JournalTOCs

Colloid Journal
Journal Prestige (SJR): 0.345

Citation Impact (citeScore): 1
Number of Followers: 2

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1608-3067 - ISSN (Online) 1061-933X
Published by Springer-Verlag

[2469 journals]

Granulometry of Metal Micropowders Treated in a Planetary-Type Ball Mill
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  Abstract: Industrial micropowders of metals (aluminum, tungsten, hafnium, nickel, titanium, and zirconium) and a semimetal (amorphous boron) have been mechanically treated in a planetary-type ball mill for different time periods. The integral and differential particle size distribution functions have been experimentally determined for all micropowders before and after the mechanical treatment. It has been shown that, in all cases under consideration, the found distribution functions can be represented in a lognormal form. The most informative statistical characteristics (moments) have been determined for the obtained distribution functions. The time correlations of these characteristics have been analyzed. A mathematical ansatz-model has been proposed for the process of multicycle mechanical treatment of metal powders in planetary-type mills. The model enables one to adequately describe the time evolution of the statistical characteristics for an ensemble of micropowder particles.
  PubDate: 2022-02-01
Nanoemulsions and Nanocapsules with Oleic Acid
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  Abstract: Nanoemulsions are promising disperse systems that can be used as carriers of hydrophobic drugs and biologically active compounds. In this work, nanoemulsions, which contain oleic acid as a dispersed phase and are stabilized with mixtures of nonionic surfactants, Tween 80/Span 80 and Tween 60/Span 60, have been studied. Nanoemulsions stabilized with Tween 80 and Span 80 are unstable. Dispersed phase droplets of such systems undergo intense flocculation and coalescence. Nanoemulsions stabilized with Tween 60 and Span 60 have appeared to be much more stable. The average particle diameter of the dispersed phase remains almost unchanged for a long time at 25°C, as well as in two cycles of heating to 60°C and subsequent cooling to 5°C. Microcalorimetry has been employed to determine the temperatures of phase transitions in such nanoemulsions. The obtained thermograms have two peaks due to melting of oleic acid and a mixed adsorption layer consisting of Tween 60 and Span 60 molecules. Since a solid shell is formed on the surface of oleic acid droplets, such systems can be considered to be nanocapsules.
  PubDate: 2022-02-01
Nanoemulsions with Amaranth and Sea Buckthorn Oils
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  Abstract: Nanoemulsions (NEs) containing natural components are of particular interest for use in the pharmaceutical and food industries, including the encapsulation of hydrophobic bioactive substances. In this work, the properties of NEs containing amaranth and sea buckthorn oils or a mixture thereof as dispersed phases have been studied. In NEs stabilized with a mixture of Tween 80 and Span 80, the average diameter of the dispersed phase droplets is 18–33 nm. In NEs stabilized with a mixture of Tween 60 and Span 60, the average droplet diameter is 25–40 nm. Therewith, the NEs stabilized with Tween 80 and Span 80 are unstable to flocculation and creaming. In the course of time, a network structure is formed by flocs of dispersed phase droplets in the NE dispersion medium, with this process being accompanied by partial separation of the aqueous phase. The fraction of the dispersed phase in such NEs increases, reaches a value almost equal to the dense packing of the droplets, and, then, remains almost unchanged. The NEs stabilized with Tween 60 and Span 60 are significantly more stable to flocculation, because these surfactants form a solid shell on the surface of the dispersed phase droplets. In these NEs, the rate of flocculation is extremely low and no creaming is observed. Thus, the produced NEs of amaranth and sea buckthorn oils are stable to flocculation and creaming for a long time.
