High performance colorimetric room-temperature NO2 sensing using spin-coated graphene/polyelectrolyte reflecting film.

Abstract

Nitrogen dioxide (NO2) is colorless, flammable and dangerous gas even at very low concentrations. To date, quantitative analysis of NO2 concentrations have been made using conventional techniques (e.g. electrochemical method). In light of the energy and time consuming involved in such applications, efforts have been made to develop new detection methods that are more sensitive and sustainable. At this point, structure color based sensing shows great advantages due to its sensitive, visualized and reproducible response. In this study, graphene oxide/ polystyrene sulfonate (GO/PSS) optical film was designed and prepared to evaluate the potential usage for effective detection of NO2. The uniform GO/PSS thin films was fabricated by spin-coating assisted layer-by-layer assembly method (SA-LbL). The resulting colorful films exhibited ultrafast response, obvious optical shifts and good reversibility within the visible range toward NO2. The concentration-dependent NO2 sensing characteristics and selectivity was investigated as well. Dynamic study showed that absorption/desorption time was 200 / 200 ms and detection limit was 1.0 ppm at room temperature. The sensing mechanism was investigated and verified by computer simulation. Such ultrasensitive and colorimetric properties of GO/PSS film may enable many potential applications such as disposable sensors for health and environmental monitoring.