| Quantum dots are known as Semiconductor nanocrystals, which is composed of Ⅱ-Ⅳ,Ⅲ-Ⅴ and Ⅳ-Ⅵ race elements. Quantum dots are small nanoparticals with bulk-like crystalline structures that consist of a few hundreds to a few thousands of atoms,with the size range of QDs is 1-100nm. Quantum dots grown in solutions are colloid in nature, the shape of quantum dots can be sepherical with a radius of 1-20nm, and also the shape of cubic, rod-like and tetrapod-like. Compared with the traditional organic dyes, quantum dots shows excellent optical properties, such as narrow and symmetric excitation, broad emission spectra, sizetunable, high quantum yield, stable fluorescence intensity and tunable absorbance wavelength and emission wavelength. Due to the excellent optical properties, quantum dots have got more and more attention from the researchers and been used in many areas in recent years.In this paper, CdTe quantum dots with great fluorescence properties are synthesized and capped with chitosan, and Cu2+ is determined with the two kinds of quantum dots.(1) In the first chapter, CdTe quantum dos are synthesized by the reaction of Na2TeO3 and CdCl2·2.5H2O, and NaBH4 in water with 3-mercaptopropionic(MPA) and citric acid as stabilizers, and discussed the effects of condition of the reaction on quantum dots, such as the pH value of the initial solution, the molar ratio of Cd2+/Te2-, the molar ratio of MPA and citric acid et al are investigated. The condition of reaction is investigated by fluorescence spectra, and fluorescence spectra, UV-Vis absorbance spectra, X-ray diffraction patterns and transmission electron microscopic image show that CdTe quantum dots are with great fluorescence properties, a good crystal structure, monodispersed and stable.(2) Based on the quenching effect of Cu2+ to CdTe quantum dots, set a method using quantum dots as fluorescence probes to detect Cu2+. The reaction conditions are considered in this part, like pH value and the concentration of buffer solution, concentration of quantum dots, reaction time et al. The effects of reaction conditions are discussed. The interference study shows that CdTe quantum dots as fluorescence probes for Cu2+ detection shows a high selection. The study results show the best conditions for Cu2+ detection are:①pH value is 6.6 and the concentration of buffer is 0.01mol/L;②The concentration of quantum dots is 510-9mol/L;③The order of solution addition is QDs-buffer-ions, and reaction time is 30min. The linear range for Cu2+ detection is 0～500 10-9mol/L of Cu2+,the calibration curve shows good linearity with correlation coefficient of 0.9884, the detection limit is 10 10-9mol/L.(3) CdTe quantum dots are capped with chitosan, CS-CdTe quantum dots are synthesized. The conditions of synthesizing are studied. The results show that the best concentration of chitosan is 0.005%(w/v), best reaction temperature is 25℃ and reaction time is 60min. Based the fluorescence quenching effect of Cu2+ to CS-CdTe, set a method using quantum dots as fluorescence probes to detect Cu2+. The reaction conditions are investigated, like pH value, buffer solution, concentration of quantum dots and reaction time et al. The affections of conditions to fluorescence quenching are discussed. The interference study shows CS-CdTe quantum dots as fluorescence probes for Cu2+ detection possessed high selection. The results of the study show that the optimal pH value is 6, the optimal buffer solution is HAc-NaHAc, the best order of solution addition is CS-CdTe-buffer-Cu2+ and optimal volume of quantum dots is 2mL, the detect range is from 0 to 1.75 10-7mol/L, the calibration curve shows good linearity with correlation coefficient of 0.998, the detection limit is 2.1 10-9mol/L... |
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