Construction Of Cdse Quantum Dots "Switch" And Its Application In Pharmaceutical Analysis

Quantum dots (QDs), semiconductor nanocrystals with sizes close to or less than the Bohr radius of an exciton, have uniqueoptical properties and special physical and chemical qualities which attracted wide attention. Quantum dots (QDs), compared with conventional organic fluorescent dyes, have high fluorescence quantum yield, good photochemical stability, fluorescence emission wavelength can be adjusted by changing the particle size or composition, and so on. At the same time, with the increasing maturity of preparation technology, Quantum dots (QDs) in the field of chemical analysis of fluorescently labeled researchand optoelectronic devices have been widely used. This paper was prepared by the high quality of the desired wavelength CdSe quantum dots, and analyzed for drug testing. The main contents are summarized as follows:(1) Using sodium selenite as selenium source and mercaptosuccinic acid (MSA) as stabilizer, high quality CdSe quantum dots (QDs) were conveniently prepared in aqueous solution. The influence of experimental conditions, including refluxing time, cadmium to selenium molar ratio and cadmium to MSA molarratio, on the luminescent properties of the obtained CdSe QDs were systematically investigated. The obtained QDs were characterized by UV-Vis absorption spectrometry, photoluminescence (PL) spectrometry, X-raypowder diffraction (XRD) and transmission electron microscopy (TEM). The results show that the proposedmethod lead to the formation of cubic CdSe QDs with narrow fluorescence full width at half maximum(35 nm), high photoluminescence quantum yield (up to 21%), and a broad emission spectra tunable from 518 to 562 nm.(2) CdSe quantum dots were prepared by the reaction of CdCl2-2.5H2O, Na2SeO3 and NaBH4 in water and in the presence of mercaptosuccinic acid as stabilizer. The fluorescence of quantum dots can be significantly quenched by silver ions. However, in the presence of Tiopronin, silver ions were released from the quantum dots and thus restored the fluorescence of quantum dots. A new type of fluorescence turn-on assay for detectionof Tiopronin using quantum dots/silver ion ensemble is developed. Under the selected conditions, there sponse was linearly proportional to the concentration of Tiopronin between 0.1 to 60 μg·mL-1, the limit of detection was 0.051 μg·mL-1. The developed method was successfully applied to the detection of Tiopronin in real samples with satisfactory results.(3) The fluorescence of quantum dots can be significantly quenched by copper ions. However, in the presence of Penicillamine, copper ions were released from the quantum dots and thus restored the fluorescence of quantum dots. A new type of fluorescence turn-on assay for detection of Penicillamine using quantum dots/copper ion ensemble is developed. Under the selected conditions, there sponse was linearly proportional to the concentration of Penicillamine between 0.1 to 72 μg·mL-1, the limit of detection was 0.031 μg·mL-1. The developed method was successfully applied to the detection of Penicillamine in real samples with satisfactory results.(4) CdSe quantum dots were prepared as described above. The fluorescence of quantum dots can be significantly quenched by copper ions. However, in the presence of Norfloxacin, copper ions were released from the quantum dots and thus restored the fluorescence of quantum dots. A new type of fluorescence turn-on assay for detection of Norfloxacin using quantum dots/copper ion ensemble is developed. Under the selected conditions, there sponse was linearly proportional to the concentration of Norfloxacin between 0.1 to 40 μg·mL-1, the limit of detection was 0.034 μg·mL-1. The developed method was successfully applied to the detection of Norfloxacin in real samples with satisfactory results.