Effects of the Dopant Ratio on Polyaniline Coated Fiber Bragg Grating for pH detection

•This article describes on the synthesis of novel PAni for pH detection.•The use of Fiber Bragg Grating is something novel to be applied in pH detection.•PAni coated on Fiber Bragg Grating shown good recyclability up to 10 times in pH detection with low cost and simple set-up.

Polyaniline (PAni) coated Fiber Bragg Grating (FBG) for pH detection is presented in this study. PAni was synthesized at low temperature through chemical oxidation by using aniline (Ani) as monomer, ammonium persulphate (APS) as oxidant and dioctyl sodium sulfosuccinate (AOT) as dopant. The immersion of PAni-coated FBG in different pH solutions could produce different Bragg wavelength shift (∼1557 nm) in the optical spectrum analyzer (OSA). Fourier transformed infrared (FTIR) spectroscopy, ultraviolet–visible (UV–vis) spectroscopy and conductivity measurements were carried out to investigate the chemical interaction between protonated nitrogen atom of PAni backbone and pH analytes. The sensitivity of PAni-coated FBG was adjusted by changing the ratio of Ani:APS:AOT during the polymerization reaction. PAni-coated FBG with molar ratio of Ani:APS:AOT = 5:5:5 achieved the highest sensitivity with response time of 10 s. Besides, the PAni-coated FBG also showed good recyclability up to 10 times.

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