Green hydrogen (H₂) offers a sustainable alternative to non-renewable energy sources. This study focuses on enhancing H₂ generation from sodium borohydride (NaBH₄) using a platinum nanoparticle (Pt-NP) catalyst supported on a niobium-based coordination compound, [Nb(BDC)_0.9(PDC)_0.1]_n, synthesized via a solvothermal method with 1,4-benzenedicarboxylic acid (BDC) and 2,5-pyridinedicarboxylic acid (PDC). Characterization techniques including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, and X-ray diffraction (XRD) confirm the morphology, composition, surface area (398.583 m²g⁻¹), and crystallinity of the material. The in situ synthesized Pt-NPs showed a hydrogen generation rate (HGR) of 86.588 mL min⁻¹ g⁻¹ when alone, while the supported catalyst achieved an enhanced HGR of 119.020 mL min⁻¹ g⁻¹ under optimal conditions (10 mmol% Pt, 0.5 mmol NaBH₄, 303.15 K). The low activation energy (E_a) of 16.38 kJ mol⁻¹ indicates efficient catalysis. The catalyst maintained stable performance in recycling tests, demonstrating its potential for practical applications in H₂ evolution from NaBH₄.

Due to the growing demand for miniaturization and energy efficiency in modern electronic devices, there is a renewed interest for optoelectronic memories and sensors based on 2D materials. In particular, the molybdenum ditelluride (MoTe2) is one of the most promising materials for applications in nonvolatile phase-change memory devices, as its properties can be controlled by visible-light illumination. Among the several ways to synthesize MoTe2, the molybdenum oxide tellurization through isothermal close space sublimation (CSS) annealing in gas atmosphere is a simple and low-cost effective method for large-scale production of devices based on this layered material. Therefore, the understanding of the physical properties of MoTe2 thin films produced by this technique is crucial for future applications. Surprisingly, our results indicate that there is a photoinduced growth of the crystalline phase of tellurium on the 1T′-MoTe2 matrix even when the power density of the laser is low. From Raman spectroscopy investigations, we were able to show that nanometer-sized tellurium crystallites work as seed sites for the photocrystallization of tellurium. By assuming that the overall crystallization process is described by a kinetic approach that is based on the Kolmogorov–Johnson–Mehl–Avrami theory, our results indicate that the process is governed by an anisotropic organization of the tellurium atoms in helical structures during the crystal growth.

The pulp and paper industry generates large amounts of biological sludge, which can be valorized into activated biochar (A-BC), offering environmental and economic benefits. In this work, A-BCs were produced from this residue using H₃PO₄ as an activating agent and subjected to different pyrolysis temperatures (400 to 550 °C). H₃PO₄ was selected for its superior activation performance over KOH, enhancing porosity and surface functionalization, while the temperature was chosen to match the main thermal degradation of the sludge’s lignocellulosic matrix. The A-BCs were characterized by proximate and elemental analysis (fixed carbon content ∼30%), FTIR (CO, O–H, O–Si–O, and PO functional groups), XRD (predominantly amorphous structure), and Raman spectroscopy (D and G bands). Furthermore, BET surface areas from 7.68 to 1.52 m² g^–1, a higher heating value (HHV) from 3788 to 4750 kcal kg^–1, and a point of zero charge (pH_PZC) from 3.31 to 6.15 were obtained. Increasing the temperature from 400 to 450 °C increases surface area via pore formation, while higher temperatures reduce porosity due to pore collapse and lignin condensation. The A-BC produced at 450 °C (A-BC2) exhibited more than double the surface area and higher methylene blue (MB) removal efficiency than the other samples, consistent with the characterization results. The adsorption assays indicated that the maximum adsorption capacity was 390.73 mg g^–1, with the Langmuir model fitting the experimental data best (R ² = 0.996, R ² _adj = 0.995, and χ² = 1.62). The adsorption kinetics followed the pseudo-second-order model (R ² = 0.982, R ² _adj = 0.981, and χ² = 7.78), indicating a chemisorption-controlled mechanism involving electron sharing or exchange between cationic dyes and oxygenated biochar surface groups. The study demonstrates that A-BC from cellulose industry sludge is a viable, sustainable option for dye-containing effluent treatment, supporting circular economy principles.

Biodiesel serves as a biodegradable, non-toxic, and renewable fuel option that offers an alternative to traditional fossil fuels. This study aimed to examine the impact of elevating biodiesel content to 20% and 50% within regular diesel, with a focus on comprehending how these fuel mixtures influence variations in soot composition using Raman spectroscopy. The soot samples under analysis originated from commercial S10 diesel, as well as fuel blends containing 20% and 50% portions of sunflower and macaúba biodiesel, whereupon the use of this methodology for these fuels characterizes the novelty of this work. The outcomes derived from analyzing the soot samples revealed distinct characteristics in the G, D1, D3, and D4 bands. The ratio between the intensities of these D and G bands is closely indicative of the soot's structure. Consequently, this ratio was analyzed in this investigation to assess the effects of biodiesel concentration and engine rotation speed on soot characteristics. The conclusions found in this study indicated that there was minimal variation in the spectral characteristics of the soot samples across the different fuels and varying engine speeds. As a result, it is inferred that increasing the proportion of biodiesel in commercial diesel S10 did not have a significant impact on the structural composition of soot.

Microplastics (MP) are particles under 5 mm that are widespread in the environment and can harm aquatic life by accumulating pollutants. Understanding their distribution and the effects of urbanization and seasonality is key to assessing their impact and developing mitigation strategies. This study investigated the influence of these factors on MP profiles and associated risks in the São Bartolomeu Stream in Viçosa (Minas Gerais, Brazil). Water samples were collected upstream and downstream of the urban center during dry and rainy seasons. Urbanization and seasonality were found to significantly impact MP presence. The abundance of suspected MP particles increased downstream of the urban center during the dry season, from 1.7 to 2.6 MP particles per liter (MP L⁻¹), whereas no significant difference was observed during the rainy season. Subsequent MP identification using Raman spectroscopy confirmed polymer concentrations ranging from 0.05 to 0.32 MP L⁻¹, with a predominance of polypropylene (PP) and polyethylene (PE). However, a critical paradox emerged: standard ecotoxicity tests with the most abundant polymers (PE and PP) revealed no acute or chronic effects on Daphnia similis. However, a risk assessment driven by the chemical identity of less abundant but highly hazardous polymers found in the stream (including polyvinyl chloride, polyacrylonitrile, and polyurethane), classified the aquatic environment with a ‘high’ to ‘extremely high’ ecological risk, highlighting a potential threat from the mixed polymer composition. Thus, the present study reinforces the need for continuous monitoring and mitigation measures to reduce MP contamination in urban aquatic environments.