Preparation Of The Hierarchical Core-shell Nanostructues And Their Applications

Smart combinations of different nanostructured materials such as QDs, noble metal silica and so on, will exhibit multiple functionalities for applications that are difficult to achieve with single-component nanoparticles.Recently, the kind of nanostructures, the "hierarchical core-shell nanostructures", has attracted more and more attention. In many applications, such as drug delivery systems, cell imaging and catalysts, the hierarchical core-shell nanostructures show considerable advantages.The colloidal nanocrystals, especially, the quantum dots (QDs), have attracted extensive scientific and industrial interests as a consequence of their strong size-dependent properties, unique optical and electronic features, which give rise to their potential use in a variety of fields such as light-emitting devices, biological labels, and nonlinear optical devices so on. At present, as a new kind of nano-materials, people are paying more and more attention to do research on the QDs and applying them to the field of biological fluorescence labeling, as well as the criminal investigation field. In this paper, a hierarchical SiO2-QDs@SiO2(QDs=CdTe, PbTe, PbS) nanostructures, that was the3-10nm QDs covered with a1-2nm SiO2shell were deposited over the surface of the50nm silica nanobead carriers separated, fabricating the resulting hierarchical SiO2-QDs@SiO2nanostructures. The main research content and achievements are as follows:1. Synthesis of hierarchical SiO2-QDs@SiO2nanostructures and their photoluminescence applications for fingerprint detecting and cell imaging.(1) SiO2nanomaterials with good water-solubility and biocompatibility are often chosen as the combination to make various nanocomposite materials such as core-shell nanostructure with the QDs. As a result, we chose SiO2nanomaterials as the bracket combination and QDs as another combination to form the hierarchical SiO2-QDs@SiO2(QDs=CdTe, PbTe, PbS) nanostructures. Meanwhile, a thin layer SiO2covering the QDs was about1-2nm, which not only can protect the Cd2+and Pb2+ions from releasing to the surroundings to obtain the seccure environment atmosphere for the vivo imaging and fingerprints detecting, but also can protect the QDs from being susceptible to external environment such as PH and temperature result making the fluorescence quenching.(2) The free carboxyl (-COOH) group conjugated on the surface of hierarchical SiO2-CdTe@SiO2nanostructures is available for covalent coupling to various biomolecules such as (proteins, peptides, and nucleic acids) by cross-linking to reactive amine (-NH2) groups. In this paper, the hierarchical SiO2-CdTe@SiO2nanostructures modified by-COOH group exhibited excellent application in the bioimaging and fingerprints detecting.2. Hierarchical core-shell Pt@SiO2@Pt@SiO2@TiO2nanostructues and catalytic applications.(1) The hierarchical core-shell Pt@SiO2@Pt@SiO2@TiO2nanoparticles were parepared by a template method. The method contained five steps as follows:(â… ) the core-shell nanostructure of Ag@SiO2nanospheres was prepared and then,(â…¡) the Pt nanoparticles were deposited on the surface of Ag@SiO2nanospheres through a simple reflux reaction process, so the Ag@SiO2@Pt nanoparticles was obtained, and (â…¢) by the hydrolysis of TEOS, a layer of SiO2was covered on the surface of the Ag@SiO2@Pt nanoparticles with to protect Pt nanoparticles, forming the Ag@SiO2@Pt@SiO2nanospheres,(â…£) the Ag@SiO2@Pt@SiO2@TiO2nanoparticles were synthesisd by hydrolysis of TBOT. Lastly, the hierarchical core-shell Pt@SiO2@Pt@SiO2@TiO2nanoparticles were finally prepared through the galvanic replacement reaction.(2) The hierarchical core-shell Pt@SiO2@Pt@SiO2@TiO2nanostructues show excellent catalytic performance as catalyst to catalyze p-nitrophenol while NaBH4as reductant and it is demonstrated that the nanoparicles showed excellent catalytic performance.