Controlled bridge growth of ZnO nanowires on laser-scribed graphene-based devices for NO gas detection

This research proposed a facile low-cost hydrothermal method to control a bridge growth of ZnO nanowires on laser-scribed graphene-based devices applied for NO gas detection. The picosecond laser processing system was used to scribe graphene/glass substrates and to form V-shaped grooves. During the growing process of ZnO nanowires, the surfactant solution of methanol was added into the growth solution to decrease surface tension of V-shaped grooves. Hence, the grown ZnO nanowires could increase their contact area from both sides of the groove edge. The experimental results showed that the V-shaped grooves of graphene/glass substrates were obtained by using optimal laser processing parameters including the pulse repetition rate of 300 kHz, scanning speed of 100 mm/s, laser fluence of 1.81 J/cm², and number of scribed passes of 3 times. Then, the ZnO nanowires were grown via the immersed processes of the seed layer solution for 80 min and the growth solution with surfactant solution for 8 h. Consequently, the ZnO nanowires had a lowest electrical resistance of 453 Ω. Moreover, the sensitivities of gas sensors were approximately 14.7%, 21.2%, and 40.2% when the ZnO nanowires were exposed to 50 ppm, 150 ppm, and 300 ppm NO gas, respectively.