Abstract

Carbon nanotubes (CNTs) are considered to be ideal channel materials for building highly sensitive gas sensors. However, achieving high purity of semiconductor single-walled carbon nanotubes (sc-SWCNTs) is still a challenging. In this research, fluorene, thiophene (side-chain imine-contained) and different molar ratio (0%, 15%, 33%, 50%, 67%) of pyrimidine contained donor-accepter type conjugated polymers were synthesized in order to separate the sc-SWCNTs from commercially available plasma SWCNTs, and the released sc-SWCNTs were applied to fabricate devices to detect the low concentrations of ammonia vapor. Based on UV characterization, the polymer with a ratio of 50% pyrimidine ring showed excellent selectivity to sc-SWCNTs, and purity of the released sc-SWCNTs reached to 99%. A comparative study of the sensing performance of resistive-type gas sensors based on four SWCNTs for ammonia vapor showed that the released sc-SWCNT-based sensor responds rapidly to ammonia vapor at ambient temperature and exhibits high response and selectivity. At the similar level of 5 ppm ammonia vapor concentration, the sensing response of the released sc-SWCNTs-based sensor (16.7%) was 1.1, 1.7, and 7.9 times higher than those of the polymer@sc-SWCNTs compound, sc-SWCNTs-excess polymer mixture and raw SWCNTs-based devices respectively. The theoretical detection limit of the released sc-SWCNTs-based device reached to 14.9 ppb.

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