Resumo em Inglês:

Nanofibers play a crucial role in energy storage and conversion, catalysis, and environmental remediation applications. These nanomaterials, characterized by their high surface-to-volume ratio and porous structure, exhibit exceptional properties that render them ideal for various energy applications such as in fuel cells, lithium-ion batteries, supercapacitors, catalysis, and hydrogen production. This discussion outlines the historical context of electrospinning (ES), acknowledging its limitations in terms of commercial viability. Introducing the supersonic solution blowing (SSB) technique as a promising alternative, its energy-efficient process holds potential for commercial feasibility. The ES has remarkable advantages in nanofiber fabrication but faces limitations due to high operating costs. Solution blow spinning (SBS) offers speed and versatility; however, fibers have a broad distribution of diameters. SSB therefore overcomes some of the limitations of both ES and SBS techniques to produce defect-free nanofibers with smaller diameters at higher throughput rates. In this concise perspective paper, we emphasize the primary contributions of nanofibers to the development and optimization of materials used in energy applications. Drawing parallels with the prevalent ES and SBS techniques in the literature, we conclude with a discussion on the potential benefits that may arise as researchers increasingly explore this emerging and more efficient technique.

Resumo em Inglês:

Three groups of unexpected experimental findings were published in the past twenty years in different research areas, opposing current paradigms, and supporting the following statements: (i) water is becoming the ideal medium for chemical synthesis; (ii) water is an electrifying agent of most materials; (iii) macroscopic matter is formed by charge mosaics that are often the outcomes of surface processes at the aqueous interfaces. These statements provoke major changes in chemical thinking that have a common feature: the behavior of chemicals in aqueous electrified interfaces may largely differ from their behavior in bulk and theoretical predictions. This review discusses eight widely accepted statements familiar to chemists, students, professors, and teachers, but challenged by many experimental findings obtained in systems having aqueous interfaces. A broader statement that is being used in this context is that the thermodynamic properties of ionic species change depending on the local electric potential, modifying their reactivity, mass transfer, and other properties. Beyond synthetic applications, atmospheric moisture is becoming a promising source of electricity. These new views create huge opportunities for chemical research and development, based on the most abundant and environmentally compatible chemical. Aqueous interfaces are thus a powerful toolbox for building a sustainable economy.

Resumo em Inglês:

In the nanoscale, matter presents different properties compared to its bulk counterparts, owing to the considerable increase of the surface/bulk ratio, as well as the occurrence of quantum confinement effects. One method to fine control the growth of nanoparticles, their size and nanostructure is to use metalorganic deposition combined with a porous matrix as host, where pores act as nanoreactors for nanoparticle growth, resulting in chemically integrated systems. In this review, we look at the history and achievements of the chemical method of impregnation-decomposition cycles for the precise size control, property tuning and tailored synthesis of metal oxide nanoparticles. We give an overview of the various oxide nanoparticles and nanomaterials developed over the years, and how the method of impregnation-decomposition cycles allowed the synthesis of pure, doped and core-shell oxide nanoparticles, as well as the tuning of their properties through the combined fine control of nanoparticle size, nanostructure, and composition.

Resumo em Inglês:

Lead-free halide double perovskites with the formula A2BIBIIIX6, and ordered vacancy perovskites, with the general formula A2BIVX6 have recently emerged as alternative materials for advancements in lead-halide perovskites. While the main obstacles to the development of lead-halide perovskites are the use of lead and the instability of the structure, halide double perovskites allow multiple metal combinations resulting from the replacement of the lead in single perovskites by two metal-complexes or alternating vacancy metal-complexes in their crystalline structure. Although many advances have already been made in lead-free halide double perovskites, there are still some challenges to be overcome, such as the indirect and high bandgap, and the transitions prohibited by parity, which are intrinsic features of their electronic structure, and result in low energy conversion efficiency and photoluminescence quantum yields as well. Emphasizing the need to review the results of the literature so far, considering the advances and challenges presented, this work involves a systematic and embracing bibliographical research on lead-free halide double perovskites, encompassing central aspects such as their historical evolution, crystalline structure, synthesis methods, challenges faced in the field, optoelectronic properties and perspectives for the development and application of these materials.

