Colloid Journal最新文献

This work is devoted to studying mechanical durability of a superhydrophobic coating obtained on the basis of commercial EP-140 epoxy enamel. To achieve the superhydrophobic state, the applied coating is modified by pulsed laser texturing and fluorosilane chemisorption. The goal of the research is to assess the coating resistance to various mechanical actions typical for outdoor service, namely, long-term contact with water, exposure to high-speed water jet, abrasive wear under the action of falling sand, and multiple detachments of an adhesive tape. It has been shown that the combined approach used for the superhydrophobization provides coatings not only with pronounced water-repellent properties but also with significant resistance to degradation. For example, the performed experiments have revealed only a slight decrease in the wettability characteristics with retaining the heterogeneous wetting regime, thereby confirming that the coating retains its functionality even under extremal mechanical impacts. The data obtained have indicated the promise of applying the developed coating in industry fields that require a combination of high wear resistance and economic efficiency.

Mushroom polysaccharides are biologically active substances with strong reduction, capture, and stabilization capabilities. They have great potential in the synthesis of metal nanoparticles. This study developed a method for the electrochemical synthesis of silver nanoparticles from polysaccharide extracts (AgNP-AcPOLY) of the Amanita pantherina mushroom. Silver nanoparticles (AgNPs) were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), electrophoretic light scattering (ELS), UV-vis spectroscopic (UV-Vis), and laser diffraction spectroscopy (LDS) methods. XRD and TEM studies showed that the silver nanoparticles are spherical with a size of about 11.6 nm. The electrochemical performance of AgNP-AcPOLY nanoparticles was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that AgNP-AcPOLY exhibits outstanding electrochemical properties, significantly enhancing the performance of screen-printed electrodes (SPE). In addition, the antibacterial activity of nanosilver was evaluated through the methods of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against two strains of bacteria, Staphylococcus aureus and Escherichia coli. The results of this study indicate that the silver nanoparticles synthesized from the polysaccharide extract of A. pantherina are clean and environmentally friendly and have broad-spectrum antibacterial ability.

This study presents a rapid and eco-friendly approach to synthesize gold nanoparticles (AuNPs) using waste avocado seed extract (AV) as a reducing and capping agent. Microwave irradiation enables the synthesis of AuNPs within a minute, as evidenced by the solution’s characteristic red color and confirmed by a surface plasmon resonance (SPR) peak at ~530 nm in the UV-visible spectrum. Synthesis parameters, including pH and concentrations of AV and gold chloride, were optimized, revealing that mild alkaline conditions favor AuNP formation, while acidic conditions are detrimental. The AuNPs, characterized by transmission electron microscopy (TEM), exhibited a small size (9.9 ± 3.6 nm) and spherical morphology without aggregation. X-ray diffraction (XRD) confirmed the face-centered cubic (FCC) crystal structure of the AuNPs, and Fourier transform infrared (FTIR) spectroscopy indicated the involvement of functional groups in AV in the reduction and stabilization of the nanoparticles. The AV@AuNPs demonstrated excellent stability, as indicated by a high negative zeta potential (–27.0 ± 6.4 mV). Additionally, the nanoparticles showed strong antioxidant activity comparable to ascorbic acid and significant antibacterial efficacy against both Gram-positive (S. aureus and B. subtilis) and Gram-negative (E. coli and P. aeruginosa) bacteria, with a pronounced effect on Gram-negative strains.

Macroporous physical (noncovalent) cryogels have been prepared via freezing at –20°C for 12 h followed defrosting by heating at a rate of 0.03°C/min of aqueous poly(vinyl alcohol) (PVA) solutions without and with additives (0.1–0.5 mol/L) of basic α-amino acids (arginine, histidine, lysine, ornithine) in nonprotonated or salt forms, and the influence of such additives on the physicochemical properties of the gel materials formed in this way has been studied. It has been shown that additives of arginine, its hydrochloride, as well as histidine, exhibit a chaotropic action on the cryotropic gelation of PVA by hindering hydrogen bonding, thus leading to a decrease in the elasticity and heat endurance of the resultant cryogels, whereas additives of lysine, ornithine and their hydrochlorides, as well as histidine hydrochloride, act as kosmotropic agents causing an increase in the compressive elasticity modulus and the fusion temperature of the samples due to the promotion of hydrogen bonding. The kinetic study of releasing amino acid additives used in the work has shown that the hydrochlorides are released from a gel carrier into an external aqueous environment somewhat slower than are nonprotonated forms, but without noticeable diffusion hindrances in all cases. Taking into account that such amino acids are used in cosmetology, the results obtained in this study suggest that PVA cryogels loaded with amino acid additives may be of practical interest when developing carriers for cosmetics such as nourishing masks, coatings for problem areas of skin, “patches”, etc.

