Resumo em Inglês:

The reaction of metal hexafluoroacetylacetonato [MII(hfac)2, M = Cu, Mn] with the stable nitronyl nitroxide 2-(3-isobutyl-pyrazole)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (L), resulted in one dimensional zig-zag chain systems [{Cu(hfac)2}2L2]n and [CuMn(hfac)4L2]n. The main feature inherent in the nature of [{Cu(hfac)2}2L2]n single crystals is their ability to undergo reversible structural rearrangements with temperature variation, accompanied by anomalies of magnetism. The value of χmT shown strongly antiferromagnetic at low temperature and becomes ferromagnetic when the temperature increases. And the heteronuclear complex [CuMn(hfac)4L2]n shows antiferromagnetic interactions between manganese and nitronyl nitroxide.

Resumo em Inglês:

Aniline vapor must be immediately detected at low concentrations since it is a hazardous gaseous chemical. Here, ppb level aniline vapor is detected using the metal-organic framework of UIO-66-SO3H. Utilizing a quartz crystal microbalance (QCM) sensing platform, the aniline adsorption-induced mass change of UIO-66-SO3H is converted to a signal of frequency shift. The sensor can detect a concentration of 20 ppb of aniline vapor and has good sensitivity for this purpose. Additionally, the sensor’s repeatability and stability are satisfactory. Notably, the sensor’s selectivity is prominent. Its response to aniline is much higher than that of ten interfering gases and BTEX vapor. And even in conditions with varying levels of humidity, this sensor maintains response stability.

Resumo em Inglês:

The determination of total organic carbon in soils, fertilizers, sewage sludge, sediments, and humic extracts is widely performed by chemical oxidation methods with K2Cr2O7. The Yeomans-Bremner (YB) method is currently the one that stands out the most. The drawback of these methods is the large amount of concentrated H2SO4 used, which generates a large amount of hazardous waste. This work proposes using KMnO4 as an alternative to K2Cr2O7 for a lower consumption of H2SO4. The method uses the back titration of Fe2+ added to consume both the MnO2 produced and the excess KMnO4 that was not consumed in the OM oxidation. A non-trivial and yet not explored stoichiometry was applied for this purpose, providing a success not yet achieved in using permanganate to determine TOC by titration. The ideal condition for the oxidation of OC was determined by the analysis of a potassium hydrogen phthalate standard and involved the use of 0.125 mol L-1 H2SO4 and temperature of 70 °C, obtaining a significant advantage over the YB method (concentrated H2SO4 and 170 °C). The proposed method was applied to the analysis of soil samples, producing conversion factors for soil organic carbon that varied between 0.652 and 1.12.

Resumo em Português:

Flare type countermeasures that use the composition designated as MTV (Magnesium, Teflon®, Viton®), are the most used by Air Forces around the world. In Brazil, these “flares” are used in several locations and are subjected to different handling, storage and operation conditions that can affect their performance and compromise their service life. In this work, the Monte Carlo method was applied to estimate an empirical model to predict the lifetime of these countermeasures, using as variables the temperature and the relative humidity of the place where the material is used. The results were analyzed using multiple linear regression and analysis of variance. The kinetic parameters of material thermal degradation, such as Activation Energy and Pre-exponential Factor, and the estimated failure times of these countermeasures were determined. The results pointed out to strong temperature influence on material degradation resulting in different lifetimes for each site studied.

Resumo em Inglês:

