Colloid Journal最新文献

Janus particles represent one of the forms of existence of heterogeneous micro- and nanoparticles. A convenient mathematical prototype of Janus particles is a double bubble, which was described by Plateau when solving the problem of minimal surfaces. The main difference between a double bubble and a Janus particle is an additional condition that interfaces can have different elastic properties. The solution for this case has been obtained using the Young’s method. The limits of the existence of this solution have been revealed. The dependence of the configuration of Janus particles on the relation between the surface properties and the volumes that form the particles has been shown.

A novel method has been proposed for preparing stable highly concentrated Pickering emulsions stabilized with 2D particles of carbon nitride (g-C₃N₄) and its mixtures with graphene oxide (GO) in a water/n-hexane system due to electrostatic interactions with zinc acetate (Zn(OAc)₂). Optical microscopy and sedimentation stability analysis have been employed to determine optimal conditions for preparing emulsions with g-C₃N₄ concentrations up to 6 mg/mL. The formation of oil-in-water (o/w) emulsions stabilized with either g-C₃N₄ particles or GO/g-C₃N₄ binary dispersions has been confirmed by fluorescence microscopy using a water-soluble dye, fluorescein. Measurements of the ζ-potentials of g-C₃N₄ sols and emulsions stabilized with g-C₃N₄ have made it possible to determine the main stabilization mechanism of the highly concentrated Pickering emulsions. It has been found that acetate ions (CH₃COO⁻) promote migration of negatively charged g-C₃N₄ particles from the aqueous phase to the interfaces, while zinc cations (Zn²⁺) are adsorbed on the g-C₃N₄ surface, thereby suppressing the mutual repulsion of the particles in the shells of emulsion droplets. During the formation of Pickering emulsions based on GO/g-C₃N₄ binary disperse systems, metal clusters contribute to the stabilization of emulsions due to coordination bonding between GO carboxyl groups and g-C₃N₄ particles. This mechanism provides efficient particle integration at the interfaces and prevents the highly concentrated Pickering emulsions from separation. The results obtained open up prospects for developing universal catalytic systems with controllable properties to be used for the degradation of organic pollutants and the synthesis of functional materials.

The results of decontamination of heat- and radiation-resistant organosilicate coatings intended for the protection of nuclear power plant equipment have been analyzed as depending on their composition and surface roughness. The possibility of improving the physicomechanical properties of these coatings by adding detonation nanodiamond has been tested.

A new strategy of controlled non-covalent assembly is applied for tuning of the properties of ultrathin film hybrids based on graphene oxide (GO), tetracarboxyphenylporphyrin (TCPP), and polydiacetylene surfactant (PDA). It is shown how, using layer-by-layer deposition or one-step self-assembly of components at the air/water interface, it is possible to influence the mechanisms of energy and charge transfer while maintaining the chemical composition of the ultrathin film. Zinc acetate was used to integrate the active components of the hybrid through coordination bonds with the carboxyl groups of the GO and organic components. Atomic force microscopy showed that layer-by-layer assembly results in an ordered structure with a dense monolayer of GO at the base, an intermediate layer of TCPP, and an upper layer of PDA crystallites. Single-stage assembly leads to the formation of a mixed layer of GO–Zn²⁺–TCPP with a folded GO morphology covered with PDA. Spectroscopic studies revealed Förster resonance energy transfer in both hybrids, in which porphyrin acts as both an energy donor and acceptor depending on the structural form of the polydiacetylene surfactant associated with it. Hybrids obtained by layer-by-layer assembly, when integrated into photovoltaic cells with an electron-hole transport layer, demonstrated pronounced diode properties and significant photoresponse due to effective spatial separation of charges and directed transport in the layered structure. Hybrids obtained in a single stage produce symmetrical volt-ampere curves and low photoresponse due to exciton recombination in a disordered structure. The results demonstrate the fundamental possibility of controlling charge transport in photoactive hybrids by controlling their supramolecular organization through the choice of assembly method.

