A Room Temperature Gas Sensor Based on Sulfonated SWCNTs for the Detection of NO and NO₂.

Eusebiu Ionete,Elena Stratulat,Bogdan Monea,Stefan Spiridon

doi:10.3390/s19051116

Abstract

The electrical response of sulfonated single-walled carbon nanotubes (SWCNTs) to NO and NO2, for gas sensing applications, at room temperature, is reported in this work. A specific configuration based on SWCNT deposition between double pair configuration gold electrodes, supported on a substrate, was considered for the sensing device; employed characterization technique where FTIR and SEM. The experimental results showed a p-type response of the sulfonated SWCNTs, with decrease in resistance, under exposure to NO gas (40–200 ppb) and NO2 (40–200 ppb). Also, the sensor responses to successive exposures at NO2 800 ppb together with investigation of long term stability, at 485 ppb for NO, are reported. The reaction mechanism in case of NO and NO2 detection with sulfonated SWCNTs is presented.

Highlights

The need for gas detection as a safety issue has been recognized even since the beginning of the industrial revolution, when well before the emergence of modern electronic sensors, unconventional alternative solutions, less reliable and less accurate, such as birds, have been applied to detect hazardous gases.Nowadays, technology has evolved and extended to various technical solutions for gas sensing, with the market covering an entire series of commercial products
We propose an innovative solution for high-sensitivity detection of NO and NO2, at room temperature, by fabricating a gas sensor with an active substrate based on single-walled carbon nanotubes (SWCNTs) functionalized with concentrated sulfuric acid (H2 SO4 )
Sulfonated SWCNTs were prepared by treatment of pure SWCNT with sulphuric acid (H2 SO4 ), from 60 ◦ C up to elevated temperatures (300 ◦ C)

Summary

Introduction

The need for gas detection as a safety issue has been recognized even since the beginning of the industrial revolution, when well before the emergence of modern electronic sensors, unconventional alternative solutions, less reliable and less accurate, such as birds (e.g., canaries used as a carbon monoxide and methane detector in coal mines, due to their sensitivity to airborne poisons), have been applied to detect hazardous gases.Nowadays, technology has evolved and extended to various technical solutions for gas sensing, with the market covering an entire series of commercial products. The need for gas detection as a safety issue has been recognized even since the beginning of the industrial revolution, when well before the emergence of modern electronic sensors, unconventional alternative solutions, less reliable and less accurate, such as birds (e.g., canaries used as a carbon monoxide and methane detector in coal mines, due to their sensitivity to airborne poisons), have been applied to detect hazardous gases. The most used detection mechanisms include, but are not limited to, electrochemical, catalytic combustion, and recently sensing polymers and semiconductor metal oxides devices [1,2,3,4,5]. With technological progress, need for achieving lower detection thresholds has increased, partly because of the necessity to confirm the purity of gases for special applications, but more importantly due to the growing concern relative to the global warming and its consequences for future generations. Mainly NO and NO2 , together referred to as NOx, are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures, Sensors 2019, 19, 1116; doi:10.3390/s19051116 www.mdpi.com/journal/sensors

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