterized by size distribution analysis, P NMR spectroscopy (Fig. 3), and by zeta potential measurements (Fig. 4). The size of liposomes with 20 mol% incorporated STPP was determined to be 132 zb 59 nm, which did not change significantly upon storage at 4°C over several days. The P NMR spectrum of STPP liposomes shows two chemical shifts correlating to the phosphorus in the lipid s phosphate groups and to the positively charged phosphorus of STPP. No differences in both chemical shifts between the free compounds (i.e., free STPP and free... 

In the quantitative sections of this chapter the primary emphasis has been on establishing the relationship between the electrophoretic properties of the system and the zeta potential. We saw in Chapter 11 that potential is a particularly useful quantity for the characterization of lyophobic colloids. In this context, then, the f potential is a valuable property to measure for a lyophobic colloid. For lyophilic colloids such as proteins, on the other hand, the charge of the particle is a more useful way to describe the molecule. In this section we consider briefly what information may be obtained about the charge of a particle from electrophoresis measurements. 

Fig. 25 Characterization and luciferase expression of PGP DNA condensates in vivo. These results show that luciferase expression is dependent on galactose incorporation but independent of amount of melittin. (a) Represents the input mol ratio of Cys-terminated melittin, PEG-peptide, and glycopeptide. (b) Represents the measured mol ratio of Cys-terminated melittin, PEG-peptide, and glycopeptide for each purified PGP. (c) Values are the calculated MW based on polylysine standards, (d) Values are the calculated MW based on PEG standards, (e) The mean particle size determined at a stoichiometry of 0.3 nmol of PGP per mg of DNA. The value represents the mean diameter (nm) based on unimodal analysis, (f) The zeta potential of PGP DNA condensates at a stoichiometry of 0.3 nmol of PGP per mg of DNA. (g) The metabolic half-life of PGP 125I-DNA in triplicate mice. The results are derived from Fig. 6. (h) The PC/NPC ratio of DNA-targeted liver, (i) Represents a control PGP 3 in which galactose has been removed. Figure adapted with permission from [182], 2007 American Chemical Society...

Vol. 14 Complex Wave Dynamics on Thin Films. By H.-C. Chang and E.A. Demekhin Vol. 15 Ultrasound for Characterizing Colloids. Particle Sizing, Zeta Potential, Rheology. 

Fig. 14.3 Analytical characterization of an emulsion formulation of GLA (EAS) indicates the localization of the TLR4 agonist, (a) Aqueous phase extraction followed by HPLC indicates that GLA is found in the oil phase of the emulsion, (b) A decrease in zeta potential due to incorporation of GLA in the emulsion indicates that the TLR4 agonist associates with the oil droplet interface. ES represents the emulsion alone. Reproduced with permission from Anderson et al. (2010) Coll Surf B 75, 123-132...

The aim of the present study was a closer investigation of the properties of LDPE surfaces subjected to photosulfonation processes. Until today no zeta potential studies had been carried out on photosulfonated LDPE. In the present investigation such modified LDPE surfaces were characterized by FTIR spectra, contact angle testing and zeta potential measurements were carried out. To improve the stability of modified LDPE surfaces, polyethylene samples were crosslinked by e-beam irradiation and... 

In another part of this study we wished to see the effects of post-modification treatments on the properties of the modified LDPE surface. Polyethylene samples were photosulfonated for different periods of time. Afterwards they were subjected to an after-treatment by conditioning in an electrolyte solution (aqueous KC1, 10-3 M) for 48 hours and then characterized by zeta potential measurements. This conditioning process resulted in a shift of f to even less negative values (see Fig. 8). This finding may be explained by the swelling of the polymer samples (water adsorption) in water that causes a shift of the shear plane of the electrochemical double layer into the liquid phase. This effect demonstrates that storage conditions and pre-conditioning may exert a pronounced influence on the zeta potential recorded for surface-modified polymers. Phenomena of this kind have already been described in previous literature [26,27],... 

It can be summarized that ellipsometric measurements proved the formation of a surfactant adsorption layer on the photoresist surface. At ceg- it is assumed to form a monolayer. To get more information about the adsorption layer and its influence on the surface properties of the photoresist, an electrokinetic characterization of unexposed and processed photoresist in solutions of the cationic surfactant was carried out. The zeta potential of the photoresist layers is given in Fig. 8 as a function of the surfactant concentration. The measurement was performed at pH = 6 in a background electrolyte (KC1) concentration of 10-5 M to ensure the minimum conductivity of the solution necessary for the measurement. 

Zeta potential was the first, experimentally available value characterizing edl. The potential of the solid particles in the electrolyte solutions may be determined on the basis of one of the four following phenomena microelectrophoresis, streaming potential, sedimentation potential and electroosmosis. The most popular of them and the best described theoretically and methodically is the electrophoresis. Other papers, concerning the electrophoretic mobility, stationary level determination and the theory of the charged particles transportation in the electric field are still published. 

With electro-osmosis data, on the other hand, interpretation is not subject to the complexities of the electrophoretic measurement. Analysis of zeta potential is straightforward, and a wide range of pH can be employed. In this light it would be promising to characterize ceramic and mineral materials of a wide variety of compositions and forms, e.g., powders and processed plates. 

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