WO3–graphene–Cu nanocomposites for CO, NO2 and acetone gas sensors

Abstract

The control of indoor air quality and the detection of toxic gases and volatile organic compounds are important tasks for improving life and work conditions, and are highly demanded in a variety of industrial, agricultural and environmental applications. This requires the development of special gas sensing materials with a high sensing response to a variety of gases of a different chemical nature. Herein we report a study on the synthesis, characterization and investigation of the gas sensing properties of WO3 -graphene–Cu composite nanomaterials. The nanomaterials have a closely interconnected defective structure with developed surfaces and are characterized by an enhanced sensing response to CO, NO2 and acetone. The composite nanomaterials with WO3 crystallite sizes of 13–17 nm were synthesized by a modified sol–gel method, where pre-synthesized graphene@Cu nanopowder, obtained by the solution combustion method, was added into an H2WO4 gel before the xerogel formation stage. The graphene@Cu flakes played the role of the centers of WO3 crystallite nucleation, leading to the formation of mutually interconnected crystalline structures. The graphene@Cu composite tends to accumulate on the tungsten oxide surfaces, causing the formation of structural defects, influencing the surface energy state and concentration of free electrons. The concentration of defects decreases with the increase of graphene@Cu from 1 to 4 wt%, which also affects the gas sensing properties of the WO3-graphene@Cu composites. The highest sensing response to CO and acetone of 19.7 and 21.4, respectively, were detected for the composite with 1 wt% of graphene@Cu. The composite with 2 wt.% of graphene@Cu additive showed the highest sensing response to NO2.