IQ - TCC - Química (bacharelado)

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Estudo químico e avaliação do potencial antioxidante e antimicrobiano do extrato metanólico da vagem de libidibia ferrea
(Universidade Federal do Rio Grande do Norte, 0002-07-26) Oliveira, Joyce Fernanda Assis de; Renata Mendonça Araújo; Macedo, Ana Rafaela Silva de; https://orcid.org/0000-0002-9085-6683; http://lattes.cnpq.br/0663537857626464; https://orcid.org/0000-0001-5514-5192; http://lattes.cnpq.br/4163879756935913; https://orcid.org/0009-0001-7042-6037; https://lattes.cnpq.br/1375972997212385; Araújo, Renata Mendonça; https://orcid.org/0000-0001-5514-5192; http://lattes.cnpq.br/4163879756935913; Cavalcante, Maria Gorette; http://lattes.cnpq.br/2069510469317474; Santos, Sarah Pollyana Dias dos; https://orcid.org/0000-0002-5326-3459; http://lattes.cnpq.br/2486254748932219
Libidibia ferrea (Fabaceae), commonly known as jucá or pau-ferro, is a species widely distributed in Brazil and recognized for its therapeutic potential, which is attributed to the diversity of bioactive metabolites found in its different plant tissues. This study aimed to chemically characterize the methanolic extract obtained from the pods of the species and its fractions, evaluate the antimicrobial activity of the methanolic extract and the antioxidant potential of the fractions, and investigate possible mechanisms of action through molecular docking studies. Chemical characterization by gas chromatography–mass spectrometry (GC–MS) enabled the proposal of possible structures for the metabolites present in the samples, highlighting fatty acids, phytosterols, and triterpenes. Antimicrobial activity was evaluated against Salmonella enterica strains and avian pathogenic Escherichia coli (APEC), and bacterial growth inhibition was observed for all strains tested. Molecular docking studies demonstrated favorable interactions between selected metabolites and the DNA gyrase subunit B (GyrB) protein, suggesting potential activity against this important bacterial target. In the antioxidant assays, the fractions exhibited metal-chelating activity, DPPH radical scavenging capacity, and reducing power in a concentration-dependent manner, with the methanolic and n-butanolic fractions showing the highest activities. Overall, the results indicate that Libidibia ferrea is a promising source of bioactive compounds with antioxidant and antimicrobial potential, reinforcing its relevance for pharmacological and biotechnological applications.
Obtenção de carboximetilcelulose termorresponsiva como aditivo para sistemas de fluidos de perfuração pump and dump
(Universidade Federal do Rio Grande do Norte, 2026-06-22) Lemos, Jamile Fabrine da Silva; Balaban, Rosangela de Carvalho; Lima, Bruna Luiza Batista de; Marques, Nívia do Nascimento
The objective of this study was to synthesize and evaluate carboxymethylcellulose grafted with poly(N-isopropylacrylamide) (CMC-g-PNIPAM) for use in pump-and-dump drilling fluids. To this end, PNIPAM was grafted onto CMC chains via a radical reaction. To characterize the structural properties of the resulting products, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and zeta potential analyses were performed. The formation of hybrid macromolecules resulting from the combination of the anionic nature of CMC with the thermoresponsive nature of PNIPAM was demonstrated. The thermoresponsive behavior was investigated by determining the clouding temperature using ultraviolet-visible (UV-Vis) spectroscopy. The results demonstrated that the LCST can be modulated as a function of the ratio between the components and the polymer concentration. Furthermore, the addition of NaCl led to a reduction in the LCST, bringing forward the conformational transition. Rheological tests revealed that the copolymers exhibited superior performance, notably by maintaining or increasing viscosity at elevated temperatures, in contrast to the behavior of pure CMC, which exhibited a decrease in viscosity with increasing temperature. This effect was intensified in saline media, such as synthetic seawater, where hydrophobic interactions between the polymer chains compensated for the shielding of electrostatic charges. For rheological measurements of concentrated and diluted solutions, using the methodology employed for “pump-and-dump” fluids in the field, it was observed that the copolymers exhibited thermoviscifying behavior, and the presence of salts caused some diluted concentrations to outperform the concentrated ones in terms of viscosity. When added to drilling fluids, the copolymers demonstrated good stability after aging and rheological behavior suitable for operating conditions, combining low surface viscosity at high shear rates—which facilitates pumping—and high proppant transport capacity at higher temperatures due to increased viscosity.
