Resumo em Inglês:

Pesticides offer a simple, cost-effective solution to ensure food supplies for a growing world population. However, their environmental performance needs improvement if pesticides are to continue contributing importantly. This study explores the insecticidal potential of a magnesium (II) metal complex containing 1,10-phenanthroline and isovanillic acid (MgPhenIso) against leaf-cutting ant (Atta sexdens rubropilosa) and its symbiotic fungus (Leucoagaricus gongylophorus). The MgPhenIso complex is easy-to-prepare, stable in solid state and in aqueous solution, and resistant to sunlight irradiation. The insecticidal activity of MgPhenIso-containing bait against A. sexdens rubropilosa and L. gongylophorus showed a delayed action mode at 2 mg g-1 (100% kill, 6th day, S50=2b) and suppressed fungus development and growth. These results, together with earlier investigations on MgPhenIso regarding its absence of toxicity to Zebrafish and Wistar male rats, emphasize the potential of this complex as an environmentally friendly insecticide candidate.

Resumo em Inglês:

In the bentonite industry, the most common procedure for quality control of the ore and the sodium activation process is the swelling method. However, this tool is restricted only to the differentiation of the sodium and non-sodium types, not considering the other cationic varieties. The objective of this study was to establish parameters for cationic differentiation of bentonites based on Near Infrared (NIR) and Medium (MIR) spectroscopy, which proved to be an effective technique in the cationic differentiation of bentonites using the characteristic bands “7072 cm-1” and “3620 and 3430 cm-1” under the condition of the dry-hydrated sample and not under the anhydrous condition. NIRS can be considered a measure of great scientific and technological contribution, as it allows the cationic differentiation of bentonites in a practical way and with low analytical cost.

Resumo em Inglês:

In the present work, a silver(I) complex with the antimycobacterial drug isoniazid (inh) is described. Elemental and thermogravimetric analyses confirmed a 1:1 metal:ligand ratio for the silver-isoniazid (Ag-inh) complex with molecular composition AgC6H7N3O·NO3. Infrared (IR) analysis suggests a bidentate coordination of isoniazid to silver by the nitrogen of the NH2 group and by the oxygen of the C=O group, and also confirms the presence of free nitrate anion. Coordination by the NH2 group was reinforced by NMR measurements. Computational simulations using the density functional theory (DFT) reinforced that the ligand coordinates to the silver atom by the NH2 and C=O groups. The silver complex presented a minimal inhibitory concentration (MIC90) of 0.78 µg/mL against the standard Mycobacterium tuberculosis strain H37Rv. The data reported herein warrants further investigation on Ag-inh complex as a potential agent against tuberculosis.

Resumo em Inglês:

Sinningia reitzii (Hoehne) L. E. Skog (Gesneriaceae) is a subshrub native to Brazil, where it is distributed in two disjunctive populations around the 26°S and 23°S parallels. In this work, tubers of plants from the wild population growing at the 26°S parallel (Santa Catarina state) yielded two new naphthoquinones, 5,6-dihydroxy-7-methoxy-a-dunnione and 8-hydroxy-6,7-dimethoxy-a-dunnione. Three known compounds were also isolated: 6,8-dihydroxy-7-methoxy-a-dunnione, 5-hydroxy-6,7-dimethoxy-a-dunnione, and 6,8-dihydroxy-7-methoxy-2-O-methyldunniol. The naphthoquinones 6,8-dihydroxy-7-methoxy-2-O-methyldunniol, 6,8-dihydroxy-7-methoxy-a-dunnione, and 5,6-dihydroxy-7-methoxy-a-dunnione displayed antioxidant activity in the ORAC-FL method, with values of relative trolox equivalent in the range of 1.39-4.83 mmol g-1.

Resumo em Inglês:

In the face of environmental changes concerns, the study of climate change becomes essential to understand the life trajectory of planet earth. For this purpose, this work seeks to understand climate change and fluctuations in the amount of atmospheric oxygen across geological ages, carbonizing the Araucaria columnaris wood in varying oxygen concentrations, and comparing them to the fossil coal from Quiteria Outcrop. In this study, pyrolysis of Araucaria columnaris wood occurred with the use of TGA, under an atmosphere of 21% and 30% O2, analyzed in FTIR, distinguishing the constituent compounds of the wood. Multivariate analysis of the mains components (PCA) was applied, for data crossing. There is a distinction between carbonized wood and fossil charcoal, the charcoal burning temperature as well as the atmospheric oxygen composition being inconclusive. However, FTIR results indicate that the amount of oxygen has an influence on the degradation of the wood, and samples at 450 °C have greater similarities with fresh wood. Thus, it was observed that the temperature and the burning time are the main factors of the fires, being that the amount of oxygen available in the atmosphere influences the firing process.

