Highly Linear Relationship Between Nanocomposite Film Thickness and Sensitivity in Mercury Ion Plastic Optical Fiber Sensor

This study introduces a novel plastic optical fiber (POF) probe for detecting mercury ions in solution. The sensor is designed to be cost effective and enhance sensing capabilities by applying a layer of nanocomposite film to the end face of the POF. This film is composed of silver nanoparticles (AgNPs) molecularly imprinted with sodium alginate (SA) and embedded in polyvinyl alcohol (PVA). The research reveals a strong correlation between the thickness of the coated film and the sensor’s sensitivity. The results demonstrate that with a film thickness of $5.2~\mu $ m, the probe exhibits a wavelength sensitivity of 303.825 a.u./ppm and a high linearity of 0.955 within the mercury ion concentration range of 0.01–10 ppm. Furthermore, the study discovers a highly linear relationship between film thickness and sensitivity, reaching a value of 0.975. This research is consistent with the development of the United Nations Sustainable Development Goal SDG 3.