Desenvolvimento e fabricação assistida por impressão 3D de sensor eletroquímico modular à base de grafite reciclado e modificado com cobre para detecção de glifosato em cerveja
(Universidade Federal do Rio Grande do Norte, 2026-06-19) Cruz, Jonathan Johnson Fernandes; Castro, Pollyana Souza; https://orcid.org/0000-0001-6768-1865; http://lattes.cnpq.br/4538444915937772; 0009-0004-6100-0685; https://lattes.cnpq.br/7696200288523073; Regiart, Daniel Matias Gaston; http://lattes.cnpq.br/2816816156208804; Queiroz, Jorge Leandro Aquino de; https://orcid.org/0000-0002-3128-5665; http://lattes.cnpq.br/1991504504377731; Neves, Ana Carolina de Oliveira; https://orcid.org/0000-0001-7741-8454; http://lattes.cnpq.br/9435525521723320
Glyphosate is a widely used herbicide in agriculture, and its potential occurrence in food and beverages has driven the development of simpler, more accessible, and sustainable analytical methods. This study aimed to develop a modular electrochemical platform for the analysis of glyphosate in beer samples using graphite rods recovered from discarded zinc–carbon batteries and components fabricated by 3D printing. The modular graphite electrode, designated GR-E, was designed with a removable electroactive region, allowing its characterization before and after surface modification. The electrode surface was modified by copper electrodeposition, exploiting the interaction between glyphosate and copper species as an indirect recognition strategy for the analyte. Surface characterization by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy provided complementary information on the morphological, elemental, and structural changes promoted by the modification. The influence of pH was investigated, and a 0.1 mol L⁻¹ phosphate buffer at pH 5.0 was selected for the analytical studies. The electrochemical response of the GR-E-Cu electrode was evaluated by differential pulse voltammetry, showing a linear relationship between the integrated peak area and the decimal logarithm of glyphosate concentration over the range of 1.0 × 10⁻⁸ to 1.0 × 10⁻⁴ mol L⁻¹, with a coefficient of determination (R²) of 0.9958. The limits of detection and quantification were estimated at 0.597 and 1.811 μg L⁻¹, respectively. When applied to nine commercial beer samples, one sample exhibited a response above the limit of quantification, whereas the remaining samples showed signals between the limits of detection and quantification, allowing analyte detection but not reliable quantification. The results demonstrate the feasibility of the proposed platform as a modular, sustainable, and low-cost strategy for electrochemical analysis. However, matrix effects associated with beer samples indicate the need for further studies on selectivity, recovery, and analytical validation.
Síntese e estudo fotofísico de sistemas Π-Estendidos derivados de Quinoxalinas fusionadas a núcleos Benzotiazínico, Benzooxazínico e Benzodiazínico
(Universidade Federal do Rio Grande do Norte, 2026-06-18) Aleixo, Ilan Victor Martins; Menezes, Fabrício Gava; Medeiros, José Vitor de Souza; 0000-0003-2153-1647; http://lattes.cnpq.br/2848745987784319; 0009-0007-6899-1743; http://lattes.cnpq.br/6216649854953066; Gomes, Fabiano do Espírito Santo; 0000-0002-0244-5228; http://lattes.cnpq.br/3759170729682136; Souza, Miguel Angelo Fonseca de; 0000-0003-4680-4445; http://lattes.cnpq.br/3530941218204965
Fluorescent quinoxaline derivatives constitute a class of compounds of interest for several applications, such as chemical sensors and materials for optoelectronic devices. This work aims to synthesize, structurally characterize, and investigate the photophysical properties of the quinoxaline derivatives 12H-benzooxazino[2,3-b]quinoxaline 12H-benzothiazino[2,3-b]quinoxaline (BOQX), (BTQX), and 5-methyl-5,12-dihydroquinoxalino[2,3-b]quinoxaline (BDQX), evaluating the influence of structural differences on the optical properties of these π-conjugated systems. The compounds were obtained from the reactions of the precursor 2,3-dichloroquinoxaline (DCQX) with 2-aminothiophenol, 2-aminophenol, and N-methyl-o-phenylenediamine, and characterized by infrared spectroscopy, ¹H and 13C nuclear magnetic resonance spectroscopy, and mass spectrometry. The photophysical properties were investigated by UV–Vis absorption and fluorescence spectroscopies, evaluating parameters such as Stokes shift and fluorescence quantum yield (ΦF) in different media and in the solid state. The results showed that the nature of the heteroatom significantly influences the optical properties of the derivatives. BTQX was associated with the most red-shifted bands, BDQX showed the highest emission intensity, and BOQX exhibited the highest fluorescence quantum yields in solution, reaching ΦF = 0.86 in dichloromethane. The photophysical studies revealed positive solvatochromic behavior and evidence of intramolecular charge transfer (ICT), consistent with donor–acceptor (D–A) architectures. In aqueous medium, the three derivatives exhibited aggregation-caused quenching (ACQ), attributed to π–π stacking interactions. In the solid state, the compounds showed low quantum yields when directly deposited on quartz; however, a significant increase in emissive efficiency was observed when they were dispersed in Zeonex® films, reaching ΦF values between 0.405 and 0.495. Additionally, the derivatives demonstrated sensitivity to pH variations, with BDQX standing out due to its more complex spectral response and visible color changes. Overall, the results contribute to the understanding of the relationships between molecular structure and photophysical properties in quinoxaline derivatives, especially for the BDQX core, highlighting the potential of these systems for the development of luminescent materials.
