Resumo em Português:

HYDROMETALLURGY PROCESS FOR EXTRACTION OF COPPER PRESENT IN PRINTED CIRCUIT BOARDS USING HYDROGEN PEROXIDE AND ACIDS AS LEACHING AGENTS. With the increasing use of electronic devices and the reduction of their useful life, the generation of electronic waste has grown significantly. This study investigates the hydrometallurgical process of copper extraction from computer printed circuit boards, using hydrochloric acid and hexafluorosilicic acid, combined with hydrogen peroxide, as leaching agents. The process optimization was performed using response surface methodology, evaluating the influence of variables such as hydrochloric acid concentration, temperature and volume of hexafluorosilicic acid. Two factorial designs were conducted to analyze the significance of the variables. Temperature showed a positive influence, being fixed at 40 °C in the subsequent experiments. Hydrochloric acid concentration was identified as the most significant variable, with high extraction rates associated with higher concentrations of H3O+ ions. Using 3 mol L−1 of hydrochloric acid, 17.7 mL of hexafluorosilicic acid and 20 mL of hydrogen peroxide, an extraction of 58.3% of copperII ions was obtained in relation to the theoretical concentration present in the samples. Additionally, the leaching reaction generated pure hydrogen gas, according to gas chromatography analysis.

Resumo em Inglês:

The use of efficient and reliable methods is extremely important for analyzing food samples suspected of containing toxic substances. Due to the difficulty in obtaining highly toxic illicit poisons of the carbamate type (aldicarb/carbofuran) and organophosphates (terbufos), popularly known as chumbinho, which were banned by Agência Nacional de Vigilância Sanitária (ANVISA), there is an increase in cases of suicide and attempted murder using another type of poison: commercial coumarin rodenticides based on brodifacoum which are freely sold in pesticide product stores. The low concentration of the active ingredient (0.005%, m/m) in formulated products containing coumarins makes it difficult to identify these substances in samples with a small amount of poison or when mixed in food, requiring more complex extraction methodologies and instrumentation that many forensic investigations do not have, often generating inconclusive reports. In this work we studied a new analytical methodology for the extraction and identification of brodifacoum, one of the coumarins commonly found in these poisons, using gas chromatography coupled with mass spectrometry (GCMS). In extraction by sonification, we use acetone and methanol/formic acid 50:1 as extracting solvents, followed by concentration and subsequent analysis by chromatography, obtaining excellent results in identifying the main degradation product of brodifacoum in the formulated products, even when mixed with food in cases of poisoning, relating its concentration to that of the commercial standard. This work provides an alternative method of analyzing these materials, helping scientific police prepare more conclusive reports in cases of coumarin poisoning, thus reducing impunity.

Resumo em Inglês:

Curcumin (Cur), extracted from turmeric rhizomes (Curcuma longa), exhibits antiparasitic properties, making it a promising candidate for schistosomiasis mansoni treatment due to its low cost and absence of side effects. However, its chemical instability and water insolubility limit its therapeutic application. Green iron oxide nanoparticles (Fe3O4-green NPs), synthesized following Green Chemistry principles, serve as biocompatible carriers with magnetic properties. When combined with chitosan (Chit), a biopolymer capable of encapsulating curcumin, they create a controlled release system to enhance curcumin’s stability and bioavailability. The objective of this study is to develop the Chit-Cur-Fe3O4-green controlled release system. Fe3O4-green NPs were synthesized using Fe2+ ions, potato peel, and sodium carbonate. The system was prepared by combining chitosan, Fe3O4-green NPs, curcumin, N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC), and N-hydroxysuccinimide (NHS). Characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), fluorescence, thermal analysis and magnetic property. Controlled release was tested over 500 h in phosphate-buffered saline (PBS), with curcumin concentration determined by UV-Vis. Pharmacokinetics were analyzed using kinetics models. The system achieved 100% encapsulation efficiency and released 50% of curcumin over 400 h, reaching equilibrium at 370 mg L–1. The release followed a diffusion-controlled mechanism. The Chit-Cur-Fe3O4-green system enhanced curcumin’s bioavailability and stability, demonstrating potential for therapeutic applications.

