Study The Interaction Between CdTe Quantum Dots And Inorganic Micromolecule And Biomolecule Using Optical Spectroscop

The optical properties of CdTe QDs was closely interrelated with their surface states, the physical or chemical process of QDs with analytes could influence the surface states of QDs and caused the change of fluorescence intensity of QDs. We could analysis the mass and properties of some substances based on the fluorescence quenching and fluorescence enhancement extent of QDs which was affected by the substance. This experiment, glutathione (GSH)-capped CdTe quantum dots (QDs) were synthesized in aqueous solution, the shapes and sizes of the particles were determined by SEM. The interaction of CdTe QDs with amino acids、dye molecules-nucleic acid、Mn2+-histidine were studied at molecular level by Fluorescence spectrum(FL), Ultraviolet-Visible (UV-vis) absorption spectra and resonance Rayleigh scattering (RRS) spectra. The interaction mechanism was discussed and corresponding model of interaction were built. As CdTe QDs for fluorescent probe, we built a new methold for selective determination L-glutamic acid、L-Aapartic acid and L-Cysteine acid in the twenty kinds of amino acids, and a new methold basing on fluorescence reversible control, selective determination histidine and calf thymus DNA was bult. Main investigated systems are listed as follow:1. Study on the interaction between CdTe QDs and three kinds of amino acids by fluorescence, RRS and ultraviolet-visible absorption spectraGlutathione (GSH)-capped CdTe quantum dots (QDs) with the diameter of2-3nm were synthesized in aqueous solution. In pH5.4BR buffer medium, only L-glutamic acid (L-Glu)、L-Aapartic acid (L-Asp) and L-Cysteine acid (L-Cys) which isoelectric point(pl) under5.4in twenty kinds of amino acids could quench of the fluorescence of QDs, at the same time, the RRS remarkable enhancement of the system. From the change of absorption spectra and fluorescence measurement was affected by temperature and ion concentration, we can judge that in pH5.4BR buffer medium, amino acid molecule and QDs formed ground state complex via electrostatic attraction, which result in the remarkable quencher fluorescence of QDs and the remarkable enhancement of RRS of the system. The fluorescence and RRS intensity change of systems aroused by the addition amino acids were proportional to the amino acids concentration in a certain range. The sensitivity of fluorescence method was higher (the detection limit for L-Glu was0.011ng. mL-1、0.016ng. mL-1、L-Asp was0.0099ng. mL-1), so a new sensitive fluorescence method for the selectivity determination of L-Glu、L-Asp、L-Cys was established by using QDs as a probe. In addition, take L-Glue for example, the optimum conditions of the reaction and the influences of coexisting substances were tested by FL method, which could be satisfactorily applied to the determination of L-Glue residues in urine samples and in human serum. This mothed not only can use for the selectivity determination of L-Glu、L-Asp、L-Cys, but also for the simple and quick determination other amino acids provided the potential by adjusting the pH values of the system.2. Study on the Interaction between CdTe Quantum dot-Acridine Orange-Calf Thymus DNA by Fluorescence Reversible ControlGlutathione (GSH)-capped CdTe quantum dots (QDs) were synthesized in aqueous solution. In pH7.4Tris-HCl buffer medium, acridine orange (AO) was adsorption to the surfaces of QDs via electrostatic attraction and formed ground state complex, which result in the quench of the fluorescence of QDs. Adding ctDNA to QDs-AO system leaded to the fluorescence intensity of QDs recover, which can be explained by that the addition of ctDNA to the system induced AO to dissociate from the surface of QDs and embed into its double helix structure. According to the fluorescence quencher and restoration for QDs, fluorescence reversible control of QDs was realized. The fluorescence intensity change of QDs-AO system aroused by the addition of ctDNA was proportional to the ctDNA concentration in a certain range, and its detection limit was0.13ng-mL-1. Based on it, the simple, rapid, accurate and sensitive methods had been proposed to determine ctDNA. The interaction of QDs-AO-ctDNA was studied by RRS, absorption spectra and image of atomic force microscopy. The interaction mechanism was discussed and corresponding model of interaction was built.3. A sensitive sensor for Mn2+and histidine based on CdTe QDs fluorescence reversible controlGlutathione (GSH)-capped CdTe quantum dots (QDs) were synthesized in aqueous solution. The photoluminescence of QDs can be effectively quenched by Mn2+due to the binding of Mn2+to the GSH which on the surface of QDs and the electron transfer from the photoexcited QDs to Mn2+. Adding histidine (His) to QDs-Mn2+system leaded to the fluorescence intensity of QDs recover, which can be explained by that the addition of His to the system induced Mn2+to dissociate from the surface of QDs and formed more stable complex with QDs. The fluorescence intensity change of QDs aroused by the addition of Mn2+was proportional to the Mn2+concentration in a certain range, and the fluorescence intensity change of QDs-Mn2+system aroused by the addition of His was proportional to the His concentration in a certain range, based on it, the simple and sensitive methods had been proposed to determine Mn2+and His. This mothed could selectivity recognize His in20kinds of amino acid. The detection limits of FL for Mn2+was0.20μg-mL-1, for His was0.21ng-mL-1, The developed sensor was applied to the determination of histidine in human urine samples with recoveries from99.9%to102.0%. The interaction of QDs-Mn2+-His was studied by RRS and absorption spectra. The interaction mechanism was discussed and corresponding model of interaction was built.