| Summary: | With polymerization duration and Au<sup>3+</sup> concentration of the electrolyte regulated, a desirable nitrate-doped polypyrrole ion-selective membrane (PPy(NO<sub>3</sub><sup>−</sup>)-ISM) and Au solid contact layer of anticipate surface morphology were obtained, and the performance of nitrate all-solid ion-selective electrodes (NS ISEs) was improved. It was found that the roughest PPy(NO<sub>3</sub><sup>−</sup>)-ISM remarkably increases the actual contact surface area of the PPy(NO<sub>3</sub><sup>−</sup>)-ISMs with nitrate solution, which leads to better adsorption of NO<sub>3</sub><sup>−</sup> ions upon the PPy(NO<sub>3</sub><sup>−</sup>)-ISMs, and produces a larger number of electrons. The most hydrophobic Au solid contact layer avoids the formation of the aqueous layer at the interface between the PPy(NO<sub>3</sub><sup>−</sup>)-ISM and Au solid contact layer, and ensures unimpeded transporting of the produced electrons. The PPy-Au-NS ISE for polymerization duration 1800 s and at Au<sup>3+</sup> concentration 2.5 mM of the electrolyte displays an optimal nitrate potential response, including a Nernstian slope of 54.0 mV/dec, LOD of 1.1 × 10<sup>−4</sup> M, rapid average response time less than 1.9 s, and long-term stability of more than 5 weeks. This indicates that the PPy-Au-NS ISE is an effective working electrode for the electrochemical determination of NO<sub>3</sub><sup>−</sup> concentration.
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