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A new fiber Bragg grating (FBG) sensor based on polyaniline (PAni) has been developed for chloroform detection. PAni was synthesized through chemical oxidation method by using equimolar amount of aniline monomer (Ani), dioctyl sodium sulfosuccinate dopant (AOT) at different three polymerization temperatures (−5, 0 and 25 °C). The chemical structure and conducting behavior of PAni were confirmed using Fourier transform infrared (FTIR) spectroscopy, ultraviolet‐visible (UV‐vis) spectroscopy and conductivity measurements. In this study, the FBG sensor was produced by removing the cladding layer and replaced with PAni coating. The immersion of sensor in varying concentration of chloroform (from 10 to 100 ppm) produced different Bragg wavelength shift at ∼1557 nm in the optical spectrum analyzer (OSA). The effect of PAni polymerized at different polymerization temperatures affect the sensor performance. It was found that the FBG sensor coated with PAni polymerized at 0 °C exhibited the highest sensitivity for chloroform detection and good recyclability up to 10 cycles with fast response time of 7 s and recovery time of 8 s. The FTIR, UV‐vis and conductivity analyses supported the proposed mechanism for the interaction between PAni and chloroform being the dipole‐dipole interaction (physical interaction) between the partial negative charge (Clδ−) of chloroform and the partial positive charge (NHδ+) of PAni.

Fiber Bragg Grating (FBG) sensor coated with PAni was designed as a sensing device in chloroform detection. PAni thin film was synthesized through chemical oxidation method by using aniline (Ani) as a monomer, ammonium persulphate (APS) as an initiator and dioctyl sodium sulfosuccinate (AOT) as a dopant. The chemical structure of PAni thin film was confirmed by using Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectrometer. The conducting behaviour of PAni thin film (1.157 × 10−2 S/cm) was determined by using four-point probe measurement. In the optical sensor part, FBG was etched in hydrofluoric acid solution (48% HF) to remove the cladding layer on fiber before coated with PAni. The response of this sensor was monitored based on the different of Bragg wavelength shift at ∼1557 nm in an optical spectrum analyzer (OSA) detector. PAni-coated FBG significantly increased in the Bragg wavelength shift (sensitivity = 0.0009) compared with uncoated FBG (sensitivity = 0.0002). The interaction between PAni and chloroform was significantly confirmed by the “polaron peak ratio” (Pf/Pi) and “quinoid and benzenoid peak ratio” (IQ/ IB) through UV-vis and FTIR spectroscopy analysis. In this study, FBG sensor coated with PAni thin film had been found as an efficient sensor in chloroform detection with fast response time (7 s).