Imobilização de metaloftalocianinas em Poli(dimetilsiloxano): preparação, caracterização e propriedades eletroquímicas

Abstract

Ascorbic acid, also denominated as Vitamin C, is present in several foods, especially in fruits, vegetables and participates in the prevention of various infectious diseases. Present too in the pharmaceutical and food industries, because it is an antioxidant, helps to avoid undesirable changes in aroma, taste and color; thus prolonging the storage time of these products. Nowadays, different techniques are employed to determine this substance, among them the electroanalytical techniques. Researches in this area aim to obtain electrodes that present characteristics of high sensitivity and selectivity, looking for to improve these techniques. This work aimed to synthesize Nickel, Zinc and Cobalt Metallophthalocyanines (MPc). By the techniques of Infrared spectroscopy in the infrared region (FT-IR), Spectroscopy in the UV / visible region and Thermogravimetric Analysis (TG) evidentiated the formation of de polymeric network, Which was used in the syntheses of polymer networks of PDMS and ATPMS (3-aminopropyltriethoxysilane). This material served as a support for the MPCs and it was possible to obtain a material that was used as a chemically modified electrode with graphite paste. These polymer networks containing the MPCs were also characterized by infrared, UV / visible spectroscopy and by thermogravimetric analysis. Among these techniques only UV / visible showed that Cobalt and Nickel phthalocyanine should be occluded in the network, since Zinc phthalocyanine may have had some interaction with the network, but only with this technique could not be established as this occurs. Electrochemical measurements were made to study the behavior of the materials using the cyclic voltammetry technique, using the carbon paste material, without and with the presence of a probe molecule, K3[Fe(CN)6]. The results showed that a higher content of metallophthalocyanines in the network results in the favoring the electron transfer process of the redox reaction of the probe molecule. The materials prepared with the highest percentage of metallophthalocyanine was applied in the determination of ascorbic acid (AA) by Square Wave Voltammetry, evidencing that these can be used in the determination of this analyte as an electrochemical sensor.