Obtenção de carboximetilcelulose termorresponsiva como aditivo para sistemas de fluidos de perfuração pump and dump
(Universidade Federal do Rio Grande do Norte, 2026-06-22) Lemos, Jamile Fabrine da Silva; Balaban, Rosangela; Lima, Bruna; Marques, Nívia
The objective of this study was to synthesize and evaluate carboxymethylcellulose grafted with poly(N-isopropylacrylamide) (CMC-g-PNIPAM) for use in pump-and-dump drilling fluids. To this end, PNIPAM was grafted onto CMC chains via a radical reaction. To characterize the structural properties of the resulting products, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and zeta potential analyses were performed. The formation of hybrid macromolecules resulting from the combination of the anionic nature of CMC with the thermoresponsive nature of PNIPAM was demonstrated. The thermoresponsive behavior was investigated by determining the clouding temperature using ultraviolet-visible (UV-Vis) spectroscopy. The results demonstrated that the LCST can be modulated as a function of the ratio between the components and the polymer concentration. Furthermore, the addition of NaCl led to a reduction in the LCST, bringing forward the conformational transition. Rheological tests revealed that the copolymers exhibited superior performance, notably by maintaining or increasing viscosity at elevated temperatures, in contrast to the behavior of pure CMC, which exhibited a decrease in viscosity with increasing temperature. This effect was intensified in saline media, such as synthetic seawater, where hydrophobic interactions between the polymer chains compensated for the shielding of electrostatic charges. For rheological measurements of concentrated and diluted solutions, using the methodology employed for “pump-and-dump” fluids in the field, it was observed that the copolymers exhibited thermoviscifying behavior, and the presence of salts caused some diluted concentrations to outperform the concentrated ones in terms of viscosity. When added to drilling fluids, the copolymers demonstrated good stability after aging and rheological behavior suitable for operating conditions, combining low surface viscosity at high shear rates—which facilitates pumping—and high proppant transport capacity at higher temperatures due to increased viscosity.
Avaliação da produção de hidrogênio por eletrólise alcalina utilizando um sistema híbrido de geração de energia
(Universidade Federal do Rio Grande do Norte, 2025-11-19) Souza, Maria Eduarda Cavalcante de.; DUARTE, Lindemberg de Jesus Nogueira
The pursuit of sustainable energy solutions and the need to reduce greenhouse gas emissions highlight the importance of technologies for green hydrogen production. However, there remains a gap in the literature regarding low-cost electrolyzers integrated into hybrid microgeneration systems. This study aimed to evaluate green hydrogen production via alkaline electrolysis using an energy system composed of photovoltaic panels, a micro wind turbine, and a battery storage module. A low-cost acrylic electrolytic cell was built using nickel and stainless-steel electrodes and different electrolyte concentrations to investigate the influence of operational parameters on process efficiency. The hybrid system was installed at CTEC/UFRN and monitored during October and November 2025. Although designed to integrate solar and wind generation, the operation recorded during the monitoring period was sustained solely by photovoltaic energy. The system registered a solar power peak of 1.65 kW, fully supplying the electrolyzer demand, which ranged from 180 to 200 W. Additional tests using a controlled DC power supply enabled performance comparison under different energy-feeding conditions. The results showed that electrolyzer efficiency ranged from 23% to 102%, with values above the theoretical limit attributed to uncertainties in manual volume and time measurements. Efficiency increased with NaOH concentrations between 3.0 and 5.0 mol·L⁻¹ and voltages below 4.0 V, above which overpotential reduced energy performance. The nickel electrode exhibited satisfactory structural stability and efficiency. Thus, the developed electrolytic cell demonstrated viable operation, and the hybrid system showed potential to support green hydrogen production, particularly with future optimizations of the wind component and direct coupling to renewable sources.