Resumo em Português:

Nuclear safety necessitates rigorous monitoring of environmental radioactivity, which in turn requires the development of efficient and high-resolution radioanalytical methodologies. Regulatory standards restrict the marketing of food products containing cesium-137 (137Cs) activity levels exceeding 1.0 kBq kg-1, making radiometric analysis of sugar essential for export compliance. This analysis enables the detection of gamma signatures from radionuclides, facilitating the identification of environmental contamination. In this study, we developed a calibration model for gamma spectrometers, utilizing 3D printing technology to fabricate a specialized container. Soil samples weighing 300 g were treated with cesium solutions, yielding specific activities of 695 and 1,042 Bq kg-1. The relative dispersion of these activities was measured at 2.96%, with a remarkably low relative error of 0.04% in the characterization of gamma transitions. The achieved energy resolution of 0.64% reflects significant enhancements in the interaction parameters between the material and the detector. Additionally, strategies to minimize gamma auto absorption were implemented, thereby improving the safety and accuracy of radionuclide qualification and quantification. These practices not only ensure compliance with safety regulations but also contribute to the protection of public health and the environment.

Resumo em Inglês:

The chemical nickel plating process generates large volumes of wastewater. This wastewater contains NiII citric acid complexes (Ni-Cit) that are difficult to treat. This study addressed the challenging Ni-Cit waste streams, focusing on development and implementation of a highly efficient and stable single-compartment approach for nickel recovery through electrocatalytic oxidation in synergistic electrodeposition. Our findings demonstrate that high-purity nickel (Ni) may be successfully recovered from Ni-Cit waste streams by combining electrocatalytic oxidation and electrodeposition. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) techniques were utilized to thoroughly examine the nickel recovered from the cathode. The study found that optimal electrochemical treatment was achieved with a current density of 100 mA cm−2, an initial pH of 4.05, and an initial Ni ion concentration of 0.01 M. Ni healing was achieved in 100% of cases after two hours of treatment. By investigating the degradation process of nickel waste solution complexed with citric acid, we proposed the mechanism of Ni-Cit electrocatalytic oxidation for complexation breakdown, and our findings provide a theoretical foundation for the effective treatment of nickel complex-containing wastewater and recovery of nickel metal monomers.

Resumo em Inglês:

Carbamazepine is widely used in the treatment of psychomotor epilepsy; however, its low aqueous solubility can limit therapeutic efficacy. In this study, solid dispersions were developed via hot melt extrusion to enhance the solubility of the drug and dissolution profile. Notably, the extrusion process induced a partial polymorphic conversion of carbamazepine from forms III to I, a less stable but more soluble form, which likely contributed to the improved performance. Dispersions were prepared using Gelucire® 50/13, polyethylene glycol (PEG) 4000, PEG 6000, and a PEG 4000/6000 blend at drug-to-carrier ratios of 1:9, 1:5, and 1:1. The formulation containing Gelucire® 50/13 at a 1:9 ratio exhibited the highest solubility (approximately three times greater than that of the pure drug) and a significantly enhanced dissolution profile. Characterization by X-ray diffraction, infrared spectroscopy, hot-stage microscopy, and thermal analysis confirmed the absence of physicochemical interactions between the drug and the carriers. Among the carriers tested, Gelucire® 50/13 emerged as the most promising for improving carbamazepine solubility and dissolution, potentially enhancing therapeutic efficacy and minimizing adverse effects.

Resumo em Inglês:

This work evaluated mid-infrared spectroscopy combined with chemometrics for qualitative and quantitative analysis of flavonoids in plant extracts. The exploratory data analysis was conducted using principal component analysis (PCA) and hierarchical cluster analysis (HCA), while the calibration model was developed using the partial least squares (PLS) regression technique. Methanolic extracts were obtained from 15 plant species collected during rainy and dry seasons, totaling 26 samples. Ultraviolet-visible (UV-Vis) spectroscopy was used as a reference method for the determination of flavonoids. PCA and HCA grouped the samples according to their chemical composition, with no significant variations due to seasonality. The extract of “quebra-pedra” (Phyllanthus niruri) formed a distinct cluster related to the spectral bands at 1012 and 1047 cm−1, attributed to C-O stretching in carbohydrates and cellulose derivatives. The regression model presented a root mean square error of calibration (RMSEC) of 0.06, root mean square error of cross-validation (RMSECV) of 0.13, root means square error of prediction (RMSEP) of 0.20, and residual predictive deviation (RDP) of 1.62. These results demonstrate that the combination of Fourier transform infrared spectroscopy (FTIR) and PLS presents itself as an alternative to predicting the concentration of flavonoids in complex samples, such as plant extracts.