Water–salt solutions of interpolyelectrolyte complexes (IPECs) represent a classical example of “smart” systems, the phase equilibrium in which is regulated by many factors associated with both the parameters of the polymer components and the physical and chemical properties of an environment. This paper presents a model created on the basis of machine learning for predicting the region of existence of water-soluble IPECs. An approach is proposed for independent account of the physicochemical properties of polyelectrolytes and the properties of the environment. The developed model is universal and can be used to predict the properties of multicomponent systems of various chemical natures.

Composite films based on silver organosols stabilized with an anionic surfactant (AOT, sodium bis(2-ethylhexyl)sulfosuccinate) have been formed on polystyrene substrates by the dip-coating method. The process of film formation has been shown to be accompanied by the appearance of silver aggregates with interparticle distances exceeding the particle diameters. At the same time the aggregation has no effect on the optical properties of the nanoparticles. The obtained films exhibit plasmon absorption signal and the absence of plasmonic delocalization. Variations in the the number of substrate immersions in the sol makes it possible to affect the intensity of the plasmon absorption signal and the functional properties of the resulting coatings, such as their morphology, roughness (from 9 ± 2 to 25 ± 4 nm), thickness (from 585 ± 13 to 831 ± 28 nm), and the wettability of the surface by water (from 36 ± 6 to 53 ± 9°).

This study considers the potential of application of graphene-based nanofluids as heat-transfer agents in direct absorption solar collectors. It has been revealed that graphene-based nanofluids have superior absorption ability when interacting with monochromatic (520 nm) and near-IR radiation. As compared with distilled water, the use of graphene-based nanofluids as working fluids in direct absorption solar collectors increases their efficiency even at very low concentrations of dispersed phase particles. However, in order to apply graphene-based nanofluids as working fluids in energy systems, some issues need to be solved, primarily those related to their low stability and thermal instability.

A set of methods (tensiometry, conductometry, dynamic light scattering, spectroscopy, and fluorimetry) has been employed to study the self-assembly of long-chain bis-quaternized hydroxyethyl group-containing derivatives of 1,4-diazabicyclo[2.2.2]octane. The critical micelle concentrations, adsorption characteristics of the air–water interface, solubilization capacities with respect to poorly water-soluble OrangeOT dye, aggregation numbers, and sizes of aggregates have been determined. The influence of the structure (alkyl chain length and head group charge) of the studied compounds on their micelle-forming and antimicrobial properties, as well as hemolytic activity, has been determined.

Uniform rough films containing up to 73 at % silver have been obtained by the Doctor Blade method from concentrated silver nanoparticle organosols stabilized with sodium bis(2-ethylhexyl) sulfosuccinate. Variations in the wettability of the films have been studied in detail as depending on the conditions of their heat treatment within a temperature range of 50–500°C. The temperature dependence of the contact angles is not monotonic and implies the transition from superhydrophilic to weakly hydrophilic systems due to the processes of sintering of nanoparticles and thermal decomposition of the stabilizer. It has been experimentally shown that a transition from nonconductive to conductive coatings (from 500 to 105 mΩ/sq) is accompanied by a drastic increase in the contact angle (from 25 to 78°).

The electrostatic interaction between two identical charged dielectric spherical particles in a symmetric electrolyte solution has been studied on the basis of the Poisson–Boltzmann equation. Particular attention has been focused on the case of high surface potentials of the particles, whose radii are significantly larger than the Debye radius. Using the finite element method, the interaction forces between the particles have been calculated under the conditions of a uniform charge distribution on their surfaces and the absence of an external electric field. It has been shown that allowance for the nonlinearity of the Poisson–Boltzmann equation may be necessary even when the surface potentials of the particles are rather low and the formal application of the linearized Poisson–Boltzmann equation may be employed. The results obtained can be useful for understanding the processes that occur in colloidal systems and analyzing experimental data on the interaction of micron-sized particles in electrolyte solutions.