http://repositorio.ufc.br/handle/riufc/226 2026-04-19T09:15:19Z 2026-04-19T09:15:19Z Martins, Vitor Carvalho http://repositorio.ufc.br/handle/riufc/85329 2026-03-13T18:05:42Z 2026-01-01T00:00:00Z

Título: Molibdato de zinco (ZnMoO4) e seus compósitos com TiO2 para aplicações em componentes de alta frequência em comunicações Autor(es): Martins, Vitor Carvalho Abstract: Currently, the telecommunications area presents new demands and, consequently, challenges in the development of antennas, among them, the need for higher data transmission and greater information transport capacity. Thus, research into new dielectric ceramics ensures the evolution of telecommunications systems. In this work, the dielectric properties of composites based on zinc molybdate and titanium dioxide (ZnMoO4-TiO2) and possible application as dielectric resonator antenna (DRA) was investigated. The ZnMoO4 phase (ZMO) and its ceramic composites were obtained at low sintering temperatures in the proportions of 0.22, 0.27, and 0.36 in mole % of TiO2 and identified by X-ray diffraction. The insertion of TiO2 in the ZMO altered the structural characteristics and consequently the dielectric properties. In the radio frequency (RF) range, the samples exhibit low values of relative permittivity (εr) and dielectric loss tangent (tan δ), where their values decrease as frequency increases. The normalization curves showed the presence of short-range movement of charge carriers, with a thermally activated relaxation process (formation of relaxation peaks). The conductivity (σ) inthe samples obeys Jonscher's power law. Similar activation energies (Ea) (σdc e pela Z”) indicate that the samples have the same insulating character. The ZMT36 sample is the only one that does not show RF thermal stability in the range of 100 kHz to 1 MHz. The Nyquist diagrams were well adjusted using an equivalent electrical circuit, making it possible to measure the contributions of the grain region and grain boundary of the material in the electrical response of the samples. The measurements in microwaves (MW) show that these materials have low εr and tgδ, and the TiO2 addition in mol of 0.22 and 0.27 have a resonant frequency temperature coeficiente tend to zero (– 7.39 and + 2.18 ppm °C-1, respectively). In antenna measurements, ZnMoO4 showed a gain of 4.63 dBi, radiation efficiency of 82.37%, and bandwidth of 1.147 GHz. All composites had their properties improved and exhibited good performance in terms of gain above 5 dBi, bandwidth (498 – 622 MHz), efficiency above 97%, and operating frequency range of 5.288 – 5.428 GHz. Thus, ZMO forms LTCC composites with TiO2 showing its applicability in RF and MW devices. Tipo: Tese

2026-01-01T00:00:00Z Braga, Ednara Joice http://repositorio.ufc.br/handle/riufc/85301 2026-03-11T13:38:05Z 2025-01-01T00:00:00Z

Título: Synthesis and characterization of a hybrid perovskite with an imidazole spacer for optoelectronic applications Autor(es): Braga, Ednara Joice Abstract: Perovskites are an emerging class of materials that have attracted significant attention from the scientific community due to their semiconductor properties. Three-dimensional hybrid perovskites demonstrate good performance in optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). The predominant use of lead ions (Pb²⁺) in the composition of perovskites, although effective in terms of efficiency, raises concerns related to toxicity and limited stability under ambient conditions. In this context, tin (Sn) has emerged as a promising substitute for lead, reducing toxicity without compromising performance. In addition to replacing Pb with Sn, the incorporation of novel organic cations into the structure of hybrid perovskites has been considered a promising strategy to improve their chemical and environmental stability. This modification leads to the formation of hybrid organic-inorganic metal halides, which enhance the structural integrity and influence the electronic and optical properties of the material. In this work, the hybrid perovskite (C₁₁H₁₁N₂O)₂SnBr₆ was synthesized using a slow evaporation method in an acidic medium. The structure incorporates the organic cation 2-(1H-imidazol-1-yl)-1-phenylethanone, while Sn⁴⁺ coordinates six bromide atoms, forming the [SnBr₆]²⁻ octahedron. The resulting crystalline organization is classified as a zero-dimensional (0D) perovskite, composed of isolated octahedral units. The compound exhibits broad-band emission across a large portion of the visible spectrum. This feature is associated with the radiative recombination of self-trapped excitons (STEs), a phenomenon commonly observed in hybrid halide perovskites. In addition to its structural stability, a key factor for practical applications, the perovskite displays a direct optical bandgap of 2.99 eV, making it a potential candidate for optoelectronic devices. Thus, this research contributes to the development of alternative materials that not only offer competitive performance compared to conventional lead-based perovskites but also address challenges related to sustainability and toxicity, broadening the scope for safe and efficient technological applications. Tipo: Dissertação

2025-01-01T00:00:00Z Santos, Aline Teixeira dos http://repositorio.ufc.br/handle/riufc/84906 2026-02-25T12:58:12Z 2025-01-01T00:00:00Z

