Electrochemical synthesis of multilayered PEDOT/PEDOT-SH/Au nanocomposites for electrochemical sensing of nitrite.

A multilayered film of poly(3,4-ethylenedioxythiophene)/poly(thiomethyl 3,4- ethylenedioxythiophene)/gold nanoparticle (PEDOT/PEDOT-SH/Au) nanocomposites was successfully synthesized on indium tin oxide (ITO) and glassy carbon electrode (GCE) via an electrochemical technique. The structure and morphology of the composite was characterized by FT-IR, UV-vis, EDS, XPS, and SEM analyses. The prepared multilayered PEDOT/PEDOT-SH/Au nanocomposite was used for the electrochemical catalytic oxidation of nitrite by amperometry. The results showed that the microstructures of PEDOT/PEDOT-SH/Au nanocomposites are not strongly dependent on the substrate. Fibrous PEDOT as hard template absorbed EDOT-SH on it to form porous PEDOT/PEDOT-SH. Porous structure had the advantages of large specific surface area and high porosity for nitrite ion adsorption. The thiol group in PEDOT/PEDOT-SH stabilized Au nanoparticles (NPs) effectively through Au-S bond and allowed Au NPs to have high dispersion and excellent electrocatalytic activity. The PEDOT/PEDOT-SH/Au composite prepared on GCE had a good performance in its electrochemical response to nitrite ions. PEDOT/PEDOT-SH/Au/GCE displayed a low oxidation potential (0.74 V), a fast response time (< 3 s), a low detection limit (0.051 μM), two linear ranges (0.15-1 mM and 1-16 mM), good sensitivity (0.301 μA μM cm and 0.133 μA μM cm) with good reproducibility, stability, and selectivity. Graphical abstract Schematic representation of the preparation process of the nitrite ion electrochemical sensor.