Gas sensors for CO2 detection based on RGO–PEI films at room temperature

Abstract

In this paper, polyethyleneimine (PEI) and reduced graphene oxide (RGO) were selected as sensing materials for carbon dioxide detection. Two kinds of sensors with different sensitive film structures, i.e., RGO–PEI composite film and RGO–PEI bi-layer film were fabricated by airbrushing the sensitive films on interdigitated electrodes. Response performances of both sensors at room temperature were investigated. Results showed that sensors with bi-layer film exhibited smaller baseline drift and more stable sensing characteristics than the counterparts with composite film. Furthermore, bi-layer film sensors with different quantity of PEI solution deposited were studied. Performances of long-time stability, repeatability, low concentration of detection for carbon dioxide, and measurements of response time and recovery time were investigated. It was found that appropriate weight ratio of RGO and PEI was critical for sensing response. In addition, the sensor with bi-layer film exhibited a better repeatability but had longer response time and recovery time than RGO single-layer sensor, and both of them could detect as low as 20 parts per million carbon dioxide gas. Sensing responses of the prepared sensors to carbon dioxide under dry air or nitrogen were compared. The relevant sensing mechanisms were studied as well.