Water-soluble Quantum Dot CdX(X=Se ZnS) Synthesis And Its Analytical Application

Quantum dots（QDs）or semiconductor nanocrystals are specific kind ofnanoparticles which have been developed in recent years． They are idealbioconjugated fluorescence dye because of their special optical features such asbroader excitation spectrum, narrower emission spectrum and longerlifetime．Synthesis and application of QDs have generated a tremendous amount ofinterests in the fields of nanoanalytical chemistry and bioanalyticalchemistry．Chapter1is the review about synthesis and applications of QDs，andchapter2-6are research works of the author during the study of master’s degree.1. CdSe QDs were synthesized in aqueous solution using CdCl2, NaHSe asprecursor and mercaptoacetic acid （MAA） as stabilizer. The effect of reaction time,reaction temperature and the molar ratio of Cd:Se were also studied．The synthesizedQDs were characterized by ultraviolet-visible （UV-vis） absorption spectra,fluorescence （FL） spectra and transmission electron microscope （TEM）. The resultsshowed that CdSe QDs were mono-dispersed with average size about2nm. Good FLsignal of CdSe QDs can be observed when the ratio of Cd:Se at2, the temperature at30℃and the reaction time at40min．2. Based on the characteristic fluorescence quenching of the CdSe QDs byVitamin B1，a simple, rapid, sensitive and selective quantification method wasproposed for determination of vitamin B1for the first time. Under optimumconditions, a linear relationship was observed between0.5-60.0μg/mL, with acorrelation coefficient of0.9941and the limit of detection was15ng/mL．Theproposed method was applied to determination vitamin B1in medicament samplesand obtained successful results．3. The CdSe/ZnS composite quantum dots （QDs） that capped with L-cysteinewere synthesized and applied for ultrasensitive Pb²⁺sensing. The fluorescence of theas-obtained CdSe/ZnS QDs was quenched only by Pb²⁺. Under optimal conditions,the response of the optical sensor was linearly proportional to the concentration ofPb²⁺ranging from1.60μg/L to240.0μg/L. The detection limit was0.23μg/L. Arelative standard deviation of0.13%for7replicates of a20μg/L Pb²⁺solution wasobtained. The proposed method has been successfully applied to the detection of Pb2+in water samples.