Resumo em Inglês:

This work produced chemically activated sugarcane bagasse-based activated carbon (AC) for the controlled release of urea. Fourier transform infrared (FTIR) and Raman analysis confirmed the presence of graphitic structures and multiple oxygen-containing functional groups. After the solid-state reaction that formed the material, their surface area reached 1401 m2 g-1 for the sample prepared with a pyrolysis temperature of 400 °C, a concentration of sodium hydroxide equivalent to 11 mol L-1, and an activation temperature of 900 °C (AC 400-11-900). Zeta potential measures indicated negative charges at pH > 4, reaching almost (–50 mV) at pH 9. The adsorptive capacity of the AC with the highest surface area was equal to (758.7 ± 263.8) mg g-1. Nevertheless, the matrix did not release the urea molecules previously adsorbed into it, which is appealing for fertilizer-releasing purposes because the activated carbon would be able to re-adsorb the non-absorbed urea molecules, sustaining nutrient availability for longer periods.

Resumo em Inglês:

The increase in anthropogenic activity over time has led to an exponential increase in greenhouse gas emissions, especially CO2. Proftable technologies for CO2 capture and separation are conspicuous, and porous biochars derived from biomass waste can be a useful solution. Herein, we produced activated nitrogen-doped biochars for CO2 capture from corn husk waste, urea and K2CO3, named N-Bio-X (X = 600, 700, and 800 °C). N-Bio-X exhibited microporosity and different nitrogen contents and thus played an important role in the adsorption of CO2. N-Bio-700 exhibited the highest CO2 adsorption capacity, fastest adsorption kinetics and excellent stability after multiple adsorption-desorption cycles. N-Bio-600 showed excellent CO2/N2 selectivity, induced by nitrogen sites, particularly pyridinic and graphitic nitrogen. The cost-effectiveness of the raw material, coupled with its high adsorption capacity, rapid kinetics, and stable properties, provided highly promising N-doped biochars for practical implementation in CO2 capture and separations in postcombustion processes.

Resumo em Inglês:

This study presents the synthesis and characterization of five Schiff bases derived from the reaction of 4-(2-aminoethyl)-benzenesulfonamide (compound 1) with corresponding aldehydes, (benzaldehyde, 2-pyridinecarboxaldehyde, 2-quinolinecarboxaldehyde, 8-hydroxy2-quinolinecarboxaldehyde and 4-imidazolecarboxaldehyde, for compounds 2-6, respectively). Characterization was performed by various spectroscopic techniques and supported by density functional theory (DFT) calculations. The crystal structures revealed how the substituent groups influenced the present supramolecular interactions. Compounds 1-4 and 6 showed no cytotoxicity to BHK-21 and VERO E6 cells at the highest concentration of 50 µmol L-1, while compound 5 was cytotoxic at this concentration. Compound 5 was active against the Chikungunya virus at the concentration of 10 µmol L-1, highlighting the effect of the 8-hydroxyquinoline substituent for the antiviral activity. For Zika virus, compound 6 was the only one active at 50 µmol L-1. The results suggest the potential of combining sulfonamides with other chemotypes for further development of antiviral agents, especially in the treatment of arboviral diseases.

Resumo em Inglês:

Pure and cobalt-doped 3D ZnO were produced using the microwave (MW)-ultraviolet (UV)-visible (Vis) radiation-assisted hydrothermal method (MW-UV-Vis HM). Using experimental design, the effects of cobalt and UV-Vis radiation during the synthesis stage on the physicochemical properties of the materials were evaluated with different characterization techniques such as X-ray diffraction, scanning and transmission electron microscopy, diffuse reflectance, and electrochemistry. The presence of cobalt had a great influence on the reduction of charge donors in the ZnO matrix and had their photocatalytic properties improved when produced under the effect of UV-Vis radiation. The catalytic activity of the materials has been verified in important environmental remediation reactions, such as the electrochemical reduction of CO2 and the photocatalytic degradation of emerging pollutants. The results achieved in this study show competitive efficiency values for CO2 reduction (97%) and photocatalytic degradation (91%) of emerging pollutants in natural waters, illustrating the great versatility of the produced material in distinct applications.

