Study on phenyl series of polymers wrapping of different diameters of semiconducting single-walled carbon nanotubes for ammonia gas sensors

In this study, the fluorene-alt-benzene (PFOB), fluorene-alt-bisbenzene (PFDB), and fluorene-alt-tribenzene (PFTB) were synthesized via Suzuki coupling. The phenyl units in PFDB and PFTB are linked by imine bonds (-CH=N-). These three polymers were employed to selectively sort the semiconducting single-walled carbon nanotubes (sc-SWCNTs) from two types of single-walled carbon nanotubes (SWCNTs) with different tube diameters (Plasma (0.9–1.7 nm) and Hipco (0.8–1.2 nm)). The six polymer/sc-SWCNTs composites were prepared for chemiresistor devices via a simple drop-coasting method for detecting the ammonia vapor. The results indicate that all six devices based on polymer/sc-SWCNTs composites demonstrate excellent sensitivity to ammonia vapor. Additionally, they exhibit a low theoretical detection limit and good reproducibility. The PFTB and PFOB showed higher efficiency of selection of plasma and Hipco, respectively. The corresponding sensors showed a good response to ammonia vapor at 3 ppm (PFTB/sc-SWCNTs (Plasma): 5.8% and PFOB/sc-SWCNTs (Hipco): 5.0%). The results suggest that the specific type of polymer needs to be designed for effectively sort sc-SWCNTs from different SWCNTs. This will enable the fabrication of polymer/sc-SWCNTs composite sensors with better response to ammonia.