Functionalized multiwalled carbon nanotubes based hydrogen gas sensor

Carbon nanotubes (CNTs) are extremely sensitive to environmental gases. Detection of H2 gas at room temperature with fast response and recovery time is still a challenge. Here, we report that 0.05% H2 gas at room temperature can be detected using acids functionalized multiwalled carbon nanotubes (F-MWCNTs). F-MWCNTs showed faster response to H2 gas as compared to pristine multiwalled carbon nanotubes (P-MWCNTs). The effect of functionalization on the P-MWCNTs structure and their electrical properties are investigated using different techniques. The calculated crystallite size of the acids treated nanotubes from the Raman spectra is found to decrease to 14.6 nm as compared to 15.2 nm for the pristine. Also, due to attchements of functional groups on the nanotubes, the interplanar size of F-MWCNTs is increased, as identified from high resolution transmission electron microscopy (HR-TEM) and the X-ray diffraction (XRD) analysis. The presence of functional groups at the nanotubes walls after acids treatments is confirmed by fourier transform infrared (FTIR) spectra. Furthermore, the current carrying capacity of F-MWCNTs is found to increase to 35 mA from 49 μA at low sweep voltage. It is also observed that, the recovery time of F-MWCNTs sensor decreases to 100 s for 0.05% of H2 gas as compared to 190 s for the P-MWCNTs.