Electrochemistry with Ion Transfer Processes at Microhole-Liquid/Gel Interfaces for Sensing Applications

Abstract

There have been extensive efforts made on developing highly sensitive and selective electrochemical sensing technologies for a wide spectrum of environmental, biological and food research applications. In this talk, we will discuss our latest achievements made on creating electrochemical sensing platforms composed of microhole supported-water/gel interfaces (micro-ITIES) for the highly selective and sensitive detection of environmentally toxic and pharmaceutical reagents. A single or an array of microholes fabricated on a thin polymer film (e.g., polyethylene terephthalate) was filled with a hydrophobic polyvinylchloride-nitrophenylocytylether (PVC-NPOE) gel to create microhole-ITIES. For example, a Cu(II) ion selective sensor was designed utilizing the assisted transfer reaction of Cu(II) by a novel Cu(II) selective ionophore, picolinamide-PV in the gel layer [1]. In addition, sodium, potassium and calcium selective sensing platforms incorporating each target selective ionophores in the gel was developed for ion analysis in biological fluids including urine, serum and plasma [2]; the concentration of each ions was determined by measuring the current associated with the transfer of Na+, K+ and Ca2+ across the microhole-ITIES assisted by dibenzo-18-crown-6, valinomycin and ETH-129, respecively. These sensors can also be fabricated on a disposable sensing chip platform for convenient field applications. Last example is the use of microhole-ITIES for developing selective sensing platforms for pharmaceutical drugs such as topotecan [3], doxorubicin, tetracycline, levofloxaxin in biological fluids and stream and river water samples. In order to enhance the sensitivity of the sensors, differential pulse stripping voltammetry was used via holding the transferring potential of each analytes for a certain time to enrich the target ions in the gel layer followed by stripping of the ions from the gel to water phase. Lastly, future aspects of microhole-ITIES for ion sensing applications will be discussed.