Caracterização eletroquímica de poli(dimetilsiloxano) funcionalizado com grupo sulfônico contendo nanopartículas metálicas

Abstract

Functionalized materials have been the target of study in several areas of interest, among them, the manufacture of chemically modified electrodes for application as electrochemical sensors. In this work, a polymeric network of poly (dimethylsiloxane) (PDMS) functionalized with sulphonic group containing metallic nanoparticles was prepared to obtain an electrode material for use as electrochemical sensor. For this porpouse, a functionalized polymeric network was prepared with PDMS and 3-mercaptopropyltrimethoxysilane (3- MPTMS), then hydrogen peroxide was added to promote oxidation of the thiol group, obtaining the functionalized material with sulphonic group (PSO). Materials containing metallic nanoparticles silver (PSOAg) and gold (PSOAu) were also prepared, adding these species during the preparation of the networks. The prepared materials were characterized by thermogravimetric analysis (TG) and Fourier Transform Infrared Spectroscopy (FTIR). Results indicate the formation of the proposed polymeric network. Then, working electrodes were prepared: Graphite was added to PSO, PSOAg and PSOAu, in the proportion 1:0.5, network:graphite, m:m. The electrochemical behavior of the material was evaluated by cyclic voltametry (CV) and electrochemical impedance spectroscopy (EIS). The electrodes containing the metallic nanoparticles (PSOAg/Graphite and PSOAu/Graphite) presented the best responses in the study with the probe molecule ([Fe(CN) 6 ] 3-/4 . Among them, a smaller difference in anodic and cathode potential, ratio of anodic/cathodic current density near to one and also higher intensities of peak current densities. In order to evaluate the applicability of the electrode as a sensor, CV measurements were performed to determine copper, where oxidation potentials of -0.05 V were obtained for the PSOAg/Graphite electrode and 0.06 for the PSOAu/Graphite electrode. With square wave voltametry, oxidation potentials of -0.27 V were obtained for the electrode containing silver nanoparticles and -0.25 V for the electrode containing gold nanoparticles, while the detection limits were 0.13 μmol.L -1 and 0.04 μmol.L - 1 , respectively.