Detecção do vírus SARS-COV 2 Usando Espectroscopia NIR e Análise Multivariada
(Universidade Federal do Rio Grande do Norte, 2025-11-18) Siqueira, Camila Ferreira; LIMA, Kassio Michell Gomes; https://lattes.cnpq.br/2466125645456039
SARS-CoV-2, identified in December 2019, rapidly stood out due to its high transmission capacity and the devastating global impact it caused, distinguishing it from previous outbreaks involving other coronaviruses, such as SARS-CoV and MERS-CoV. Although real-time Reverse Transcription Polymerase Chain Reaction (RT-PCR) is recognized as the gold-standard method for COVID-19 diagnosis, it requires complex laboratory infrastructure, trained personnel, and high-cost reagents, in addition to demanding longer processing times for result acquisition. Conversely, rapid serological tests, despite being more accessible and practical, present limitations in sensitivity and specificity, increasing the risk of false-negative results, particularly in the early stages of infection. Within this context, the present study proposes an innovative and accessible alternative to conventional diagnostics: the use of biospectroscopy, specifically Near-Infrared (NIR) spectroscopy, combined with multivariate chemometric techniques for the rapid and accurate detection of SARS-CoV-2. A total of 173 saliva samples were analyzed, including 84 negative and 89 positive for COVID-19. NIR spectroscopy was employed to record spectral variations related to the molecular vibrations of the samples, and due to the complexity of these spectra, multivariate analysis methods were applied to interpret these variations, enabling the differentiation between positive and negative samples for COVID-19. This non-destructive and low-cost approach has shown promise not only for pathogen identification but also across broader interdisciplinary applications. The integration of multivariate analysis with spectroscopy provided a significant improvement in diagnostic sensitivity and specificity. Among the tested models, SPA-LDA (Successive Projections Algorithm – Linear Discriminant Analysis) demonstrated the best performance, achieving 85% sensitivity and 100% specificity, indicating high accuracy in distinguishing SARS-CoV-2 positive and negative samples. Therefore, this research offers a faster, more economical, and precise diagnostic alternative to conventional methods, supporting early detection and advancing spectroscopic techniques within the biomedical field, ultimately contributing to improved clinical management of COVID-19.
Adsorção de fármacos em sistemas aquosos usando a paligorsquita: avaliação cinética, equilíbrio e termodinâmica.
(2025-11-07) Nobre, Daniel Queiroz; Luciene da Silva Santos
Zeólita natural Clinoptilolita modificada com troca iônica e aminas para adsorção de CO2.
(Universidade Federal do Rio Grande do Norte, 2025-11-19) Lima, Gidiângela Cecília Cavalcante da Silva; Pergher, Sibele B. Castellã; Mello, Mariele I. Soares de; http://lattes.cnpq.br/1442415652290393; Dra Lindiane Bieseki; Me. Aryandson da Silva
Carbon dioxide (CO₂) is one of the main gases responsible for global warming, and the search for efficient and economically viable materials for its capture and storage has become an environmental and scientific priority. In this work, we studied the natural zeolite clinoptilolite from Chile, modified by different physical and chemical treatments with the aim of improving its CO₂ adsorption capacity. The material was subjected to thermal and aqueous pretreatments, ion exchange with Na⁺ and Li⁺ cations, and impregnation with monoethanolamine (MEA) and diethanolamine (DEA) amines. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and total organic carbon (TOC) techniques. The results indicated that the crystal structure of clinoptilolite was preserved after the modifications and that the exchange with Na⁺ showed better incorporation compared to Li⁺. Amine impregnation was confirmed by TOC analysis, with percentages between 0.91 and 2.01%. Adsorption isotherms showed a significant increase in CO₂ adsorption capacity, with the clinoptilolite sample impregnated with MEA (2.27 mmol/g) standing out. Thus, it is concluded that the modification of natural clinoptilolite by ion exchange and amine impregnation represents a promising, sustainable, and low-cost alternative for application in processes to mitigate greenhouse gas emissions.
Fabricação de microeletrodos de ouro utilizando impressão 3D e microchips reciclados: uma abordagem sustentável para detecção de olanzapina
(Universidade Federal do Rio Grande do Norte, 2025-11-19) BEZERRA, Heloisa Maria Silva; CASTRO,Pollyana Souza; https://orcid.org/0000-0001-6768-1865; http://lattes.cnpq.br/4538444915937772; https://orcid.org/0009-0006-9835-4836; http://lattes.cnpq.br/5130595264024923
This work describes the development of a sustainable 3D-printed electroanalytical platform employing gold microelectrode arrays (Au-μEA) obtained from recycled electronic microchips for the determination of the antipsychotic drug olanzapine (OLZ) in pharmaceutical formulations. The fabrication of the device involved 3D prototyping and printing of customized molds, the production of silicone molds, encapsulation of the microchips, and controlled polishing of the surface until the exposure of the electroactive area of the microelectrodes. As an electrochemical modification step, a nanoporous gold film was formed on the microelectrode surface through selective corrosion, resulting in a significant increase in the active surface area and enhancement of the electroanalytical response. The proposed sensor exhibited excellent analytical performance, with a linear range between 6.2 and 74.5 µmol L⁻¹, a limit of detection (LOD) of 5 µmol L⁻¹, and a limit of quantification (LOQ) of 14 µmol L⁻¹. The recovery obtained using the electrochemical method was 98.7 demonstrating high precision and accuracy, in accordance with the limits established by the United States Pharmacopeia (USP). Comparative analyses with the spectrophotometric method (UV-Vis) showed strong agreement between results, confirming the reliability of the developed platform. Therefore, the proposed sensor integrates technological innovation, sustainability, and low cost, highlighting the potential of 3D printing and electronic waste reuse in the fabrication of modern analytical devices.
