Concentric-electrode organic electrochemical transistors: case study for selective hydrazine sensing

TL;DR

This study introduces concentric-electrode organic electrochemical transistors (OECTs) for selective hydrazine detection, demonstrating high sensitivity, selectivity, and potential for miniaturized biosensor applications.

Contribution

The paper presents a novel concentric-electrode OECT design with detailed geometry analysis, enhancing understanding of electrochemical sensing mechanisms and improving device performance for hydrazine detection.

Findings

Sensitivity down to 10^-5 M hydrazine in water

Higher selectivity for hydrazine over other analytes

Effective recovery of baseline signal after water flushing

Abstract

We report on hydrazine-sensing organic electrochemical transistors (OECTs) with a design consisting in concentric annular electrodes. The design engineering of these OECTs was motivated by the great potential of using OECT sensing arrays in fields such as bioelectronics. In this work, PEDOT:PSS-based OECTs have been studied as aqueous sensors, specifically sensitive to the lethal hydrazine molecule. These amperometric sensors have many relevant features for the development of hydrazine sensors, such as a sensitivity down to 10-5 M of hydrazine in water, an order of magnitude higher selectivity for hydrazine than for 9 other water soluble common analytes, the capability to recover entirely its base signal after water flushing and a very low voltage operation. The specificity for hydrazine to be sensed by our OECTs is caused by its catalytic oxidation at the gate electrode and enables increasing the output current modulation of the devices. This has permitted the device-geometry study of the whole series of 80 micrometric OECT devices with sub-20-nm PEDOT:PSS layers, channel lengths down to 1um and a specific device geometry of coplanar and concentric electrodes. The numerous geometries unravel new aspects of the OECT mechanisms governing the electrochemical sensing behaviours of the device, more particularly the effect of the contacts which are inherent at the micro-scale. By lowering the device cross-talking, micrometric gate-integrated radial OECTs shall contribute to the diminishing of the readout invasiveness and therefore promotes further the development of OECT biosensors.