High sensitivity amperometric and voltammetric determination of persulfate with neutral red/nickel oxide nanowires modified carbon paste electrodes

A novel, highly sensitive sensor for detection of persulfate (S2O82−) is demonstrated by modification of carbon paste electrode (CPE) with nickel oxide nanowires (NiOx NWs) and neutral red (NR). Ni NWs are prepared by DC electrodeposition of Ni in the cylindrical pores of anodized aluminum oxide (AAO) templates. NWs are released, oxidized and immobilized with NR on the surface of CPE. Cyclic voltammetry studies demonstrate a pair of well-defined nearly reversible redox couples (E°′ = −0.2 V in a buffer solution pH 2.0) at a wide pH range of 1-12. The surface coverage and heterogeneous electron transfer rate constant of the adsorbed redox couple are 7.368 × 10−12 mol cm−2 and 7.9 s−1, respectively, indicating a high NR loading efficiency for NiOx NWs and efficient electron transfer between redox couple and the electrode. The modified CPE exhibits an excellent electrocatalytic activity for a S2O82− reduction, with a measured kcat of ∼7.14 × 103 M−1 s−1. This catalytic reduction allows an amperometric detection of S2O82− at a potential of −0.2 V with detection limit of 30 nM, concentration calibration range of 0.1 μM to 12 mM and a linear sensitivity of 647.33 nA μM−1, respectively.