Plataforma sensorial a base do metalopolímero de [Ni(Salpn)] para determinação voltamétrica de peróxido de hidrogênio

Many electrochemical sensors havebeen developed using biological materials in the construction of biosensors for peroxide detection. The strategy to construct semiconducting polymeric films by electropolymerization of the organometallic complex of Ni(salpn) on platinum electrode surface and its electrocatalytic properties in the hydrogen peroxide reduction in aqueous solution have been investigated. The film was prepared and electropolymerized at a platinum electrode (0.071 cm2) in CH2Cl2/0.1 mol L-1 TBAP by cyclic voltammetry between 0.0to 1.4V vs. SCE.The structure of poly[Ni(salpn)] on the electrode surface is the generation of stacked polymer complexesformed due to the donor-acceptor interaction between the ligand of one monomer fragmentand the metal center of another[1]. The electrochemical behavior and stabilization of poly[(Ni(salpn)] film was done for 15 potential cycles in 0.5mol L−1 KCl solution with cycling the potential between -0.6 to 0.8V vs.SCE. In order to evaluate the poly[Ni(salpn)] properties as a voltammetric sensor for hydrogen peroxide determination, voltammetric measurements at 0.5 mol L-1 KCl solution in absence and presence of H2O2 was realized. A typical voltammetric response was obtained by the progressive addition of H2O2 solution. In H2O2 . presence an increase of anodic current at -0.18 V vs.SCE can be observed, that indicate a electrocatalytic process by metal centers of the conducting polymer. The observed increase can be explained by the fact that hydrogen peroxide diffuses up to the electrode surface and oxides the Ni(I) electrochemically produced. The overall reaction scheme can be represented by an initial electrochemical step (Eq. 1) followed by a chemical step (Eq. 2): The reaction can be brought about electrochemically where in the nickel(II) is first reduced to a nickel(I) at the electrode surface. The nickel(I) then undergoes a catalytic oxidation by the H2O2in solution back to the nickel(II) in polymer, which can then be electrochemically re-reduced to produce an enhancement of the cathodic current. At the unmodified electrode the electrochemical reduction of H2O2 is represented by an irreversible peak at -0.45 V vs.SCE in KCl solution 0.5 mol L-1. A significant decrease in the overpotential (about 270 mV) for hydrogen peroxide reduction using the sensor based on poly[Ni(salpn)] modified platinum electrode was verified when compared with the unmodified platinum electrode. The sensor studied presented a linear range in the 4.99 × 10-5 and 2.44 × 10−3mol L−1 concentration range, the concentration limit was 7.68 × 10−6 mol L−1. The sensor based on poly[Ni(salpn)] modified platinum electrode showsstrong promise for potential application as a voltammetric sensor for hydrogen peroxide.