Cdse/zns Core/shell Quantum Dots Synthesis And Modification

Quantum dots (QDs) are nanometer-scale semiconductorcrystals composed of groups II–VI or III–V elements, and are defined as particles with physical dimensions smaller than the exciton Bohr radius. The properties of QDs result from quantum-size confinement, which occurs when metal and semiconductor particles are smaller than their exciton Bohr radii (about 1 to 5 nm). QDs have many desirable properties for biological imaging, such as narrow emission spectra(typically 20–30 nm full width at half maximum), allowing excitation by a wide range of wavelengths, high quantum yields, high molar extinction coefficients (1–2 orders of magnitude higher than organic dyes), strong resistance to photobleaching and chemical degradation, continuous absorption spectra spanning UV to near-infrared (NIR:700–900 nm), long fluorescence lifetimes (>10 ns), and large effective Stokes shifts. Therefore, quantum dots have been widely used in biology, material, and optics.Research about Qds synthesis and related modification have been done, including:(1) Synthesis of QDs core Set up a procedure to achieve stable and repeatable QDs. The wavelength covers 520nm to 590nm with narrow FWHM, high quantum yields. TEM, X-ray, fluorescence and ultraviolet absorbing show the microstructure, element constitution, emission peak, Abs, quantum yields and concentration. Factors affect QDs formation have been investigated systematically.(2) Shelling of QDs Two shelling methods, one-pot shelling and two-step shelling, have been carried out. There are obvious changes in size and optical properties after shelling. The shelling factors related help to control.(3) Poplymer modification MePEG-PLA successfully entraps QDs. The fluorescence, stability, diameters and entrapment efficiency all have been obtained. Besides, two factors stongly influence the stability of the complex.(4) Small molecule modification 1, 4-dithiothreitol(DTT) transfers the hydrophobic QDs into hydrophilic Qds. Further, 1, 1'-Carbonyldiimidazole(CDI) prepares the QDs for future coupling.