Síntese e caracterização de formulações de filmes poliméricos à base de alginato e aditivos para aplicações sustentáveis
(Universidade Federal do Rio Grande do Norte, 2025-11-18) Mendonça, Stephany da Silva; Wanderley Neto, Alcides de Oliveira; Lima, Meyrelle Figueiredo; Neto, Alcides de Oliveira Wanderley; Fonseca, José Luís Cardozo; Lima, Meyrelle Figueiredo
Faced with the environmental impacts caused by conventional plastics, there is a growing need to develop biodegradable materials that combine functionality and sustainability. Biopolymers, derived from renewable sources, stand out for their rapid decomposition and lower dependence on fossil fuels, although they still have limitations regarding thermal resistance, permeability, and cost. In this sense, the improvement of their properties can be achieved through the incorporation of additives or natural agents. Thus, this work proposed the development of biodegradable films based on sodium alginate as a matrix, fumaric acid as a crosslinking agent, glycerol as a plasticizer, and Tween 20 as a surfactant. The films were produced by the casting method, from the previously prepared film-forming solution. Fifteen formulations were developed based on a D-optimal experimental design, which were characterized in terms of solubility, moisture content, thickness, and water vapor permeability to determine the optimum point. The results revealed that glycerol exerted a predominant influence on solubility and moisture content, while fumaric acid acted as a modulator of the biopolymer's structure and crosslinking. Film E3 was defined as the optimum point, presenting solubility values of 27.99%, moisture content of 21.56%, thickness of 0.059 mm, and PVA of 1.2 [(g·mm)/(m2·day·kPa)]. Complementary analyses indicated that the presence of Tween 20 favored the formation of a more homogeneous and thermally stable matrix, as observed by FTIR, SEM, and TGA/DTG. Biodegradability tests indicated gradual degradation, reaching approximately 13% after 30 days of exposure to soil. Thus, the results confirm that the combination of alginate, glycerol, fumaric acid, and Tween 20 is effective for the production of biopolymer films with properties suitable for sustainable applications, especially in biodegradable packaging and controlled-release systems.
Modelagem Molecular de Sistemas Micelares Pré-organizados
(Universidade Federal do Rio Grande do Norte, 2025-11-14) Bezerra, Armenia Maria de Albuquerque Melo; Vieira, Davi Serradella; http://lattes.cnpq.br/4185159774625471; http://lattes.cnpq.br/6428528659731297; Cavalcante, Maria Gorette; http://lattes.cnpq.br/2069510469317474; de Oliveira, Igor Rafael Resende
This work presents a methodological proposal for the investigation of pre-assembled micelles through molecular dynamics (MD) simulations, focusing on the analysis of structural and energetic properties that influence the stability of these systems. The understanding of the behavior of micellar aggregates is of paramount importance for elucidating the factors that determine their organization in solution, contributing to the development of applications in different areas of science and technology. The methodology employed involved the modeling and optimization of the sodium dodecyl sulfate (SDS) molecule in the BIOVIA Discovery Studio software, parameterization via ACPYPE with the GAFF 2 force field, and the assembly of micelles containing 20 to 160 surfactant molecules in the Packmol program. The energy minimization and initial equilibration steps of the systems were performed in GROMACS 2022 under the NVT ensemble using the Nosé–Hoover thermostat, while the production simulations were carried out under the NPT ensemble employing the Parrinello–Rahman barostat. The analyses of structure, radius of gyration, and intermolecular potential energy made it possible to evaluate the degree of packing and the stability of the micelles. It is observed that the micelles become more uniform with the addition of monomers. The results of the radius of gyration (Rg) showed that the radius grows in a correlated manner with the number of molecules, implying an increase in the dimension and mass dispersion of the aggregate; larger micelles presented a more stable Rg time series. Energetically, the system is shown to be more stable (more negative energy) as the size increases, indicating greater stability for larger micelles; however, the average energy per molecule decreases up to approximately 60 molecules, stabilizing beyond that point, evidencing that an optimal micellar size for SDS exists around this value. In summary, the findings corroborate the usefulness of MD as a complementary tool to experimentation for studying the stability of micellar systems. The presented study will serve as a protocol for the molecular modeling of diverse micellar systems, including surfactants applied in the oil and gas industry.