  PubDate: 2022-02-01
Work of Formation of Direct and Inverse Micelle as a Functions of
Aggregation Number
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  Abstract: The derivation of an expression for the minimal work of micellization (aggregation work) on the basis of the extended droplet model has been considered for the cases of direct and inverse spherical micelles. The contributions of the following factors to the aggregation work have been taken into account: the hydrophobic effect upon the formation of the core of a direct micelle; the electrostatic interaction upon the formation of the core of an inverse micelle; the influence of the conformations of hydrocarbon tails and polar head groups in the corona and core of the direct and inverse micelle, respectively; and the effect of the surface tension at the boundary between a micelle core and a solution. The equation of state of molecular groups on a micelle core surface has been shown to play an important role in describing the stabilization of both direct and inverse micelles. The account of the contributions to the aggregation work makes it possible to explain the mechanism of surfactant aggregation in a nonpolar solvent in the absence of water and ascertain the existence of a critical micelle concentration, as well as to determine the average aggregation numbers of dry inverse micelles at different total surfactant concentrations.
  PubDate: 2022-02-01
The Processes of Crown-Substituted Magnesium Phthalocyaninate Dissolution
in Water in the Presence of Alkyltrimethylammonium Bromides
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  Abstract: — Electronic absorption and luminescence spectroscopies have been employed to analyze the processes of octa-crown-substituted magnesium phthalocyaninate (Mgcr8Pc) dissolution in water in the presence of dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromides. In the premicellar region of surfactant concentrations, surfactant-induced aggregation of Mgcr8Pc prevails. Above the critical micelle concentration of the surfactants, Mgcr8Pc is completely disaggregated to monomers. At the same time, an increase in the alkyl chain length in a surfactant molecule enhances the tendency to its monomerization, as is evident from the results of measuring the electronic absorption and fluorescence spectra, as well as the fluorescence decay kinetics data. A rise in the fluorescence lifetime of Mgcr8Pc with compacting micelles suggests a decline in the degree of their hydration, which leads to a decrease in the polarity of Mgcr8Pc microenvironment. Mgcr8Pc exhibits intense fluorescence in hexadecyltrimethylammonium bromide solutions both at room temperature and after rapid freezing to 77 K, thus confirming that the disaggregated state of Mgcr8Pc molecules remains preserved in micelles even at this low temperature. The results obtained indicate that Mgcr8Pc dissolved in solutions of alkyltrimethylammonium bromides can be used in photodynamic therapy of tumors in combination with cryolysis procedures.
  PubDate: 2022-02-01
Highly Charged Aerosols
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  Abstract: Previously discovered properties of an ensemble of highly charged droplets obtained by electrostatic dispersing of liquids have been discussed. It has been shown that the mechanical strength, glow, and other properties of the ensemble of such droplets are also inherent in ball lightnings. The properties of solid particles, the limiting charges of which exceed the Rayleigh charges of droplets by several orders of magnitude, have also been considered, and the hypothesis of that ball lightnings are of the aerosol nature has been substantiated.
  PubDate: 2022-02-01
Synthesis of Gold Nanorods in a Binary Mixture of Cationic Surfactants
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  Abstract: It has been found that gold nanorods with maxima of longitudinal plasmon resonance at wavelengths of 750–1150 nm can be synthesized in a binary mixture of cetyltrimethylammonium bromide and a benzyl-substituted surfactant. The length of the resulting particles has been shown to depend on the molar ratio between the surfactants and the length of the hydrocarbon chain in the benzyl-substituted surfactant, with this length affecting the properties of the bilayer micellar structure in which the nanorods are formed.
  PubDate: 2022-02-01
The Influence of Acidic Treatment and Mechanical Grinding on the
Structural Characteristics and Morphology of Pores in Iron-Containing
Sodium-Borosilicate Porous Glasses
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  Abstract: The method of low-temperature equilibrium nitrogen adsorption and desorption has been employed to study the porous structure and morphology of porous glass (PG) with a composition of (wt %) 1.54Na2O·6.02B2O3·82.24SiO2·10.20Fe2O3 as depending on the acidic treatment of initial phase-separated glass and mechanical grinding of PG obtained by the through acidic leaching of phase-separated glass with an interconnected structure. It has been found that all studied PG samples have a polymodal mesopore size distribution and contain micropores. Judging by the desorption isotherms, the main modes of the mouth sizes of the mesopores correspond to 3.6–3.8 and 23–25 nm. The micropores have sizes of 1.1–1.4 nm. The calculated structural coefficient indicates that the mesopores have predominantly cylindrical shapes. The comparison between the modes in the distribution curves obtained from the data on adsorption and desorption has indicated the presence of bottle-shaped and conical pores. Mechanical grinding of PGs to the powdered state does not changes the general pattern of the adsorption-desorption isotherms but enhances the volume of mesopores due to the opening of internal dead-end pores and widens the mode of 24-nm liquation channels. An increase in the duration of the acidic leaching under boiling from 7 to 14 h leads to a rise in the mesopore volume and average mesopore diameter by 35 and 25%, respectively. At the same time, the fraction of the micropores in the total pore volume decreases by nearly 10%, while the 8.0-nm mode increases. The results obtained may be useful for improving the synthesis conditions and widening the application fields of PGs exhibiting magnetic properties.
