NGQDs modified nanoporous TiO2/graphene foam nanocomposite for excellent sensing response to formaldehyde at high relative humidity

Abstract

In the vast majority of early breathing detection, nano-semiconductor gas sensors were widely used due to their high sensing activity and a relatively simple manufacturing process. We developed a simple post-synthetic hydrothermal treatment to fabricate a novel 3-dimensional (3D) structure gas micro-sensor, in which Au modified nanoporous N doped graphene quantum dots (NGQDs)/TiO2 nanospheres were uniformly distributed throughout the graphene foam frameworks. The obtained graphene network-based nanoporous TiO2 gas micro-sensors with a high specific surface area provided a wealth of reaction sites for gas molecular diffusion and improve the response to target gas. The nanocomposites exhibited excellent gas-sensing performance toward ppb-level formaldehyde vapor by contrast gas detection, implying the application prospect in the aspect of breathing detection. More importantly, the graphene foam-based nanocomposites also presented outstanding selectivity and long-term stability. The excellent gas sensing properties were mainly attributed to the combination of NGQDs with TiO2 nanospheres, which indicated that the number of adsorbed oxygen and nano-heterojunction played an important role in enhancing the formaldehyde (HCHO) sensing performance of nanocomposites. Our work has updated a versatile synthesis strategy so that it can be programmed to design a broad series of nanoporous functional composites according to high sensing performance and general adaptability.