▎ 摘　　要

In this work, we have grown ZnO/CuO nanoflowers on graphene printed paper substrates by the hydrothermal method. The hypothesis of the present work is the role of ZnO and CuO composited graphene structures as affordable substrates for room temperature ammonia gas sensor. To fabricate the conductive substrate, the biomass derived graphene has been formulated as conductive ink and printed (20 mu m) on the paper substrate. The optical, structural, and morphological studies confirm the formation of hierarchical nanoflower like ZnO/ CuO@graphene substrate. The chemiresistive gas sensor studies evident that, the ZnO/CuO@graphene substrates have higher sensing performance in the presence of ammonia (4.9%) for the concentration as low as 5 ppm at room temperature. It also shows a quick response and recovery time of 4.1 s and 2 s, respectively. Our present method will be an effective methodology for the fabrication of cost-effective and rapid detection of ammonia gas in the ambient environment and can be also further suitable for non-invasive earlier diagnosis of diseases from exhaled breath.