Laser methods are successfully used to prepare complex functional nanomaterials, especially for biomedicine, optoelectronics, and heterogeneous catalysis. In this paper, we present complex oxide and composite nanomaterials based on Bi and Si produced using laser ablation in liquid followed by subsequent powder annealing. Two synthesis approaches were used, with and without laser post-treatment of mixed (in an atomic ratio of 2:1) laser-generated Bi and Si colloids. A range of methods were used to characterize the samples: UV-Vis diffusion reflection, IR and Raman spectroscopy, synchronous thermal analysis, X-ray diffraction, transmission electron microscopy, as well as specific surface-area evaluation. We also followed the dynamics of phase transformations, as well as composition, structure and morphology of annealed powders up to 800 °C. When heated, the non-irradiated series of samples proceeded from metallic bismuth, through β-Bi₂O₃, and resulted in bismuth silicates of various stoichiometries. At the same time, in their laser-irradiated counterparts, the formation of silicates proceeded immediately from the amorphous Bi₂SiO₅ phase formed after laser treatment of mixed Bi and Si colloids. Finally, we show their ability to decompose persistent organic molecules of Rhodamine B and phenol under irradiation with a soft UV (375 nm) source.

In this work, we studied the catalytic performance of a β-Bi₂O₃/Bi₁₂SiO₂₀ nanocomposite material in the reactions involving the photodecomposition of rhodamine B and selective photooxidation of 5-hydroxymethylfurfural (HMF). The semiconductor composite nanomaterial was obtained by means of the mechanical grinding of a mixture of nanopowders of β-Bi₂O₃ and sillenite, both individually produced via pulsed laser ablation. The crystal structure of the prepared composite particles was confirmed by means of X-ray diffraction, while the optical properties of both individual components and their composite (with different ratios of Bi₂O₃ and Bi₁₂SiO₂₀) were also studied. The photocatalytic activity of the composite particles was studied in the course of their decomposition of rhodamine B under LED excitation at wavelengths of 375, 410 and 470 nm. It was shown that the optimal β-Bi₂O₃/Bi₁₂SiO₂₀ ratio in the composite particles resulted in their photocatalytic activity exceeding those of both single-phase β-Bi₂O₃ and Bi₁₂SiO₂₀, as well as that of their mixtures (by ~2.3 times for the excitation of an LED with λ = 375 nm). The novel composite particles were also found to perform better in the selective photocatalytic oxidation of HMF: at a conversion of ~5%, the selectivity toward DFF of the nanocomposite was significantly higher (10.3%) than that of sample Bi₂O₃ (−4.2%). A model was proposed that explains the increase in activity of the newly prepared photocatalyst due to the formation of a type II heterojunction in its particles.

Electrospray is a promising method for fabricating semipermeable polytetrafluoroeth-ylene (PTFE) membranes. These membranes exhibit high hydrophobicity and a large specific surface area. They can be used in various sectors, including the chemical and energy industries, aerospace, and microelectronics manufacturing. In this study, we investigated the effect of different spray solution compositions, heat treatment re-gimes, and exposure to various media on the physicochemical properties of these membranes. We used scanning electron microscopy to determine the optimal range of spray solution compositions for electrospraying. We found that quenching the mem-branes after electrospraying reduced shrinkage, increased tensile strength, and in-creased relative elongation. This was attributed to a decrease in the degree of crystal-linity in the quenched membranes. We also investigated the effects of various aggres-sive media, including concentrated acids, alkalis, organic solvents, and mineral oil, on the tensile strength and relative elongation of the membranes. No significant changes in tensile strength or relative elongation were observed after immersion for 48 h at 100 °C, indicating the high chemical stability and operational reliability of the elec-trosprayed PTFE membranes.

Electrospray is a promising method for fabricating semipermeable polytetrafluoroethylene (PTFE) membranes. PTFE membranes are attractive for filtration and separation in harsh environments, but their mechanical properties depend strongly on crystallinity and thermal history. In this work, PTFE/poly(ethylene oxide) (PEO) membranes were fabricated by electrospraying aqueous solutions with PTFE/PEO ratios of 98.8/1.2, 97.5/2.5, 95/5, and 90/10 wt.%. Increasing the PEO content increased the solution viscosity from 43–78 to 124 mPa·s and caused a transition from sphere-based to mixed fiber–sphere morphology. After sintering at 330 °C, PEO was completely removed and the membrane architecture was preserved. Annealing (slow cooling) produced a more developed folded surface, higher crystallinity, and greater shrinkage, whereas quenching (rapid cooling) retained a less ordered structure, lower shrinkage, and generally higher tensile strength and relative elongation. The highest tensile strength (4.12 ± 0.25 MPa) was obtained for the quenched 97.5/2.5 wt.% membrane, and the highest relative elongation (259 ± 16%) for the quenched 90/10 wt.% membrane. Exposure to nitric acid, potassium hydroxide, dimethyl sulfoxide, motor oil, and distilled water at 100 °C for 48 h caused no statistically significant changes in tensile strength or relative elongation. These results demonstrate that electrosprayed PTFE membranes offer tunable morphology and mechanical properties together with high chemical resistance, making them promising for aggressive-media filtration and separation.