Resistant infectious microorganisms are causing a worldwide emerging problem, called antimicrobial resistance. To avoid this outbreak, new antimicrobial technologies are necessary. Silver nanoparticles (AgNPs) are known for their antibacterial properties and several studies have focused on their synthesis, characterization, and biological assays. One possibility to synthesize AgNPs is through gamma radiation, known as radiolytic synthesis. This work focuses on the radiolytic synthesis of AgNPs capped into a mesoporous silica nanoparticle aiming at an antimicrobial application. The variants of the radiolytic synthesis, which may influence the AgNPs formation, were studied and statistically compared by Design of Experiments Factorial Design in Minitab Software. The Ag content is statically dependent on dose, volume, and pH, as well as on two parameters interaction: [Ag+]-pH and [Ag+]-volume pH interaction. Transmission electron microscopy and nitrogen adsorption analyses indicated the presence of subnanometric AgNPS located inside the mesopores. Silver nanoagglomerates were also found by transmission electron microscopy, which could be formed by silver oxides, as shown in X-ray photoelectron spectroscopy. AgNPs reduce the specific surface area of the silica nanoparticle, while the matrix morphology remains. The nanocomposites presented preliminary biocompatibility observed in in vitro biological assay using fibroblasts, which support their application in biological systems as antimicrobial substitutes.

Resumo em Inglês:

Ignis fatuus, a luminous phenomenon witnessed over the centuries by observers around the world, is no longer seen in modern times, suggesting that it is extinct. An explanation for this disappearance can be found in the description of ignis fatuus as a cool flame of methane. Unlike a conventional flame, which generates large amounts of heat, ignis fatuus is a flame that glows without heat through a chemiluminescence process. Its characteristic bluish color is due to the emission of excited formaldehyde, which is formed in the slow combustion of methane. It is generally accepted that the phenomenon is a spontaneous combustion of swamp gas in contact with the oxygen in air, but an analysis of the energies involved in the cool flame process indicates that the phenomenon is not spontaneous in nature. Experiments carried out in the 19th century show torches being used to ignite ignis fatuus. The abandonment of fire in favor of night lighting may hold the secret to this mystery of ignis fatuus’s extinction.

Resumo em Português:

Gasoline is a complex mixture of hydrocarbons whose detailed study of its chemical profiles is a challenging task. This type of product of great commercial importance has its quality measured in Brazil from classical physical-chemical tests. Although robust, physical-chemical analyses generally require large amounts of assays, solvents, and samples, in addition to not being indicated for the detection of small compositional changes. In this work, NMR and chemometrics were used in the quantitative study of different samples of gasoline with varying ratings of octane and ethanol contents. The results demonstrated the usefulness of NMR spectroscopy both to characterize as well as to distinguish the chemical profiles of regular and premium gasoline. With the application of the ERETIC, the chemical profiles mentioned were quantitatively differentiated and the proportions between hydrocarbons were determined for both types of gasoline. The application of the ERETIC was also successful in the quantitative determination of ethanol contents in regular and premium gasoline. The aforementioned method, which dispenses with the use of quantification standards inserted directly into the sample of interest, was unequivocal in accounting for the volume of ethanol, in addition to showing excellent agreement with the method currently adopted by the Brazilian government.

Resumo em Português:

Bibliometric reviews, carried out from access to databases of scientific articles associated with software for data processing, can be helpful for qualitative and quantitative assessments of existing publications on a given topic. Several petroleum hydrocarbons are carcinogenic and immunotoxic agents, causing adverse effects on the biota, and the study of metabolites generated in bioremediation processes has been the object of current research. Therefore, in this work, the use of bibliometric analysis as a tool for surveying studies on the applied metabolomics bioremediation of areas impacted by hydrocarbons is presented. A bibliometric review was carried out in the Scopus Preview and Web of Science databases with data analysis using RStudio software with the bibliometrix package. The survey gathered the studies and prominent publications of the last seven years, making it possible to present gaps and opportunities in the area.

Resumo em Português:

Phosphorus is a non-renewable element essential for the existence of life and also for food security. This resource has the property of limiting plant growth, becoming a fundamental part of agricultural production. On the other hand, when this element is present in high concentrations in aquatic environments, it can start a phenomenon called eutrophication, which causes a series of changes in biological succession processes and strongly negative impacts on species’ biodiversity and wealth. In this context, this work aimed, from an extensive bibliographical review, to gather strategic and essential information related to phosphorus sustainability, provoking a reflection regarding scenarios that involve this indispensable nutrient, focusing on the current situation of the State of São Paulo, Brazil, an important case study, both for the Brazilian and international scenario, by a gathering of data on the current situation of two of the main watersheds in the corresponding region. Relevant technologies used for phosphorus removal in eutrophicated environments are also addressed. Finally, the possibility of reusing the nutrients present in eutrophicated water bodies as an alternative source of phosphate fertilizer for agriculture is demonstrated.

