The Synthesis And Characterization Of Multifunctional Magnetic Nanocomposites And Their Application In Biological Detection And Catalytic Reaction

With the progress of nanotechnology and the appearance of new nanomaterials, the unique magnetic properties and easy surface modification of magnetic nanoparticles make them broad research and application in biomedicine, such as cell targeting, drug delivery, organic catalysis, and other fields. Magnetic nanoparticles will also bring new changes and rapid development to these areas. The various combination of magnetic nanoparticles and graphene oxide (GO) can be not only used as a new type of recyclable magnetic nanocomposites, directly used in biomedical detection and organic catalysis, but also used as a kind of magnetic carrier, loading other functional materials, endowing them magnetic recyclability and stability.Therefore, this dissertation, based on the results of previous studies, preparation of nanocomposites, and their application in biomedical detection and organic catalytic reaction, carried out the following studies:i. Based on the heterostructure of Au-Fe3O4nanoparticles, a multifunctional nanoprobe with dual-mode imaging and quantify detection for cancer cells was prepared by surface functionalization to Au and Fe3O4side, respectively, ii. Based on the catalytic property of Fe3O4nanoparticles for the A3-coupling reaction of aldehyde, acetylene and imine, Fe3O4-rGO magnetic nanocomposites were prepared by a one-step method to decomposite Fe(CO)5on the surface of graphene oxide. The corresponding catalytic activity for A3-coupling reaction was investigated; iii. Polyethylene imine (PEI) and3,4-dihydroxy benzaldehyde chemically modified graphene oxide, respectively. Pd/Fe3O4/PEI/rGO magnetic nanocomposites were prepared by the in-situ growth of Pd NPs and the assembly of Fe3O4NPs on reduced graphene oxide (rGO) and were further investigated the catalytic activity for Tsuji-Trost reaction in air and water condition.This dissertation was divided into four chapters, stated as follows:Chapter I:The first part briefly describes the properties and functional methods of magnetic nanomaterials and their application in the biomedical detection and organic catalysis reactions. The latter part briefly introduces magnetic functionalization method of graphene oxide and applications of nanocatalysts on the catalysis of acetylene, aldehydes and imines (A3-coupling) coupling reaction and Tsuji-Trost reaction.Chapter II:Based on the heterostructure of Au-Fe3O4magnetic nanoparticles and biocompatibility and water-soluble of polyethylene glycol derivatives, a Au-Fe3O4magnetic nanoprobe was prepared by surface functionalization with folic acid, europium complexes, and fluorescein isothiocyanate. The multifunctional nanoprobe is useful in simultaneously observing FR-positive cancer cells using magnetic resonance (MR)/fluorescence dual-modal imaging, and for counting cancer cells by colorimetric/fluorigenic dual-modal detection with a detection limit as low as100cancer cells.Chapter III:Based on the catalytic activity of Fe3O4nanoparticles for the A3-coupling reaction of aldehyde, acetylene and imine, Fe3O4nanoparticles with uniform size were in situ formed on the surface of graphene by a one-step thermal decomposition reaction of Fe(CO)5in a GO dispersion system. Graphene oxide turned to reduced grapheme oxide by an endogenous reducing agent (CO) from thermal decomposition of Fe(CO)5in the formation of Fe3O4-rGO nanocomposites. The resulting Fe3O4-rGO nanocomposites exhibited a high catalytic activity for A3-coupling reaction. With the help of magnet, the catalyst can be harvested and conduct more than6times catalytic cycles.Chapter IV:In order to solve the defects of noble metal nanocatalyst in the catalytic process, such as easy aggregation, poor stability and difficult separation and recovery, we used graphene oxide as a carrier of noble metal nanocatalyst. Polyethylene imine (PEI) and3,4-dihydroxy benzaldehyde chemically modified graphene oxide, respectively, and then Pd/Fe3O4/PEI/rGO magnetic nanocomposites were prepared by the in-situ growth of Pd NPs and the assembly of Fe3O4NPs on reduced graphene oxide (rGO). This nanocomposites exhibited excellent catalytic activity for Tsuji-Trost reaction in air and water system and could be easily separated from the reactant with the simple application of an external magnetic field. More importantly, the noble metal nanocatalyst on the magnetic support allows reaching at least92%of Tsuji-Trost catalysis yield during30cycling tests.