Colloid Journal最新文献

This study numerically investigates the electroosmotic flow (EOF) of power-law fluids in soft nanochannels whose inner walls are coated with pH-sensitive polyelectrolyte layers (PELs) containing basic functional groups. We focused on the combined effects of ion size and ion partitioning on the fully developed EOF within these channels. Our model uses modified Poisson−Boltzmann and Cauchy momentum equations to describe the electrostatic potential and flow velocity, which we solved numerically using the finite difference method. The results highlight the significant influence of ion size and ion partitioning (due to permittivity differences between the PEL and electrolyte) on both the electrostatic potential and the flow velocity, along with the role of other key parameters. We also emphasize the importance of the basic functional group present throughout the PEL on the selectivity of mobile electrolyte ions.

This study uses wintergreen (Gaultheria procumbens) plant extract as a reducing agent in a green synthesis technique to create silver nanoparticles (AgNPs). Numerous analytical methods, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and zeta potential analysis, were used to characterize the synthesized AgNPs. The results revealed the successful synthesis of AgNPs with an average size of approximately 25 nm and a face-centered cubic (FCC) crystalline structure. Furthermore, the synthesized AgNPs effectively removed direct yellow 4 (DY4) dye from aqueous solutions, displaying a maximum adsorption capacity of 92 mg/g. The adsorption kinetics of DY4 on AgNPs followed the pseudo-second-order model, indicating that chemisorption mechanisms predominantly govern the adsorption process. Additionally, the adsorption isotherms of DY4 on the surface of AgNPs adhered closely to the Langmuir isotherm model, suggesting monolayer adsorption on the uniform surface of AgNPs through strong adsorbate-adsorbent interactions. Moreover, the AgNPs demonstrated promising potential for reusability, as evidenced by the retention of approximately 97% adsorption efficiency even after undergoing four consecutive adsorption-desorption cycles. This highlights the robustness and durability of the AgNPs as effective adsorbents for wastewater treatment applications.

The interaction of fish gelatin and agar in the bulk of an aqueous phase with the formation of supramolecular protein–polysaccharide complexes has been studied using spectroscopy (FTIR and UV), turbidimetry, quasi-elastic laser light scattering, and scanning electron microscopy. The effects of gelatin structure (content of amino acid residues), agar/fish gelatin ratio Z (weight/weight), and medium (pH and ionic strength I) on the boundaries of the regions of stoichiometric and non-stoichiometric complex formation, the size and ζ-potential of particles and, hence, the phase state of the aqueous mixtures (colloidal solutions) of the biopolymers have been considered. Phase diagrams have been plotted for aqueous mixtures of fish gelatin and agar in the Z–characteristic pH and I–characteristic pH coordinates. The regions of different phase states of the systems have been determined, such as a single-phase solution of non-complexed biopolymers, a dispersion of fish gelatin–agar complexes, the region of the onset of the separation of coacervates from the dispersion, and the region of the complete separation of the coacervate phase and the supernatant. It has been shown that the formation of fish gelatin–agar complexes affects the microstructure of gels formed as a result of cooling aqueous mixtures of the biopolymers.

Samples of a magnetic fluid stabilized with a double surfactant layer have been synthesized in water using a nonionic stabilizer TWEEN 20 (Polysorbate 20) as the second layer. The rheological properties of the synthesized samples have been studied as depending on their concentration. In contrast to fluids containing dissociated surfactants, the viscosity of the magnetic fluid decreases with increasing temperature faster than does the viscosity of the base medium (water). The main advantage of using a nonionic surfactant is the possibility of synthesizing low-temperature magnetic fluids based on water–alcohol mixtures and aqueous salt solutions. Fluids stabilized with TWEEN 20 in ethylene glycol and propylene glycol solutions remain mobile to temperatures of –40 and –50°С. When calcium chloride (CaCl₂) solutions are used as base media, the test samples of the fluid retain their working capacity to a temperature of –30°С. Magnetic fluids based on alcohol and salt solutions can be indispensable in the fields of engineering, in which their high fire and environmental safety are required. The chemical inertness of particles stabilized with TWEEN 20 makes them to be applicable in biology and medicine.

The research work presents the eco-friendly synthesis of titanium dioxide (TiO₂) nanoparticles using an aqueous extract of Syzygium samarangense through a green synthesis approach. The biofabricated TiO₂ nanoparticles were characterized using various techniques, including Field Emission Scanning Electron Microscopy, which revealed a distinctive ball-like morphology. The crystalline size of nanomaterials were determined by X-ray diffraction method. Ultraviolet spectroscopy analysis indicates band gap energy of 3.1 eV, which confirms that nanoparticles are suitable for photocatalytic applications. Phytochemical analysis of the Syzygium samarangense extract demonstrated the presence of key biomolecules such as alkaloids and phenolic compounds, which likely played a crucial role in nanoparticles synthesis and stabilization. The photocatalytic activity of the synthesized TiO₂ nanoparticles was evaluated using methylene blue dye degradation under ultraviolet light. The nanoparticles exhibited significant photocatalytic efficiency, with a marked decrease in methylene blue concentration over time, highlighting their potential for environmental remediation. These results demonstrate the viability of green-synthesized TiO₂ nanoparticles for photocatalytic applications, offering a sustainable alternative to conventional methods of nanoparticles fabrication.