Resumo em Português:

We developed and validated an UHPLC-MS/MS method for the quantification of phosphatidylethanol (PEth) in dried blood spots (DBS). Sample preparation was a liquid extraction and chromatographic separation was performed in an Acquity C8 column. The mobile phases were 4 mM ammonium acetate in water (A) and acetonitrile (B) at 24:76 (v/v). The total analytical run time was 6 minutes, with retention time of 3.36 min for PEth and 4.13 min for phosphatidylpropanol. The method was linear from 10 to 3000 ng mL-1, specific, with, precise and accurate. The analyte was stable in DBS stored from -20 to 45 °C for 21 days. Matrix effect was compensated with the internal standard (-5.21% to + 6.09%). The method was applied in the evaluation of alcohol consumption in DBS from 25 chemical dependents. The PEth concentrations ranged from 14.5 to 2380.8 ng mL-1, with significant correlation with the self-report alcohol consumption AUDIT scores (r=0.41).

Resumo em Português:

Considering the chemical and pharmacological properties of semicarbazones, an interdisciplinary didactic sequence was developed to be applied in experimental classes of undergraduate courses in Pharmacy, Chemistry and related areas. This didactic sequence was planned in three steps, starting from the planning of the target molecule, a semicarbazone derived from helional, to its synthesis, physicochemical characterization (CCD, melting point, FTIR and UV-Vis) and in silico tests of its pharmacokinetic properties using the free software ADMETlab 2.0. The proposed target molecule has as molecular scaffold the 1,3-benzodiaxole nucleus and the semicarbazone function, aiming to obtain a molecule with promising anticonvulsant action and that can be obtained by a low cost and easy to execute methodology, which makes it attractive for use in experimental classes. Thus, the application of this didactic sequence aims to provide undergraduate students the opportunity to experience the process of drug development, applying techniques for planning, synthesis, characterization, and pharmacokinetic evaluation in silico. Besides reinforcing the interdisciplinary teaching of Medicinal Chemistry, applying in an integrated way the theoretical and practical knowledge of the disciplines of Organic Chemistry, Physical Chemistry, Pharmacology and Computational Chemistry.

Resumo em Português:

Fingermark dusting powders are an important tool of forensic practitioners, being a first-choice process for most crime scene investigators. The development of new products is of utmost importance for forensic science. Hydrazones comprise compounds derived from ketones or aldehydes in reaction with hydrazines. These reactions are widely studied in organic chemistry because of the versatility of these compounds in organic synthesis. The study of these reactions leads to the understanding of the nucleophilicity of hydrazines, as well as the electrophilicity of aldehydes and ketones. The present work presents one proposal of experimental organic chemistry, aiming at a new application of this classic class of organic substances in forensic chemistry, specifically as a developer of latent fingermarks due to the variations of the color of the compounds, with spectra ranging in a range from 250 to 500 nm. These compounds were identified by Infrared Spectroscopy, Ultraviolet-Visible Spectroscopy and Mass Spectrometry. The development on glass surfaces demonstrated the potential application of these compounds in everyday life situations.

Resumo em Português:

The use of metrics to evaluate scientists is widespread in the present time, with implications for hiring, fellowships, and research grants. Such fact requires that metrics must be constantly scrutinized to be improved. This work analyzes the use of metrics in the area of chemistry in Brazil and discusses its limitations and shortcomings. The main findings indicate that the use of the impact factor must be complemented by the cited half-life of the journals, and a composite metric named influence factor is proposed, similar to the R-impact. The h-index is not a good metric anymore because does not correct for authorship inflation. The individual h-index (hi), which takes into account fractional counting of citations, is more reliable than the h-index. An analysis on the use of hi-index with randomly selected 15 Brazilian chemists among the top 500 more productive shows an important effect on the ranking order.