Structure dependence of gas sensing responsivity on graphene nanoribbons covered TiO 2 nanotubes, nano-bugles array

Titrating various amount of graphene nanoribbons on titanium dioxide nanotubes (Gr/TNTs) and nano-bugles (Gr/TNBs) with different apertures to form composite nanostructures, and using them as gas sensing layers, have been achieved successfully and confirmed by FESEM observation, Raman spectra comparisons, XRD and FTIR measurements. The Gr/TNBs sensors show higher hydrogen gas response than corresponding Gr/TNTs sensors over the 100–2000 ppm range; this suggests that altering sensing morphology can improve gas sensing capability. A composition effect is found on Gr/TNBs sensors, and this effect is more pronounced with higher graphene concentration. On the other hand, heavier graphene content on Gr/TNTs sensors does not seem to affect their sensing capability much. Also, measuring hydrogen gas sensitivity under fixed gas concentration for 40 V Gr/TNB sensors shows a strong linear correlation between graphene concentration and responsivity. Yet measurement on 40 V Gr/TNTs sensors, at relatively low gas concentration of 100 ppm, shows that increase in graphene content hardly affects their responsivity. Gr/TNTs sensors fabricated with both smaller and larger tubular apertures produce this same result, too. Lastly, gas diffusion interactions between two-dimensional layered graphene structure and various geometries of TiO 2 are fully discussed.