In order to determine the optimal condition for the fabrication of find more sensing devices based on assembled rGO, the response of different sensing devices fabricated under different assembly concentration of GO selleck chemical solution were studied, and the exposure time of 12 min was defined here as the effective response time [29]. From Figure  7c,d, we can observe that the resistance of the devices increases significantly

when NH3 was introduced into the chamber. As the assembly concentration of GO solution decreases, the response of the resultant Hy-rGO-based sensors increased from 1.6% to 5.3%, suggesting that fewer rGO sheets bridged in between the gaps of electrodes benefited for the final sensing performance of the sensing devices. Two main reasons may account for the decrease of sensing performance as the increase of GO concentration: (1) the large size of graphene sheets, which is different from the sheets reported before; the interconnecting point is much less and not good for the penetration of gas molecules, which causes the little variation of the resistance of the interior sheets; (2) the stacking structure of the graphene sheets with a dense structure can prevent the gas molecules from rapidly penetrating into the inner space of the films, GW3965 ic50 which is different from the situation of graphene films with

the porous or three-dimensional structure. This was also the case for Py-rGO-based sensors. When the assembly concentrations of GO solution was high (1 mg/mL), much more Py-rGO sheets were deposited on the surfaces of Au electrodes; as a result, it is hard for NH3 gas to penetrate into the rGO flakes and the complete interaction between NH3 and rGO sheets could not be ensured. Hence, a lower response value of 9.8% was obtained. When the assembly concentration of GO solution decreased to 0.5 mg/mL, the response of the resultant Py-rGO device increased to 14.2%, which was much higher than that of Py-rGO device fabricated with GO concentration at 1 mg/mL. However,

further decrease of GO concentration did not increase the response of the resultant rGO sensing device. Instead, a much lower response N-acetylglucosamine-1-phosphate transferase value of 5.5% was obtained. This might be due to the crack of rGO sheets as mentioned above. The majority of rGO sheets were cracked between the electrode gaps, resulting in a rapid change of resistance of the resultant device and consequently leading to a lower response value. Most importantly, it was noticed that all of the responses of Py-rGO devices were higher than those of sensing devices based on Hy-rGO (as shown in Figure  7c,d), suggesting that Py-rGO-based sensing devices could be used as better sensors for the detection of NH3 gas. Since 0.5 mg/mL was the optimal parameter for the fabrication of the Py-rGO sensors, which exhibited the best sensing performance during the NH3 detection, further studies would focus on Py-rGO device fabricated under assembly concentration of GO solution at 0.