Vol 85, No 2 (2023)

This study investigated the controllable fabrication of anisotropic particles with different sizes and morphologies via self-assembly and photoinduced deformation of azo colloidal microspheres, which were formed from a typical azo molecular material (IAC-4) that contains a 1,4,3,6-dianhydrosorbitol core and the cinnamate peripheral groups. Firstly, azo colloidal microspheres were obtained by self-assembly via gradually adding deionized water into IAC-4 solution of tetrahydrofuran. For precisely controlling the length of short axis of anisotropic particles, IAC-4 colloidal microspheres with different and uniform sizes were obtained by adjusting the IAC-4 concentration, adding rate of water and stirring rate. The size of colloidal microspheres becomes smaller with the increase in IAC-4 concentration, the adding rate of water and the stirring rate. Finally, IAC-4 colloidal microspheres in the solid state, perpendicularly irradiated by the linearly polarized laser beam (λ = 488 nm), were irreversibly and controllably stretched into anisotropic particles with the different morphologies, length of long axis and axial ratio via adjusting the irradiation time and the power of laser beam.

The article presents the results of experimental studying the hysteresis of water contact angles at crystalline surfaces. Receding and advancing contact angles and their hysteresis at hydrophilic and hydrophobic substrates with different surface structures (silica, mica, and calcite) have been studied under the action of an external pressure applied to the three-phase contact line of a sessile air bubble. Hysteresis of the contact angles has been observed on hydrophobized samples of silica and mica. The anchoring of the three-phase contact line (pinning) facilitates a change in the contact angles under the applied external pressure. When the three-phase contact line moves along the hydrophilic surfaces of silica and mica no marked changes in the advancing and receding contact angles are observed, and the hysteresis is actually absent. The stable pinning observed on the polished surface of a calcite crystal brought in contact with water leads to the appearance of contact angle hysteresis and hydrophilization of the calcite surface, with the hydrophilization being related to structural displacements in the crystal lattice.

The present article deals with the comprehensive parametric study on electroosmotic flow and transportation of ions through polymer grafted soft nanochannel containing non-Newtonian fluid. We consider the fully developed flow in a slit rectangular channel. The charged poly-electrolyte layer (PEL) carries a monovalent acidic ionizable group attached to a rigid wall. The ion partitioning effect is considered in our study, which arises from the difference in relative permittivity of the polyelectrolyte region and the bulk electrolyte. The non-linear Poisson−Boltzmann equation and the modified Cauchy momentum equation, which are coupled, are used to describe the mathematical model. The main objective of this analysis is to demonstrate the impact of bulk pH on the charge regulation of mono-ionic functional groups residing in PEL, the impact of flow behavior index and different electrohydrodynamic parameters, including EDL thickness, ion-partitioning parameter, the Debye−Hückel parameter, and softness parameters etc, on the overall flow modulation and selectivity parameter. This study is expected to constitute a significant step forward in the real-world continuum mathematical modelling of interfacial flow physics in the scenario of electrohydrodynamics in soft nanochannels.

The processes of laser dispersion of materials for high-performance generation of colloidal nanoparticles in liquids have been considered. Various laser and material parameters affecting this process have been studied. Efficiencies and ergonomics of the generation of colloidal nanoparticles with the help of laser systems having nano-, pico-, and femtosecond pulse durations have been compared using optical and mass criteria by the example of laser ablation of a chemically inert model material (gold) in distilled water without the use of chemical stabilizers. The main characteristics of gold and silver nanoparticles obtained by ablation in water using pulsed laser radiation of different durations have been comprehensively compared. The types of colloidal interactions between nanoparticles in aqueous media have been discussed, and the contributions of structural and ion-electrostatic interactions to the long-term stability of gold and silver nanoparticle dispersions have been analyzed.

New biocompatible microemulsion and liquid-crystalline sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/isopropyl myristate systems have been obtained for the delivery of drugs and physiologically active substances. A combination of dynamic light scattering and X-ray diffraction methods has been used to determine their structural and size characteristics. The Primus and SasView software packages have been employed to simulate the shape and arrangement of particles as depending on AOT content. It has been shown that, as the concentration of the surfactant increases, the shape of micelles varies from spherical to cylindrical, and, at high concentrations, a structural phase transition occurs with the formation of a liquid-crystalline phase. The influence of a model bioactive compound, L-lysine, on the size and structure of the system has been studied. It has been revealed that the addition of the amino acids to the samples leads to an increase in the microemulsion droplet size, and, in the case of the liquid-crystalline phase, to the disintegration of the hexagonal packing into individual cylinders. The results obtained can be useful for the analysis of the mechanisms of L-lysine release from the AOT/water/isopropyl myristate transport system.