Typically, evanescent-field optical fiber sensors utilize tapered fiber structure to enhance the evanescent filed interaction with the sensing medium. A nanostructured sensing layer is applied to further enhance the sensitivity of the sensor. This paper investigates the use of tapered fiber sensor coated with graphene oxide (GO) nano-film. Optimization of the GO layer and the tapering parameters were performed and the sensing capability of the device is tested using different concentrations of ethanol. The sensor demonstrates fast response and recovery to aqueous ethanol when interrogated in the visible region using a spectrometer and light source which is 20 seconds and 30 seconds respectively.

In this study, the used of tapered optical fiber tip as sensors coated with reduced Graphene Oxide (rGO) is investigated. The resultant rGO nanocomposites coated on the tapered fiber sensor were characterized by X-ray Diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM). Optimization of the rGO layer and the tapering parameters are found and the sensing capability of the device is tested using different concentrations of ethanol in water. The nanocomposite layer improved the performance of the sensor by demonstrating high sensitivity to aqueous ethanol when interrogated in the visible region using a spectrometer in the optical wavelength range of 500-700 nm. The reflectance response of the rGO coated fiber tip reduced linearly, upon exposure to ethanol concentrations ranging between 20-80 %.

Background: Optical fiber sensors gains popularity as an alternative and a better solution compared to its electronics counterpart. Especially in detecting hazardous materials, optical fiber sensors prove to have many advantages such as miniaturization, remote yet real-time sensing and immune to electromagnetics interference. Methods: In this paper, we used a 40um tapered standard multi-mode fiber coated with gold (Au), palladium (Pd) and mixtures of Au-Pd nano-composites to detect hazardous ethanol in its various concentration in aqueous environment. Interrogation were made possible using UV-VIS light source, and changes in absorbance and intensity were recorded via spectrometer. Results and Conclusion: Ethanol ranging from 20% till 100% were investigated. It was found that the composition of nanomaterial coating on the developed sensors strongly affected the sensing performance. From the experiments carried out, the sensor with a gold palladium nanocomposite layer with a 2: 1 ratio of gold to palladium produced the highest sensitivity, which is 0.74/vol% concentration of Ethanol. The fabricated fiber sensor also exhibits fast response and recovery time of 13 s and 6 s respectively.