Highly sensitive surface plasmon resonance based fiber optic pH sensor utilizing rGO-Pani nanocomposite prepared by in situ method

Abstract Reduced graphene oxide-polyaniline (rGO-Pani) nanocomposite based highly sensitive fiber optic pH sensor utilizing SPR technique is fabricated and characterized. The rGO-Pani nanocomposite is successfully synthesized using in-situ method. The sensing probe is fabricated by coating a thin film of silver over the unclad core of the optical fiber which is further coated by a film of rGO-Pani nanocomposite. The preparation of rGO, Pani and rGO-Pani nanocomposite are confirmed using different characterization tools such as X-ray diffraction (XRD), Raman and Fourier-transform infrared spectroscopy (FTIR). The morphology of the rGO-Pani nanocomposite is characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The operating pH sensing range of the present sensor is checked by performing experiments on samples of pH lying from 2.4 to 11.35. The sensor's performance is excellent for low and high pH and it possesses the maximum sensitivity of 75.09 nm/pH at pH 11.35. The high sensitivity of the sensor is because of the change in the optical band gap of the rGO-Pani nanocomposite at the low and high pH values of the samples which is confirmed by using Tau plot. The sensor has many advantages such as compact size, low cost, high sensitivity, stability, repeatability and capability of remote sensing.