Farid F. Orudzhev

Hierarchical porosity and iron speciation govern the balance between adsorption and catalytic oxidation in Fe-modified ZSM-5. This study compares a microporous low-iron material, Z0–Fe0.1 (0.9 wt.% Fe), with a hierarchically porous high-iron material, Z0.4–Fe1.0 (25 wt.% Fe). Structural, textural, optical, X-ray photoelectron, and Mössbauer characterization was combined with methylene blue removal experiments under adsorption, photocatalytic, Fenton-like, and photo-Fenton-like conditions. Both materials retained the MFI structure. UV–Vis analysis indicated a greater relative contribution of oligomeric Fe_xO_y species in Z0.4–Fe1.0. Mössbauer spectroscopy identified predominantly Fe³⁺ environments and revealed a magnetically ordered component in the high-iron material at 78 K. Despite an almost 28-fold difference in iron loading, both materials achieved nearly identical final methylene blue removal (~99%) under photo-Fenton-like conditions, yet this similar efficiency was reached through fundamentally different dominant pathways: predominantly adsorption for the microporous Z0–Fe0.1 (dark adsorption ~82%) and predominantly catalytic oxidation for the hierarchical Z0.4–Fe1.0 (dark adsorption only ~38%, rising to ~87% under dark Fenton-like conditions). These results indicate a shift in the balance between adsorption and H₂O₂-dependent removal accompanying changes in porosity and iron loading. The findings highlight the need to consider pore architecture, adsorption, and iron speciation jointly when interpreting the performance of Fe-containing zeolites for water treatment.

Local magnetoelectric interactions in polymer-based nanocomposites remain insufficiently understood at the nanoscale, particularly in systems with spatially heterogeneous distributions of magnetic fillers. This work investigates the local magnetoelectric effect in electrospun α-Fe2O3/polyvinylidene fluoride (PVDF) composite nanofibers using piezoresponse force microscopy under an applied magnetic field. The incorporation of α-Fe2O3 nanoparticles serves a dual role, providing magnetostrictive functionality while promoting the formation of the electroactive β-phase in the PVDF matrix, enabling effective magnetoelectric coupling at the nanoscale. Local magnetoelectric measurements performed under a static magnetic field of 180 mT revealed a pronounced increase in deformation amplitude together with modifications of the polarization behavior. Unlike macroscopic measurements, nanoscale analysis revealed pronounced spatial heterogeneity of the magnetoelectric response, directly associated with the nonuniform distribution of hematite nanoparticles within the PVDF matrix. The practical applicability of the developed composite was further demonstrated through magnetic-field-driven catalytic activity, resulting in up to 49% degradation of methylene blue. The results provide strong evidence for local magnetoelectric coupling in α-Fe2O3/PVDF composite nanofibers and highlight the potential of such nanocomposites for magnetically controlled catalytic and biomedical applications.

Multifunctional polymer–ferrite composites based on poly(vinylidene fluoride) (PVDF) and magnetic fillers are of increasing interest for applications requiring coupled electrical, dielectric, and magnetic responses. However, the relationship between magnetic filler concentration, PVDF phase composition, and the resulting multifunctional properties remains insufficiently understood. In this work, PVDF/BaFe₁₂O₁₉ (PVDF/BaF) composite membranes containing 2–20 wt.% BaF were fabricated using a combined non-solvent and thermally induced phase-inversion (NIPS–TIPS) method. Structural evolution was analyzed by X-ray diffraction and quantitative FTIR spectroscopy, thermal behavior by differential scanning calorimetry, optical properties by diffuse reflectance spectroscopy, dielectric response in the frequency range 10³–10⁶ Hz, and magnetic characteristics by vibrating sample magnetometry. At moderate filler concentrations (2–10 wt.%), BaFe₁₂O₁₉ nanoparticles acted as effective β-phase nucleating centers, leading to electroactive phase fractions of 97.7–99.9% and a maximum β-phase content of 86.7% for PVDF/BaF10. At higher loadings (15–20 wt.%), particle agglomeration and restricted chain mobility promoted a transition toward α-phase-dominated crystallization. Thermal analysis indicated competing nucleation and confined crystallization processes, while optical and dielectric measurements revealed nonmonotonic changes associated with interfacial interactions and Maxwell–Wagner–Sillars polarization. Magnetic measurements showed a linear increase in saturation magnetization with filler concentration and a nonmonotonic coercivity dependence with a pronounced change near the critical agglomeration concentration. These results demonstrate that the multifunctional response of PVDF/BaFe₁₂O₁₉ membranes is governed by the interplay between β-phase nucleation, interfacial polarization, and magnetic particle interactions, with approximately 10 wt.% ferrite providing the most balanced electrical, dielectric, and magnetic characteristics.

The development of advanced semiconductor-based catalysts for the rapid degradation of emerging pharmaceutical pollutants in water remains a critical challenge in environmental science. In this study, we present the synthesis, characterization, and catalytic performance of zinc oxide (ZnO) microtetrapods decorated with plasmonic Ag nanoparticles. These microtetrapods have been designed to enhance piezo-, photo-, and piezo-photocatalytic degradation of metronidazole (MNZ), a persistent antibiotic contaminant. ZnO microtetrapods were synthesized by high-temperature pyrolysis and using atmospheric-pressure microwave nitrogen plasma, followed by photochemical deposition of Ag nanoparticles at various precursor concentrations (0–1 mmol AgNO₃). The structural integrity of the samples was confirmed through X-ray diffraction (XRD) analysis, while the morphology was examined using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Additionally, spectroscopic analysis, including Raman, electron paramagnetic resonance (EPR), and photoluminescence (PL) spectroscopy, was conducted to verify the successful formation of heterostructures with adjustable surface loading of Ag. It has been shown that ZnO microtetrapods decorated with plasmonic Ag nanoparticles exhibit Raman-active properties. A systematic evaluation under photocatalytic, piezocatalytic, and combined piezo-photocatalytic conditions revealed a pronounced volcano-type dependence of catalytic activity on Ag content, with the 0.75 mmol composition exhibiting optimal performance. In the presence of both light irradiation and ultrasonication, the optimized Ag/ZnO composite exhibited 93% degradation of MNZ within a span of 5 min, accompanied by an apparent rate constant of 0.56 min⁻¹. This value stands as a significant improvement, surpassing the degradation rate of pristine ZnO by over 24-fold. The collective identification of defect modulation, plasmon-induced charge separation, and piezoelectric polarization as the predominant mechanisms driving enhanced reactive oxygen species (ROS) generation is a significant advancement in the field. These findings underscore the synergistic interplay between plasmonic and piezoelectric effects in oxide-based heterostructures and present a promising strategy for the efficient removal of recalcitrant water pollutants using multi-field activated catalysis.