Achieving preeminent stability and reproducibility in an ion-selective electrode for copper ion via introducing a hydrophobic NiCo2S4/PFOA solid-contact

Abstract

In this work, an ion-selective electrode (ISE) for copper ion with excellent stability and reproducibility is prepared by introducing a solid-contact (SC) layer between the screen-printed electrode (SPE) and ion-selective membrane (ISM). The SC layer is fabricated by the electrodeposition of nano-arrayed NiCo2S4 on SPE, and thereafter is surface-modified by perfluorooctanoic acid (PFOA) to realize superior double layer capacitance (CDL) and hydrophobicity. The results show the water contact angle of the SC is 134°. The CDL of the modified ISE, named as Cu2+-SC(25)ISE, is 48.53 μF·cm−2, about 6.5 times of the ISE without SC. The detection limit of the Cu2+-SC(25)ISE is 4.62 μM. The SC with nano-structured NiCo2S4 frameworks and hydrophobic PFOA chains provides outstanding capacitance and high potential stability simultaneously, and further endows Cu2+-SC(25)ISE with excellent detection accuracy. For the detection of Cu2+ in soil leachate, the average detection errors of the Cu2+-SC(25)ISE and ICP-OES are 4.14 % and 3.02 % respectively, revealing the potential application prospect of this technic. This work puts forward a novel concept to achieve the accurate measurement and flexibility of ISE.