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-1 cm-2 and 0.133 μA μM-1 cm-2) with good reproducibility, stability, and selectivity. Graphical abstract Schematic representation of the preparation process of the nitrite ion electrochemical sensor.