Aqueous Synthesis Of CdX(X=Te Te/ZnS) Quantum Dots And Their Application In Spectral Analysis

Quantum dots（QDs） have narrow, tunable, symmetric emission spectrum andbroad, continuous excitation spectrum. They are photo-chemically stable and havehigh fluorescence quantum yields, which have been widely used in bio-medicalapplications. In this article, we prepared the QDs in aqueous solution usingthioglycolic acid as stabilizer. Under optimum conditions, we discussed molecularspectroscopy properties of QDs. A novel method for quantitative determination oftrace pefloxacin （PEF） and cetyltrimethylammonium bromide （CTAB） has beendeveloped based on the fluorescence of QDs. And we also found that CdTe QDs couldenhance the chemiluminescence intensity of luminol-potassium ferricyanide system.The main contents and the results of this paper are as following:⑴Chapter one introduced the physical properties of QDs, the luminescencemechanisms of QDs, the synthesis methods of QDs and the application of QDs influorescence and chemiluminescent analysis.⑵In this Chapter we described some strategy for synthesis CdTe and CdTe/ZnSQDs in water with mercaptoacetic acid as stabilizer. The synthesis conditions weresystematically optimized, which included the pH, the reaction time, the Cd/Te ratioand the temperature. The chemical and optical properties of theas-prepared products were investigated by the UV-Vis spectrophotometer,fluorescence spectrophotometer and transmission electron microscope, we found theQDs had good optical properties.⑶The CdTe QDs showed selective response for pefloxacin （PEF）. A novelmethod for determination of PEF has been developed based on quenching of thefluorescence of CdTe QDs by PEF in aqueous solutions. Under the optimizedconditions, the quenched fluorescence intensity of CdTe QDs was linearlyproportional to the concentration of PEF from6.40×10^-5to1.28×10^-3mg/mL withcorrelation coefficient r=0.9917, and the detection limit for PEF was1.30×10^-5mg/mL. The amounts of PEF in pill were determined by the proposed method and theresults agreed with the claimed value. This method has the advantages of highersensitivity and selectivity.⑷A novel method for determination of hexadecyl trimethyl ammoniumbromide （CTAB） has been developed based on sensitizing of the fluorescence ofCdTe/ZnS QDs by CTAB in aqueous solutions. Under the optimized conditions, the fluorescence intensity of CdTe/ZnS QDs was linearly proportional to theconcentration of CTAB from0.1-50μg/mL with correlation coefficient r=0.9966,and the detection limit for CTAB was0.048μg/mL. The proposed method has beenapplied to the determination of CTAB in water samples and the results agreed withthe claimed value.⑸It was found that CdTe QDs could enhance the chemiluminescence intensityof luminol-hydrogen peroxide system. On the basis of enhancement effect, a flowinjection method was developed for the determination of protocatechuic acid. In theoptimum conditions, the linear range was1×10^-78×10^-5g/L and the detection limitwas1.0×10^-8g/L. The method has been successfully applied to the determination ofprotocatechuic acid in samples.