  PubDate: 2022-02-01
Synthesis of Polymer Nanoparticles in the Presence of Diatoms as
Sustainable Bio-Templates
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  Abstract: — Preparation of complex nano- and micron-sized non-spherical particulate geometries still remains a challenge. One potential approach is the utilization of natural templates with diverse shapes. In this report, the siliceous diatoms were served as bio-templates for the preparation of organic/inorganic composite particles through shell suspension polymerization of methyl methacrylate as a model monomer. This led to an efficient encapsulation and entrapment of poly(methyl methacrylate) nanoparticles inside the diatoms. Such a simple approach has a great potential for the synthesis and encapsulation of other types of nanoparticles (e.g., metallic and inorganic) as well.
  PubDate: 2022-02-01
Nanoemulsions Containing Incorporated Lipophilic Drug, Felodipine, and
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  Abstract: Oil-in-water nanoemulsions (NEs) have been obtained with a simple composition, in which a lipophilic non-micelle-forming nonionic surfactant (Tween 85) serves as both a dispersed phase and a stabilizer. The NEs remain in a metastable state for a long time (several months) and have a highly developed specific surface area (Ssp ≅ 63 m2/g) and a high solubilization capacity with respect to a lipophilic hypotensive drug, felodipine (FD). Nanosized droplets (dav ≅ 95 nm) of the NEs efficiently transport FD in an aqueous medium. The oil-in-water NEs of Tween 85 with incorporated FD and a solution of a polymer adhesive (a blend of polyisobutylenes having different molecular weights and polybutene) in heptane have been used to obtain oil1/water/oil2 double emulsions, which are used as premixes for polymer microheterogeneous matrices. Obtained polymer films are characterized by a good adhesion to skin, the absence of FD crystallization, and a constant rate of its release for several hours.
  PubDate: 2022-02-01
Modeling of Colloidal Crystallization of Cadmium Selenide
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  Abstract: This article is devoted to the Monte Carlo simulation of the colloidal crystallization kinetics of cadmium selenide (CdSe) nanoparticles (NPs), i.e., the growth of nanoparticles from individual CdSe molecules. The model of CdSe NP crystallization is modified taking into account available experimental data. This model comprises the rate constants of crystallization in a colloidal solution. It is assumed that the control over the sizes, size distribution, and yield of NPs plays the key role in improving the properties of NPs. The model constants of particle nucleation, growth, and subsequent crystallization are determined under the dynamic equilibrium approximation. The frequencies of attachment and detachment transitions of monomer–NP complexes as depending on the sizes and concentration of NPs are the key parameters of NP formation process. The processes of predecessor particle transformation into a monomer, the formation of an effective monomer, and the nucleation pass to the stage of CdSe NP growth. The Monte Carlo method is used to approximate the kinetic model of the nucleation and growth of CdSe NPs with allowance for individual contributions (concentrations of formed monomers and their diffusion coefficients) to the rate constants of NP formation. The kinetic dependences of the average radius and concentration of CdSe NPs, as well as the NP size distributions, are simulated at different kinetic constants of the colloidal crystallization process.
