Effects of Architecture and Surface Chemistry of Three-Dimensionally Ordered Macroporous Carbon Solid Contacts on Performance of Ion-Selective Electrodes

Abstract

The effects of the architecture and surface chemistry of three-dimensionally ordered macroporous (3DOM) carbon solid contacts on the properties of ion-selective electrodes (ISEs) were examined. Infiltration of the plasticized PVC membrane into the pores of the carbon created a large interfacial area between the sensing membrane and the solid contact, as shown by cryo-SEM and elemental analysis. This large interfacial area, along with the high capacitance of the 3DOM carbon solid contacts (as determined by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy) results in an excellent long-term stability of the potentiometric response, with drifts as low as 11.7 µV/h. The comparison of 3DOM carbon solid contacts with an untemplated carbon solid contact shows that the pore structure is an essential feature for the excellent electrode performance. However, the surface chemistry of the 3DOM carbon cannot be ignored. While there is no evidence for an aqueous layer forming between the sensing membrane and unoxidized 3DOM carbon, electrodes based on oxidized 3DOM carbon exhibit potentiometric responses with the typical hysteresis indicative of a water layer. A comparison of the different techniques to characterize the solid contacts confirms that constant-current charge-discharge experiments offer an intriguing approach to assess the long-term stability of solid-contact ISEs but shows that their results need to be interpreted with care.

An all-solid-state polymeric membrane Pb2+-selective electrode with bimodal pore C60 as solid contact

“…In recent years, carbon-based nanomaterials such as graphene [8,9], three-dimensionally ordered macroporous carbon [10], colloid-imprinted mesoporous carbon [11] and carbon nanotubes [12] have been used as solid contacts for the fabrication of ASS-ISEs. Due to the large double layer capacitances and hydrophobic properties of carbon materials, these ASS-ISEs possess high potential stability, and show the absence of an interfacial aqueous layer between the polymeric sensing membrane and the underlying solid contact.…”

A solid-contact Pb2+-selective electrode using poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) as ion-to-electron transducer

“…As a key component, the solid contact plays a critical role in the electrode characteristics, such as linear response range, selectivity and potential stability in particular [3][4][5]. Until now, many kinds of materials, including redox-active monolayers [6], carbon materials [7][8][9][10][11], and conducting polymers (CPs) [12] have been introduced between the conducting substrates and the ion-selective membranes to obtain thermodynamically defined electrochemical interfaces.…”

A ladder conjugated polymer transducer for solid-contact Cu2+-selective electrodes

“…It has been realized that a thin aqueous film can form unintentionally between the sensing membrane and its solid contact [23][24][25]. To test for the presence of aqueous layer, the fabricated electrode was investigated by the method introduced by Fibbioli et al [26].…”