Título: Desenvolvimento de nanocomplexos eletrolíticos de quitosana e metotrexato com potencial aplicação antirreumática e anticancerígena Autor(es): Santos, Aline Teixeira dos Abstract: Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovial inflammation. It is associated with progressive disability, systemic complications, premature death, and socioeconomic costs. One of the challenges related to treatment is the occurrence of undesirable side effects. Methotrexate (MTX) is an antirheumatic and anticancer drug used in the treatment of RA, as well as breast cancer, leukemia, lymphoma, lung cancer, among others. It presents some systemic side effects, even at low concentrations, mainly due to the nonspecific accumulation of the drug in certain organs. To minimize the effects of traditional drug administration, this study aims to develop chitosan – methotrexate polyelectrolyte nanocomplexes with potential antirheumatic and anticancer applications. The polyelectrolyte nanocomplexes (PNCs) QTS/MTX were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA), with the resulting signals confirming the presence of the formulation components within the nanostructures. Nanoparticle formation was observed through the unimodal size distribution obtained by Dynamic Light Scattering (DLS). Samples with QTS/MTX molar ratios of 0.75 and 1 presented a polydispersity index (PDI) below 0.3, indicating better homogeneity of particle sizes in solutions. The particles exhibited diameters below 300 nm, making these systems suitable for use as nanocarriers. Scanning Electron Microscopy (SEM) confirmed that the nanostructures are spherical. Encapsulation efficiency was determined by Ultraviolet-Visible Absorption Spectroscopy (UV-Vis), with the QTS/MTX 0.75 sample showing the highest drug encapsulation efficiency and loading, at 79% and 62%, respectively. Stability in solutions were analyzed over six months in the absence of the stabilizer Pluronic® F-127. Nanoparticles with a QTS/MTX ratio of 1 demonstrated better stability. Tests using HL-60 leukemia cells and nontumoral MRC-5 cells showed differentiated selectivity in the presence of F-127. Zebrafish tests showed that the PNC was non-toxic at concentrations of 40, 200, and 400 µg kg⁻¹, reversed the inflammatory phase at all three concentrations, and reversed the neurogenic phase only at the 400 µg kg⁻¹ concentration. In rat models, the PNC reduced edema and leukocyte migration induced by the arthritis model and showed, through biochemical analysis, that it causes less hepatic damage compared to free MTX. Histopathology of the organs showed that the use of NCE resulted in the preservation of renal and hepatic morphology. The PNCs show promising results for antirheumatic and anticancer applications. Tipo: Tese

2025-01-01T00:00:00Z Santos, Sarah Brenda Ferreira dos http://repositorio.ufc.br/handle/riufc/84900 2026-02-23T22:28:24Z 2025-01-01T00:00:00Z

Título: Síntese e caracterização de compostos multifuncionais obtidos do óleo das sementes de Annona Squamosa L. Autor(es): Santos, Sarah Brenda Ferreira dos Abstract: This research aimed to explore the utilization of oil extracted from Annona squamosa Linn. seeds (ASSO), a byproduct of the food industry, as a raw material for obtaining multifunctional compounds with higher added value. In the first chapter, ASSO was subjected to chemical modification aiming at the synthesis of lubricating esters with potential industrial application. In the second chapter, the oil was used in the development of nanoemulsions (NEs) intended for the encapsulation of carvacrol, with the purpose of improving its pharmacological effect. The polyol esters were obtained by an esterification route, preceded by basic hydrolysis, using the polyols neopentyl glycol (NPG), trimethylolpropane (TMP), and pentaerythritol (PE). Characterization was conducted by Hydrogen Nuclear Magnetic Resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), physicochemical, thermal (thermogravimetric analysis – TGA and differential scanning calorimetry – DSC), and rheological analyses. Structural analyses confirmed the chemical modification of ASSO. The synthesized polyol esters showed high conversion rates (>90%), low acidity indices (~0.5 mg KOH g-1), and high viscosity indices (>180). Furthermore, according to the kinematic viscosity, the NPG, TMP, and PE derivatives may be classified into ISO VG 32, 46, and 68, and SAE 20, 30, and 40 categories, respectively, demonstrating suitability for use as hydraulic and automotive lubricants. Thermal analyses revealed that the polyol esters showed greater stability compared to the unmodified oil, especially the PE derivative. DSC analysis revealed crystallization and melting events in positive temperature ranges, demonstrating that the polyesters are suitable for applications in tropical climates. The rheological properties obtained demonstrated that the samples exhibited Newtonian fluid behavior up to 40 °C and pseudoplastic behavior above 60 °C. In the second stage, ASSO-based nanoemulsions (NEs) were obtained by the high-energy emulsification method using the ultrasonic irradiation process. The formulations were subjected to physicochemical characterization and evaluation of their pharmacological potential. Cytocompatibility was verified by means of the lactate dehydrogenase (LDH) enzyme release assay, while anti-inflammatory activity was investigated by neutrophil degranulation assays stimulated with phorbol-12-myristate-13-acetate (PMA). In addition, the antifungal activity of the formulations against different species of the Candida genus was evaluated. The NEs showed colloidal stability, with a hydrodynamic diameter in the range of 170 nm, polydispersity index (PDI) values close to 0.1, and a ζ potential greater than |30 mV|. The formulations exhibited high encapsulation efficiency (%EE >99%) and sustained release capacity of the active ingredient, reaching a cumulative release of 26% (745 μg) in 72 h, whose release kinetics fit the Korsmeyer-Peppas model, with a release mechanism denominated super case II. Cytocompatibility assays did not indicate a toxicity effect on human neutrophils, neither for free carvacrol (CARV) nor for the carvacrol-loaded nanoemulsion (CNE). Microbiological tests showed that the antifungal potential of the CNE formulation is considerably superior to the unencapsulated active ingredient. Furthermore, anti-inflammatory assays demonstrated that the NEs were able to potentiate the biological effect of carvacrol, with efficacy at concentrations ten times lower (5 μg mL-1) compared to free CARV (50 μg mL-1). Taken together, the results confirm that both the ASSO-derived polyesters and the developed NEs represent promising alternatives for industrial and pharmacological applications, highlighting the high potential of this natural resource as a renewable base for the development of high value-added products. Tipo: Tese

2025-01-01T00:00:00Z