Electrodeposition of gold nanostructures on polypyrroleelectrodes for electrochemical sensing

E. GUTIÉRREZ PINEDA; A. E. BOLZÁN; C. A. GERVASI; M.J. RODRÍGUEZ PRESA

La Haya

Congreso; 67th Meeting of The International Society of Electrochemistry, ISE; 2016

International Society of Electrochemistry

Polypyrrole (PPy) films were electroformed on stainless steel (SS) AISI 304 electrodes at a constant potential of 0.8 V in 0.25 M PPy + 0.1 M C7H5NaO3. Depending on the electropolymerization time, the surface morphology varied from a rather smooth to a rough one as the formation of polymeric columns increased. The voltammetric response of the films exhibited an increasing irreversible behaviour as the columnar structure became more compact along with the increase in the double layer capacitance of the film. Considering SEM and voltammetric results, a growth time of 3 min was selected to produce the optimal PPy columnar-structured film that was afterwards decorated with gold atoms. Electrodeposition of gold on the PPY film was performed by means of a double potential step routine to control separately the nucleation and growth processes of gold on the composite electrode. Therefore, electrodeposition of gold involved a potential step to -0.8 V for 0.1s followed by a second potential step to 0.1 V for a variable time, the latter allowing gold nuclei to grow and reach different sizes. On the other side, current transients were also recorded by applying a single potential step within the potential range corresponding to the voltammetric peak for gold electrodeposition on PPy. This procedure was used to study the nucleation mechanism of gold on the PPy films. Dimensionless analysis of the current transients suggested the occurence of a progressive nucleation process. The possible application of these composite electrodes decorated with nanostructured gold domains for electrochemical sensing was tested for the analytical quantification of hydrazine in phosphate buffer solutions (PBS), by means of differential pulse voltammetry. For this purpose, normal and differential pulse voltammograms were run at different pH values of the PBS to determine the pH at which the electro-oxidation peak of hydrazine exhibited a maximum value. Accordingly, DPV runs were made in 0.1 M PBS at pH 9.0, using a pulse height of 0.005 V, pulse amplitude of 0.05 V and pulse duration of 200 ms. The resulting peak current vs. concentration plots exhibit two linear portions, one between 0.05 and 10 μM, and another one covering the 10 to 100 μM concentration range.