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Preparation and biological analysis of semiconductor nanomaterials

Author: DingJie
Tutor: TangBo
School: Shandong Normal University
Course: Analytical Chemistry
Keywords: synthesize CdTe nanotube and nanowire Cy-5 CdTe nanoparticle quantum dots FRET DNAzyme
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 253
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Abstract


In recent years, quantum dots have been widely investigated as a class of luminescent material. When their size is comparable to the size of Bohr diameter for exciton, they exhibit special physical and chemical properties which possess the quantum size effects, dielectric confinement effects, surface effects, macroscopic quantum tunneling effect and so on. So the quantum dots with these special optical characteristics applied in the fluorescent biological analytical applications have become a wide research focus. Compared to conventional organic dyes, QDs possess many advantages, such as narrower emission spectra, tunable maximum emission wavelength with changeable sizes and compositions, photostability, high brightness, long fluorescence lifetime and biocompatibility, which have been successfully used as fluorescent probe or sensor in the imaging of biological samples and cells. Following the development on the nanotechnology, sensitive chemical and biology sensor can be designed from nanomaterial. Nanoparticles and biological material compose the nano-biological sensor which can respond to special analyte. One-dimensional (1D) nanomaterials (nanorods, nanobelts, nanotubes and nanowires) have drawn more attention particularly in view of physical and nanoapparatus applications. In the meantime, 1D semiconductor nanomaterials appears different optical properties, which have attracted more interest. The photoemission of CdSe nanorods is highly polarized along the longer axis and surface-modified CdSe/CdS/ZnS core/shell QRs as a biological label can be used in a variety of bioimaging applications. Furthermore, for single molecule fluorescence imaging, they are much brighter than QDs. Recently the syntheses of 1D semiconductor nanomaterial have been widely reported. However, the synthesis of 1D semiconductor nanotube was rarely researched.It is well known that Cyanine is a kind of fluorescence dye which modulated the wavelength of abortion and emission by alter the length of conjugated chain. Cy-5 is the member of the family which has an absorption band centered at 600 nm. The fluorescence resonance energy transfer (FRET) process is highly efficient when there is an appreciable overlap between the emission spectrum of the CdTe QDs donor and the absorption spectrum of the Cy-5 acceptor. Thus,FRET is widely used for the research in molecule structures, properties, reaction mechanism and quantitative analysis. DNA was carried out catalytic functions, and thus became the newest member of the enzyme family after proteins and RNA. Metal ion as cofactor increased the active of DNAzyme. Utilizing the property, appropriate DNA chain by in-vitro selection can be used to direct metal ion.In this study, reviews were given on the application of QDs in multiplexed biological detection, the synthetic methods and the potential biological application of semiconductor materials with hollow nanostructures, and the detection of metal ions by DNAzyme. On the bases of mentioned above, we carried out two aspects of investigation: 1, High aspect ratio CdTe nanostructures were fabricated by hierarchical assembly of nanoparticles at the water–oil interface. The new method overcomes the disadvantages of traditional organic synthesis. In addention, we investigated the effect of several factors, including reaction temperature, reaction time, additional components, and reactant ratio. Finally, optimal synthesis conditions have been chosed in research. 2, A new nanobiosensor QDs-DNAzyme-Cy.5 was assembled for the direct determination of copper ions (Cu2+) based on the fluorescence resonance energy transfer (FRET) between CdTe QDs and Cy.5. The sensing mechanism is based on the switching off FRET through the high specific recognition of DNAzyme to copper ions. In the absence of copper ions, Cy.5 as excellent fluorescent acceptor in CdTe-QDs-DNAzyme-Cy.5 composites. FRET switches off by the factor of copper ions-induced strand breaks in DNAzyme, which restores the fluorescence of the CdTe QDs.

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