  PubDate: 2022-02-01
Gold Nanorods with Functionalized Organosilica Shells: Synthesis and
Prospects of Application in Tumor Theranostics
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  Abstract: The features of the formation of organosilica shells from γ-mercaptopropyltrimethoxysilane on the surface of gold nanorods and the possibilities of using the prepared composite particles as means of combined tumor therapy are discussed. It is shown that the presence of SH functional groups, which are able to coordinate platinum ions, in the shells makes it possible to load rather large amounts of an anticancer drug, cisplatin, into them. Quantitative data are obtained on the regularities of the sorption of this drug and the influence of the pH and ionic strength of a solution on the kinetics of its desorption.
  PubDate: 2022-02-01
Effect of Low Concentrations of Thrombin on the Dynamic Surface Properties
of Fibrinogen Solutions
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  Abstract: The interaction between fibrinogen and thrombin with the formation of fibrin is a key stage in the formation of a blood clot during blood coagulation, with the morphology of the clot being determined by the concentrations of the components. It has previously been shown that, at low thrombin concentrations, long fibrillar aggregates of fibrin are formed. In this paper, we consider the features of the formation of fibrin aggregates in the surface layers of aqueous solutions at relatively low concentrations of both fibrinogen (5 × 10–9–2 × 10–7 M) and thrombin (5–25 U/L). At a low thrombin concentration (5 U/L), nonmonotonic dependences of elasticity are observed probably due to the unfolding of protein macromolecules in the surface layer. At higher enzyme concentrations (10 and 25 U/L), these dependences become monotonic, and the dynamic surface elasticity reaches higher values that exceed those for pure protein solutions. Atomic force microscopic examinations have suggested that this effect is caused by the formation of fibrillar aggregates in the surface layer.
  PubDate: 2022-02-01
The Use of the Finite-Element Method for Calculating the Photophoresis
Force Applied to a Large Spheroidal Aerosol Particle
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  Abstract: The finite-element method has been employed to calculate the photophoresis force applied to a solid spheroidal aerosol particle, the size of which is much larger than the mean free path of gas molecules. The thermal electromagnetic radiation from the particle surface and the temperature dependences of the density, viscosity, and thermal conductivity of the gaseous medium and the particle material thermal conductivity have been taken into account. The photophoresis force applied to the particle heated by an electromagnetic radiation flux directed along the particle symmetry axis has been numerically calculated.
  PubDate: 2022-02-01
Approaches to the Sample Preparation of Food Emulsions for Their Efficient
Separation and Precipitation of Nonvolatile Polymer Components
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  Abstract: Gas chromatography is the main method for the analysis of volatile substances in food products, in particular, additives that improve their taste and appearance. However, food matrices are, usually, complex disperse systems (emulsions, gels, or foams), the direct gas chromatographic analysis of which is difficult. In addition, such matrices can damage chromatographic columns and contaminate evaporators and detectors, thereby leading not only to improper analytical data (unacceptable peak shapes or loss of sensitivity), but also to a decrease in the service life and the need for frequent maintenance of an entire system. Therefore, in order to obtain reliable results and protect expensive analytical equipment, it is necessary to use methods of preliminary preparation of samples with the purposed of purifying them from high-boiling natural compounds. In this work, we have compared two fundamentally different approaches to sample preparation of food emulsions, i.e., the liquid-liquid and solid-phase extraction in order to choose the most acceptable method both from the viewpoints of the accuracy and reliability of the results obtained and from the standpoints of economic advisability and time consumptions. The study was carried out by the example of determining the content of ethanol, as well as the qualitative analysis of impurity alcohols in an alcohol emulsion of shellac (E904).
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X21060181
Some Questions Concerning a Small Sessile Bubble
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  Abstract: Equations have been derived for the size dependence of the interfacial tension and contact angle of a small spherical sessile bubble under isothermal conditions. It has been shown that the account of the size dependence of the interfacial tension may violate the consistency condition for the contact angles of small bubbles and droplets. This dependence is manifested in the fact that the interfacial tension at a concave surface of a bubble is higher than that at a convex surface of a droplet.