Resumo em Inglês:

To detect melamine in packaging materials, terahertz time-domain spectroscopy (THz-TDS) was employed to measure the terahertz absorption spectra of melamine-polyethylene mixtures with varying mass ratios (1:0-3). The results revealed distinct characteristic absorption peaks of melamine at 2.0, 2.28, and 2.6 THz. Among these, the peak at 2.0 THz was the most prominent and remained clearly observable even within packaging materials. Several common packaging materials, including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and paperboard, were examined individually to assess their spectral interference. Characteristic melamine absorption peaks at 2.0 and 2.28 THz were used to establish a calibration model based on Gaussian distribution functions. Based on the International Union of Pure and Applied Chemistry (IUPAC) method, the limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 15 and 80%, respectively. Even at a concentration close to the LOD (10%), the signal remained distinguishable (signal/noise (S/N) > 3). X-ray powder diffraction (XRD) was utilized as a complementary technique to confirm the presence of melamine in the transparent plastic zip bag. These results support the effectiveness of THz-TDS in detecting melamine through packaging materials and highlight its potential application for detecting specific molecules in packaging materials.

Resumo em Inglês:

Cedrela odorata L. (Meliaceae), popularly known as cedar, is a species that is valued for the quality of its wood, though its exploitation for decades has led it to be included on the list of Brazilian species of flora as an endangered species. The recycling of wood residues of this species generated by demolition is an excellent strategy for a circular economy. In this paper, we present the phytochemical study of C. odorata demolition wood for the sustainable production of antileishmanial compounds against promastigote forms of Leishmania (V.) guyanensis and Leishmania (L.) amazonensis. Classical chromatographic techniques were used in the purification of one sesquiterpene, eight triterpenes and five limonoids. The limonoid 7-deacetoxy-7a-hydroxy-gedunin was able to inhibit promastigote forms of L. guyanensis [IC50 (50% inhibitory concentration) of 26 μg mL–1] for 48 h, and gedunin showed moderate activity. The present study indicates that cedar demolition wood (Cedrela odorata), despite being about forty-five years old, still had its secondary metabolites, including those that are characteristic of the species such as limonoids, triterpenes of the tirucallane- and cycloartan-types.

Resumo em Português:

This study investigated the chemical composition of honeys produced by three species of native stingless bees of Brazil (Tetragonisca angustula, Melipona quadrifasciata, and Scaptotrigona depilis) and their respective fermented beverages (meads) using metabolomic approaches. The honeys were subjected to spontaneous fermentation, as well as fermentation with commercial yeasts. Spontaneous fermentation occurred from microorganisms already present in the honey. In commercial fermentation, the honeys were sterilized and inoculated with selected yeast. Chemical characterization was performed by high-performance liquid chromatography coupled to tandem mass spectrometry with electrospray ionization (HPLC-ESI-MS/MS) and molecular network analysis using the Global Natural Products Social Molecular Networking (GNPS) platform, and by gas chromatography (GC MS) to evaluate volatile compounds. It was observed that the annotated flavonoids, phenolamides, and glycosylated amino acids were preserved even after the fermentation process. Furthermore, the fermentation products presented a wide diversity of volatile compounds, with variations between species and fermentation processes. The results highlight the potential of honeys and meads as sources of bioactive compounds, contributing to the valorization of Brazilian biodiversity and possibilities for innovation in the fermented beverage market, as well as applications in functional foods and pharmaceutical products.

