The Design, Synthesis And Sensing Properties Studies Of The Novel Cadmium Fluorescent Sensors

Fluorescent chemosensor has received considerable attention due to its high selectivity, sensitivity, simplicity and low cost. Many have been designed for detecting various metal ions. Cadimum poses detrimental effects on the environment and human health, and few fluorescent sensors for Cd²⁺ have been reported. As a result, novel fluorescence chemosensors for the detection of cadmium were exploited and their photophysical properties and sensing for cadmium were investigated in this thesis. Several interesting results were obtained.1. A novel fluorescent chemosensor TM1, a difluoroboron dibenzoyl fluorophore with an amide-containing receptor, has been designed, synthesized and fully characterized. TM1 displays high selectivity and sensitivity toward Cd²⁺ ion with the fluorescence intensity enhancing about eight times. Meanwhile, other relevant metal ions have little or no effect on the detection. The binding ratio between Cd²⁺ ion and TM1 is 1:1, and the fluorescence enhancement in the prescence of Cd²⁺ is due to t remove the photoinduced electron transfer (PET) process.2. By introducing the group of–N (CH₃)₂ in TM1, TM2 has been designed, synthesized and characterized. TM2 displays low selectivity and sensitivity toward Cd²⁺ ion with the fluorescence intensity enhancing a little. Moreover, the presence of other metal ions can interference with the detection. The emission of TM2 displays a red-shift as we expected but could not be used of sensing Cd²⁺ ion.3. To improve the water-solubility, TM3 has been designed, synthesized and characterized by introducing the OCH₂CH₂OCH₃ group. Similarly, it shows high selectivity and sensitivity toward Cd²⁺ ion with the fluorescence intensity enhancing about five fold. The advantages of TM3 , such as the high quantum yield of Cd-TM3, the ability of binding Cd²⁺ ion and the lowest detection concentration, were also observed. Moreover, other metal ions show limited fluorescence enhancement or no response, even quenching the fluorescence. The binding ratio between Cd²⁺ ion and TM3 is 1:1, and the fluorescence enhancement in the prescence of Cd²⁺ is due to the coordination of Cd²⁺ with amino group to remove the photoinduced electron transfer (PET) process.