Detection of ultra-low concentration NO2 in complex environment using epitaxial graphene sensors

TL;DR

This paper demonstrates the development of graphene sensors capable of detecting ultra-low NO2 concentrations in complex environments, with enhanced sensitivity at higher temperatures and insights into the effects of graphene layer number.

Contribution

The study introduces a robust graphene-based NO2 sensor that operates effectively in complex environmental conditions and compares single-layer and bilayer graphene responses.

Findings

Sensor detects NO2 at 10-154 ppb in complex environments.

Higher sensitivity achieved at 150°C, reducing water interference.

Single-layer graphene shows twice the response of bilayer graphene.

Abstract

We demonstrate proof-of-concept graphene sensors for environmental monitoring of ultra-low concentration NO2 in complex environments. Robust detection in a wide range of NO2 concentrations, 10-154 ppb, was achieved, highlighting the great potential for graphene-based NO2 sensors, with applications in environmental pollution monitoring, portable monitors, automotive and mobile sensors for a global real-time monitoring network. The measurements were performed in a complex environment, combining NO2/synthetic air/water vapour, traces of other contaminants and variable temperature in an attempt to fully replicate the environmental conditions of a working sensor. It is shown that the performance of the graphene-based sensor can be affected by co-adsorption of NO2 and water on the surface at low temperatures (<70 C). However, the sensitivity to NO2 increases significantly when the sensor operates at 150 C and the cross-selectivity to water, sulphur dioxide and carbon monoxide is minimized. Additionally, it is demonstrated that single-layer graphene exhibits two times higher carrier concentration response upon exposure to NO2 than bilayer graphene.