Polymer sorted and released semiconductive single-walled carbon nanotubes for highly sensitive NH3 vapor detection

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.