| Water is the source of life, and it is one of the most important indispensable and material resources for human beings to survive and develop on the earth. However, with the progress of industry, the pollution of environment is increasing, especially the pollution of water resources. When the amount of toxic mental ions reaches a certain amount, it can cause chronic poisoning in animals and humans. So looking for a highly efficient and sensitive method to detect heavy metal ions in water is imminent.Traditional detection methods include inductively coupled plasma mass spectrum, organic dyes, etc. They have some disadvantages such as low sensitivity, narrow detection range, tedious operation steps, time-consuming, expensive, etc.Quantum dots were used as fluorescence sensors to detect ions and molecules because of tunable size, good fluorescence stability, broad excitation spectrum, and narrower fluorescence emission spectrum.Sulfur compound semiconductor quantum dots have overcome a lot of shortcomings compared with the traditional organic dyes as a fluorescent probe and have been gradually applied in clinical medicine, environmental monitoring, biological imaging and other fields.In this experiment, glutathione cladding of sulfur compound quantum dots were synthesized by hydrothermal method and the crystal structure, morphology and optical properties were characterized by X-ray diffraction, transmission electron microscopy (TEM), UV-vis spectrophotometer and fluorescence spectrophotometer. The influence of the reflux time, reaction temperature, pH and the concentration on the optical properties of QDs was also studied. And the binding sites of glutathione and its compounds were analyzed by infrared spectrum. Results showed that the sulfur compounds combined with glutathione through sulphur. The research content and conclusions are as follows:(1) The effection of reflux time, reaction temperature and concentration on quantum dots fluorescence was studied. The results showed that quantum dots were with small size, good uniformity, and good crystalline in optimal conditions. Quantum dots were synthesized by hydrothermal with good fluorescence stability and biocompatibility.(2) A fast, sensitive fluorescent sensors was developed. GSH@CdX (X=S, Se, Te) were synthesized as fluorescent probes and was used as fluorescence probes to identify the heavy metal ions in water. The experimental results show that GSH@CdTe QDs has good selectivity with silver ion. However, the GSH@CdSe QDs showed good selectivity with Cu2+.Specific as follows:the fluorescence intensity increase (F-Fo) showed good linear relationship with the concentration of Ag+([Ag+]) in the range of 0.02μM to 0.2μM. The calculated limit of detection of Ag+ was 1.3 nM, which was further lower than the Environmental Protection Agency (EPA) drinking water standard for Ag+(0.1 mg·L-1, ～925 nM). Thus, the GSH@CdTe can be as a novel selective quantificational analysis fluorescence sensor to detect Ag+ rapidly in water solution. GSH@CdSe quantum dots can be used to detect Cu2+ in the environment using fluorescence speetrometry. The fluorescence enhancement of cadmium selenide quantum dots happened with copper ions. So GSH@CdSe quantum dots can be used as fluorescence sensor to detect Cu2+. |
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