For the first time, one-dimensional phase-modulated structures consisting of two different layered Aurivillius phases with alternating five and six perovskite-like layers were obtained by atomic layer deposition (ALD) on the surface of TiO₂ nanotubes (Nt). It was shown that the use of vertically oriented TiO₂ Nt as the substrate and the ALD technology of a two-layer Bi₂O₃-FeO_x sandwich-structure make it possible to obtain a layered structure due to self-organization during annealing. A detailed study by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the coating is conformal. Raman spectroscopic analysis indicated the structure of the layered Aurivillius phases. Transient photocurrent responses under Ultraviolet–Visible (UV-Vis) light irradiation show that the ALD coating benefits the efficiency of photon excitation of electrons. The results of the photoelectrocatalytic experiments (PEC) with methyl orange degradation as a model demonstrate the significant potential of the synthesized structure as a photocatalyst. Photoluminescent measurement showed a decrease in the probability of recombination of photogenerated electron–hole pairs for ALD-coated TiO₂ Nt, which demonstrates the high potential of these structures for use in photocatalytic and photoelectrochemical applications.

Iron oxides are widely used as catalysts for photo-Fenton-like processes for dye oxidation. In this study, we report on the synthesis of an α/γ-Fe₂O₃ mixed-phase catalyst with magnetic properties for efficient separation. The catalyst was synthesized using glycine–nitrate precursors. The synthesized α/γ-Fe₂O₃ samples were characterized using scanning electron microscopy, X-ray diffraction spectroscopy (XRD), Raman shift spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). The diffraction peaks were indexed with two phases, α-Fe₂O₃ as the main phase (79.6 wt.%) and γ-Fe₂O₃ as the secondary phase (20.4 wt.%), determined using the Rietveld refinement method. The presence of Fe²⁺ was attributed to oxygen vacancies. The mixed-phase α/γ-Fe₂O₃ catalyst exhibited remarkable photo-Fenton-like degradation performance for Rhodamine B (RhB) in neutral pH. The effects of operating parameters, including H₂O₂ concentration, catalyst concentration, and RhB concentration, on the degradation efficiency were investigated. The removal rates of color were 99.2% after 12 min at optimal conditions of photo-Fenton-like oxidation of RhB. The sample exhibited a high saturation magnetization of 28.6 emu/g. Additionally, the α/γ-Fe₂O₃ mixed-phase catalyst showed long-term stability during recycle experiments, with only a 5% decrease in activity.

The creation of multi-stimuli-sensitive composite polymer–inorganic materials is a practical scientific task. The combination of photoactive magneto-piezoelectric nanomaterials and ferroelectric polymers offers new properties that can help solve environmental and energy problems. Using the doctor blade casting method with the thermally induced phase separation (TIPS) technique, we synthesized a hybrid polymer–inorganic nanocomposite porous membrane based on polyvinylidene fluoride (PVDF) and bismuth ferrite (BiFeO₃/BFO). We studied the samples using transmission and scanning electron microscopy (TEM/SEM), infrared Fourier spectroscopy (FTIR), total transmission and diffuse reflection, fluorescence microscopy, photoluminescence (PL), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM), and piezopotential measurements. Our results demonstrate that the addition of BFO increases the proportion of the polar phase from 76.2% to 93.8% due to surface ion–dipole interaction. We also found that the sample exhibits laser-induced fluorescence, with maxima at 475 and 665 nm depending on the presence of nanoparticles in the polymer matrix. Furthermore, our piezo-photocatalytic experiments showed that under the combined actions of ultrasonic treatment and UV–visible light irradiation, the reaction rate increased by factors of 68, 13, 4.2, and 1.6 compared to sonolysis, photolysis, piezocatalysis, and photocatalysis, respectively. This behavior is explained by the piezoelectric potential and the narrowing of the band gap of the composite due to the mechanical stress caused by ultrasound.