Resumo em Português:

AUTHENTICITY STUDY OF ONE-HUNDRED REAL BANKNOTES BY MID- AND NEAR-INFRARED SPECTROSCOPY COMBINED WITH CHEMOMETRICS. Counterfeiting of banknotes is a growing concern in Brazil and has become increasingly sophisticated, demanding more advanced analytical methods. Spectroscopic techniques have gained popularity in forensic analyses due to their non-destructive, rapid, and quantitative nature. The development of portable spectrometers makes analyses more accessible, and their combination with chemometric methods ensures greater accuracy and precision. This study evaluated the use of micro spectrometer in the near-infrared region (MicroNIR) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic techniques, combined with chemometrics, to differentiate authentic and counterfeit 100-Real banknotes. A total of 100 banknotes (50 genuine and 50 counterfeit) were analyzed in triplicate at 10 different points. Data was processed using principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA). The greatest differences between genuine and counterfeit notes were observed in the holographic strip and intaglio printing regions. PCA revealed variance above 70% with MicroNIR and above 75% with FTIR at the most discrepant points. Using PLSDA, satisfactory classification metrics were obtained, with accuracy, sensitivity, and specificity values close to 100%, demonstrating the applicability and efficiency of the proposed method. MicroNIR proved particularly suitable for rapid and portable analyses, while FTIR provided excellent laboratory resolution. The proposed method proved efficient and promising for identifying counterfeits, contributing agile and robust tools to forensic science.

Resumo em Português:

STUDY OF THE CATALYTIC ACTIVITY OF THE [RuCl2(p-cymene)]2 COMPLEX IN THE METATHESIS/ISOMERIZATION OF SUBSTITUTED ALLYLBENZENE OLEFINS. [RuCl2(p-cymene)]2 (PCM) was applied for the first time as a precursor in the transformation of three substituted allylbenzenes: methyleugenol (ME), eugenol (EU), and estragole (EST). ME and EU were mixed in chloroform with the PCM complex, and 5 μL of ethyl diazoacetate (EDA) was added. The reaction was stirred for 72 h at 50 °C, with cat:sub (catalyst:substrate) ratios of 1:100 or 1:10 mol. For EST, the same conditions were applied, but only the 1:100 mol cat:sub ratio was studied. The final reaction mixtures were analyzed by 1H NMR (nuclear magnetic resonance), with peaks properly assigned to the corresponding compounds. The integration values of the peaks were used to quantify the relative amounts of products concerning the remaining substrate. The compounds iso-ME and iso-EU were synthesized with yields of approximately 70% at a 1:100 mol cat:sub ratio. At a 1:10 mol ratio, iso-ME yields remained constant, whereas iso-EU yields decreased to approximately 10%. The compounds bis-ME and bis-EU were also observed, with yields of < 10 and 18%, respectively, under the best conditions. Studies with EST were conducted to understand the yield reduction of iso-EU at a 1:10 mol ratio, correlating this phenomenon with the equilibrium of the isomerization mechanism.

Resumo em Inglês:

The consumption of cocaine represents a significant challenge for public health and safety, given its impact on brain functionality and its direct connection to drug trafficking and the strengthening of organized crime. The Scott test, developed by L. J. Scott Jr. in 1973, offers a practical and rapid alternative for the on-site identification of cocaine, although it has low selectivity regarding the purity of the substance. This study aimed to classify high and medium purity cocaine samples, provided by the Scientific Police, through digital image conversion, utilizing machine learning algorithms: Naive Bayes, support vector machines (SVM), logistic regression, K-nearest neighbors (KNN), decision tree, random forest, and extreme gradient boosting (XGBoost). The results were satisfactory, with most algorithms achieving accuracy values of 90% or higher in classifying the samples, except for Naive Bayes, which showed an accuracy of 86%. The KNN and XGBoost algorithms stood out, achieving performances of 94 and 93%, respectively. The classification models generated by these algorithms proved effective in characterizing seized cocaine samples, providing a valuable tool to guide public policies and enhance police intelligence through the monitoring of these substances.

