Abstract in English:

Zircon is fundamental to geochronology, yet its crystal lattice accumulates radiation damage from α-decay of U and Th, progressively modifying physical properties. Raman spectroscopy provides a non-destructive probe of this damage through peak shifts and linewidth broadening, but mode-specific sensitivity and the role of thermal annealing remain poorly constrained. Here, we correlate effective uranium (eU), accumulated α-dose, and Raman linewidths in zircons from the Brazilian Carajás Province, Peixe Alkaline Suite, and the Fish Canyon Tuff standard using confocal micro-Raman spectroscopy and LA-ICP-MS. Linewidths increase non-linearly with dose and exhibit strong inter-mode correlations, with the external rotation (ER) mode providing the most robust proxy for structural disorder. Variability in linewidth–eU relationships indicates that Raman broadening primarily records time-integrated α-dose. Inter-band comparisons reveal mode-dependent annealing, while high-resolution mapping highlights micrometer-scale heterogeneity. These results demonstrate that robust quantification of radiation damage requires spatially resolved, multi-parameter calibration.

Abstract in English:

The discharge of synthetic dyes into industrial effluents represents a major environmental challenge due to their high stability and persistence in aquatic systems. Among available treatment strategies, membrane-based separation processes have emerged as promising alternatives for removing organic contaminants from water. However, improving membrane selectivity and efficiency toward different classes of dyes remains an important challenge. In this study, commercial PVDF membranes were modified with polydopamine (PDA) and a graphene oxide/polydopamine (GO/PDA) composite to evaluate their performance in removing methylene blue (MB, a cationic dye) and Congo red (CR, an anionic dye). The modified membranes were prepared through surface deposition of active layers and characterized using UV–Vis spectroscopy, FTIR spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) measurements. Filtration experiments were carried out to assess dye removal efficiency and selectivity. The results showed that PDA-modified membranes achieved the highest retention efficiency for MB and the mixture, indicating a significant improvement over the unmodified PVDF membrane. However, the pristine membrane exhibited a higher retention of the anionic dye. The incorporation of GO contributed to a more homogeneous surface and enhanced selective filtration behavior. In mixed dye solutions (1:1 MB: CR), the GO/PDA membrane demonstrated a greater ability to preferentially remove CR, with a selectivity factor of 3.50. Overall, the deposition of PDA-based layers proved a promising strategy for enhancing nanofiltration membrane performance in the treatment of dye-containing effluents, while GO/PDA modification improved membrane selectivity.

Abstract in English:

Glass-ceramics based on the Na2O–Al2O3–SiO2 (NAS) system have attracted attention due to their potential in dental, refractory, and electronic applications, particularly associated with the nepheline (NaAlSiO4) phase. This study investigated the non-isothermal crystallization kinetics of a NAS glass containing CaO and TiO2 precursors (19.7 mol%) for the in situ formation of a glass-ceramic composed of nepheline and calcium titanate (CaTiO3). The kinetic parameters were determined using the Ligero method. The activation energy for crystallization (Ea) was equal to 195 ± 1 kJ/mol, remaining constant within the crystallized fraction range (x) of 0.40 to 0.50. The average Avrami index (n ≈ 2), associated with a saturated nucleation mechanism (m = 2), indicates a volumetric crystallization process. In addition, the time ratio (t0.75/t0.25 = 1.48) suggests crystal growth limited by diffusion, leading to the development of polyhedral morphologies. X-ray diffraction (XRD) analysis confirmed the formation of nepheline and CaTiO3 phases after heat treatment, while scanning electron microscopy (SEM) revealed a microstructure composed of polyhedral crystals, supporting the kinetic interpretation.

Abstract in English:

The discharge of synthetic dyes into industrial effluents represents a significant environmental concern due to their high chemical stability and persistence in aquatic environments. Among these pollutants, methylene blue (MB) is widely used and may cause harmful effects on ecosystems and human health. In this study, ZnO and Fe3O4 nanoparticles were synthesized through green routes using okra and potato peel extracts, followed by the preparation of ZnO-Fe3O4 nanocomposites by a mechanical mixing method. The materials were characterized by XRD, SEM/EDS, FTIR, and UV-Vis DRS. Photocatalytic tests under solar irradiation showed high degradation efficiencies of MB, reaching 95.63% for ZnO, 95.92% for 4ZnO-1Fe3O4, 91.66% for 1ZnO-1Fe3O4, and 53.63% for Fe3O4. The results indicate that the incorporation of Fe3O4 into ZnO contributes to the photocatalytic performance of the nanocomposites and highlights their potential for the treatment of dye-contaminated wastewater.

