Abstract
Highly orientated polypyrrole (PPy)–coated polyacrylonitrile (PAN) (PPy–PAN) nanofiber yarn was prepared with an electrospinning technique and in-situ chemical polymerization. The morphology and chemical structure of PPy–PAN nanofiber yarn was characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR), which indicated that the PPy as the shell layer was homogeneously and uniformly polymerized on the surface of PAN nanofiber. The effects of different concentration of doping acid on the responses of PPy–PAN nanofiber yarn sensor were investigated. The electrical responses of the gas sensor based on the PPy–PAN nanofiber yarn to ammonia were investigated at room temperature. The nanoyarn sensor composed of uniaxially aligned PPy–PAN nanofibers with a one-dimensional structure exhibited a transient response, and the response time was less than 1 s. The excellent sensing properties mentioned above give rise to good potential application prospects in the field of ammonia sensor.
Highlights
Gas sensors have been developed very fast all over the world due to their wide application in various fields such as environmental monitoring, modern industry and agriculture, military affairs, national defense, and even disease diagnosis [1,2,3,4,5,6,7,8,9]
The glass slide (25.4 mm 76.2 mm 0.8 mm) winded the PAN nanofiber yarns was dipped into a beaker containing an aqueous solution of pyrrole (0.04 M), FeCl3 ̈ 6H2O (0.2 M), a different concentration of p-toluenesulfonic acid (p-TSA) (0.004 M, 0.02 M, 0.04 M, and 0.08 M), which had been magnetically stirred for several minutes in advance
The morphologies and structures of coaxial PPy–PAN nanofiber yarns were observed with environment scanning electron microscopy (ESEM, Quanta-250, FEI, Brno, Czech Republic), field emission scanning electron microscopy (FESEM, S-4800, Hitachi, Ltd., Tokyo, Japan), and transmission electron microscopy (TEM, JEM-2100, JEOL Co., Ltd., Tokyo, Japan)
Summary
Gas sensors have been developed very fast all over the world due to their wide application in various fields such as environmental monitoring, modern industry and agriculture, military affairs, national defense, and even disease diagnosis [1,2,3,4,5,6,7,8,9]. The conductivity of the doped PPy is susceptible to the reduction gas When such a sensor material exposed to ammonia (electron-donating molecules), this electron transfer between ammonia molecule and PPy’s positive hole induce a reduction of the sensitive positive charge density, which leads to a decrease in the conductance layer. In the case of the proton transfer phenomenon, ammonia gas molecules react with protons that are acidic, forming ammonium ions These reactions result in the formation of a negative charge on the chain of PPy that can integrate with the cavity and undope the PPy. The ammonium-anion complex can freely diffuse on the surface of the PPy. Reverse process takes place on exposure to air and removing the ammonia gas. For long term usability and repeatability, the materials must be fully dried
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