Resumo em Inglês:

The cathode materials of spent lithium-ion batteries are rich in various valuable metal elements, making their recycling economically beneficial and environmentally significant. Addressing the limitations of pyrometallurgical and hydrometallurgical processes, this study innovatively employs a novel eco-friendly solvent, a lactic acid-based deep eutectic solvent, to investigate its effectiveness in recycling lithium iron phosphate (LiFePO4) cathode materials. The research first determined the optimal pre-treatment parameters through thermogravimetric analysis. Subsequently, a lactic acid (LA)-based deep eutectic solvent (DES) was prepared using choline chloride, lactic acid, and ultrapure water, and applied in leaching experiments for the LiFePO4 cathode material. The experimental results demonstrate that during the pre-treatment stage, calcination at 400 °C for 5 h can effectively remove organic binders and conductive carbon impurities. Under the conditions of a reaction temperature of 140 °C, leaching time of 8 h, liquid-to-solid ratio of 1:100, and a molar ratio of choline chloride (HOCH2CH2N(CH3)3+Cl-, ChCl) to LA of 1:3, the leaching efficiencies of lithium and iron reach 94.57 and 92.98%, respectively. Fourier transform infrared spectroscopy analysis indicates that the synthesized DES has a distinct hydrogen bond network, which plays a crucial role in the leaching process of cathode materials and is the main factor in enhancing metal leaching efficiency.

Resumo em Português:

Understanding the interactions between small ligands and (bio)macromolecules is essential for the development of bioactive compounds. This study investigated the interaction between CT-DNA (calf thymus-deoxyribonucleic acid) and bendamustine (BE), a nitrogen mustard with antineoplastic potential, using spectroscopic techniques and theoretical studies. The results revealed the formation of a fluorescent supramolecular complex with moderate affinity (Kb = 4.71 × 103 L mol-1). The interaction is spontaneous and stabilized by hydrogen bonds, van der Waals forces, and electrostatic interactions. The hydrodynamic radius increased from 4.63 ± 0.02 nm (free CT-DNA) to 17.50 ± 0.52 nm (BE-DNA), indicating complexation. Thermal denaturation studies (∆Tm < 5 °C), tests with potassium iodide (KI), and competition with ethidium bromide suggest a non-intercalating binding mode. 1H nuclear magnetic resonance (NMR) spectroscopy indicated that the interaction occurs preferentially via the alkylated nitrogen of the heterocyclic ring. Molecular docking studies confirmed the presence of hydrophobic interactions in DNA grooves and electrostatic regions. Although BE is known to form covalent bonds with biomolecules, the data suggest that non-covalent interactions with DNA may also contribute to its mechanisms of action.

Resumo em Inglês:

Green synthesis of two dihydropyrimidine-thione derivatives, i.e., 1-(4-bromo-2-fluorophenyl)-4,4,6-trimethyl-3,4-dihydropyrimidine-2(1H)-thione (SA1) and 1-(3-chloro-4-fluorophenyl)-4,4,6-trimethyl-3,4-dihydropyrimidine-2(1H)-thione (SA2), was accomplished through a convenient and simple protocol by the reaction of acetone, potassium thiocyanate, and corresponding anilines (4-bromo-2-fluoroaniline and 3-chloro-4-fluoroaniline). The single crystal X-ray diffraction (SCXRD) studies along with Hirshfeld surface analysis were conducted to gain insight of the structural details and intermolecular interactions within the crystal lattice. An extensive network of intermolecular interactions was observed in the SA2 crystal packing implying its higher reactive potential. The density functional theory (DFT) calculations conducted to estimate the global reactivity parameters underscored the high reactivity of both derivatives. Our in vitro experiments demonstrated that compound SA2 showed greater inhibition than SA1 against the targeted enzymes, acetylcholinesterase and butyrylcholinesterase, which were inhibited with IC50 (half-maximal inhibitory concentration) values of 27.2 ± 2.4 µM and 51.8 ± 2.7 µM, respectively. Also, the correlation between the descriptors of DFT reactivity and the biological activity was empirically observed. The favorable binding and interaction potential for SA2 can be explained by the optimized electronic structure, which increased the binding to the enzyme targets. In addition, the potential drug-like properties of both compounds, including their toxicity profiles, were evaluated through computational predictive modeling.

