Self-oscillating chemoelectrical interface of solution-gated ion-sensitive field-effect transistor based on Belousov\u2013Zhabotinsky reaction

Toshiya Sakata,Ryo Yoshida,Kenta Homma,Yusuke Yasuoka,Tsukuru Masuda,Shoichi Nishitani,Shogo Himori,Aya Mizutani Akimoto,Kazuaki Sawada

doi:10.1038/s41598-022-06964-4

Abstract

The Belousov–Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system. However, there are only a few studies on the electrical behavior of pH oscillation induced by the BZ reaction, although numerous studies have been carried out to investigate the mechanisms by which the BZ reaction interacts with redox reactions, which results in potential changes. Needless to say, the electrical characteristic of a self-oscillating polymer gel driven by the BZ reaction has not been clarified. On the other hand, a solution-gated ion-sensitive field-effect transistor (ISFET) has a superior ability to detect ionic charges and includes capacitive membranes on the gate electrode. In this study, we carried out the electrical monitoring of self-oscillation behaviors at the chemoelectrical interface based on the BZ reaction using ISFET sensors, focusing on the pH oscillation and the electrical dynamics of the self-oscillating polymer brush. The pH oscillation induced by the BZ reaction is not only electrically observed using the ISFET sensor, the electrical signals of which results from the interfacial potential between the solution and the gate insulator, but also visualized using a large-scale and high-density ISFET sensor. Moreover, the N-isopropylacrylamide (NIPAAm)-based self-oscillating polymer brush with Ru(bpy)3 as a catalyst clearly shows a periodic electrical response based on the swelling–deswelling behavior caused by the BZ reaction on the gate insulator of the ISFET sensor. Thus, the elucidation of the electrical self-oscillation behaviors induced by the BZ reaction using the ISFET sensor provides a solution to the problems of nonequilibrium chemistry.

Highlights

The Belousov–Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system
Considering the above, we examined the self-oscillating chemoelectrical interface based on the BZ reaction using a solution-gated ion-sensitive field-effect transistor (ISFET) sensor
We demonstrated the electrical monitoring of self-oscillation behaviors at the chemoelectrical interface based on the BZ reaction between the electrolyte solution and the T a2O5 gate insulator of the ISFET sensor

Summary

Introduction

The Belousov–Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system. The N-isopropylacrylamide (NIPAAm)-based self-oscillating polymer brush with Ru(bpy)[3] as a catalyst clearly shows a periodic electrical response based on the swelling–deswelling behavior caused by the BZ reaction on the gate insulator of the ISFET sensor. The gate insulator is often composed of oxide or nitride membranes such as Ta2O5, Al2O3, Si3N4, and S iO2; hydroxyl groups at the oxide or nitride surface in the solution undergo the equilibrium reaction with hydrogen ions through protonation (–OH + H + ⇄ –OH2+) and deprotonation (–OH ⇄ –O− + H +) This is why the change in the surface charge is detected from the change in pH without being mostly affected by other cations in accordance with the principle of the field effect[23,24]. This sensor had the smallest pitch of 2 mm, which resulted in a high spatial resolution

Methods

Results

Conclusion