Search results for: R. Hidalgo-Alvarez
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Progress in Colloid and Polymer Science > Trends in Colloid and Interface Science XV > Structure and Dynamics at Interfaces > 115-118
We show how single-cluster light scattering may be used to study the aggregation kinetics of surface-modified colloidal particles. The surface characteristics of the particles were modified by adsorbing different amounts of bovine serum albumin (BSA). All aggregation measurements were performed at high salt concentration and at the protein’s isoelectric point. Single-cluster light scattering was employed...
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Negatively charged polystyrene latexes with relatively high surface charge density have been prepared by the emulsifier-free method. Three samples of approximately the same particle size and different surface charge density have been obtained. The effect of pH and ionic strength on electrophoretic mobility has been studied and the experimental mobility converted into ζ-potential according to the O’Brien-White...
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For quite some years ago, up to present, the high cost and complexity of diagnostic techniques in the immunochemistry field have prompted alternative approaches, such as the immunoprecipitation of colloidal particles carrying antibodies or antigens on their surfaces, which are less expensive and simpler. It has been demonstrated that the use of antibody fragments (i.e., F(ab′)2), instead of...
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Progress in Colloid and Polymer Science > Surfactants and Macromolecules: Self-Assembly at Interfaces and in Bulk > 313-320
the microelectrophoretic behavior of dilute dispersions of positively charged polystyrene particles has been studied. The effects of particle concentration, ionic strength, pH, and temperature on microelectrophoretic mobility have been analyzed. Change in mobility on the addition of different co-ions and counterions was investigated. The pH at which the isoelectric condition is established was found...
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Recent studies have demonstrated the huge interest in the inversion of charge in systems such as solid particles, DNA molecules, charged membranes, etc. in the presence of electrolyte. Electrophoresis measurements show the charge of colloidal particles can be inverted when an electric field is applied. Some researchers suggest this fact could be due to the size of the counterions as well as electrostatic...
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Recent studies have demonstrated the huge interest in the inversion of charge in systems such as solid particles, DNA molecules, charged membranes, etc. in the presence of electrolyte. Electrophoresis measurements show the charge of colloidal particles can be inverted when an electric field is applied. Some researchers suggest this fact could be due to the size of the counterions as well as electrostatic...
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The microelectrophoretic behavior and colloid stability of dilute dispersions of calcium oxalate monohydrate (COM) in solution have been studied. The COM crystals were precipitated at different experimental conditions of the nucleation process. In a first step, we have investigated the influence of predominant cations or anions on the sign of the COM surface charge. In a second step, the effect of...
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Progress in Colloid and Polymer Science > Trends in Colloid and Interface Science XV > Structure and Dynamics at Interfaces > 87-90
A sticking probability model for irreversible aggregation processes is developed. It allows a kernel capable of describing not only the diffusion-limited and reaction-limited aggregation regimes but also the whole transition region to be deduced. According to the definition given by van Dongen and Ernst, the kernel establishes λ = 0 for the entire range of sticking probabilities. The model presented...
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We studied the aggregation of polystyrene latex in two dimensions. We observed under microscope how salt-induced aggregation of both monomers and clusters’ fractal dimension increases with increasing aggregation time. However, it does not depend on the salt concentration in the range studied (0.2–1.0 mol dm−3 of NaCl). The question of cluster restructuring is invoked.
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A new generalized collision efficiency model for bridging flocculation was developed. It comprises the La Mer, the Moudgil and the Molski models. The extended model allows to separate and quantify the contributions of the different aggregation mechanisms (slow coagulation, weak flocculation and bridging flocculation). The model was tested for polystyrene particles covered with different amounts of...
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Progress in Colloid and Polymer Science > Optical Methods and Physics of Colloidal Dispersions > 144-147
In this work, the influence of particle surface charge density on the mechanism of bridging flocculation is studied. Different amount of bovine serum albumin (BSA) molecules were adsorbed onto the surface of two almost identical systems of polystyrene particles which differ only in their surface charge density. Flocculation was induced by adding a small amount of electrolyte to a dilute suspension...
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Charge-heteroaggregation processes arising in 1:1 mixtures of positively and negatively charged particles were studied at low and high electrolyte concentration. Single-cluster light scattering was employed to monitor and resolve the detailed cluster size distribution up to hexamers. The results obtained show that long-range electrostatic interactions between oppositely charged particles favour aggregation...
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The interaction potential between colloidal particles is the key to understand and control the aggregation processes in which they are involved. However, interaction forces are also responsible for spatial ordering. This kind of phenomena has been used to obtain valuable information on the interaction potential in three-dimensional dispersions. In this work, this possibility is investigated for colloidal...
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Progress in Colloid and Polymer Science > Trends in Colloid and Interface Science XV > Structure and Dynamics at Interfaces > 123-126
We present some results obtained in 2D aggregation experiments. Experiments were made using a salt subphase of 2.0 M KBr and pH values ranging from 1.5 to 6.0. We used two latex polystyrene samples with different contact angles (i.e. different hydrophobic properties) and similar particle sizes. Digitised images were obtained at different aggregation times. These images were analysed to obtain the...
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In this work the electrophoretic mobility of two polystyrene latexes was measured versus the concentration of NaCl. A conventional sulfate latex obtained by emulsion polymerization of Styrene and an aldehyde latex prepared by emulsion copolymeri-zation of Styrene and Acrolein were used throughout this work. The latexes were subjected to a heat treatment (at 115°C for 17h) and after this were characterized...
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Progress in Colloid and Polymer Science > Optical Methods and Physics of Colloidal Dispersions > 104-106
The structure factor S(q) was measured for a colloidal dispersion of latex microspheres (40 nm of diameter) by both static and dynamic light scattering (using a Malvern Instruments spectrometer, λ=488 nm). The structure was formed for a sample of particle number density 2×1013 ml−1. The interaction potential was determined from the experimental S(q) by means of the straightforward use of three different...
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The interaction potential between colloidal particles is the key to understand and control the aggregation processes in which they are involved. However, interaction forces are also responsible for spatial ordering. This kind of phenomena has been used to obtain valuable information on the interaction potential in three-dimensional dispersions. In this work, this possibility is investigated for colloidal...
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This work deals with certain kinetic aspects of the coagulation of polymer colloids by immuno gamma globulin molecules. Negatively and positively charged polystyrene microspheres were used as a carrier of antibody molecules and the coagulation was studied experimentally by measuring the change in turbidity with time after addition of various amounts of rabbit immuno gamma globulin (IgG). Coagulation...
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The electrokinetic behavior of negatively charged polystyrene dispersions in methanol-water mixtures has been studied. Data obtained from streaming potential and electrophoresis measurements have been compared. The theory of Levine et al. (J. Colloid Interface Sci., 52 (1975) 136) for systems consisting of narrow capillaries has been used to convert streaming potential data into zeta-potentials. For...
