Studies On The Fluorescent Chemosensors For Cd2+Based On Quinoline Amide Ligands

Cadmium is also an extremely toxic and carcinogenic metal. A major exposure source is smoking and through food, but inhalation of cadmium-containing dust is the most dangerous route. Cadmium can be found in electroplated steel, pigments in plastics, electric batteries and so on. A high exposure level of cadmium is associated with increased risks of cardiovascular diseases, cancer mortality, and damage to liver and kidneys.Some money consuming and difficult methods, such as atomic absorption and ICP (inductively coupled plasma) atomic emission spectroscopy, for the detection of toxic ions have been employed to detect cadmium ions. Compared with all of these sophisticated experimental methods, fluorescent chemosensors are often used to detect many ions due to their simplicity and sensitivity, high selectivity and instantaneous response. They could be considered as molecular receptors that convert their fluorescent messages into analytically useful signals upon binding to specific guests. What is more, researchers have been concerned about the development of new fluorescent chemosensors due to their potential for easy detection and quantification of the pollutant species in medical, biological and environmental applications. It has been a significant challenge to develop a Cd2+-selective fluorescent chemosensor that can discriminate Cd2+from Zn2+under physiological conditions as they have very similar chemical properties.The thesis is divided into three parts:1. A brief review of investigation progress of fluorescent chemosensor for cadmium ions was summarized.2. Quinoline-amide type ligands have been designed and synthesized from2-substituted-8-hydroxyquinoline as the central skeleton. In99%water solution, fluorescence spectroscopy, DFT calculations and biological imaging were used to compare the distinctions of two different end groups of the fluorescent chemosensors to identify the nature of the selectivity of cadmium ions. The results determined that the sensor FQDIPA with an end group of an aliphatic amine can recognize Cd2+from other metal ions more selectively and sensitively than FQDPA with that of aromatic amines.3. Quinoline-amide type ligands have been designed and synthesized from 2-substituted-8-hydroxyquinoline as the central skeleton. Then they could be covalently bonded to the surface of the silica to obtain a single-molecular functionalized "nanocontainer" NC-FQDIPA. The hybrid materials were characterized by Fourier transform infrared spectra,29Si NMR Spectra, transmission electron microscope (TEM), and TGA. The results demonstrated that NC-FADIPA can release fluorescence sensor to recognize cadmium ion in water with relatively stronger fluorescence intensity and better selectivity. DFT calculations were used to evaluate the compatibility between the cadmium ion and the ligands that were separated from the surface of the silica. What is more, the experiment of the cell imaging demonstrate the sensitive detection of Cd2+on the membrane of HeLa cells, which indicate the potential applications of this detection in biological systems.