Resumo em Inglês:

Pt/TiO2 nanoparticles were prepared by a simple two-step aqueous solution method, which consists of a low temperature hydrothermal step and a photoreduction deposition step. The as-prepared samples were characterized by XRD, TEM, XPS, UV-vis, and BET techniques. The as-prepared samples exhibited enhanced photocatalytic activity towards the degradation of rhodamine B (RhB) under visible light irradiation. With increasing Pt content from 0.25 to 1 wt.%, the band gap energies shift from 2.32 to 1.64 eV. The 0.75 wt.% Pt/TiO2 sample showed the best photocatalytic activity, which could be ascribed to the formation of a Schottky barrier and the localized surface plasmon resonance effect of Pt nanoparticles. And the as-prepared samples also displayed excellent stability and reusability in multiple experimental cycles.

Resumo em Inglês:

Ruthenium and iridium polypyridine complexes are among the most employed photocatalysts described in literature. The broad applicability is due to the redox potentials and long half-life times of the excited state which these molecules presented. The pursuit for metal-free alternatives has been intensified in the last few years, therefore, many organic fluorophores were successfully employed as photocatalysts. Among them, 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicianobenzene (4CzIPN) recently drawn attention of the community, and it’s been widely employed by distinguished research groups. Recent studies have shown that this catalyst do not only present similar properties to transition metal complexes, but also, its synthesis can be accomplished more easily and less expensive when compared with the metallic photocatalysts above mentioned. Therefore, 4CzIPN constitutes a metal-free alternative to replace transition metal complexes in conventional photochemical protocols. Moreover, it’s as a powerful ally in the development of new photochemical approaches. In this work, we aim to summarize recent applications of 4CzIPN as catalyst in the emerging field of redox photocatalysis.

Resumo em Inglês:

The imidazole (IMZ) ring presents several chemical properties that turns it into a versatile acid-basic/nucleophilic catalyst. The discovery of the biological properties of histidine (amino acid with IMZ ring) instigates the study of this class of compounds. It is found in nature in several enzymes such as chymotrypsin and RNAses due to these properties. This review is focused on the catalytic role of IMZ towards the cleavage of acyl and phosphate esters and is structured in the following topics: chemical properties, biological catalysis (RNAses, phosphohistidines, chymotrypsin), intermolecular and intramolecular catalytic models and polymer and nanomaterials-based catalysts. Besides we discuss some properties such as tautomerism, stability, basicity and spectroscopic behavior, correlating with its reactivity in deacylation and dephosphorylation reactions. The main reaction mechanisms and kinetics promoted by IMZ as an acid, basic and nucleophilic catalysts are explored showing some examples. In addition, the importance of IMZ in enzymatic sites and their mechanisms and further combining properties of IMZ with some materials such as (bio)polymers, graphene, and cyclodextrines are covered. In this sense, with the wide IMZ data presented here, we are evidencing the perfect match between IMZ and catalysis.

Resumo em Inglês:

Benzene is an important environmental and occupational pollutant, and recognized as human carcinogen. S-phenylmercapturic acid (SPMA) is a highly specific biomarker of exposure to benzene, applied in occupational toxicology to assess low levels of benzene exposure. The objective of this study was to develop and validate a one-step liquid extraction bioanalytical method for the quantification of SPMA in urine by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method was applied to the evaluation of benzene exposure in an occupational setting. The assay was linear from 0.5 to 500 ng mL-1 (r>0.99), accurate (91.4-105.2%) and precise, with CV% between 4.73 and 9.96%. SPMA was stable in urine for 90 days at -20 °C. Airborne benzene concentrations, urinary levels of SPMA and t,t-MA were significantly higher in gas station workers (n=30) in comparison to outdoor workers (n=14) and individuals non-occupationally exposed to benzene (n=34). Benzene airborne levels had higher correlation with urinary SPMA (r=0.532, p<0.001) than with t,t-MA (r=0.338, p=0.04), demonstrating the applicability of this biomarker for monitoring low levels of benzene exposure.

