http://repositorio.ufgd.edu.br/jspui/handle/prefix/5144 2026-01-21T07:38:38Z http://repositorio.ufgd.edu.br/jspui/handle/prefix/6260 Título: Sínteses e caracterizações estruturais de complexos de FeIII, CoII , CuII, ZnII e CdII com ligantes bases de schiff acilhidrazonas e estudo de interação com o dna Autor(es): Moreira, Jeniffer Meyer Primeiro Orientador: Carvalho, Cláudio Teodoro de Abstract: In this work, three acylhydrazone Schiff base ligands were synthesized: salicylaldehydeisonicotinoyl hydrazone (H2La), salicylaldehyde-4-chlorobenzoyl hydrazone (H2Lb) and o-vanillin-4-chlorobenzoyl hydrazone (H2Lc). The characterization of the ligands involved techniques such as melting point (m.p.), nuclear magnetic resonance (NMR) spectroscopy, vibrational spectroscopy in the mid-infrared region (IR) and electronic absorption in the ultraviolet-visible (UV-Vis). Once the structure was elucidated, these ligands were used in complexation reactions with different metal ions, resulting in seven unprecedented crystalline complexes, numbered from 1 to 7, which were divided into three specific groups: I) (1) Zn(H2L a)2(Cl)2]·2/3(CH3OH)·2/3(H2O); (2) [Cd(H2La)2(NO3)2(CH3OH)2]; II) (3) [Fe(HLb)Cl)2(CH3CH2OH)]·(CH3CH2OH); (4) [Co2(HLb)2(CH3OH)4](NO3)2·2(CH3OH); (5) [Cu2(HLb )2(ClO4)2]·2(H2O); III) (6) [Cu(HLc)(CH3OH)(H2O)](NO3) and (7) [Cd2(HLc)2(NO3)2(CH3OH)2]·4(CH3OH). Structural analysis of single-crystalline complexes by X-ray diffraction (XRD) revealed detailed information, including the metal coordination sphere, the presence of counter ions and solvent molecules, intramolecular and intermolecular interactions. Using IR spectroscopy, information about molecular vibrations corroborated the crystallographic data, highlighting the points of coordination of the ligand with the metals, such as the C=O and C=N stretching bands that were displaced by approximately 1650 cm-1and 1620 cm-1, respectively, in the ligand spectra for lower wavenumbers in those complexes where coordination occurred in a tridentate manner. Furthermore, using this technique it was possible to observe the stretching vibrations, characteristic of the nitrate ions in complexes 2, 4, 6 and 7 and of the perchlorate ion in complex 5. Spectroscopy in the UV-Vis region revealed characteristic bands of the intra- π→π* ligand around 300 nm, coming from the aromatic rings of the ligand structure and n→π* transitions around 330 nm. In addition to charge transfers occurring between ligand and metal in the 400 nm region in the spectra of the complexes. Biological study of the complexes was carried out using calf thymus DNA (CT-DNA). The study by spectroscopic titration and viscosity revealed the presence of intercalative DNA-complex interactions, highlighting them as moderate with Kb values ranging from 104-105 L mol-1, in addition to showing significantly greater hypochromism compared to free ligands, indicating that complexation resulted in stronger interaction with DNA. The partition coefficients, with positive log P values, obtained in water and n-octanol, suggest potential for easy permeation of these complexes through biological membranes, indicating a notable preference for the organic phase, similar to lipids. This characteristic is advantageous in drug development and design, especially when compounds require efficient access to intracellular targets. Editor: Universidade Federal da Grande Dourados Tipo: Tese 2024-02-20T00:00:00Z http://repositorio.ufgd.edu.br/jspui/handle/prefix/6259 Título: Construção de dispositivos microfluídicos usando técnicas alternativas de baixo custo: aplicação na determinação de contaminantes em amostras de interesse socioambiental Autor(es): Maximiano, Elizabete Maria Primeiro Orientador: Trindade, Magno Aparecido Gonçalves Abstract: Channel-based microfluidic devices have been useful in the miniaturized analytical system, however, the most critical part in the development of microfluidic platforms remains the detection system and its integration into the channel. Currently, electrochemical detectors are the most suitable for its integrations. There are many ways to manufacture the channel on microfluidic platforms, and, one way involves the use of alternative technologies that enable use of low-cost materials. This allows to produce several designs of microfluidic devices and new configurations of electrochemical detectors directly integrated. In this work, unconventional protocols were developed for building microfluidic devices based on polydimethylsiloxane (PDMS). As such, microfluidic devices with planar geometries, in which the