Licenciatura em Química (Sede)
URI permanente desta comunidadehttps://arandu.ufrpe.br/handle/123456789/26
Siglas das Coleções:
APP - Artigo Publicado em Periódico
TAE - Trabalho Apresentado em Evento
TCC - Trabalho de Conclusão de Curso
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Resultados da Pesquisa
Item Estudo voltamétrico da oxidação e eletropolimerização da anilina sobre eletrodo de carbono vítreo(2024-05-06) Silva Neto, José Gouveia da; Oliveira, Severino Carlos Bezerra de; http://lattes.cnpq.br/7976654736038580; http://lattes.cnpq.br/5157702058443274This work carried out a voltammetric study for the oxidation and electropolymerization of aniline (ANI) in aqueous electrolytes on the glassy carbon electrode (GCE). Different experimental conditions were explored, such as: different voltammetric techniques, cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), applied potential window, scanning speed, pre-treatment of the surface of the GCE, ANI concentration, nature and pH of the supporting electrolyte. Regarding the oxidation of ANI, the electrochemical data indicated an anodic mechanism controlled by diffusion of several steps, all dependent on the pH of the supporting electrolyte. Oxidation initially occurred in the anilinium group with the removal of an electron and a proton and the formation of an intermediate radical cation. These electrogenerated radical cations formed dimers and other electroactive byproducts. The oxidation mechanism of ANI on GCE was revisited in the literature and discussed. The diffusion coefficient of ANI was established in sulfuric acid as 1.14 x 10-5 cm2 s-1 and phosphate buffer as 7.82 x 10-6 cm2 s-1. SWV was explored for detection and quantification of ANI and under optimized conditions an analytical proposal was achieved in phosphate buffer, in a concentration range 0.10 to 2.11 umol L-1, limit of detection (LOD) of 0.12 umol L-1 and limit of quantification (LOQ) of 0.40 umol L-1. The voltammetric data also demonstrated the electropolymerization of ANI and the deposition of the polyaniline film (PANI) on the GCE, under different experimental conditions, mainly from a concentration of 5.00 mmol L-1 of the monomer and in the extended potential window (- 0.20 to + 1.40 V). The voltammetric data from ANI and PANI presented here will also be explored as teaching material for physical-chemistry, electrochemistry and electroanalytical subjects at the Department of Chemistry at UFRPE and two practical class scripts were also developed and presented here.Item Estudo eletroanalítico do ácido úrico e da guanina sobre eletrodo de carbono vítreo(2024-03-28) Alves, Arthur Silva; Oliveira, Severino Carlos Bezerra de; http://lattes.cnpq.br/7976654736038580; http://lattes.cnpq.br/8761819971294000The main objective of this work was to demonstrate the electrochemical activity of UA and GUA, in different aqueous media, on the glassy carbon electrode (GCE), through different voltammetric techniques, namely cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The results were exploited for simultaneous detection and quantification of these species using DPV. Furthermore, the experimental results will be used to prepare teaching material for theoretical and practical classes in electrochemistry and electroanalytical subjects offered at the Department of Chemistry at UFRPE. The results clearly indicated that both molecules are easily electro-oxidized through complex, multi-step mechanisms. The oxidation of UA occurred from a main anodic process (peak 1a), with the loss of two electrons and two protons, generating a quinonoid diimine, which partially underwent electroreduction (peak 1c) and/or reacted with water generating allantoin. GUA underwent electro-oxidation in N7 (peak 1a), forming an electroactive dimer (peak 2a) and/or 8-oxoguanine, reversibly electroreduced (peak 3c/3a). Both AU and GUA showed that their anodic processes were controlled from mass transport via diffusion. Under suitable conditions, UA and GUA were detected and quantified simultaneously at neutral pH, using DPV. The limits of detection (LOD) and quantification (LOQ) for UA were LOD = 0,51 μmol L-1 and LOQ = 1,70 μmol L-1 and for GUA they were 0.82 μmol L-1 and 2.73 μmol L-1.