Figure 4
From: A room-temperature ultrasonic hydrogen sensor based on a sensitive layer of reduced graphene oxide
Conductivity variation of the sensor towards H2. (a,b) The velocity V of the Rayleigh wave transmitting in the sensor versus the normalized surface conductivity \({\sigma \mathord{\left/ {\vphantom {\sigma {\sigma_m}}} \right. \kern-\nulldelimiterspace} {\sigma_m}}\). It is observed that the Rayleigh wave velocity varies rapidly with the conductivity in a narrow conductivity window, indicating a high conductivity sensitivity. (c,d) Responses of the conductivity of the sensor to 100 ppm H2 mixed in (c) dry argon and (d) argon with a relative humidity of 60%. (e,f) Responses of the conductivity of the sensor to 1000 ppm H2 mixed in (e) dry air and (f) air with a relative humidity of 60%.
