A novel flexible substrate-free NH3 sensing membrane based on PANI covered rGO functionalized fiber

To alleviate the lack of sensors on the Internet of Things (IoT), a novel flexible substrate-free sensing membrane has been put forward, of which the fabrication is simple, low-cost and has potential of large-scale production via a vacuum filtration method. After alkaline hydrolysis, paper fibers were covered with reduced graphene oxide (rGO) and further functionalized with a layer of polyaniline (PANI) by in-situ polymerization. The rGO functionalized fiber (GF) played a competent role as the embedded conductive network, efficiently transferring the charge signal from the surface sensing layer. Eventually, the functionalized fibers were re-filmed under a 0.1 MPa negative pressure by vacuum filtration method. The surface area of the film was about 23.76 cm2 and 1 × 1 cm2 square was cut for the following test. The sensing membrane based on PANI covered rGO functionalized fiber (PGF) has shown superb sensing performance to NH3, with excellent stability, selectivity and sensitivity at room temperature. The linear response range of sensor based on PGF was 25 ppm, the correlation coefficient was 0.9908 and the limit of detection (LOD) was 34 ppb. The response to NH3 was ∼14% while the responses of other testified interfering gases were all below 0.5%. Most importantly, the sensing membrane has exhibited an excellent capability of resisting bending, and maintained the response to 10 ppm NH3 (13.55–14.3%) even after 1200 bends, indicating that the sensor has a bright prospect of future wearable applications.