Fabrication, Characterization And Application Of Fluorescent-magnetic Multifunctional Nanospheres With Different Magnetic Susceptibility

With the rapid development of nanotechnology, nanomaterials have been widely used in the field of functional materials, fine chemicals, biomedicine etc. due to their unique physical structures and excellent optical, electrical, magnetic and mechanical properties. Quantum dots (QDs) had become ideal fluorescent marker due to their excellent fluorescence properties. Magnetic nanomaterials had been paid much attention in the field of biomedicine because of their excellent magnetic manipulation/separation abilities. Based on the important superiority of QDs and magnetic nanoparticles in biomedical research, the preparation of fluorescent-magnetic composite nonmaterials had become the popular project in biomedical research. A lot of works based on fluorescent-magnetic composite nanomaterials have been carried out, such as protein separation and detection, cell sorting and imaging, etc.. In the previous work, the fluorescent-magnetic composite nanomaterials were commonly applied to the separation and detection of a variety of target substances from mixed samples by single-component analysis mode. However, this mode has a series of flaws, such as complicated operation, time-consuming, laborious and low efficiency.In order to overcome these obstacles, we proposed fluorescent-magnetic composite nanomaterials which were able to complete the separation and detection of target substances in one-step, and improve work efficiency ultimately. On the other hand, the optical studies of fluorescent-magnetic composite nanomaterials have been reported. For example, multi-color quantum dots (QDs)-based encoded fluorescent-magnetic multifunctional probes had been used for the detection of multiple target proteins. However, the study of the magnetic properties of fluorescent-magnetic composite nanomaterials, which had different magnetic response intensity and were able to achieve magnetic manipulation separation, had not been studied extensively.In order to overcome the obstacles existing in current work, it was very urgent to manufacture multifunctional nanomaterials, which had different magnetic response intensity and were able to be used for the simultaneous or nearly simultaneous multi-component analysis. Therefore, this thesis aimed to fabricate fluorescent-magnetic multifunctional nanospheres which have different magnetic response intensity. Then, they were expected to conjugate with fluorescent reagent labeled immunoglobulin (IgG) acted as model molecules. The preliminary applications of fluorescent-magnetic multifunctional nanospheres with different magnetic response intensity were investigated by studying magnetic capture efficiency. According to the capture efficiency analysis, the prepared multifunctional nanospheres with different magnetic response intensity could be achieved effectively magnetic separation and capture under certain applied magnetic field. It may be used in simultaneously separation and detection of multiple targets from complex samples system. The strategy exhibits great potential to accomplish nearly simultaneous separation and analysis of multi-components from complex samples system, which are significantly benefit for disease diagnosis, food safety control, environmental monitoring and so on. Based on discussed above, the work as the following:(1) Preparation of (CdTe/Fe3O4)@SiO2fluorescent-magnetic multifunctional nanospheres with different magnetic response intensityFirst of all, the water-soluble CdTe QDs were prepared by the water phase synthesis method. The effects of reflux time, n(Cd2+):n(Te) and the pH value on the fluorescent properties of CdTe QDs were studied. Through the characterization of fluorescent properties, particle size and crystal structure of CdTe QDs, it could be inferred that the water soluble CdTe QDs with high fluorescence intensity, narrow half-peak width, high fluorescence stability, the diameter of3.2nm and zinc-blende structure were obtained.Secondly, the aqueous phase Fe3O4magnetic nanoparticles were fabricated by co-precipitation method. The effects of n(Fe2+):n(Fe3+), pH value, reaction temperature, reaction time, precipitating agent and the ripening process on the performance of products were studied. Through the characterization of magnetic properties, particle size and crystal structure of Fe3O4nanoparticles, it could be inferred that the aqueous phase magnetic nanoparticles with saturation magnetization of78.13emu/g, the diameter of12nm and tetragonal spinel structure were successfully prepared. Then, in order to improve the dispersion and stability of Fe3O4nanoparticles, Fe3O4magnetic nanoparticles were modified by citric acid (CA).Most importantly, the fluorescent-magnetic multifunctional nanospheres with different magnetic response intensity were fabricatied by embedding CdTe QDs and Fe3O4into a silica shell based on inverse microemulsion method. The different magnetic response intensity of nanospheres were achieved by controlling the different initial added amount of Fe3O4in the process. At last,(CdTe/Fe3O4)@SiO2fluorescent-magnetic multifunctional nanospheres with high fluorescence intensity and different magnetic response intensity were successfully prepared.(2) The study of capture efficiency and preliminary application of fluorescent-magnetic multifunctional nanospheres with different magnetic response intensityMultifunctional nanospheres were conjugated with fluorescent reagent labeled immunoglobulin (IgG) acted as model molecules. Based on the fluorescence signal of fluorescent reagent, the capture efficiency of multifunctional nanospheres was investigated. Our results showed that the multifunctional nanospheres could be achieved magnetic separation and capture under certain external magnetic field. The strategy exhibits great potential to accomplish nearly simultaneous separation and analysis of multi-components from complex samples.