This paper presents the results of experimental studying the effect of single-wall carbon nanotube (SWCNT) additives on the viscoelastic and thermophysical properties of hydrocarbon-based drilling fluids. The rheology, viscoelastic properties, thermal conductivity and thermal diffusivity of SWCNT-modified drilling fluids with different hydrocarbon phase contents have, for the first time, been investigated. The work has shown that the addition of SWCNTs can significantly improve the functional properties of hydrocarbon-based drilling fluids. The introduction of the nanotubes into a drilling fluid can, in a number of cases, increase the apparent viscosity by an order of magnitude, enhance the consistency parameter and yield point values by many times, and almost double the thermal conductivity, thereby opening up broad prospects for using single-wall nanotubes as regulators of drilling fluid properties.

The review examines research studies in the field of electrorheology in recent years. The main actively developing research areas are presented. The latest achievements in both the development of novel materials and the theoretical description of the effect are summarized. The progress in the field of practical application is considered and origin al promising applications of the electrorheological effect are noted.

A simple condensation method is proposed and implemented for obtaining a niosomal form of an actually water-insoluble biocide (chlorhexidine base, CHX), with this form being an efficient carrier of CHX in an aqueous medium. The approach is based on the solubilization of CHX in aqueous micellar solutions of polyoxyethylated surfactants (Tween 80 and Tween 20) without using organic solvents, high-energy dispersing, and a rotary evaporator, which are necessary attributes in the common practice of obtaining niosomes. The proposed method provides a high degree of biocide encapsulation (96 ± 2%). Aqueous dispersions of two-component niosomes (Tween 80 + CHX and Tween 20 + CHX) stable for a long time are obtained. The sizes and structure of niosomes, as well as their solubilization capacity and transport properties with respect to CHX are determined. The effect of the hydrocarbon chain length of the surfactants on the sizes and stability of niosomes with incorporated CHX is analyzed. A mechanism is proposed for the transformation of micelles of the polyoxyethylated surfactants with solubilized CHX into niosomes at a CHX/surfactant molar ratio of 1/2.

In this research, water-soluble functionalized gold nanorods (Au NRs) with low toxicity were synthesized by a seed-mediated growth method. For this purpose, a seed solution of the gold nanoparticles was added to the growth solution containing a weak reducing agent to form a controlled size of gold nanorods. After that, to explore the applicability of gold nanoparticles in biomedicine, particularly in photothermal therapy as a noninvasive therapeutic tool, the prepared Au NRs were functionalized using (11-Mercaptoundecyl)tetra(ethylene glycol) as a monohydroxy thioalkylated PEG (MUTEG) ligand, for the first time. To confirm the formation of Au NRs and determination of their size and aspect ratio, UV−Vis spectroscopy and TEM techniques were applied. The CHNS analysis was employed to characterize the attached MUTEG ligands on the surface of the Au NRs. The HeLa cells were used to determine the cytotoxicity of the prepared Au-MUTEG NRs. The surface of the prepared Au-MUTEG NRs was conjugated with BSA to obtain Au-MUTEG−BSA NRs, as the final product, and confirmed by FT-IR analysis. The zeta potential analysis was also used to determine the charge and stability of the functionalized Au-MUTEG and Au-MUTEG−BSA NRs in comparison with Au NRs.

An express method of solvent-free dry mechanochemistry using fine grinding in air for 3 and 6 minutes in a mill (0.94 kW; 26 000 rpm) is employed to targetedly change the structure of kaolin and increase its sorption capacity. During the same process, kaolin is modified together with hydrolytic lignin to hydrophobize its surface and improve its sorption properties. The influence of the mechanical activation on the structure and properties of kaolin, hydrolytic lignin, and their composites with different component ratios is studied using electronic microscopy, X-ray diffraction, infrared spectroscopy, low-temperature nitrogen adsorption, and UV absorption spectroscopy. The dense structure of kaolinite remains preserved, hydrogen bonds in hydrolytic lignin are ruptured, and the number of carbonyl groups increases, while fragments of the natural polymer are grafted to kaolinite. It has been found that an agglomeration–aggregative microstructure is formed in the composites. Kaolin and the kaolin–hydrolytic lignin composite (10 : 1, weight/weight) treated at a mechanical energy dose of 0.83 kJ g^–1 undergo significant structural changes and exhibit rather high sorption characteristics. The Brunauer−Emmett−Teller specific surface area of these sorbents is ∼16 m² g^–1, while their adsorption capacities for bovine serum albumin are 83.63 and 44.10 mg g^–1, respectively. Thus, the dry mechanical activation in air under “mild” conditions makes it possible to increase the sorption of bovine serum albumin on kaolin by 104%.