Preparation, Characterization And Analytical Application Of Cdte Quantum Dots As Fluorescent Probes

Owing to conquering lots of disadvantages of organic fluorescent dyes, QDs is becoming a substitute of organic dyes to be applied in the fields of biolodical analysis, chemical determination and clinic detection because of its many potential applications. However, the key problems such as how to prepare QDs with high fluoresent intensity and good biocompatibility and how to eliminate the toxicity of QDs in their application surrounding, remain to be resolved.A new purification method of QDs was proposed. According to the properties of colloid solution, solvent with smaller polarity was added into the solution of thioglycolic acid-capped CdTe QDs, so that QDs were deposited and separated from the solution. The parameters at the purification process were optimized and discussed. The as purified QDs exhibited good fluorescent properties, and were able to be conjuncted with large biological molecules. The characterizing results of purified QDs indicated that the cell wall of microzyme was well labeled by QDs directly. A good linearity between the fluorescent intensity of QDs purified and the concentration of lysozyme was obtained. The detection limit of 1.7 mg/L was obtained with the RSD of 3.2%(14.0 mg/L, n=11).A new method for synthesizing L-cysteine-capped CdTe QDs was reported for the first time. Compared with other preparing methods, the new method showed following merits:the precursors can be prepared at room temperature (20℃); the synthesis period was shortened to be 0.5 h for green quantum dots, and 5h for red quantum dots; the rang of pH value during the preparation was broaden to be 7.2-9.0; no incubation needed; the wavelength of the fluorescent emission peak was ranged from 480 nm to 650 nm (blue to red). The as prepared QDs were purified by the purification method mentioned above. The universality and significance of the purification methods were proved further by applying the method to L-cysteine-capped CdTe QDs.The experimental results for the condition optimization suggested that the fluorescence of as prepared QDs responded selectively to Cu2+. A good linearity between the fluorescence intensity and the concentration of Cu2+ in the range of 0.4-64.0μg/L was obtained with a correlation coefficient of 0.9993 and the linear regression equation isΔF=4.859+10.713 c. The detection limit, calculated following the 30 IUPAC criteria, of 0.1μg/L was obtained with the RSD of 0.8%(15.9μg/L, n=11). As prepared QDs were used as ion probes for the detection of copper in cucumber. The determination results were in a good agreement with those obtained with the classical graphite furnace-atomic absorpiton spectrometry (GFAAS).