Assembly Of Fluorescent Nanoparticles On Microspheres

Semiconductor nanocrystals are also referred to as Quantum dots (QDs). Compared with organic dyes, QDs have a narrow and tunable emission spectrum, good photostability, chemical stability, and high brightness. The absorption spectra of nanocrystals with different sizes all extend from the onset to deep UV. These spectral features make it possible to carry out multiple labeling with a single-laser setup. QDs prepared by traditional non-aqueous synthesis can't be directly applied in bio-labeling. Compared with the non-aqueous synthesis, aqueous synthesis is much cheaper, less toxic, better water-soluble and bio-compatible. Unfortunately, the conventional aqueous synthesized QDs have much lower QY. Core/shell nanocrystals formed by growing a lattice-matched, higher band gap material on the top of the core have a higher quantum yield. In the thesis, the preparation of water-soluble core/shell CdTe/CdS nanocrystals, as well as bionic assembly of CdTe nanocrystals with polymer were investigated, and some innovative results were abtained. The major contents are as follows:(1) A series of water-soluble core/shell CdTe/CdS nanocrystals were prepared, using MPA as stabilizer, their properties were characterized by means of TEM, UV-visible absorption spectroscopy and fluorescence spectroscopy. The mean size of CdTe/CdS nanocrystals was 10 nm, and it had an absorption perk of excitonic luminescence and a narrow emission perk. With the prolonging of refluxed time, the PL perk position shifted to a longer wavelength, and the fluorescence intensity experienced a process just like a trapezoid.(2) PDDA/PSS/PDDA/CdTe multilayer films were prepared on the PS microspheres through layer-by-layer self-assembly technic, and their properties were characterized by means of UV-visible absorption spectroscopy and fluorescence spectroscopy. Further more, the influence of number of action cycles and different sizes of nanocrystals to the property of films were investigated. As-prepared PDDA/PSS/PDDA/CdTe multilayers had a strong photoluminescence. With the increasing of nanocrystals size, the FL perk position shifted to a longer wavelength. The fluorescence intensity became stronger With the increasing of action cycles.(3) Many kinds of medical ions were added into Qds and Qds films to study the influence and it is found that most of them can decrease the FL intensity except Zn²⁺ especially when the concentration was 1×10^-3mol/L.(4) Goat anti- Rb IgG/FITC and Rabbit IgG were labeled by PS microspheres with Qds films on them by self-assembly technique and the process were validated by the FL spectrums because two emission peaks were observed in the fluorescent emission spectra of the Goat anti- Rb IgG/FITC-microspheres due to FITC and Qds and the FL intensity of Goat anti- Rb IgG/FITC-microspheres- Rabbit IgG changed when Rabbit IgG was added into the mixture.