Ion-Selective Electrodes with Colloid-Imprinted Mesoporous Carbon as Solid Contact

Abstract

A new type of solid-contact ion-selective electrode (SC-ISE) has been developed that uses colloid-imprinted mesoporous (CIM) carbon with 24 nm diameter, interconnected mesopores as the intermediate layer between a gold electrode and an ionophore-doped ISE membrane. For a demonstration, valinomycin was used as K(+) ionophore, and a good Nernstian response with a slope of 59.5 mV/decade in the range from 10(-5.2) to 10(-1.0) M was observed. The high purity, low content of redox-active surface functional groups and intrinsic hydrophobic characteristics of CIM carbon prepared from mesophase pitch lead to outstanding performance of these sensors, with excellent resistance to the formation of a water layer and no interference caused by light, O2, and CO2. When a redox couple is introduced as an internal reference species, calibration-free SC-ISEs can be made with a standard deviation of E° as low as 0.7 mV. Moreover, the interconnected mesopore structure of ISE membrane-infused CIM carbon facilitates both ion and electron conduction and provides a large interfacial area with good ion-to-electron transduction. Because of the large double layer capacitance of CIM carbon, CIM carbon-based SC-ISEs exhibit excellent potential stability, as shown by chronopotentiometry and continuous potentiometric measurements. The capacitance of these electrodes as determined by chronopotentiometry is 1.0 mF, and the emf drift over 70 h is as low as 1.3 μV/h, making these electrodes the most stable SC-ISEs reported so far.

An effective solid contact for an all-solid-state polymeric membrane Cd 2+ -selective electrode: Three-dimensional porous graphene-mesoporous platinum nanoparticle composite

“…The proposed Cd 2+ -ISE is robust to the interferences from O 2 and CO 2 and there are no obvious potential drifts during the measurements. The results are consistent with those of other carbon nanomaterialbased ASS-ISEs [12,16,25,51]. In addition, the influence of light on the potential stability was also measured by immersing the proposed GC/PGR-MPN/Cd 2+ -ISE in 10 −5 M Cd(NO 3 ) 2 while turning on and off the ambient light.…”

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.…”

Pre-Polarized Hydrophobic Conducting Polymer Solid-Contact Ion-Selective Electrodes with Improved Potential Reproducibility

“…The mainstream of the SCISE research is based on electrically conducting polymers (ECPs) [34][35][36] , large surface area carbon materials 32,[37][38][39][40] and their (nano)composites [41][42][43] , but also many other important types of SC materials have been reported such as redox polymers 44 , electronion exchange resins 45 , redox-active self-assembled monolayers 32 , tetrakis(4-chlorophenyl)borate anion doped nanocluster films 46 , nanoporous Au films 47 , and threedimensional molybdenum sulfide nanoflowers. 48 SCISEs with adequate potential stability were reported for both the ECP and carbon materials, but the use of large surface area inert carbon materials apparently results in better potential stabilities and less susceptibility to environmental conditions.…”