Contamination by heavy metal compounds poses a risk to the environment and the human health. Among others, the industrial use of mercury is more and more limited and the corresponding emission limits of mercury are intensified. A rising interest exists on simple analytic procedures capable of detecting low concentrated mercury in aqueous media. Also the interest in mercury online monitoring systems increases. Mercury selectiv, fluorescent chemosensors provide a flexible tool for a broad range of industrial and environmental monitoring demands. This thesis investigates a highly sensitive rhodamine-based mercury chemosensor which is synthesized by a 2-step chemical conversion. The complexation exploits the high affinity of Hg(2+) to sulfur. The chemosensor forms a 1,3,4-oxadiazole and obtains fluorescent properties which are proportional to the mercury concentration in the assay. The product characterization and identification was carried out by thin layer chromatography experiments, UV detection and detection by dip solutions.