| Nanocrystals have attracted a great deal of attention due to their fundamental size-andshape-dependent optical, magnetic, dielectric, and other unique properties, along with theirmany important technological applications in light emitting diodes （LED）, fluorescenceprobe,solar cells, and so on. Therefore, the development of new techniques to synthesizedifferent kinds of high quality size-and shape-controlled nanocrystals has been widelystudied in the last two decades.More and more high-quality nanocrystals gradually beensynthesized,However, in order to make nanocrystals have a better applicationperformance,Appropriate surface modification or modification of these nanocrystals isnecessary.the main work in this article is on the surface modification of nanocrystals to makeit water-solublity, And initially explored the application performance of water-solublenanocrystals in the preparation of composite films,as well as in the field of bio-detection.Thefollowing researches were conducted and the main results and conclusions are as follows:1. First, we have prepared high quality water-soluble fluorescent CdSe/ZnS quantumdots （QDs） by a phase transfer method, in which amphiphilic oligomers （polymaleic acidn-hexadecanol alcohol ester, PMAH） was used as surface coating agents. Then, a silica shellwith different thickness was coated on the CdSe/ZnS QDs by a modified St ber procedure. Toform the composite emulsion, different concentration of water-soluble QD-PMAH-SiO2nanoparticles were dispersed in poly（acrylic acid） co-polymer emulsion. TheQD-PMAH-SiO2-polymer composite fluorescent films were then fabricated using thecomposite emulsion with a spin-coating method. We have found that the PL intensity of thecomposite films showed increment with the increase of coating layer number and the concentration of QD-PMAH-SiO2nanoparticles within each film.2. A new method for preparation of ultra-stable aqueous and multi-shells fluorescentCdSe/ZnS QDs by combining two current encapsulation technologies based on silica shellsand amphiphilic polymers was developed. Such CdSe/ZnS QDs with multi-shell protectionwere prepared by various shell encapsulating strategies include preparing aqueousamphiphilic oligomer-CdSe/ZnS QDs, encapsulating aqueous CdSe/ZnS QDs with a silicashell, grafting the silica surface with long-chain hydrocarbons, and retransferring thehydrophobic QDs-SiO2nanoparticles into water with amphiphilic oligomer. The size ofCdSe/ZnS QDs with multi-shell protection could be tuned from11.7to27.3nm. It can bestabilized in a broad range of chemical conditions including strong acidic solutions （pH=1）,thermal treatment at80°C, and high concentrations of salts. Even in swine urine, themulti-shell protecting CdSe/ZnS QDs can still retain their high fluorescence. Eventually, thereliable detection limit for Rac residue by using CdSe/ZnS QDs with multi-shell protection inswine urine is successfully down to0.1ng/mL, which is over30times higher thancommercial Rac-LFIA strips. |