internal channel (in the form of a serpentine), and a new configuration of electrochemical detection system were mounted onto a single chip. Target technology for produce microdevices is simple, low cost and requires minimal knowledge in microfabrication process. The proposed microfluidic platforms were tested for solve some problems arising from the use of automatic micropipettes during discrete injections as well as the use of surfactants into the carrier solution. The experimental results demonstrated the high performance of the integrated electrochemical detector system, showing high tolerance to the presence of air bubbles and no disturbance during the discrete injections. Also, we also showed the analytical performance of the PDMS-based microfluidic device for amperometric detection of salicylic acid (SA) in some aqueous samples. Then, this device was also used for separation of SA and caffeine (CAF) after activation of the inner channel wall with sodium hydroxide solution (2.0 mol L-1) and further simultaneously detection of both analytes in amperometric mode. Editor: Universidade Federal da Grande Dourados Tipo: Tese 2021-06-10T00:00:00Z http://repositorio.ufgd.edu.br/jspui/handle/prefix/5145 Título: Compósitos de grafeno amassados decorados por nanopartículas de metais de transição: viabilidade de aplicação como sensores eletroquímicos Autor(es): Alencar, Leticia Machado Primeiro Orientador: Martins, Cauê Alves Abstract: Graphene-based materials have great potential for a myriad of applications such as energy storage devices, flexible electrodes for photovoltaic cells, sensors, and nanocomposites, among others. The structure of graphene directly influences the performance of the material and the production of 3D graphene-based materials is an alternative to retain the intrinsic properties of 2D graphene and improve other properties such as specific surface area, porosity, mechanical properties, etc. In this sense, nanocomposites based on 3D graphene (crumpled graphene, CG) were synthesized, maintaining the high active area and minimizing the material's aggregation behavior. The synthesis of composites is an alternative to achieve a synergistic effect, where graphene acts as a substrate to immobilize other components such as inorganic nanoparticles, improving the electrochemical properties of the carbon nanostructure. The aerosol-assisted capillary compression strategy adopted to synthesize the composites results in transition metal nanoparticles directly connected to the CG. The carbon nanostructure controls the nucleation and growth of nanoparticles during capillary compression, making carbonaceous structures one of the main research focuses to develop materials for various technological applications, such as electrochemical sensors. In this context, the goal of this work was to synthesize and characterize crumpled graphene nanostructures decorated with nanoparticles of transition metals, such as copper, palladium, and nickel, exploring its promising application as an efficient electrocatalyst in the electrochemical detection of hydrogen peroxide, glycerol, caffeine. The synthesis of CG with the different metallic precursors was carried out in a single step using a horizontal tube furnace, in a spray pyrolysis process. The materials obtained were characterized by scanning electron microscopy, transmission electron microscopy and X-ray excited photoelectron spectroscopy, energy dispersive spectroscopy, X-ray diffraction and thermogravimetric analysis in which the morphology attributed to the crumpled graphene and the presence of metal nanoparticles covering the surface of the carbonaceous material were verified. In addition, electrochemical measurements were performed to investigate the electrocatalytic properties of the sensors by the techniques of cyclic voltammetry and chronoamperometry. The 1:5 CG:Cu nanocomposite showed good sensitivity and linearity in the response curves for H2O2, with detection limit and sensitivity of 0.64 µmol L-1 and 0.37 A L mol-1 cm-2 , respectively. The Pd/CG composite showed sensitivity for the detection of H2O2, caffeine and glycerol of 0.742, 0.848 and 8.24x10-4 A L mol-1 cm-2 , respectively. And the CG:Ni-Acet and CG:Ni-Nit nanocomposites showed excellent electrocatalytic activity in the oxidation of H2O2 with the sensitivity of 0.357 and 0.317 A L mol-1 cm-2 , respectively. In addition, the synthesized composites are reproducible, selective, stable and have a rapid electrochemical response. Editor: Universidade Federal da Grande Dourados Tipo: Tese 2022-06-02T00:00:00Z