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:

Cement production, the primary material used in construction industry, accounts for around 8% of global CO2 emissions. In addition to the demand for materials that emit greenhouse gases, the sector generates approximately 50% of solid waste in Brazilian cities. Geopolymers, which utilise industrial by-products rich in chemically activated aluminosilicates, are emerging as a sustainable alternative to Portland cement. One of the main components of brazillian construction and demolition waste (CDW) is red ceramic, which, due to its firing temperature, contains a high proportion of metakaolinite, an amorphous, pozzolanic and highly reactive aluminosilicate. This study aims to develop a sustainable sealing brick using CDW as the main geopolymer precursor. CDW was activated with highly basic NaOH solutions to form the geopolymer paste. Pulverised CDW was analysed by XRF and XRD, confirming presence of Al and Si, as well as crystalline phases such as α-quartz (SiO2), hydrated calcium silicate (CaH2O4Si) and calcite (CaCO3). After determining the solid/liquid ratio (Casagrande apparatus), cylindrical test specimens were prepared using mixtures of CDW, hydrated lime and alkaline solution in four compositions. Compression tests on the probes exceeded the minimum compressive strength value specified by brazilian (>1.5 MPa) and european (>2.5 MPa) standards for fired ceramic bricks.

Abstract in English:

The effects of chemical zoning and radiation damage on U-Pb isotopic behavior were investigated in apatite from the Borborema Province and zircon from the Carajás Province, Brazil, using optical microscopy and LA-ICP-MS. Sample BJ19C, characterized by homogeneous fission-track distributions, yielded a concordia age of 569.6 ± 1.7 Ma, however, individual analyses showed 87.7 Ma of age dispersion and intra-grain offsets of up to 29.2 Ma. In contrast, chemically zoned CEBP035 yielded a concordia age of 538.6 ± 1.2 Ma and intra-grain age offsets of up to 85.6 Ma. A separate Raman case study of a single representative grain (CEBP035-G01) showed broader ν1 (PO4) bands in U-rich domains, with FWHM increasing from 3.2 to 4.4 cm−1, while the phosphate framework remained largely crystalline. For zircons, etched aliquots exhibited distinct spot distributions along similarly oriented discordia trends. Isotopic patterns were sample-dependent: sample C16 showed tighter regression alignment, C20 displayed a wider spatial distribution, and C23 showed no statistical change. Etched and unetched populations yielded equivalent upper-intercept ages. The results indicate that chemical heterogeneity and radiation damage contribute to U-Pb dispersion in apatite and zircon, while chemical etching modifies the analytical response of metamict zircon without systematically changing the inferred crystallization age.

Abstract in English:

Thin films of tin dioxide (SnO2) are deposited by the sol-gel dip-coating technique with varying intermediate thermal annealing temperature between layers. Lower intermediate temperature contributes to more crystalline films. Quinoline derivative (QD) 4-(6-(diethylamine)-4-phenylquinoline-2-yl)benzoic acid is dissolved in acetone and deposited as thin films by the spin-coating method. In the solutions of both semiconductors is added surfactant Triton X100 and Brij L4, for SnO2 and QD respectively, contributing to film transparency and interface charge accumulation, as shown in FTIR spectra and IxV measurements. The QD exhibits a blue-green broad emission band, which has enhanced intensity triggered by the presence of surfactant Brij L4 in the precursor solution. Also, PL measurements showed a redshift of 45 nm with the addition of surfactant. An average crystallite size of 5.8 nm was evaluated from SnO2 XRD data using software based on Scherrer equation. The coupling of these films forms an organic-inorganic p-n junction due to the n-type behavior of SnO2 and p-type of QD. The current-voltage curves of devices assembled by the heterostructure SnO2/QD, perpendicularly biased, shows an asymmetrical behavior with diode-like nature at low forward bias, but exhibiting a saturation current in the order of picoA for higher bias, (from 1 to 3 V range), whose value depends on number of SnO2 layers and surfactant concentration in the QD solution. It can be attributed to a bias-induced transport, in which the interface barriers and defect-mediated trapping accumulate charge at interface, along with grain-boundary-limited conduction that constrains the effective carrier flow. Within the assembled device architecture, applications such as gas sensors or optoelectronic gating can be visualized.

Abstract in English:

The textile industry is responsible for significant environmental impacts due to the generation of effluents that are difficult and costly to treat. Adsorption has emerged as an efficient and cost-effective technology for treating these effluents, particularly by utilizing waste materials, such as Water Treatment Plant Sludge (WTPS) and Yellow Passion Fruit Peel (YPP). This study aims to develop an adsorbent material from WTPS and YPP to remove the reactive blue dye BF5G from contaminated water. A ceramic adsorbent pellet (CAP) was produced, composed of 70% WTPS, 20% YPP, and 10% clay material, which was pressed and sintered at 210ºC. The CAP was characterized using XRF, XRD, FTIR, SEM, BET, and pH-PZC, and showed promise characteristics for use in adsorption. The CAP demonstrated a removal efficiency of 49.1%, with an adsorption capacity of 0.57 mg g-1 under optimal conditions of pH 3, 25ºC and a 120-minute stirring time.

Abstract in English:

Electrospun poly(methyl methacrylate)/polypyrrole (PMMA/PPy) nanofibrous mats were engineered as ammonia-vapor sensing materials by varying the PPy content from 0 to 16 wt.%. The effect of composition on fiber morphology, electrical transport, structural features, and sensing performance was systematically investigated. PPy addition reduced the mean fiber diameter from 1130 to 730 nm and increased electrical conductivity by more than five orders of magnitude, reaching 9.06 × 10−5 S m−1 at 8 wt.% PPy. FTIR confirmed successful PPy incorporation while preserving the characteristic PMMA structure. Under cyclic N2/NH3 exposure, the 4 wt.% PPy mat exhibited the largest relative resistance variation together with stable and reproducible cycling behavior, whereas further increases in PPy content reduced the response amplitude. These findings highlight electrospun PMMA/PPy mats as low-cost candidates for ammonia sensing.