Multi-walled carbon nanotubes/polyaniline on the ethylenediamine modified polyethylene terephthalate fibers for a flexible room temperature ammonia gas sensor with high responses

The flexible room-temperature gas sensors are highly desirable to apply in wearable and portable equipment owing to their wearability. The research mainly focuses on the gas-sensing materials and few studies paid attention to the conjunction between flexible substrates and sensing materials. In this work, the polyethylene terephthalate (PET) fibers substrate is modified by ethylenediamine (EDA) to expose the amino group on the surface (PET-NH₂). This method is simple, cost-efficient, and easy to operate. The positively charged amino group could interact with negatively charged carboxyl (−COOH) of multi-walled carbon nanotubes (MWCNTs) by electrostatic attraction. The EDA treatment on PET effectively strengthens the connection between the flexible PET substrate and gas sensing materials with carboxyl as evidenced by SEM images. After the in situ polymerization process, the polyaniline (PANI) is successfully decorated on the MWCNTs. The fabricated PET-NH₂-MWCNTs/PANI sensor exhibits strongly enhanced ammonia (NH₃) sensing performance as compared to the PET-MWCNTs/PANI sensor without the EDA treatment. The results suggest that the EDA treatment is an effective method to conjunct between flexible substrates and sensing materials, which shows great potential in the field of flexible gas sensors.