Characterization of Screen-Printed Organic Electrochemical Transistors to Detect Cations of Different Sizes

Abstract

A novel screen-printing fabrication method was used to prepare organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) doped with polysterene sulfonate (PEDOT:PSS). Initially, three types of these screen-printed OECTs with a different channel and gate areas ratio were compared in terms of output characteristics, transfer characteristics, and current modulation in a phosphate buffered saline (PBS) solution. Results confirm that transistors with a gate electrode larger than the channel exhibit higher modulation. OECTs with this geometry were therefore chosen to investigate their ion-sensitive properties in aqueous solutions of cations of different sizes (sodium and rhodamine B). The effect of the gate electrode was additionally studied by comparing these all-PEDOT:PSS transistors with OECTs with the same geometry but with a non-polarizable metal gate (Ag). The operation of the all-PEDOT:PSS OECTs yields a response that is not dependent on a Na+ or rhodamine concentration. The weak modulation of these transistors can be explained assuming that PEDOT:PSS behaves like a supercapacitor. In contrast, the operation of Ag-Gate OECTs yields a response that is dependent on ion concentration due to the redox reaction taking place at the gate electrode with Cl− counter-ions. This indicates that, for cation detection, the response is maximized in OECTs with non-polarizable gate electrodes.

Membrane‐Free Detection of Metal Cations with an Organic Electrochemical Transistor

“…A few other studies, using conventional electrode materials at the gate, reported the selectivity of the OECT to the cation size and charge, but not the type. [15,31,44] Here, we use a gate electrode containing crown ethers that capture target cations and generating a current specific to the concentration of these cations (Figure 2a). Figure 4c shows that under the same operation conditions, the gate current (IG) of a PEDOT-gated OECT was significantly lower than that of the device gated by the Na + -selective CP due to the Faradaic processes of the latter.…”

An overview of sensors and sensing materials for heavy metals in aqueous environments

“…This is especially the case for electrode‐based sensors where anions in solution can interact with the electrode. For example, Contact‐Rodrigo et al [ 80 ] found that if a silver gate electrode were used, the Cl − and Ag would react through a redox reaction, resulting in no potential drop at the gate‐electrolyte interface. In addition, it has been shown that the addition of I − , along with a non‐ionic surfactant can remove Cd +2 from contaminated soil.…”

“…Sensing materials which have smaller pores or more restricted sensing sites due to steric interference can be used to reduce the ability of larger sized cations to bind to a sensing material. [12,80] This in turn can be used to increase the sensitivity of a sensing material to smaller cations.…”

Organic Electrochemical Transistors (OECTs) Toward Flexible and Wearable Bioelectronics

“…The first organic conductive material, polyaniline, was described in 1862 by Henry Letheby [ 27 ]. Almost a century passed by until this research field gained the general interest of the scientific community, and it was only from 1970 onward that efforts focused on the development of organic electronics thanks to novel polymers similar to polyaniline [ 28 , 29 ].…”