Resumo em Português:

In this work, we continue our series of tutorial articles published in the Química Nova exploring different features of the GAMMA-GUI app (Grupo de Análise Multivariada em Matrizes Alimentares), a user-friendly interface for the multivariate analysis in Matlab®. This time, we demonstrate five types of exploratory data analysis (unsupervised learning), complemented by video demonstrations on our YouTube channel. Applications consist of demonstration with: (i) principal component analysis (PCA); (ii) self-organizing maps (SOM); (iii) hierarchical cluster analysis (HCA); (iv) k-means, and (v) common dimensions analysis (ComDim). Additionally, a demonstration of descriptive statistics with Tukey HSD (honest significant difference) has been included in this tutorial. Suggestions for improvements or new ideas for the app are welcome and can be directed to the developers.

Resumo em Português:

CASE STUDIES: OPPORTUNITIES FOR THE DEVELOPMENT OF CRITICAL ENVIRONMENTAL EDUCATION IN GRADUATE CHEMISTRY COURSES. The objective of this research is to analyze the potential of developing Case Studies (CS) in a graduate Chemistry course as a means of incorporating the principles of Critical Environmental Education (CEE). Sixteen CS, produced by 33 students enrolled in the Sustainability and Environmental Education course offered as elective discipline in the graduate program in Chemistry at the Federal University of Rio Grande do Sul (UFRGS) over four consecutive semesters were analyzed using content analysis. The findings reveal a diverse range of scientific and socioscientific issues that can be addressed through CS in higher education in Chemistry. The skills most emphasized by the research participants were research, decision-making, and critical thinking. Furthermore, the study identified a convergence between the CS and the indicators and parameters of CEE. Through the process of developing CS, students were able to engage in discussions about contemporary socio-environmental problems and their connections to economic, political, and cultural factors, thereby enhancing their understanding of Environmental Knowledge in the context of graduate education.

Resumo em Português:

Most of the case studies disseminated in chemistry teaching environments in Brazil are short and end with a question to students about the subject. This paper focuses on a different type of case study, interrupted case studies, which are divided into parts, occupy several pages, and are characterized by the gradual addition of information to the narrative, usually inspired by original research texts, so that they portray a problem that has actually been faced by researchers. From this perspective, an innovative experience in undergraduate teaching is reported, involving the process of producing and applying interrupted case studies in a scientific communication course, and the perceptions of the students about the activity are analyzed. The aim is to contribute to the dissemination of the method, providing support for educators with regard to the resources and considerations necessary for its production, as well as for its application in classrooms.

Resumo em Inglês:

This study investigated, from the perspective of university professors, the fundamental structuring concepts in the teaching of organic chemistry and how these concepts appear in secondary school and university textbooks. The research stems from the observation that conceptual fragmentation compromises learning and contributes to high failure rates in undergraduate courses. A gap in the literature was identified concerning the systematization and articulation of organic chemistry concepts in education. Adopting a qualitative and exploratory approach, the study occurred in two stages: (i) a questionnaire was administered to forty university professors; (ii) chapters from organic chemistry textbooks were analyzed to construct conceptual maps that revealed concept hierarchies and interrelations. The findings show that professors consider chemical bonding, stereochemistry, structure, and acidity-basicity as key structuring concepts. Although these are present in textbooks, their treatment is often fragmented and poorly contextualized, hindering student understanding. The study concludes that effectively integrating organic chemistry concepts into the teaching-learning process requires a more coherent pedagogical approach. It also highlights the need for curriculum revision and the development of teaching materials that support integrated conceptual understanding. Future research should include perspectives of secondary teachers and undergraduate students to better understand the learning challenges in organic chemistry.

Resumo em Português:

This study investigates the development of conceptual subsumers in Chemical Kinetics through a pedagogical intervention focused on the operational and kinetic parameters of biomass pyrolysis. The research analyzed the profile of students across various courses, identifying significant gaps in the understanding of fundamental concepts such as activation energy and the rate equation. Findings indicate that students exhibit a superficial grasp of abstract and quantitative aspects of Chemical Kinetics, which impedes comprehensive learning. By integrating theoretical and practical components and contextualizing the content through a real-world application, the intervention led to a notable improvement in students’ accuracy, fostering the formation of new conceptual subsumers and the reorganization of prior knowledge. In conclusion, the adoption of innovative pedagogical strategies that emphasize the progressive and integrated construction of knowledge is essential to foster a deeper understanding of Chemical Kinetics, ultimately contributing to the development of critically engaged professionals ready to address future academic and industry challenges.

