Photoisomerized azo-polyfluorene for carbon nanotube sorting and its influence on NH3/CO gas sensing in composite materials

Ammonia (NH 3 ) and carbon monoxide (CO) are typical toxic gases found in industrial emissions and indoor environments, posing serious threats to human health and ecological stability. Consequently, developing sensitive, highly selective, and multifunctional gas sensors holds significant practical importance. This study constructed sensors based on semiconducting single-walled carbon nanotubes (sc-SWCNTs) through non-covalent coating with azo polymers, focusing on investigating the impact of azo compound cis-trans isomerization on carbon nanotube separation efficiency and gas sensing performance. Results indicate that both isomers exhibit excellent sc-SWCNT separation capability, yielding sc-SWCNTs with purity exceeding 99.9%; sensors fabricated from the two composite materials exhibit significant differences in transient response performance under 35 s exposure conditions. At a 1 ppm NH 3 concentration in air, the trans-PFAAB/sc-SWCNTs and cis-PFAAB/sc-SWCNTs sensors exhibited response values of 12.1% and 3.8%, respectively. When exposed to 1 ppm CO in air, their response values were 6.8% and 4.7%, respectively. This study demonstrates that the trans configuration of azo groups confers greater application advantages in azo polymer/sc-SWCNTs composite sensors, offering novel insights for developing high-performance polymer/semiconducting single-walled carbon nanotube composite sensors.