Synthesis And Application Of Water-soluble Quantum Dots As Fluorescence Sensors For Small Molecules

Quantum dots (QDs) or semiconductor nanocrystals are specific kinds of nanoparticles newly developed in recent years. They are ideal bioconjugated fluorescence dye because of their special optical features such as broader excitation spectrum, narrower emission spectrum, and longer lifetime. Synthesis and application of QDs have generated a tremendous amount of interests in the fields of nanoanalytical chemistry and bioanalytical chemistry. Chapter 1 is the review about synthesis and applications of QDs, and chapter 2-4 are some research works of the author during the study of master's degree.Chapter 1, the review about QDs includes basic knowledge and characters, synthesis and modification route, labeling approach, recent progress and prospect in potential application to life science , especially to analysis application and immunoassay.Chapters 2, CdSe QDs modified with citrate were synthesized directly in aqueous solution. The transmission electron microscopy and optical spectra were adopted to verify this synthesized QDs. Based on the characteristic fluorescence quenching of the CdSe QDs by vitamin B1, a simple rapid sensitive and selective quantification method was proposed for the first time and the reaction mechanism was also discussed here. Under optimum conditions, a linear relationship was observed between 5.00 and 40.0μg mL^-1 with a correlation coefficient of 0.9963 for vitamin B1 and the limit of detection was 70 ng mL^-1. The proposed method was applied to determination vitamin B1 in its medicament samples and obtained successful results.Chapter 3, CdTe QDs stabilized by thioglycolic acid was synthesized directly in aqueous solution. The transmission electron microscopy and optical spectra were adopted to verify this synthesized QDs. Based on the characteristic fluorescence quenching of the CdTe QDs by vitamin B6, a selective quantification method was proposed. Effects of buffer, pH and reaction time on quantification of vitamin B6 were examined and the mechanism of reaction was also discussed. Under optimum conditions, a linear relationship was observed between 33.22 and 445.9μg mL^-1 with a correlation coefficient of 0.9998 for vitamin B6 and the limit of detection was 0.15μg mL^-1. The proposed method was applied to determination vitamin B6 in its medicament sample and obtained successful results.Chapter 4, the CdS and CdSe quantum dots have been obtained directly in aqueous solution using environmentally benign surfactant polyoxyethylene (20) sorbitan monolaurate (Tween-20) as stabilizing agent at room temperature under N₂ protection. The transmission electron microscopy and X-ray diffraction results indicated that these nanocrystals have small size and cubic zinc blende structure. Elucidating interaction between the CdS and CdSe quantum dots and Tween-20 was attempted using fourier transform infrared spectra. Especially, these synthesized quantum dots were modified by chemically denatured bovine serum albumin, thereby efficiently improving chemical stability of them in a wide pH range.