Resumo em Português:

The study analyzes the initial conceptions and transformations in the use of multimodal representations by future Chemistry teachers after a formative intervention. The study took place in a workshop with nine Master’s students in Physics and Chemistry Teaching at a Portuguese public university. Data collection included a pre-intervention questionnaire and a post-intervention activity in which participants suggested multimodal representations. Thematic analysis was used for qualitative data. The questionnaire results showed that, despite recognizing the potential of multimodal representations, participants had conceptual and practical gaps in using them. The thematic analysis identified two central dimensions: personal and conceptual. In the personal dimension, the highlights were the lack of teaching experience, the lack of experience with multimodality, and the view of its use as digital technology. In the conceptual dimension, confusion between multirepresentations and multimodality was observed. In the post-intervention activity, participants demonstrated a change in how they understood and used multimodal representations, incorporating concrete, symbolic, and gestural modes. The results highlight the need for deeper teacher training in multimodals. As the intervention was specific, courses should provide future teachers with opportunities to experience multimodal use in real teaching contexts, ensuring better preparation for their practical application in chemistry education.

Resumo em Português:

OPPENHEIMER IN BELO HORIZONTE, BRAZIL: A HISTORICAL RESCUE. Julius Robert Oppenheimer was a man of humanistic training, but at the same time an individual of the exact sciences. Due to his peculiar characteristics, he faced important challenges from both a scientific and political point of views. The scientist led the Los Alamos National Laboratory in New Mexico, USA. Due to the repercussions that the Manhattan Project caused in the global nuclear scenario, fundamentally by making possible the creation of the first atomic bombs, several institutions sought the collaboration of the scientist. The work presented here is specifically related to the visit of Oppenheimer to Belo Horizonte on his first scientific trip to Brazil, which took place between June and August 1953. The visit of the scientist contributed to broader discussions and initiatives related to nuclear research and development in the state of Minas Gerais and in Brazil.

Resumo em Inglês:

Large language models (LLMs) are a machine learning technique that has transformed natural language processing. However, their large computational demands limit their accessibility, leading to the development of small language models (SLMs), which, by running locally on a microcomputer, made artificial intelligence (AI)-driven language processing and enhanced control for text analysis widely accessible. In this work, we use an SLM to analyze the evolution of Chemistry in Brazil by comparing data from the 2019 and 2024 Brazilian Chemical Society meetings (RASBQ). We demonstrate the viability of SLMs for extracting and structuring large volumes of text from scientific events collected in books of abstracts, thus enabling comprehensive comparative analyses that would otherwise be impractical. Our methodology extracts abstracts from the RASBQ digital proceedings and processes them using SLMs. These models converted the textual content into structured, manipulable data, thus enabling us to conduct a semantic and statistical analysis of the two events. The results highlight how SLMs can efficiently transform unstructured scientific proceedings into tractable data, thereby saving significant time and resources. The comparison between the 2019 and 2024 events revealed notable changes in thematic distribution, institutional participation, and potential regional impacts, underscoring the importance of data standardization in automated analyses.

Resumo em Português:

Biocatalysis, based on the use of enzymes as selective and sustainable catalysts, has become a strategic pillar in the modernization of industrial processes. This article analyzes the evolution and outlook of the enzyme market through an integrated approach that combines market data, international trade statistics, and advances in biotechnology. The application of enzymes has been expanding in sectors such as food, biofuels, pharmaceuticals, and detergents, driven by innovations including heterologous expression, directed evolution, and enzyme immobilization. Market projections indicate annual growth rates between 5 and 15% by 2032, with emphasis on industrial and specialized enzymes. Although enzymes still represent a small share of the overall chemical industry volume, their growth has been significantly faster evidenced by a cumulative increase of nearly 40% in global exports between 2018 and 2023. Finally, the strategic role of enzymes in the bioeconomy is highlighted, positioning them as key technologies for enhancing sustainability and industrial competitiveness in the 21st century.