Economia circular na indústria de placas solares: zeólita lta obtida de resíduo rico em SiO2
(Universidade Federal do Rio Grande do Norte, 2025-11-19) Breno, Mikael Gomes Neves; Pergher, Sibele Berenice Castellã; Oliveira, Manuela Silva Martins de; Profa. Dra. Sibele Berenice Castellã Pergher.; Dra. Manuela Silva Martins de Oliveira.; Prof. Dr. Fernando José Volpi Eusébio de Oliveira; Dra. Lindiane Bieseki
This work investigated the feasibility of using a silica-rich industrial waste generated from metallic silicon production for solar panels as an alternative silicon source in the synthesis of LTA zeolite. Systematic studies were carried out to evaluate the effects of crystallization time, waste dissolution stage, reaction medium alkalinity, and the use of mechanochemical milling in gel preparation. The synthesized samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), allowing the assessment of crystalline phase formation and crystal morphology. The results showed that the waste material has potential to partially replace conventional silicon sources, enabling the formation of the LTA structure under controlled synthesis conditions. Therefore, the study demonstrates both the technical feasibility and the environmental potential of using industrial residues in the production of high-value zeolitic materials.
Síntese e avaliação das propriedades fotoluminescentes de derivados de 12h-benzo[5,6][1,4]thiazino[2,3-b]quinoxalina
(Universidade Federal do Rio Grande do Norte, 2025-06-25) Araújo, Yasmim Lima Neves de; MENEZES, Fabrício G.; NERI, Jannyeli M.
Modificação de kit-6 com óxidos metálicos para aplicação catalítica na conversão de glicerol
(Universidade Federal do Rio Grande do Norte, 2025-06-16) Oliveira, Lívia Cortês; OLIVEIRA, Fernando José Volpi Eusébio de; SOARES, Patricia Kaori; CAVALCANTI, Wesley Eulálio Cabral
The production of biodiesel is undergoing continuous expansion; however, the increase in its main byproduct, glycerol, grows proportionally, leading to a decrease in its market value. In this scenario, the search for alternatives to utilize glycerol has been gaining momentum, aiming to make biodiesel production more sustainable. In this context, the present study aimed to investigate the synthesis of catalysts based on copper, zinc, and zirconium oxides supported on KIT-6-type mesoporous silica for application in the glycerol dehydration reaction. The inorganic support was synthesized via a standard hydrothermal method, and two distinct methodologies were employed for metal precursor impregnation — wet impregnation and precipitation-deposition — in order to evaluate the influence of each method on the structural properties and catalytic activity of the materials. The catalytic tests were conducted in a fixed-bed system, and the products were analyzed by Gas Chromatography. The solids were characterized by X-ray diffraction (XRD), which confirmed the successful synthesis of both KIT-6 and the catalysts, with characteristic peaks corresponding to the Miller indices: 211, 220, and 332. X-ray fluorescence (XRF) confirmed the presence of all metallic phases in the KIT-6-Cu-Zn-Zr catalyst. The textural properties of the samples were evaluated by nitrogen adsorption–desorption analysis, with the pure KIT-6 presenting a surface area of 719.2 m²/g, and a significant decrease observed for the catalysts, suggesting the presence of metal oxides on the surface and within the mesopores. Scanning Electron Microscopy (SEM) allowed the observation of morphological changes and impregnation effects on the surface compared to the unmodified KIT-6. The catalytic tests with materials impregnated with CuO by different methods showed similar behavior; however, the KIT-6-CuO_PU catalyst exhibited better conversion results, and the catalyst containing copper, zinc, and zirconium showed ~100% selectivity toward acetol. The formation of coke, thermogravimetric events, as well as their behavior after the reaction are discussed.