Resumo em Inglês:

Organophosphates are prevalent in agrochemicals and chemical warfare agents, posing significant health and safety concerns. These compounds are known for their high chemical stability and to address this issue, nucleophilic catalysts have emerged as a promising solution for their degradation. Herein, we focus on a novel material created through the combined effects of imidazole and crumpled graphene (CG) to develop a nanocatalyst for the neutralization (i.e., degradation) of organophosphates (OPs). The strategy involves the covalent functionalization of CG with imidazole groups without disrupting the three-dimensional structure of CG. This unique combination results in a synergistic effect between neighboring imidazole groups within CG, significantly enhancing the catalytic performance. The catalytic increment (kCAT/kH2O) achieved is in the order of 104, demonstrating the remarkable efficiency of this catalyst. The pioneering and promising use of functionalized CG for addressing concerns with chemical security can boost and be broadened to other applications.

Resumo em Inglês:

Two novel coordination polymers were synthesized through the reaction of the Hpcpa2- ligand (H3pcpa = N-(4-carboxyphenyl)oxamic acid) with cadmium(II) and lead(II) metal ions, yielding [Cd2(Hpcpa)2(H2O)6]n·H2O (1) and [Pb(Hpcpa)(H2O)]n (2). Structural analysis by single-crystal X-ray diffraction revealed that 1 consists of one-dimensional zigzag polymeric chains, while 2 is a three-dimensional polymer network. Additionally, investigations of their optical properties were carried out in a comparative study involving the previously reported pcpa-based coordination polymers {[Zn(Hpcpa)(H2O)3]·0.5H2O}n and {[Gd2(Hpcpa)3(H2O)5]·H2O}n], called here as 3 and 4, respectively. Under 330 nm excitation wavelength, all compounds exhibited broad emission bands spanning from 350 to 650 nm. Particularly, 1 and 3 displayed notable external quantum yields of 15.4 and 12.8%, respectively, highlighting their potential in luminescent applications.

Resumo em Inglês:

In this investigation, we synthesized magnetic nanoparticles coated with silica and functionalized with p-sulfonic acid calix[4]arene (CX4), to be used as heterogeneous acid catalysts for acetal synthesis. We evaluated the catalytic efficiency of these nanoparticles for acetal synthesis using various aldehydes and glycerol under microwave irradiation at atmospheric pressure, with and without solvents. Two distinct synthesis methods, Pechini (Fe/pch/Si/CX4) and precipitation (Fe/ppt/Si/CX4), resulted in variations in the physical and chemical properties of the solids produced. Structural characterization involved thermogravimetry analysis (TG), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry, scanning and transmission electron microscopy (SEM and TEM), infrared spectroscopy (FTIR), and titration for acidic site quantification. Fe/ppt/Si/CX4 exhibited goethite phases, while Fe/pch/Si/CX4 showed a substantial proportion of maghemite. Both catalysts demonstrated significant activity in acetal synthesis, achieving approximately 80% conversion without solvents. Notably, Fe/ppt/Si/CX4 exhibited higher activity likely due to its structural properties and crystalline phases of the synthesized iron oxide, suggesting a composition difference from the Pechini method.

Resumo em Inglês:

CO2 emissions into the atmosphere have been rapidly rising due to human activities, resulting in the escalation of global warming. To mitigate climate change, it is imperative to develop materials for CO2 capture with high CO2 capacity and low production costs. Herein, we developed a facile method to obtain adsorbents based on reduced graphene oxide (rGO) sheets, NrGO(1 – X)700, where X represents the mass of diethylenetriamine (DETA) (X = 1, 2 and 4 g) used in the preparation. The materials NrGO(1 – 1)700, NrGO (1 – 2)700, and NrGO(1 – 4)700 were obtained from graphene oxide dispersions, followed by DETA impregnation and chemical activation with K2CO3. N2 isotherms demonstrated that the materials simultaneously presented micro and mesopores with similar values of specific surface area (280.16 to 310.32 m2 g–1), pore volume (0.26 to 0.28 cm3 g–1) and pore size (3.78 to 3.80 nm). CO2 sorption experiments revealed that the material NrGO(1 – 4)700, containing the highest amount of pyridinic, graphitic, and amino nitrogen functionalities, showed the best CO2 adsorption capacity. Diffuse reflectance Fourier transformed infrared spectroscopy experiments indicated stronger solid-gas interactions for NrGO(1 – 4)700 than for the other materials.

