From Figure  7a, the resistances of Hy-rGO-based sensors could be calculated to be 12.3, 14.5, and 89.3 KΩ, respectively, when the assembly concentrations of GO were 1, 0.5, and 0.25 mg/mL. When the concentration was above 0.5 mg/mL, the resistances Batimastat order of the sensing devices had little changes. However, when the assembly concentration of GO solution decreased to 0.25 mg/mL, the resistance of the resultant device increased greatly. This might be due to the crack of the rGO sheets

during the reduction process, which inevitably destroyed the electrical circuit of the device. Similar situations occurred for Py-rGO devices, as shown in Figure  7b, the resistances of the devices were 13.5 and 28.2 KΩ respectively when the assembly concentrations of GO solution were 1 and 0.5 mg/mL. Further decrease of GO concentration to 0.25 mg/mL resulted in rapid increase of resistance of the resultant Py-rGO device (8.3 MΩ). This value was much higher than the resistances of Hy-rGO-based devices. This might be ascribed to the following two reasons: (1) hydrazine was a stronger reducing agent during the reduction process, and as a result, the resistances of the resultant Hy-rGO devices were generally lower than those of Py-rGO devices, and this was also in agreement with the results as shown in Figure  7a,b; (2) much more cracks existed during Selleckchem AG-120 the reduction

process when pyrrole was used as a reducing agent. This could be proved by the SEM images as shown in Figure  5e,f; comparing with Hy-rGO devices (as shown in Figure  4e, f), much more cracks appeared, which had great effects on the final resistances of the resultant rGO devices. Figure 7 The comparison of sensing properties of devices based on assembled rGO sheets. I-V curves of sensing devices based on Hy-rGO (a) and Py-rGO (b) fabricated with GO assembly concentration

at 1, 0.5, and 0.25 mg/mL. Plot of normalized resistance change versus time for the sensing devices based on Hy-rGO (c) and Py-rGO (d) fabricated with GO assembly concentration at 1, 0.5, and 0.25 mg/mL (the concentration of NH3 gas is 50 ppm). NH3, a toxic gas, is very harmful to human health [47], and it is import to develop ammonia gas sensors and monitor for NH3 leaks. Carnitine palmitoyltransferase II Hence, we used NH3 here as analyte in order to probe the sensing properties of the resultant Hy-rGO- and Py-rGO-based sensors. All of the sensors based on Hy-rGO and Py-rGO, which were fabricated with different assembly concentrations of GO solution, were tested toward 50 ppm NH3 GDC-0068 balanced in synthetic air. The sensor response (R) toward NH3 gas was calculated according to the following equation: (2) where R 0 is the resistance of rGO device before the exposure to NH3 gas, and R gas is the resistance of rGO device in the NH3/air mixed gas [29].