Original Research ARTICLE
Organic electrochemical transistors as versatile analytical potentiometric sensors
- 1University of Bologna, Italy
Potentiometric transduction is an important tool of analytical chemistry to record chemical signals, but some constraints in the miniaturization and low-cost fabrication of the reference electrode are a bottleneck in the realization of more-advanced devices such as wearable and lab-on-a-chip sensors. Here, an organic electrochemical transistor (OECT) has been designed with an alternative architecture that allows to record the potentiometric signals of gate electrodes, which have been chemically modified to obtain Ag/AgnX interfaces (X = Cl-, Br-, I- and S2-), without the use of a reference electrode. When the OECT is immersed in a sample solution, it reaches an equilibrium state, because PEDOT:PSS exchanges charges with the electrolyte until its Fermi level is aligned to the one of Ag/AgnX. The latter is controlled by Xn- concentration in the solution. As a consequence, in this spontaneous process, the conductivity of PEDOT:PSS changes with the electrochemical potential of the modified gate electrode without any external bias. The sensor works by applying only a fixed drain current or drain voltage and thus the OECT sensor operates with just two terminals. It is also demonstrated that, in this configuration, gate potential values extracted from the drain current are in good agreement with the ones measured with respect to a reference electrode being perfectly correlated, (linear slope equal to 1.00 ± 0.03). In the case of the sulfide anion, the OECT performance overcomes the limit represented by the Nernst equation, with a sensitivity of 0.52 V decade-1. The presented results suggest that OECTs could be a viable option to fabricate advanced sensors based on potentiometric transduction.
Keywords: OECT, Potentiometric sensors, chloride, chemical sensors, PEDOT:PSS
Received: 16 Aug 2019;
Accepted: 07 Nov 2019.
Copyright: © 2019 Gualandi, Tessarolo, Mariani, Tonelli, Fraboni and Scavetta. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Dr. Isacco Gualandi, University of Bologna, Bologna, 40126, Emilia-Romagna, Italy, firstname.lastname@example.org
Mx. Erika Scavetta, University of Bologna, Bologna, 40126, Emilia-Romagna, Italy, email@example.com