Abstract in English:

In response to the increasing global demand for energy, this study investigates the pyrolysis kinetics of macrophyte Eleocharis Elegans (MEE) as a potential renewable resource. Thermogravimetric analyses were performed at heating rates of 5, 10, 20, and 40 °C min−1 to better understand its thermal behavior. The physicochemical characterization revealed properties comparable to common agro-industrial residues, including a high volatile matter content (61.92%), relatively low ash content (17.87%), and an intermediate calorific value (16.15 MJ kg−1), indicating its suitability for energy applications. Morphological analysis of the resulting ash showed irregular and agglomerated particles, while energy-dispersive spectroscopy (EDS) indicated a predominance of silicon dioxide. The TGA/DTG curves exhibited three distinct stages of thermal decomposition, consistent with the degradation of lignocellulosic components. Kinetic parameters were determined using the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink methods, which showed strong agreement. The highest Ea value (194 kJ mol−1) was observed in the main decomposition stage. Furthermore, thermodynamic analysis indicated that pyrolysis occurred under non-spontaneous conditions with continuous heat supply, primarily due to the overlapping degradation of hemicellulose and cellulose. Overall, the results highlight the potential of MEE as a promising biomass for thermochemical energy conversion.

Abstract in English:

This work presents a fabrication methodology for chemiresistive gas sensors based on electrospun poly(vinylidene fluoride) (PVDF) nanofibers decorated with regiorandom poly(3-hexylthiophene) (P3HT) using a drop-casting technique. The proposed approach combines the high surface-area-to-volume ratio of electrospun PVDF nanofibers with the electrical properties of P3HT while preserving the nanofibrous architecture and its high specific surface area, resulting in a simple and low-cost platform for Volatile Organic Compound (VOC) sensing. Optical microscopy and Scanning Electron Microscopy (SEM) analyses confirmed the preservation of the nanofibrous structure after the P3HT decoration procedure, with an average fiber diameter of approximately 580 nm. Electrical characterization revealed an increase of approximately two orders of magnitude in electrical conductivity after P3HT deposition, as confirmed by current–voltage (I vs V) measurements and impedance spectroscopy. The fabricated devices exhibited measurable and reversible electrical responses upon exposure to toluene and dichloromethane, with reversibility of 82% and 64%, and a coefficient of variation of 20 and 21%, respectively, for each compound. These results demonstrate the feasibility of the proposed methodology and the potential of P3HT decorated nanofibers as a simple and promising platform for VOC sensing.

Abstract in English:

This study evaluates the interfacial morphology and optoelectronic performance of BO-PPV-based heterojunctions blended with P3BT and P3DDT. UV-Vis spectroscopy identifies a primary absorption band with a red-shifted maximum at 465 nm for the P3DDT system, suggesting subtle differences in molecular packing or effective conjugation length compared to the P3BT analogue (461 nm). Optical microscopy reveals that the P3BT matrix promotes the formation of rough, fibrous aggregates, whereas P3DDT facilitates a more homogeneous, granular morphology. These structural profiles directly modulate the transient photoconductivity; P3BT-based films exhibit pronounced photofatigue and charge trapping, whereas the P3DDT blends maintain superior cyclic stability and peak photocurrents exceeding 60 nA. The electrical perfomance depended on both polymer derivative and solution concentration. While the BO-PPV:P3BT films exhibited improved conductivity at 1 mg/mL, the BO-PPV:P3DDT system showed higher electrical performance ar 2 mg/mL, highlighting the influence of side-chain strcture on film morpholofy and photoconductive response. These findings underscore the alkyl side-chain length and solution concentration strongly influence the morphology and photoconductive response of BO-PPV/P3ATs films.

Abstract in English:

In this work, Density Functional Theory (DFT) calculations were employed to investigate the structural stability and magnetic behavior of c-BN/h-BN heterostructures with different phase proportions (20/80, 40/60, 50/50, 60/40, and 80/20). The results reveal that heterostructures containing thin c-BN regions (20/80 and 40/60) undergo pronounced structural reconstruction toward hexagonal-like configurations during relaxation. In contrast, higher c-BN concentrations (50/50, 60/40, and 80/20) preserve the coexistence of sp2- and sp3-like arrangements, exhibiting enhanced structural stability and reduced interfacial distortions. Additionally, localized magnetic ordering emerges only in the heterostructures that preserve the cubic domains, indicating a strong correlation between the magnetic response and the stability of the sp3 network. These findings demonstrate that the structural and magnetic properties of c-BN/h-BN heterostructures are strongly governed by the cubic phase proportion.