Preparation of citric acid-doped polyaniline fibrous membrane by electrospinning for ammonia sensing

Abstract

Electrospinning is one of the simplest techniques for obtaining ultrafine fibers with diameter ranging from nanometer to sub-micrometers. In this study, electrospun mats of citric acid-doped polyaniline (PANi) blended polyvinyl alcohol (PVA) were prepared. Due to electrospinning PANi alone is difficult as limited by its molecular weight and solubility, blending PANi with PVA was employed to assist in fiber formation. The morphology, diameter, and structure of electrospun fibers were investigated by Scanning Electron Microscopy (SEM). The fibers had a diameter ranging from 400 nm to 700 nm. To producing fine fibers, the flow rate at 15 mL/min, the diameter of needle at 0.55 mm, the electric potential at 15 kV and distance between the needle and the collection screen at 25 cm were used. The electrospun fibers were regular, straight and uniform. These electrospun mats were then studied for ammonia gas sensing. The decrease of their resistance was observed when exposed to ammonia gas. Additionally, the ammonia sensing of this electrospun mat was reversible. The response time and recovery time were 5 and 10 minutes, respectively. The responses of repeated sensing of ammonia gas were reproducible up to 12 cycles. In the presence of 1 to 100 ppm of ammonia gas, the changes of resistance were well related to the concentration of ammonia gas. In comparison to PANi-PVA membrane by casting, the sensing of ammonia using PANi-PVA electrospun mat was better in sensitivity and shorter in response time and recovery time. In addition, the sensing of ammonia gas in real sample was performed. The concentrations of ammonia gas using PANi-PVA electrospun mat were comparable to those using commercial ammonia sensor.