Emission Intensity Readout – Pushing the Limits of Ion-Selective Sensing

Ion-selective membranes (ISMs) were originally developed for potentiometric (open-circuit) sensors, however due to high selectivity offered they are also attractive for optical sensors or devices operating under controlled current or potential conditions in: voltammetric/ coulometric / chronopotentiometric mode of “redox-inactive” ions selective sensing e.g. 1,2. In these applications ion exchange: spontaneous or induced by an electrochemical trigger results in change of the membrane composition; and in some cases also in membrane optical properties. The latter typically requires modification of the membrane composition (compare to classical one), however allows optical readout of analytical signal. This is often preferred scenario, that allows elimination of some constrains typical for ion-selective electrochemical sensors, such as the presence of reference electrode (for purely optical sensors) or relatively high resistivity of the ion-selective membrane (for sensors operating under electrochemical trigger).
We report on in-situ transduction of electrochemical responses of ion-selective probes, operating under zero but also non-zero current conditions, into emission changes signal 3,4. Alternative, optical readout mode herein proposed offers possibility to overcome problems related to nature of ISMs ultimately to offer higher sensitivity or extending analytically useful range.

Financial support from National Science Centre (NCN, Poland), project UMO-2021/41/B/ST4/03401, is gratefully acknowledged.

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4. Kalisz, J.; Węgrzyn, K.; Maksymiuk, K.; Michalska, A. ChemElectroChem, 2021, 8, 4129.