Abstract
Classical application of ion-selective membranes is limited to either electrochemical or optical experiments. Herein, the proposed ion-selective membrane system can be used in both modes; each of them offering competitive analytical parameters: high selectivity and linear dependence of the signal on logarithm of analyte concentration, high potential stability in potentiometric mode, or applicability for alkaline solutions in optical mode. Incorporation of analyte ions into the membrane results in potentiometric signals, as in a classical system. However, due to the presence of lipophilic positively charged ions, polymer backbones, full saturation of the membrane is prevented even for long contact time with solution. The presence of both positively charged and neutral forms of conducting polymers in the membrane results in high stability of potential readings in time. Optical signal generation is based on polythiophene particulates dispersed within the ion-selective membrane as the optical transducer. An increase of emission is observed with an increase of analyte contents in the sample.
Highlights
Ionophore-based electrochemical and optical sensors allow precise monitoring of content changes of clinically or environmentally important analytes.[1−3] The pronounced emphasis of the field of ion-selective sensors is on high stability and versatility, allowing application for different analytical scenarios, regardless of operation mode
The potential recorded is linearly dependent on logarithm of the activity of analyte ions and typically covers 5−6 orders of magnitude of analyte concentration
To prepare a dual sensitivity ion-selective membranes (DS-ISM), the POT conducting polymer was added to the poly(vinyl chloride) (PVC) phase
Summary
Ionophore-based electrochemical and optical sensors allow precise monitoring of content changes of clinically or environmentally important analytes.[1−3] The pronounced emphasis of the field of ion-selective sensors is on high stability and versatility, allowing application for different analytical scenarios, regardless of operation mode. Incorporation of the analyte into the DS-ISM results in potentiometric signal formation, similar to that observed for classical systems and heterogeneous ion-selective membranes; e.g.,30,33 optical signal formation requires transformation of POT+ (immobilized in the membrane phase) to emission active POT0, due to influence of cations on redox equilibrium described earlier, Scheme 1 in the Supporting Information.[1,8,9]
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