E. V. Golikova

Flow ultramicroscopy investigation of the aggregate stability of influenza virus dispersions

Abstract The surface electrical properties and aggregate stability of a number of influenza virus strains have been investigated by microelectrophoresis and flow ultramicroscopy methods. Differences in the nature and kinetics of coagulation — reversible aggregation, superfast coagulation, the presence of an induction period, spontaneous aggregate dispersion and the reaggregation of particles — are explained by special features of the formation and structure of the electric double layer of the studied strains.

The effect of pH on aggregation kinetics of monodisperse silica sol in naCl solutions

The aggregation kinetics of monodisperse silica sols with a particle size of 220 nm in aqueous NaCl solutions is studied by flow ultramicroscopy in a pH range of 2.0–10.2. Slow coagulation of the sols is found to occur via the barrierless mechanism in the secondary potential minimum resulting from the summation of dispersion attractive and structural repulsive forces. The influence of pH and NaCl concentration on the parameters of the structural component of the energy of the interaction between SiO2 particles is demonstrated.

Electrokinetic Properties of Aluminum Oxide Nanodispersions in NaCl Solutions

Using a Zetasizer Nano analyzer, electrophoretic mobility and particle sizes are studied as depending on the pH (3–11) and concentration (10−3–10−1 M) of NaCl background solutions for two samples of aluminum oxide, namely, γ-oxide of the Degussa brand and a sample synthesized by aluminum chloride hydrolysis. The values of the electrokinetic ζ potential are calculated through the Smoluchowski equation and with allowance for the effect of the polarization of electrical double layer on the electrophoretic mobility within the framework of the Overbeek-Boes-Wiersema model (ζW). It is established that, in the region of the isoelectric point (IEP), at (pH-pHIEP) = ±1.5, the |ζW|-pH dependences are linear and their slopes are almost equal for both aluminum oxide samples. The difference between the positions of IEPs for γ-oxide and synthesized oxide sample may be related to different degrees of their surface hydration.

Photometric study of the kinetics of TiO2 hydrosol coagulation in electrolyte solutions

The aggregative stability of TiO2 sols in aqueous solutions of NaCl, KCl, BaCl2, and LaCl3 is studied by photometry at pH 3.2 and natural values of pH (5.0–5.6). Dramatic effects of coion type and charge on the aggregation kinetics and characteristics of resulting aggregates are revealed.

Aggregation stability of a positively charged γ-Al2O3 sol prepared from an air-dry nanopowder

Photometric data on the aggregation stability of Al2O3 hydrosols prepared from Aeroxide Alu C nanopowder in NaCl solutions at pH 4.5 and 5.5 have been discussed within the framework of the generalized Derjaguin-Landau-Verwey-Overbeek theory. Analysis of the pair interaction potentials in an ensemble of particles of a sol primordially containing both primary nanoparticles and their aggregates has led to the conclusion that the coagulation proceeds via the barrierless mechanism in the secondary potential minimum.

Influence of the decomposition of particle units on the coagulation kinetics of monodisperse silicon sol

Based on the results of studying the coagulation kinetics of monodisperse sol of SiO2 in NaCl solutions at various pH values, it is shown that the coagulation rate, flowing in the far potential minimum while maintaining a high repulsion barrier between the particles, depends on the formation and decomposition times of the aggregates. The boundary values of the depth and power of the far potential minimum—at the excess of which sol coagulates—are determined.

Aggregation kinetics of OX50 hydrosols in NaCl solutions studied by dynamic light scattering

The aggregation kinetics of OX50 sols in aqueous NaCl solutions (10–4–2 × 10–1 M) has been studied for 15 days or more by dynamic light scattering. The following set of characteristics has been considered to quantitatively estimate the coagulation intensity in the disperse systems: the particle size corresponding to the maximum in the differential particle size distribution curve, the height of the maximum, the polydispersity index, and the average diameter of the intensity distribution. It has been found that slow sol coagulation proceeds via the barrierless mechanism in secondary potential minimum, which arises from the predominance of the dispersion attractive forces over structural and electrostatic repulsive forces.

Aggregation stability of monodisperse silica sol in NaCl and BaCl2 solutions

The aggregation kinetics of a monodisperse silica sol with an average particle size of 220 nm and particle number concentration n0 = 1010 cm−3 in aqueous solutions of NaCl and BaCl2 at pH 6.2 is studied with the help of photometry. The stability of diluted sols (n0 = 107 cm−3) in NaCl solutions is investigated by the direct method of flow ultramicroscopy. The results obtained are analyzed in terms of the theories of the Hogg-Yang barrierless coagulation and the Muller reversible coagulation. It is established that the slow coagulation of both concentrated and diluted sols proceeds via the barrierless mechanism in the secondary potential minimum.

Colloido-chemical characteristics of zinc oxide in electrolyte solutions

The electrosurface characteristics (total surface charge, electrokinetic potential, and positions of the point of zero charge and isoelectric point) of zinc oxide have been comprehensively studied as depending on pH and background electrolyte (NaCl) concentration. The constants of surface reactions and the adsorption potentials of potential determining of background electrolyte ions have been obtained in terms of the 2pK-model. The aggregation stability of aqueous zinc oxide suspensions has been studied in a wide range of concentrations of 1: 1 and 1: 2 electrolytes, and the threshold of sol coagulation has been found. Within the framework of the DLVO theory, the interaction energy between ZnO particles has been calculated as a function of the interparticle distance. It has been demonstrated that the experimental data can be qualitatively described in terms of the classical DLVO theory, which takes into account only ion-electrostatic and molecular (dispersion) forces of interparticle interaction.

Assessment of the Extension of Water Boundary Layers at the Particle Surfaces of Monodisperse Silica Sol in a 0.15 M NaCl Solution at Different pH Values

The coagulation kinetics of a monodisperse sol of Monosphere 250 silica in a 1.5 × 10–1 М NaCl solution has been studied within a pH range of 2.0–6.2. The obtained results have been used to estimate the radius of action of the structural forces for interacting SiO2 particles. It has been shown that, depending on the pH of a medium, the extension of boundary layers varies over a range of 4–8 nm, with the thickest boundary layers being observed near the point of zero charge of the particles.