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X21060107
Influence of Vapor–Gas Medium Heating due to the Condensation Heat on
the Stage of Multicomponent Droplet Nucleation
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  Abstract: The article describes the effect of phase transition heat on the temperature of a closed multicomponent vapor–gas metastable phase and on growing supercritical droplets and their size distribution at the stage of homogeneous formation and growth (nucleation stage) of the supercritical droplets. It is assumed that, between essentially supercritical droplets and the vapor–gas medium, a stationary diffusion transfer of condensing vapor molecules and heat is established, and, then, both the composition and temperature remain unchanged and the same for all supercritical droplets. A set of equations is derived to determine the composition, temperature, and growth rate of the essentially supercritical droplets via the initial temperature and supersaturation of vapors. Expressions are obtained for the deviation of vapor–gas medium temperature from its initial value and for the droplet size distribution function as depending on time.
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X21050082
Experimental and Simulation Investigations of Magnetic Liquid Marble
Manipulation with a Permanent Magnet
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  Abstract: Magnetic liquid marbles are defined as non-stick droplets encapsulated with hydrophobic magnetic nanoparticles. These liquid marbles show great responsiveness to external magnetic force when magnetic coating or content is utilized. In this study, first, in the experimental section, for production of a magnetic liquid marble, Fe3O4 magnetic nanoparticles were synthesized. After this, the transport of the liquid marble under the influence of magnetic field of a permanent rectangular magnet was carried out. Reversible opening and closing of the nanoparticle shell by the permanent magnet was conducted. Second, in the simulation section, by modeling our liquid marble by a droplet with an elastic shell, the effects of gravity and magnetic forces on a magnetizable layer were simulated by Finite Element Method and compared with experimental data. The comparison with the experimental data validates and shows the accuracy of the simulation which is the novelty of our work. This liquid marble with the ability of opening and closing of nanoparticle shell under the magnetic field effect has the potential to be used as a miniaturized robot or bioreactor.
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X21060090
The Growth of Phosphonium Gold Nanoparticles in Alkaline Media: Kinetics
and Mechanism of the Process
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  Abstract: It has been found that the addition of ammonia water to a gold sol obtained by the Duff method induces the growth of the gold particles. The growth kinetics of such particles in alkaline solutions of ammonia and sodium hydroxide has been investigated. Using the modified Kolmogorov–Johnson–Mel–Avrami model, the aggregative mechanism of nanoparticle growth has been revealed for a system with the maximum NH3⋅H2O concentration, while a mixed mechanism, which includes the Ostwald ripening, has been found for other systems. It has been shown that the sizes and dispersity of the final particles can be controlled by varying the concentration of ammonia water and the time of preliminary incubation of an initial sol, while sodium hydroxide does not exhibit such ability. It has been assumed that the decomposition of gold–phosphine complexes, which stabilize the ultrafine particles, followed by the formation of gold–ammonia complexes is the most probable explanation for the action of ammonia water on the Duff sols.
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X21060053
Thermophoresis of Cylindrical Particle Immersed in Brinkman Fluid
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  Abstract: This paper reports an analytical study for the thermophoresis of a circular cylindrical aerosol particle embedded in a porous medium of constant porosity based on the Brinkman model. The Knudsen number is supposed to be in the slip-flow regime. The Peclet and Reynolds numbers are small, therefore the convective effects are neglected, and the problem can be considered quasi-steady. The porous medium is supposed to be homogeneous, isotropic and the solid phase is in thermal equilibrium with the fluid through the voids of the medium. In the analysis of motion, at the surface of the particle, we consider the following effects: temperature jump, thermal creep, viscous slip, and thermal stress slip. Formulas for thermophoretic velocity and force are derived. The novelty of the problem is the permeability parameter which characterizing the Brinkman flow. The effect of this parameter is shown through several plots for thermophoretic velocity and force against the thermal properties of the particle and porous medium. The limiting cases of Stokes and Darcy’s flows and the case of no thermal slip are discussed. results are also compared with the corresponding values for the case of spherical particles.
  PubDate: 2021-11-01
  DOI: 10.1134/S1061933X2106003X