Heavy metal pollution has made a serious threat to the environment and human health day by day due to developing science, technology and industrial activities, therefore, the importance of selective detection of heavy metals has increased. Heavy metals gradually accumulate in the human body, especially via water sources. Among heavy metals, cadmium is one of the most carcinogenic ones and has harmful effects even in trace amounts. Despite it, detection studies of cadmium ion are very few. This thesis study focuses on the development of Initiated Chemical Vapor Deposition (iCVD) synthesized polymer thin film based quantum dot-nitroxide radical fluorescence sensor nanoprobe, which has a multi-use property and high durability, unlike sensor probes developed for single use in liquid media, and selective detection of Cd2+ ions in real water sources. By examining the effects of pH, concentration, solvent type and reaction time, the most suitable conditions to improve the interaction between Cd2+ ion and the newly developed sensor nanoprobe were investigated. The results proved that it is possible to detect the target ion easily even in complex environments where other heavy metal ions are present. Cd2+ ion detection limit with this proposed nanoprobe was found as 0.195 μM and high recovery percentage (>90%) obtained in standard addition method. In the multi-use study, it was confirmed that nanoprobe could be used repeatedly for the selective and sensitive detection of Cd2+ ion without being influenced by the content of daily water samples. This thesis is a great guide for new fluorescent sensor applications.