Studies On The Fluorescein Based Fluorescent Chemosensors For Heavy Metal Ions

This dissertation firstly reviewed the research history and recent development of the ion enrolled photo-introduced electron transfer (PET) reaction. And then the paper focused on the application of this kind PET reaction, i.e. the development of chemosensors for metal ions. Currently there is great in interest in the development of fluorescent sensors for quantifying and exploring the role of heavy metal ions in medicine and biology as well as in the environment. Thus, in this dissertation, several kind of fluoresccin based chemosensors for heavy metal ions were designed and synthesized. The selectivity and sensitivity of the new sensors to the target ions were carefully studied.Two novel fluorescent Zn²⁺ chemosensors were designed and synthesized in four steps for inexpensive staring materials. The new sensors exhibited very strong fluorescence responses to Zn²⁺ and had remarkably high selectivity to Zn²⁺ over other metal inos including Mg²⁺, Ca²⁺, Ni²⁺, Cu²⁺, and Cd²⁺. These two new molecules could be used as low-priced yet high quality Zn²⁺ chemsensors.Then, the research interest was shifted to the developing of new chemosensors for the high toxic Hg²⁺. The fluoresccin group was equipped dithia-dioxa-monoaza 15-crown-5 unit, which shows high selectivity to Hg²⁺, to form a water soluble molecular. The test result indicated that the newly designedâ– fluoresecin derivative exhibited high selectivity to Hg²⁺ over other metal ion under physiological conditions. This research indicated that replacement of the oxygen atom in the suitable size crown ether by sulfur atom will lead to great selectivity to Hg²⁺.According to the literature, a high mercury-philic carbamodithioate moiety, which was seldom used as Hg²⁺ receptor, was introduced into fluorescein derivatives. The flowing test result suggested that the new compounds can be used as efficient Hg²⁺ chemosensor in common situations. Based on the about result, the new Hg²⁺ sensors were applied to monitor the Hg²⁺ concentrations in real samples without expensive instruments. Reasonable results were obtained compared with the results from the traditional method, i.e., atom absorption method.