We present a novel superstructure fiber Bragg grating fiber end sensor capable of detecting variations in refractive index (RI) of liquids and potentially that of gases, and demonstrated an application in the detection of heavy metal ions in water. The sensor is capable of sensing RI variations in. This tracker monitors the Horizon Europe's financial contribution to the clean air policy (National Emission Ceiling Directive) aiming to improve ambient air quality and tackle air pollution, to protect the environment and human health. The developed FBG sensors with 1538.