Resumo em Inglês:

This work describes the development of an automatic titrometric method in flow-batch with potentiometric detection using alternative and easily accessible materials. Arduino board and its modules, solenoid valves to control the flow rate, peristaltic pump to propel and suction fluids and tubes of inert material to connect the different parts of the Flow-Batch Analyser (FBA) were used. The use of solenoid valves controlled by microcontrollers proved to be efficient for controlling the flow in FBA systems, the correlations of their flow rates as a function of time showed good linearity with correlation coefficients (r) 0.9994 and 0.9997 for the valve 1 and valve 2, respectively, allowing correct addition of pre-established volumes. Accuracy was verified by comparing the results of the proposed method with the classic potentiometric titration with statistically evaluated by Student’s t-test in NaOH with HCl and vinegar with NaOH titrations. Results confirmed the efficiency to use Arduino board and its modules and automatic titrometric method in flow-batch developed in this work allow the implementation of practical disciplines, such as potentiometric titration and flow analysis system in undergraduate courses, making these instruments more accessible, especially for the chemistry students.

Resumo em Inglês:

In Part II of a three-part series, we discuss two factors absent from textbooks of general chemistry that are important in a discussion of teaching orbitals. First, atomic orbitals are shown systematically to comprise algebraic formulae in coordinates of not one but four sets (spherical polar, paraboloidal, ellipsoidal, spheroconical coordinates). Each formula has its corresponding shape as a surface of constant amplitude; some visual examples are provided. Second, the argument that molecular structure is incompatible with quantum mechanics is presented. Despite the utility of orbitals as mathematical functions in various calculations, they are intrinsically complicated for the traditional purpose of qualitative explanation of molecular structure.

Resumo em Inglês:

In Part III of this series, we undertake a critique of the nature of application of orbitals to describe or to explain the structure and the binding within molecules and materials. Teaching orbitals in introductory chemistry presents five dilemmas that cannot be easily resolved. We thus conclude, based on mathematical realties, that orbitals are not essential until advanced courses. Even in advanced courses, we question the traditional choice of presenting an inadequate set of orbitals. When one recognizes, in a context of general chemistry, the irrelevance of orbitals as algebraic formulae to the observable properties and reactions of chemical substances, one can readily proceed to teach appropriate content effectively without invoking orbitals or analogous entities, based on our actual experience in teaching general chemistry over the years.

Resumo em Inglês:

This paper describes the construction of a polarimeter for the identification of chemical substances. The device was built with low-cost materials, measures the phenomenon of optical activity and has educational applicability. The measurement of optical activity is achieved through the measurement of the resulting polarized radiation in a photodiode connected to a voltmeter after passing through polarizing and analyzing filters.

Resumo em Inglês:

This work aims to study the learning progression of students from two federal universities in Rio de Janeiro within the scope of Chemical Kinetics. For the elaboration of the research questionnaire, 46 professors from eleven Brazilian universities were consulted and from the collected data, a questionnaire was elaborated and applied to 452 students of Pharmacy, Chemistry and Chemical Engineering courses at Universidade Federal Fluminense and Universidade Federal do Rio de Janeiro. For the analysis of the questionnaires, Rasch modelling was used, which made it possible to elaborate the learning progression of these students.

Resumo em Inglês:

An adaptation on the classical synthesis methodology for 1,3-diaryltriazenes for a 4-hour experimental class has been proposed with green chemistry principles in mind by using commercial vinegar as a source for diazotization with NaNO2 and keeping the reaction workup to simple vacuum filtration. Several anilines with different substituent groups were used to evaluate how they affect the synthesis based on their electron-donating/withdrawing characteristics. The decomposition of the triazenes in acidic media was also monitored via TLC. On the overall, the reactions came up with medium to high yield and high purity. Experimental procedure, reaction mechanism and other potential discussions such as green chemistry principles and effects of electron-donating/withdrawing groups are suitable for undergraduate students.

Resumo em Inglês:

In this article, it is described the main aspects to be considered during the process of scaling up hard sciences technologies developed in the Science and Technology Institutes aiming at industrial application. Based on the experience of our group in scaling up, pre-acceleration, and acceleration of different technologies, a methodology was developed and divided into four main stages: Step 1, which involves basic research, Step 2 with a focus on product development, and Step 3 with a focus on process development, all on the laboratory scale and the last one, Step 4 focused on pilot plant development. The most important aspect of this article is to show that many critical questions can be answered even in the laboratory phase. In this way, the risks of Step 4 are minimized. Step 4 is a complicated, lengthy, and expensive process of construction and operation of a pilot plant. Aspects such as proof of concept, technical and economic feasibility studies, minimum viable product, capital expenditures, and operating expenses of pilot plants are approached in a simplified way to serve as a basis for researchers who wants to know the long path to be followed by technology before reaching the industry, consequently the market.