Flexible and disposable paper-based gas sensor using reduced graphene oxide/chitosan composite

Nitrogen dioxide (NO2) is a representative toxicant in air pollution that mostly arises from the exhaust gas released by automobiles. It is related to various respiratory diseases such as pneumonia and sudden infant death syndrome. Additionally, because the toxicity of nitrogen dioxide is high in overpopulated areas (i.e., a capital or metropolis), the development of simple, practical, and facile sensors is highly needed. This work presents a flexible and disposable paper-based NO2 sensor based on a reduced graphene oxide/chitosan (rGO/CS) composite. The synthesized rGO/CS composite can be easily flexed and deformed into various shapes, which are attributed to chitosan molecules that function as a dispersion and reduction agent and support material. In addition, this composite can be attached to paper owing to its adhesive property; hence it can be utilized in versatile applications in a disposable manner. By analyzing the conductive change of the rGO/CS composite when it reacts with NO2, we can detect nitrogen dioxide in a concentration range of 0–100 ppm with a detection limit of 1 ppm. Moreover, we performed NO2 detection in the exhaust gas released by automobiles using the rGO/CS composite for practical application. The results indicated that the rGO/CS composite has the potential to be used in feasible gas sensing as a facile and disposable sensor under various conditions.