4-Chlorobenzoic acid (4-CBA) serves as an important industrial compound, utilized as a probe for hydroxyl radicals in ozonation processes, as well as a ligand in the synthesis of luminescent lanthanide complexes. 4-CBA can be produced from 4-Chlorobenzaldehyde (4-CBZ) via oxidation using a specific oxidizing agent. The oxidation kinetics of 4-CBZ by N-Bromosuccinimide (NBS), facilitated by Ru(III), have been investigated in both the aqueous and dodecyltrimethylammonium bromide (DTAB) micellar medium. The reaction’s progression was assessed by quantifying unreacted NBS iodometrically. Throughout the range of concentrations analyzed, the 4-CBZ oxidation demonstrates a fractional-order kinetics concerning both [4-CBZ] and [Ru(III)], exhibits negative first-order reliance with respect to [HClO₄], and shows first-order dependence on [NBS]. The observed constancy in oxidation rate with the inclusion of electrolyte suggests a zero salt effect. The fractional order reliance on 4-CBZ and Ru(III) suggests that the catalyst and substrate form a complex prior to the rate-determining step. The results demonstrate that the NBS itself and [RuCl₅(H₂O)]²⁻ will be the most reactive species of NBS and Ru(III) in an acidic environment. The oxidation rate is markedly increased by Ru(III) (2.1 times) acting as a catalyst at ppm concentration. The micellar media of DTAB further accelerates the reaction rate by a factor of 4.3. Ru(III) and DTAB micelles synergistically enhanced the oxidation rate of 4-CBZ by 6.4 fold. A credible mechanism that corresponds with the kinetic findings has been emphasized, alongside an analysis of the Piszkiewicz model, to elucidate the apparent catalytic influence of DTAB micellar environments.

Printed electronic is an area of modern materials science that is undergoing rapid development. The use of printing equipment has the potential to significantly simplify and reduce the cost of producing passive and active electronic components. Several dozens of reviews and hundreds of scientific articles are published annually in this field. However, the consumer characteristics of ink formulations for printed electronic are, to a certain extent, compromise. Improvement of one property usually results in a deterioration of another. For example, increasing the content of the main component usually leads to a decrease in stability. This review will compare two main approaches to producing metal-based inks, which can be conventionally called “organometallic” and “colloidal,” consider their advantages and drawbacks, and assess the prospects for further development of printed electronics.

The features of the interaction of ultrasmall gold nanoparticles (GNPs) synthesized via Duff method with particles of optically active liquid-crystalline dispersions (LCDs) of DNA formed at varying concentrations of NaCl and polyethylene glycol were studied. It was shown that the GNPs have different effects on the LCDs with positive and negative orientation of anomalous circular dichroism (CD) signal. Apparently, this is in a measure due to the various conformation of the DNA molecules that form the corresponding dispersed particles. The kinetic aspects of the interaction of GNPs with DNA LCDs and the features of “loading” ultradispersed gold into the LCD particles are also discussed.

Nanoparticles of a chitosan–κ-carrageenan polyelectrolyte complex containing CdS/ZnS core–shell quantum dots have been obtained and characterized as models of biocompatible luminescent delivery systems for an antibiotic, vancomycin, with an encapsulation efficiency of 95–97%. The quantum dots have been obtained by the colloidal synthesis method and hydrophilized with mercaptopropionic acid. The effect of vancomycin encapsulated in the particles of the polyelectrolyte complex on the luminescent properties of CdS/ZnS quantum dots has been studied. It has been shown that the synthesized quantum dots can be employed as analytical nanosensors for determining vancomycin incorporation into and release from the developed carriers on the basis of quenching their luminescence. The binding of vancomycin to albumin as a model blood protein has been studied and the composition of the complex ([vancomycin] : [albumin] = 1.0 : 2.0) and its stability constant (β_c = 6.0 × 10⁴ M^–1) have been determined. The in vitro analysis of kinetic data on the release of vancomycin from the polymer carriers into albumin and tris-buffer solutions performed within the framework of the Korsmeyer–Peppas mathematical model has shown that the release of the antibiotic is controlled by both diffusion and relaxation of the polymer matrix.

This paper proposes a theoretical model for the magnetorheological properties of magnetic elastomers composed of micron-sized particles, which are magnetizable, have no intrinsic magnetic moment, and occur in a soft polymer medium. The study examines two types of composites: initially isotropic ones (synthesized in the absence of magnetic field) and anisotropic ones (polymerized in a magnetic field promoting aggregation of the particles into anisotropic structures). The data obtained show that the formation of anisotropic structures at the stage of the synthesis leads to a substantial increase in the macroscopic shear rigidity of the composite. The theoretical results are in quantitative agreement with experimental data.