Apart from the final concentration of the analyte, there are several facts that can be extracted from Figure 10. First, the sensing material always detected acetylene in the working range at room temperature. Although pure CNTs are able to detect C2H2, with a maximum sensitivity of 0.37% for Au-CNT-(A and B), the maximum sensitivity value was close 0.90%. These numbers indicate a relatively high increase in CX-4945 molecular weight the sensitivity to hydrocarbons for the gold-loaded CNTs. No significant differences were found between the dip-coated and the drop-casted samples. Another important fact is that sensitivity rises linearly with the analyte concentration for all samples which can be seen in the graph of Figure 10d. In

this figure, we have plotted the maximum sensitivity as a function of acetylene concentration in parts per million, which is well described by a linear fit to the data. The R values of these fit are very close to 1. Within this linear range, these materials could be used for the determination of an unknown concentration of this particular gas. Additionally, these samples display a rapid response and recovery times to variations in the gas mixture. Figure 10 Sensing response of CNT and Au-CNT samples towards the detection of acetylene (C 2 H 2 ). Response of pure CNTs (a) and response of hybrid Au-CNT samples prepared by dip-coating (b) and drop-casting

(c). Plot of the maximum sensitivity value for each peak as a function of C2H2 concentration (d). The solid lines in d graph are linear

fits to the corresponding data points. Penza et al. have Selleckchem MM-102 studied the sensing properties of CNTs decorated with gold particles [59]. They sputtered thin gold layers over thick CNT films with vacuum-evaporated Au-Cr leads. This report shows Dichloromethane dehalogenase that the substantial improvements in the gas (NO2, NH3, and H2S) sensing properties of CNTs are indeed induced by gold. Their results are consistent with a high sensitivity at 200°C; nevertheless, this material, in most cases, has larger detection and recovery times. In addition, we have performed a similar set of measurements using hydrogen as the analyte gas. The sensitivity (%) plots of H2 vs time for CNTs and Au-CNT hybrid samples are presented in Figure 11. All samples are less sensitive to H2 than acetylene. Pure CNTs display very little sensitivity. In the case of Au-CNT samples, no significant signal was detected for low H2 concentration (5,000 to 10,000 ppm), and the linearity of the signal with concentration is not as good as in the case of C2H2, (Figure 11d). Sadek et al. have electrocrystallized AuNPs on nitrogen-doped CNTs and use them in hydrogen detection [60]. In their sample, platinum metal leads were sputtered directly onto the film to improve the EX527 electrical contacts. The high sensitivity values obtained in this report could be explained as due to the large number of gold clusters interacting with hydrogen molecules and causing charge transfer to the CNT network.