Iodide (I − ) is an essential micronutrient for thyroid function. Hence, rapid and portable sensing is important for I − quantification in food and biological samples. Herein, we report the first example of a halogen bonding (XB) tripodal ionophore (XB1) which is selective for the I − anion. NMR binding studies of XB1 and its H-triazole analog HB2 with I − demonstrated the dominant influence of XB interactions between the ionophore and the I − analyte. The phase boundary model was applied to formulate iodideselective electrodes with the ionophore XB1. The optimal electrode exhibited a near-Nernstian response of −51.9 mV per decade within a large dynamic range (10 −1 to 10 −6 M) and notably anti-Hofmeister selectivity for I − over thiocyanate (SCN − ), enabling the in situ determination of I − in complex samples. This work establishes XB as a viable supramolecular interaction in the potentiometric sensing of anions.
Poly(3,−polyethylene glycol (PEDOT:PEG) is a conductive material adopted in bioelectronics due to its biocompatibility and stability. While PEDOT has established its utility in cationic solid-contact ion-selective electrodes (sc-ISEs), its anionic counterpart remains less explored. Herein, we report the first example of PEDOT:PEG as a solution-printable solid-contact for all-solid-state nitrate-selective electrodes and a simple ion exchange treatment which can significantly enhance nitrate selectivity. Electrochemical impedance spectroscopy revealed that the sc-ISEs with perchlorate (ClO 4 − )-doped PEDOT:PEG suffered a large overall resistance. Removal of the ClO 4 − dopant via ion exchange reduced the resistance, resulting in significant improvement in sc-ISE performance. The optimal sc-ISE exhibited near-Nernstian response (−55.8 mV/ decade) across a wide dynamic range (0.1 M to 1.12 μM) and excellent Hofmeister selectivity, which was maintained after prolonged continuous usage. This simple drop-cast and ion-exchange protocol is amenable to the scalable preparation of flexible anion sc-ISEs.
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