Resumo em Inglês:

The catalytic activity of layered double hydroxide (LDH) and the aqueous solution absorption capacity of ureasil polyethylene oxide (U-PEO) were combined to produce an easily recyclable solid-liquid (S-L) reactor (U-PEO:LDH). Scanning electron microscopy (SEM), X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) of LDH (CuZnAl), U-PEO, and U-PEO:LDH confirmed the layered structure of the catalyst and evidenced its inclusion in the free volume of U-PEO matrix. The catalytic activity of the CuZnAl in the composite prepared with different amounts of LDH, towards degradation of the Acid Blue 29 (AB29) dye by a heterogeneous Fenton-like process was investigated, and the results evidenced a maximum efficiency (96%) for composite with 10 wt.% of LDH. Recyclability assessments demonstrated that the superior performance of the U-PEO:LDH reactor was sustained over several cycles (4). The U-PEO:LDH reactor proposed in this work has excellent potential as a heterogeneous catalyst for effective dye removal in environmental applications.

Resumo em Inglês:

ZnO nanoparticles were synthesized for the first time, using extracts from the leaf and peel of Plinia cauliflora (jabuticaba) fruit by varying the pH level of the reaction medium. The powders were obtained after calcination at 400 ºC and characterized by thermogravimetry (TGA), X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR) and scanning electron microscopy (SEM). The results indicate that the use of jabuticaba leaf extract favored the stabilization of nanoparticles, providing smaller crystallite sizes and lower crystallinity. Crystallite sizes smaller than 50 nm were obtained using the leaf extract with pH level adjusted to 7 and 10. The morphology was strongly affected by both the extracts and the pH levels of the medium, and showed a flower-like shape when using jabuticaba peel extract at pH 7. Thus, the use of Plinia cauliflora extract showed a promising potential for the production of ZnO nanoparticles with different morphologies.

Resumo em Inglês:

The generation of clean, zero-carbon, and renewable energy is a challenge for the development of a sustainable and egalitarian society. Hydrogen gas can be produced by water electrolysis and has been claimed as the most promising option to replace fossil fuels. The oxygen evolution reaction (OER) is the most energetically demanding step of the water splitting and requires the use of electrocatalysts to overcome the kinetic barrier. Iron oxide nanomaterials have been emerging as a low-cost and Earth-abundant OER electrocatalysts. The synthesis of iron oxide assisted by plant extract is an eco-friendly approach to obtain nanomaterials with unique properties. Herein, we investigated iron oxide synthesized with the assistance of Camellia sinensis extract, under different experimental conditions towards oxygen evolution reaction electrocatalysis. Pure phases of iron oxide were obtained, ferrihydrite and maghemite showed overpotentials of 460 and 480 mV at a current density of 10 mA cm–2, respectively. After calcination, hematite was formed and the overpotential was raised to 610 and 810 m V, respectively. The lower overpotential of the amorphous materials could be related to the lower electron transfer resistance and faster reaction rate. On the other hand, the calcinated materials presented higher specific activity, stability and higher Faradaic efficiency.

Resumo em Inglês:

Niobium pentoxide shows an interesting reactivity that allows the control of different aspects of its morphology and chemistry. In this study, Nb2O5 nanoparticles were modified with protoporphyrin IX (PPIX) and tris(ethynylphenyl) pyrene derivative (PyPh3) by using 3-aminopropyltriethoxysilane as linkage group and used as photosensitizers against lung cancer. The antitumor photoactivity against the A549 tumor cell line as a model of in vitro study showed half maximal inhibitory concentration (IC50) ca. 15 μmol L-1 for both materials and the absence of dark activity, indicating the viability of dye-modified Nb2O5 as a photodynamic therapy (PDT) agent.