Introducing Cobalt(II) Porphyrin/Cobalt(III) Corrole Containing Transducers for Improved Potential Reproducibility and Performance of All-Solid-State Ion-Selective Electrodes

Abstract

A novel solid contact type for all-solid-state ion-selective electrodes is introduced, yielding high stability and reproducibility of potential readings between sensors as well as improved analytical performance. The transducer phase herein proposed takes advantage of the presence of porphyrinoids containing the same metal ion at different oxidation states. In contrast to the traditional approach, the compounds of choice are not a redox pair; although they have different oxidation states, they cannot be electrochemically driven one to another. The compounds of choice were cobalt(II) porphyrin and cobalt(III) corrole-both characterized by a high stability of the coordinated metal ions in their respective redox states and electrical neutrality, as well as relatively high lipophilicity. The porphyrinoids were used together with carbon nanotubes to yield transducer layers for ion-selective electrodes. As a result, we obtained a high stability of potential readings of the resulting ion-selective electrodes together with good reproducibility between different sensor batches. Moreover, advantageously the presence of porphyrinoids in the transducer phase results in improvement of the analytical performance of the sensors: linear response range and selectivity due to interactions with membrane components, resulting in tailoring of ion fluxes through the membrane phase. Thus, carbon nanotubes with the cobalt(II) porphyrin/cobalt(III) corrole system are promising alternatives for existing transducer systems for potentiometric sensors.

Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors

“…It showed a small standard derivation of E 0 of 1.0 mV over two weeks. Other Co complexes were reported for the SC, which further demonstrated the redox-buffer stabilized concept [65][66][67][68]. In addition to Co complexes, tetrathiafulvalene (TTF) and its radical salts have also constituted the redox buffers for SC-ISEs [69].…”

Unintended Changes of Ion-Selective Membranes Composition—Origin and Effect on Analytical Performance

“…The amount of cocktail applied is dependent on w / w concentration of membrane components and the required thickness of the ISM. Typically, 20–30 ul of membrane cocktail is applied on one substrate electrode of diameter 3 mm [ 13 ]. If SC contains material (either main component, additive or impurity) soluble in the cocktail solvent, application of the membrane can result in partition of some of the transducer components to the ISM phase.…”

“…Partition of the transducer material to ion-selective membranes in the course of sensor preparation has been also reported for other systems. Application of SC based on CNTs containing porphyrinoids resulted in spontaneous partition of the latter to the membrane phase [ 13 ]. The higher loading of SC with porphyrinoids resulted in higher contents of these in the membrane [ 13 ].…”

“…Application of SC based on CNTs containing porphyrinoids resulted in spontaneous partition of the latter to the membrane phase [ 13 ]. The higher loading of SC with porphyrinoids resulted in higher contents of these in the membrane [ 13 ]. It was also clearly confirmed that the presence of porphyrinoids affects performance of the sensor resulting in tailoring fluxes in the ISMs phase and ultimately leading to improved detection limit and selectivity [ 13 ].…”

“…It is also advantageous, if the sensor construction allows miniaturization and mass-scale production of devices. The envisaged disposable/in-fields operation sets additional demands such as high reproducibility between different sensors from a production batch, potentially allowing calibration-less operation [ 12 , 13 , 14 , 15 ].…”