Highly porous membranes based on polyvinylidene fluoride (PVDF) with the addition of nanoscale particles of non-magnetic and magnetic iron oxides were synthesized using a combined method of non-solvent induced phase separation (NIPS) and thermo-induced phase separation (TIPS) based on the technique developed by Dr. Blade. The obtained membranes were characterized using SEM, EDS, XRD, IR, diffuse reflectance spectroscopy, and fluorescent microscopy. It was shown that the membranes possessed a high fraction of electroactive phase, which increased up to a maximum of 96% with the addition of 2 wt% of α-Fe₂O₃ and α/γ-Fe₂O₃ nanoparticles. It was demonstrated that doping PVDF with nanoparticles contributed to the reduction of pore size in the membrane. All membranes exhibited piezocatalytic activity in the degradation of Rhodamine B. The degree of degradation increased from 69% when using pure PVDF membrane to 90% when using the composite membrane. The nature of the additive did not affect the piezocatalytic activity. It was determined that the main reactive species responsible for the degradation of Rhodamine B were ^•OH and ^•O₂⁻. It was also shown that under piezocatalytic conditions, composite membranes generated a piezopotential of approximately 2.5 V.

The development of advanced catalytic materials for environmental applications remains a critical challenge due to the limitations of conventional photocatalysis, such as low charge separation efficiency and dependence on external light sources. In this study, we present the synthesis and investigation of electrospun polyvinylidene fluoride (PVDF) nanofibers modified with zinc oxide (ZnO) nanoparticles for enhanced photocatalytic, piezocatalytic, and piezophotocatalytic activity. The morphology and structural properties of the composite material were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results show that the incorporation of ZnO reduces the average fiber diameter by 3.3 times and decreases the β-phase fraction from 87.3% to 71.6% due to nanoparticle agglomeration. The catalytic performance of PVDF/ZnO was evaluated in the degradation of methylene blue (MB) under different conditions: photocatalysis (71%), piezocatalysis (76%), and piezophotocatalysis (91%) within 60 minutes. Additionally, the membrane generated an average open-circuit voltage of 140 mV under mechanical stirring, demonstrating its ability to convert mechanical energy into electrical energy. These findings highlight the potential of PVDF/ZnO nanocomposites as multifunctional materials for sustainable catalytic applications and energy harvesting.

In this work, we investigate advanced photocatalyst Bi₃TiNbO₉ as promising piezophotocatalyst in terms of the effect of synthesis methods on the surface chemistry, structure, and catalytic performance in process of contaminant removal. Samples were prepared via solid-state reaction (BTNO-900) and molten salt synthesis (BTNO-800), leading to distinct morphologies and defect distributions. SEM imaging revealed that BTNO-900 consists of agglomerated, irregular particles, while BTNO-800 exhibits well-faceted, plate-like grains. Nitrogen adsorption analysis showed that the molten-synthesized sample possesses a significantly higher specific surface area (5.9 m²/g vs. 1.4 m²/g) and slightly larger average pore diameter (2.8 nm vs. 2.6 nm). High-resolution XPS revealed systematic shifts in binding energies for Bi 4f, Ti 2p, Nb 3d, and O 1s peaks in BTNO-900, accompanied by a higher content of adsorbed oxygen species (57% vs. 7.2%), indicating an increased concentration of oxygen vacancies and surface hydroxylation due to the solid-state synthesis route. Catalytic testing demonstrated that BTNO exhibits enhanced piezocatalytic efficiency of Methylene Blue degradation (~78% for both samples), whereas BTNO-800 shows significantly reduced photocatalytic activity (45.6%) compared to BTNO-900 (84.1%), suggesting recombination effects dominate in the more defective material. Synergism of light and mechanical stress results in piezophotocatalytic degradation for both samples (92.4% and 93.4%, relatively). These findings confirm that synthesis-controlled defect engineering is a key parameter for optimizing the photocatalytic behavior of Bi₃TiNbO₉-based layered oxides and crucial role of its piezocatalytic activity.