Laser surface modification on rGO/ZnO composite materials for NO2 gas sensing

The nanosecond pulsed ultraviolet laser to modify the graphene composite materials (rGO/ZnO) and improve gas sensing response. The electrical resistance decreased from 2.72 × 103 to 1.13 × 103 Ω/square. The XPS results revealed that the ratio of oxygen to carbon atoms decreased from 33.73 to 12.59%. The bonding structure indicated that the ratio of sp2 bonds of carbon atoms increased and that the sp2 bonds replaced the original sp3 bonds, yielding a material structure that is similar to a complete graphene structure. In the NO2 gas sensing experiment, tests were performed with 5 ppm concentration of NO2 standard gas. Compared with the specimens with rGO sensing materials, those with rGO/ZnO sensing materials could detect gas before laser surface modification. In the 5 ppm NO2 gas concentration, the rGO/ZnO sensing material had 4.2% gas response; after laser surface modification, the gas response with increased to 6.2%. Testing results for gas response under various NO2 standard gas concentrations after laser surface modification revealed that the specimen had a gas response of 11.0%, 14.8%, and 23.7% at the NO2 standard gas concentrations of 10, 30, and 50 ppm, respectively.