Synthesis And Analytical Application Of The Magnetic Nanomaterials

Magnetic nanomaterials have great potentials in the field of targeted delivery, bioseparation, artificial enzymes and biosensor applications. Meanwhile, noble metal fluorescent nanoclusters have also been widely used in the filed of imaging and sensing. Developing new synthetic strategies for these nanomaterials and exploring the effect of structure on properties are very important to both fundamental research and practical application.Based on the solvothermal and microwave technology, this dissertation presents a systematic research on the relationship between the structure, surface properties and bioapplication of magnetic and fluorescent metal nanoclusters materials. And several nanostructures and nanocomposites were purposeful synthesized based on application requirements in the field of life science. The main results were summarized as follows:Chapter 2, Based on oriented attachment and subsequent local Ostwald ripening in the solvothermal process. Monodispersed Fe3O4 nanospheres with hollow interior structures were fabricated by a facile one-pot route. The fabrication process is very simple with no templates or surfactants involved. Field-emission Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Superconducting Quantum Interference Device magnetometer were used to characterize the morphologies, structures and properties of the hollow magnetic nanospheres. In addition, the experiments of the hollow nanospheres decorated with polyacrylic acids as drug carriers and Rhodamine 6G as a model drug, revealed pH-or salt-responsive release profiles, thus demonstrating the potential of these nanostructures in biomedical applications.Chapter 3, A microwave-hydrothermal method was developed for the facile synthesis of polyacid-conjugated Fe3O4 superparamagnetic hybrid. Field-emission scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, Magnetic measurement and Thermogravimetric, and Cytotoxicity assay were used to characterize the morphologies, structures, compositions and properties of the polyacid-conjugated Fe3O4 superparamagnetic hybrid. The hybrid is a kind of secondary structure which is composed of nanograins and exhibits excellent magnetic properties and good biocompatibility. The hybrid size can be adjusted from about 100 to 400 nm by varying the amount of FeCl3 in the system. Furthermore, the exposure of uncoordinated carboxylate groups on the hybrid surface plays an important role not only in the formation of structure but also on the excellent surface properties.Chapter 4, The catalytic activity of nanocrystal catalysts depends strongly on their structures. In this chapter, we report three distinct structures of Fe3O4 nanocrystals, including cluster spheres, octahedra, and triangular plates, prepared by the similar hydrothermal procedure. Additionally, the three Fe3O4 nanostructures were used as peroxidase nanomimetics and the correlation between the catalytic activities and the structures was firstly explored by using TMB and H2O2 as peroxidase substrates. The results showed that the peroxidase-like activities of the Fe3O4 nanocrystals were structure-dependent and followed the order of cluster spheres> triangular plates> octahedra, which was closely related to their preferential exposure of catalytically active iron atoms.Chapter 5, Microwave-hydrothermal method was developed for the facile synthesis of core/shell nanostructures composed of Fe3O4 cores and carbonaceous shells. Noble metal nanoparticle can be loading on the surface of core/shell nanostructures through electrostatic interaction. The resulting material integrated the benefits of noble metal and magnetic properties and was expected to offer a promising template for protein immobilization and biosensor fabrication because of its satisfying biocompatibility and improved properties. The immobilized Hb exhibited fast direct electron transfer. Chapter 6, CdSeTe-Au nanotubes have been first successfully prepared based on sacrificial template and sonochemical techniques. The Element ratio can be tailored by controlling the experiment conditions. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectrometry. This is a general method for the synthesis of nanocomposites hollow structures. Due to their unique properties, the application in biosensing was investigated. The immobilized Hb in the surface of nanotubes exhibited fast direct electron transfer and showed a good electrocatalytic performance to H2O2 with high sensitivity, wide linear range from 2μmol L"1 to 200μmol L-1.Chapter 7, A rapid microwave-assisted green method was proposed firstly for facile synthesis of highly fluorescent Ag nanoclusters in aqueous solution. The reaction time is greatly reduced. The obtained Ag nanoclusters have favorable monodispersity and good stability and exhibit bright and photostable emission excited by visible light. The fluorescent Ag nanoclusters can be used as a fluorescence probe for Cr3+sensing. The proposed detection protocol provides high sensitivity, with a detection limit of 28 nmol L-1, and excellent selectivity. In addition, the microwave-assisted green method is expected to be extended to the synthesis of other fluorescent metal nanoclusters.