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The influence of graphite grinding time on the formation of carbon nanotubes (CNTs), is investigated. Graphite with different grinding time is used for the growth of CNTs by a cost-effective method using a microwave oven. The samples produced using the different grinding time contain nanotubes with an average diameter in the range 31–50 nm as observed by field emission scanning electron microscopy (FESEM). The lowest intensity ratio of D and G bands (ID/IG) and full width at half maximum of G as identified by Raman spectroscopy for grinding time 20 minute indicates the improved crystallinity of CNTs.

In this study, an inexpensive simple method for the fabrication of efficient hydrogen (H 2 ) gas sensor based on carbon nanotubes (CNTs) was presented. The CNTs were synthesized using microwave oven and deposited onto SiO 2 substrate by a dielectrophoretic method. The as-grown CNTs showed an n-type behavior because CNTs possess the characters of both metallic and semiconductor when placed between the two electrodes, meanwhile, the current was directed mostly by metallic tubes. Upon exposure to H 2 gas at room temperature, the CNTs exhibited high sensitivity up to 315% at 140 ppm H 2 , and relatively good sensitivity of 40% at a very low H 2 gas concentration of 20 ppm. To the best of our knowledge, this is the first work involving the fabrication of CNTs for detecting a low H 2 gas concentration of 20 ppm at RT with high sensitivity comparing with other previous studies.