Estudo in silico das interações intermoleculares entre antagonistas duais e o receptor OX1R
(Universidade Federal do Rio Grande do Norte, 2025-06-25) Pedro Corso de Albuquerque; Davi Serradela Vieira; Caio Patrício de Souza Sena; 0000-0001-8044-9446; http://lattes.cnpq.br/5434409236937674; 0000-0001-8353-6262; http://lattes.cnpq.br/4185159774625471; 0009-0000-1436-5965; http://lattes.cnpq.br/8567964848858147; Davi Serradela Vieira; 0000-0001-8353-6262; http://lattes.cnpq.br/4185159774625471; Caio Patrício de Souza Sena; 0000-0001-8044-9446; http://lattes.cnpq.br/5434409236937674; Anderson dos Reis Albuquerque; 0000-0001-7727-266X; http://lattes.cnpq.br/4983201442276288
Orexin receptors play a key role in modulating essential physiological processes. Their activities are associated with the regulation of energy, homeostatic functions, and, most notably, the control of the sleep–wake cycle. When in their active conformations—stimulated by interaction with the endogenous neuropeptides orexins bound to their active sites—these receptors promote wakefulness by inhibiting sleep. Due to these properties, the influence of orexin signaling in sleep disorder therapies has been widely studied, particularly through the development of receptor antagonist drugs, which have proven to be effective and less harmful alternatives. In this context, the present study aims to qualitatively and quantitatively analyze molecular dynamics simulation results involving the orexin 1 receptor and three clinically approved antagonists: daridorexant, suvorexant, and lemborexant. Qualitative analyses were performed using the BIOVIA Discovery Studio software, while quantitative energy determinations were conducted using GROMACS. Among the compounds studied, daridorexant exhibited the most intense total interactions, particularly with residues GLU160 and HIS172, while lemborexant and suvorexant showed lower interaction energies in comparison. Among the intermolecular interactions, electrostatic interactions presented the highest energy contributions, followed by hydrogen bonds. These analyses provided a deeper understanding of the drug–receptor interaction profile, contributing to a better comprehension of the chemical behavior of these systems.
Síntese e caracterização do complexo cis-[Ru(bpy)(fen)(2- amino)(NO)](PF6)3
(2025-06-18) Nobre, Marcelly de Sousa; SILVA, Francisco Ordelei Nascimento da
Nitric oxide (NO) is a biologically active molecule that plays an essential role in several physiological processes, such as vasodilation, neurotransmission and immune response. The search for systems that enable its controlled release has driven the development of metal complexes, among which ruthenium nitrosyl complexes stand out for their stability, low toxicity and ability to release NO under chemical, electrochemical or photochemical stimuli. In this context, this work aimed to synthesize, characterize and study the reactivity of the cis-[Ru(bpy)(phen)(2-amino)(NO)](PF6)3 complex, using the 2-aminobenzothiazole ligand, aiming at its potential application as a controlled nitric oxide donor. The nitrosyl complex was obtained by reacting the precursor cis-[Ru(bpy)(phen)Cl2] with 2-aminobenzothiazole and then with the addition of sodium nitrite and trifluoroacetic acid in ethanol/water under stirring. Through electronic spectroscopy in methanol, it was possible to observe intraligand transitions of the bipyridine and phenanthroline ligands, in addition to charge transfer bands from the metal center to the polypyridine ligands at 411 nm and to the NO ligand, close to 454 nm. In the infrared vibrational spectrum, in ATR crystal, the stretching of NO+ was observed at high frequencies at 1932 cm-1 , indicating the coordination of nitric oxide to the metal center. In addition, electrochemical studies, through the cyclic voltammogram, confirmed the presence of a quasi-reversible redox process associated with the NO⁺/NO⁰ pair with E₁/₂ = 178 mV. The data obtained by square wave voltammetry and by photochemical study under white light indicate that the release of nitric oxide occurs through a chemical process, where the reduction of the NO⁺ ligand to NO⁰ weakens the bond with ruthenium (Ru²⁺), favoring the exit of NO and allowing the subsequent coordination of a water molecule.
Síntese e caracterização do complexo cis-Ru(bpy)₂(pyr)₂₂
(Universidade Federal do Rio Grande do Norte, 2024-12-13) Silva, Maria Rita Hilário da; Silva, Francisco Ordelei Nascimento da; Huitle, Carlos Alberto Martinez; Sousa, Thuanny Moura de
Metal complexes have been reported in the literature as potential therapeutic drugs, encompassing applications in the treatment of inflammation, rheumatoid arthritis, cardiovascular diseases, cancer, and diabetes mellitus. Studies suggest that the coordination of bioactive molecules to metal centers can enhance the therapeutic effects of these substances. However, inorganic compounds represent only 1% of the drugs approved for clinical use, highlighting an area with untapped potential. In this context, the present paper reports the synthesis and characterization of the cis-[Ru(bpy)₂(pyr)₂](PF₆)₂ complex, where bpy = 2,2′-bipyridine and pyr = pyrazinamide. Both ligands are molecules with well-established pharmacological activities, with pyrazinamide being a first-line antibiotic used in the treatment of tuberculosis. The compound was synthesized from the precursor complex cis-[Ru(bpy)₂Cl₂] and characterized through electronic spectroscopy in the ultraviolet-visible region, vibrational spectroscopy in the infrared region, and cyclic voltammetry. Characteristic π→π* bands of the pyrazine ligand at 207 and 254 nm, as well as a metal-to-ligand charge transfer (MLCT) band at 458 nm, were observed in the electronic spectrum obtained in an aqueous medium for the synthesized compound. Additionally, its vibrational spectrum obtained via ATR displayed expected characteristic peaks for its structure, such as the carbonyl stretching at 1662 cm⁻¹ and the asymmetric and symmetric N-H stretches at 3644 and 3376 cm⁻¹, respectively. Meanwhile, the cyclic voltammogram revealed a half-wave potential (𝐸₁/₂) of 573 mV, indicating a shift of 55 mV toward higher redox potential compared to the precursor voltammogram (518 mV). This behavior is consistent with the coordination of pyrazinamide, attributed to its π-acceptor character. Furthermore, a reversibility study conducted via cyclic voltammetry at varying scan rates demonstrated that the redox process is diffusion-controlled. The results provided by the three employed techniques indicate the formation of the compound of interest.
