Åbo Akademi University , Johan Gadolin Process Chemistry Centre, Faculty of Science and Engineering, Laboratory of Analytical Chemistry, Biskopsgatan 8, FIN-20500 Turku/Åbo, Finland.
Department of Inorganic and Analytical Chemistry, MTA-BME "Lendület" Chemical Nanosensors Research Group, Budapest University of Technology and Economics , Szt. Gellért tér 4, 1111 Budapest, Hungary.
Anal Chem. 2017 Feb 21;89(4):2598-2605. doi: 10.1021/acs.analchem.6b04885. Epub 2017 Feb 9.
Electrically conducting polymers (ECPs) are one of the most popular types of materials to interface ion-selective membranes (ISMs) with electron-conducting substrates to construct solid-contact ion-selective electrodes (SCISEs). For optimal ion-to-electron transduction and potential stability, the p-doped ECPs with low oxidation potentials such as PPy need to be generally in their conducting form along with providing a sufficiently hydrophobic interface to counteract the aqueous layer formation. The first criterion requires that the ECPs are in their oxidized state, but the high charge density of this state is detrimental for the prevention of the aqueous layer formation. We offer here a solution to this paradox by implementing a highly hydrophobic perfluorinated anion (perfluorooctanesulfonate, PFOS) as doping ion by which the oxidized form of the ECP becomes hydrophobic. The proof of concept is shown by using polypyrrole (PPy) films doped with PFOS (PPy-PFOS) as the solid contact in K-selective SCISEs (K-SCISE). Prior to applying the plasticized poly(vinyl chloride) ISM, the oxidation state of the electrodeposited PPy-PFOS was adjusted by polarization to the known open-circuit potential of the solid contact in 0.1 M KCl. We show that the prepolarization results in a hydrophobic PPy-PFOS film with a water contact angle of 97 ± 5°, which effectively prevents the aqueous layer formation under the ISM. Under optimal conditions the K-SCISEs had a very low standard deviation of E of only 501.0 ± 0.7 mV that is the best E reproducibility reported for ECP-based SCISEs.
导电聚合物 (ECPs) 是将离子选择性膜 (ISM) 与电子导电基底相连接以构建固态接触离子选择性电极 (SCISE) 的最受欢迎的材料类型之一。为了实现最佳的离子-电子转换和电位稳定性，需要将具有低氧化电位的 p 型掺杂 ECP（如 PPy）保持在其导电形式，同时提供足够的疏水性界面以抵消水层的形成。第一个标准要求 ECP 处于氧化态，但这种状态的高电荷密度不利于防止水层的形成。我们通过引入高疏水性全氟阴离子（全氟辛烷磺酸，PFOS）作为掺杂离子来解决这一矛盾，使 ECP 的氧化形式变得疏水。这一概念的验证是通过使用掺杂 PFOS 的聚吡咯 (PPy) 薄膜（PPy-PFOS）作为 K 选择性 SCISE（K-SCISE）的固态接触来实现的。在施加增塑聚氯乙烯 ISM 之前，通过极化将电沉积的 PPy-PFOS 的氧化态调整到已知的 0.1 M KCl 中固态接触的开路电位。我们表明，预极化导致 PPy-PFOS 薄膜具有 97 ± 5°的水接触角，有效地防止了 ISM 下的水层形成。在最佳条件下，K-SCISE 的 E 值标准偏差非常低，仅为 501.0 ± 0.7 mV，这是基于 ECP 的 SCISE 报告的最佳 E 重现性。
