Abstract
The development of real‐life applicable ion sensors, in particular those capable of repeat use and long‐term monitoring, remains a formidable challenge. Herein, we demonstrate, in a proof‐of‐concept, the real‐time voltammetric sensing of anions under continuous flow in a 3D‐printed microfluidic system. Electro‐active anion receptive halogen bonding (XB) and hydrogen bonding (HB) ferrocene‐isophthalamide‐(iodo)triazole films were employed as exemplary sensory interfaces. Upon exposure to anions, the cathodic perturbations of the ferrocene redox‐transducer are monitored by repeat square‐wave voltammetry (SWV) cycling and peak fitting of the voltammograms by a custom‐written MATLAB script. This enables the facile and automated data processing of thousands of SW scans and is associated with an over one order‐of‐magnitude improvement in limits of detection. In addition, this improved analysis enables tuning of the measurement parameters such that high temporal resolution can be achieved. More generally, this new flow methodology is extendable to a variety of other analytes, including cations, and presents an important step towards translation of voltammetric ion sensors from laboratory to real‐world applications.
Highlights
We noted that the acidification of the electrolyte with HClO4 significantly alleviated the otherwise significant redox signal loss of the interface upon repeat voltammetric cycling
We have demonstrated the capability of the redox active molecular films 1.XB/HBSAM to reversibly recruit and respond to anions with high levels of signal stability in a standard (“static”) electrochemical set-up
We present the first proof-of-principle example of real-time continuous flow ion sensing at electroactive, receptive molecular films, as illustrated by the sensing of bisulfate, dihydrogen phosphate and chloride at electroactive halogen bonding and hydrogen bonding ferrocenyl anion receptive SAMs
Summary
The binding of anions can be significantly enhanced upon in situ electrochemical generation of an oxidised, cationic receptor state, thereby enabling anion binding, and sensing, in more polar, competitive (and real-world-relevant) solvents.[3, 22]
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