Fotodegradação de poluentes orgânicos com catalisadores à base de ferro
(Universidade Federal do Rio Grande do Norte, 2024-12-16) Soares, Pedro Vinícius Fernandes; Braga, Tiago Pinheiro; Soares, Johnatan de Oliveira; http://lattes.cnpq.br/8530907836766471; Oliveira, Fernando José Volpi Eusébio de; Rigoti, Eduardo
Organic pollutants are a group of molecules that cause a significant impact on the environment, due to their recalcitrant properties, which can come into contact with the organism of living beings and cause a series of diseases. Therefore, in this work, iron-based catalysts such as CuFe2O4/TiO2, KIT-6/CoFe2O4/TiO2 and SiO2/SrFe12O19 were used to photodegrade the contaminants paracetamol and industrial dye remazol red (CIVR) in acidic conditions, in order to carry out a comparative study of their catalytic properties. The techniques implemented to characterize the photocatalysts were X-ray diffraction (XRD), UV-Vis spectrophotometry and zeta potential. Each of the materials has the desired crystallographic phases as predicted by the synthesis. The band gap energy for the CuFe2O4/TiO2, KIT-6/CoFe2O4/TiO2 and SiO2/SrFe12O19 catalysts was 1.60, 1.56 and 1.38 eV and the zeta potentials were 13.0, 17.1, -18.5 mV, respectively. Furthermore, photodegradation was monitored with the aid of a UV-Vis Spectrophotometer at varying time intervals, resulting in degradation percentages for CuFe2O4/TiO2 of 42.2% and 18.2% of the CIVR and of paracetamol, respectively, while for KIT-6/CoFe2O4/TiO2 it was possible to convert the paracetamol structure into an intermediate in a time of 180 min and degraded CIVR by 100% over 60 minutes. Finally, the SiO2/SrFe12O19 catalyst managed to degrade contaminants in percentages of 100% and 10%, CIVR and paracetamol, respectively.
Avaliação de biossorvente a partir da fibra da ceiba paineira para remoção de óleos e graxas em água produzida
(Universidade Federal do Rio Grande do Norte, 2024-07-22) Vidal, Maria Kamilla Andrade; Gondim, Amanda Duarte; Anjos, Raoni Batista dos; https://orcid.org/0000-0002-4612-0855; http://lattes.cnpq.br/3288309475928312; https://orcid.org/0000-0001-6202-572X; http://lattes.cnpq.br/6738828245487480; http://lattes.cnpq.br/9851455082907058; Hilário, Larissa Sobral; http://lattes.cnpq.br/3644432706481811
With the development of humanity, the need for new energy sources capable of meeting the demand has become a reality. Thus, with the extraction of fossil fuels, economic and technological progress became evident in the world's leading powers. Nowadays, petrochemical industries are responsible for a large portion of all the energy used globally. However, the exploitation of this raw material is followed by by-products such as gases, sedimentable residues, oils, and produced water. This water, when produced by oil refineries at their peak production, can correspond to 90% of the waste generated. Produced water consists of organic and inorganic matter, such as metals, hydrocarbons, oils, greases, and other compounds, which, when contaminant, can become potentially harmful to ecological balance as well as human life. In light of this issue, treatments to minimize such damage are necessary, and lignocellulosic biosorbents have shown potential as an alternative for removing oils and greases (O&G) in produced water. In this work, the fiber of Ceiba paineira was evaluated as a biosorbent in its natural state, as well as chemically modified with sodium hydroxide and hydrogen peroxide for the removal of O&G in produced water. The fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and by thermogravimetry (TGA) and derivative thermogravimetry (DTG). It was found that the sample with the best removal performance was the fiber treated with 1% sodium hydroxide (CPNAOH 1%) with a removal rate of 99.8% and sorbed oils and greases amounting to 180 mg/g. However, these results did not show significant differences compared to the other samples, with removal rates ranging from 81.7% to 99.7%. Therefore, it can be concluded that the Ceiba paineira fiber has great potential as a biosorbent for removing oils and greases in produced water samples from the petroleum industry, and it can even be used in its natural form.

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