Ultra-Low Hydrogen Peroxide Detection via Synergistic Nernst Potential Effect in Organic Electrochemical Transistors

Summary

Here, we present a protocol for ultra-low detection of hydrogen peroxide based on the synergistic Nernst effect. This protocol covers the fabrication of stacked-layer poly(3,4-ethylenedioxythiophene): bromothymol blue (PEDOT: BTB)/polystyrene sulfonate (PEDOT: PSS), and platinum microelectrode (Pt), as well as the determination of the optimal operating point for the as-constructed H₂O₂ sensor.

Abstract

The organic electrochemical transistor (OECT)-based synergistic Nernst potential—generated via the Pt gate electrode catalyzing hydrogen peroxide (H₂O₂) and the interaction between bromothymol blue (BTB) molecules and hydrogen ions (the by-product of H₂O₂ catalysis)—is leveraged for the ultra-low detection of H₂O₂ down to 1.8 × 10^-12 M, with a broad linear detection range from 10^-11 M to 10^-3 M. The formation of this potential is determined by selecting a source-drain voltage (V_DS) and a gate voltage (V_G) of −0.6 V as the optimal operating points, and by adopting the stacked-layer poly(3,4-ethylenedioxythiophene):bromothymol blue/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:BTB/PEDOT:PSS) as the semiconducting channel material. In addition, relevant verification is provided by characterizing the carrier (de)doping capability of the stacked layers using UV–vis spectroscopy, identifying the optimal operating point via electrochemical measurements, and evaluating the sensing performance of the as-constructed OECT-based H₂O₂ sensor using single-stage constant-voltage scanning. Finally, the OECT-based H₂O₂ sensor is fabricated via a micro-nano manufacturing process, including the preparation of stacked semiconducting layers by spin-coating and the fabrication of microelectrodes via the lift-off process and magnetron sputtering. This methodology can open a broad avenue for the ultra-low detection of analytes through enzyme-catalyzed reactions.

Introduction

Hydrogen peroxide (H₂O₂) is a ubiquitous by-product of numerous enzyme-catalyzed biochemical reactions, including those mediated by lactate oxidase, glutamate oxidase, and glucose oxidase¹. Its pervasive presence in a wide range of physiological and pathological processes^2,3,4 makes it a critical biomolecule for understanding human health and disease states. Therefore, accurate detection of H₂O₂ at ultra-low concentrations is essential for gaining precise insights into bodily conditions, driving significant i....

Protocol

1. Fabrication and characterization of stacked PEDOT: BTB/PEDOT: PSS semiconductor film

1. Sample preparation
   NOTE: When preparing the single-layer PEDOT: PSS, do Step 1.1.1. When preparing the stacked-layer PEDOT: BTB/PEDOT: PSS, perform Step 1.1.2.
   1. Prepare the single-layer PEDOT: PSS via spin-coating.
      1. Filter the commercial PEDOT: PSS solution using a 0.45 μm filter (polyethersulfone PES).
      2. Take 884 μL of filtered PEDOT: PSS, 1 μL of 0.1 wt% dodecylbenzene sulfonic acid (DBSA), 50 μL of 5 wt% ethylene glycol (EG), and 5 μL of 0.5 wt% 3-glycidoxypropyltrimethoxysilane (GOPS)....

Results

This paper initially characterizes the stacked-layer PEDOT: BTB/PEDOT: PSS channel material using SEM, AFM, UV-vis spectroscopy, and electrochemical measurement. SEM and AFM images (Figure 1 and Figure 2) reveal that the 241 nm-thick stacked-layer PEDOT: BTB/PEDOT: PSS exhibits abundant granular structures, in contrast to the relatively smooth surface of the 120 nm-thick single-layer PEDOT: PSS film. The root-mean-square roughness (Rq) values ar.......

Discussion

The success of the protocol relies on three interdependent critical steps, each validated by experimental characterization. Firstly, the fabrication of the stacked-layer channel material (Protocol 1.1) requires precise control over PEDOT: PSS spin-coating (4200 rpm for 60 s, followed by baking at 130 °C) and PEDOT: BTB electrodeposition (where the short-circuited PEDOT: PSS channel serves as the working electrode, with an electric potential ranging from 0 to 1 V at a scan rate of 0.1 V s⁻^.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
10× Phosphate Buffered Saline (PBS)	Lanbolide Trading Co., LTD	P7209	Purity: ≥99%
3,4-ethylenedioxythiophene (EDOT)	Shanghai Aladdin Biochemical Technology Co., Ltd., China	E105649-25g	Purity: ≥99%
3-glycidoxypropyltrimethoxysilane (GOPS)	Shanghai Aladdin Biochemical Technology Co., Ltd., China	G107576	Purity: ≥97%
Developer	Suzhou Yancai Weina Technology Co., Ltd.	AZ 400K
Bromothymol Blue (BTB)	Sinopharm Group Chemical Reagent Co., LTD	B801811-25g	Purity: ≥95%
Deionized water	Shanghai Aladdin Biochemical Technology Co., Ltd., China	W119424	18.2 M cm
Digital microscope	Olympus Corporation of Japan	DSX1000	A cursory observation of the as-prepared OECT's channel
Dodecyl benzene sulfonic acid (DBSA)	Shanghai Aladdin Biochemical Technology Co., Ltd., China	D106550	Purity: ≥90%
Dual potentiostatic electrochemical workstation	Metrohm AG, Switzerland	VIONIC
Dual-port SourceMeter	Tek Technology Co., LTD	Keithley 2636B
Dual-target magnetron sputtering	Shenyang Kejing Automation Equipment Co., LTD	VTC-600-2HD
Ethylene glycol (EG)	Shanghai Aladdin Biochemical Technology Co., Ltd., China	E119700	Purity: ≥99.8%
Hydrogen peroxide (H2O2)	Huize Biochemical Company	EL	Purity: ≥35%
N-methyl1-2-pyrrolidone (NMP)	Sigma-Aldrich (Shanghai) Trading Co., Ltd.	328634	Purity: ≥99.5%
Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS)	Sigma-Aldrich (Shanghai) Trading Co., Ltd.	739332	Purity: ≥99.7%
Polyethylene terephthalate (PET)	Sigma-Aldrich (Shanghai) Trading Co., Ltd.	GF09063581
Potassium nitrate (KNO3)	Sinopharm Group Chemical Reagent Co., LTD	10017218	Purity: ≥99.0%
Photoresist	Suzhou Yancai Micro-Nano Technology Co., LTD	ROL-7133
Scanning Electron Microscope (SEM)	Carl Zeiss Company of Germany	Gemini Sigma 300
Spin coater	Jiangsu Leibo Scientific Instrument Co., LTD	EZ4
Sulfuric acid (H2SO4)	Sinopharm Group Chemical Reagent Co., LTD	10021608	95.0-98.0%
Atomic Force Microscopy (AFM)	Bruker Corporation of the United States	Bruker Dimension Icon
Ultraviolet laser marking machine	Shanghai Cifang Electrical Technology Co., LTD	RD-JW355
Ultraviolet-visible spectrophotometric spectroscopy (UV-vis)	Ocean Insight Company of the United States	OCEAN-HDX-UV-VIS