Preparation And Performance Characterization Of Composite Particles Of Magnetic Nanoparticles And Fluorescence Quantum Dots

With the development of nanotechnology, scientists have successfully prepared functional nanopaticles with unique electrical, magnetic, optical, thermal, biological and chemical properties. These functional nanoparticals are significant for biological, medical, electronic, chemical and material areas et. al. Especially, fluorescent quantum dots and magnetic nano-materials are widely used in biomedical area for the excellent optical and magnetic properties. However, with the further developmenmt of science and technology, materials with single function can not meet the demonds for people eagering for advanced materials. Therefore, providing the magnetic and fluorescent properties can be combined, gathering the seperation and signing function, the multifunctional magnetic fluorescent nanocompositional materials can be prepared through physical and chemical processes and used as probes with magnetic targeting. Based on the statements above, the topic makes use of superparamagnetic Fe3O4@SiO2 with the function of magnetic resonance imaging contrast agents as magnetic core. The ZnSe@ZnS quantum dots possessing core-shell structure with adjustable color, high luminescent efficiency provide fluorescence. By microemulsion method, SiO2 embeded with magnetic and fluorescent nanoparticles can be prepared and magnetic and fluorescent functions can be composited. This kind of composited nano-materials not only improve the potential of biomedical application, but also do favor to overcome the problems of magnetic Fe3O4 nanoparticles, such as easy oxidization, sensibility, biological toxicity and so on. This may brodern the application for the two certain nanoparticles. Otherwise, in order to improve the performance of Fe3O4@SiO2 magnetic nanoparticles, one layer siliver is doped on the magnetic nano-mateial, which may promote the stability of the nanoparticles. As well, the unique properties of siliver can be combined with that of the composited material, improving the application of the nanoparticles. The plasmon resonance for silver nanoparticle in visible region and near infrared region provides it with high photocatalysis, bactericidal effect, surface enhanced spectroscopy, optical performance and so on. Also, it is cheaper than gold, button, uranium. Therefore, it is worthy for the investigation on the composition of magnetic nanoparticles and Ag.In this papers, the composited particles with magnetic and fluorescent properties are prepared by microemulsion method. The cyclohexane, TriotnX-100 and n-hexyl alcohol are taken as continuous phase, surfactant and co-surfactant, respectively and when the volum ratio is 4:1:1, the microemulsion can be obtained appropriately. According to the analysis of ultraviolet-visible absorption spectrum and fluorescence spectrum, the promising parameters for the preparing process can be obtained and the composited particles with magnetic and fluorescent properties tend to be the best:the mole ratio of quantum dot to magnetic particles is 5:1, the volme fraction of TEOS and ammonia are 2.2% and 3.2%, respectively and the reaction timeis 24h. The magnetic fluorescent composited particles has spherical shape with radius of about 70nm. They possess good stability and the anti-light bleaching is better than the pure quantum dots, which can be placed for a long time. Meanwhile, the superparamagnetic property is promising.The Fe3O4@SiO2 prepared via microemulsion method have spherical shape with radius of about 40nm and good disperion. Also the Fe3O4@SiO2 nanoparticles exhibit good superparamagnetic properties, though a little worse than the pure Fe3O4.In this paper, the Fe3O4@SiO2 magnetic particles is doped with one layer of thin Ag shell by chemical reduction method. The radius almost remains the same and the shape is still spherical. Also, the dispersion is excellent. The MNPs/Ag magnetic particles exhibit good superparamagnetic properties. Due to the fact that the Ag shell is very thin, it possesses the magnetic property nearly to the Fe3O4@SiO2 magnetic particles and when the mole ratio of Fe3O4@SiO2 to AgNO3 is 1:0.4, the weitht ratio of Ag in MNPs/Ag reaches the most of 6.39.