Poly (3,4-ethylenedioxythiophene) (PEDOT) is an important conducting polymer that is widely studied for applications in photovoltaic devices, thermoelectric materials, batteries, capacitors and sensors [1]. In the field of sensors, PEDOT and PEDOT composites synthesized by chemical and electrochemical methods have been used for the detection of organic and inorganic analytes [2]. In particular, the performance of the composites of PEDOT with nanomaterials (mono and bi-metallic nanoparticles, graphene and nanotubes) has been thoroughly investigated in the last years because the incorporation of those nanostructures can significantly improve the sensing properties of the pristine polymer [3,4]. However, to the best of our knowledge the effect of the content of hollow PdAu nanoparticles in PEDOT composites for the detection of nitrite, an important environmental pollutant, has not been reported before.

In this work, PEDOT films were prepared by cyclic voltammetry and under amperometric and potentiostatic conditions from a solution of EDOT, LiClO₄ and SDS (sodium dodecyl suphate). The films were characterized by scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX). 500 nm- and 300 nm-thick PEDOT films deposited on glassy carbon were used for the electrochemical detection of nitrite by differential pulse voltammetry. 500 nm-thick films shown a higher sensitivity towards NO₂^- ions (0.027 μA μM^-1). Hollow nanoparticles of gold and palladium were synthesized by a galvanic replacement reaction using Na₂PdCl₄. PEDOT films were codeposited with the hollow PdAu nanoparticles at constant potential. The performance of the composites with different contents of the bimetallic nanoparticles (3,6,12,15,24 and 30% of the total mass of nanoparticles) were evaluated for the detection of nitrite ions in the range of 50 to 250 μM nitrite. All composites exhibited a higher performance in comparison to PEDOT films mainly in the range of 50 to 112.5 μM.

Figure 1.- SEM PEDOT films produced by (a) potentiostatic deposition, (b) constant current, (c) cyclic voltammetry and (d) DPV curves of nitrite detection with PEDOT + 15% mass percent of PdAu nanoparticles suspension