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The unique optical properties of semiconductor quantum dots so that it has a broad application prospects in the field of optoelectronic devices, biological imaging, fluorescently labeled magnetic nanoparticles has important applications in magnetic resonance imaging, drug carriers. The quantum dots and magnetic particles when used alone, can only be provided to a function of people, if you can be prepared both luminescent properties of quantum dots and nano-magnetic particles magnetic quantum dots / magnetic particle complex, you can greatly expand the quantum dots and magnetic nano the scope of application of the particles, the study has important scientific value and a wide range of biomedical applications prospects. In this paper, the thermal decomposition of organometallic compounds synthesized CdSe quantum dots, the Fe 3 O 4 the magnetic nano particulate and Fe 3 O 4 / CdSe quantum dot composite by UV - visible spectroscopy (UV-Vis), fluorescence spectroscopy (PL), transmission electron microscopy (TEM, HRTEM), X-ray diffraction analysis (XRD), Multifunctional Materials Physics Characteristics Measurement System (PPMS) testing methods, the physical characterization of the synthesized product, optical, magnetic performance. Focus on the reaction time, the Cd: Se ratio of ligands on CdSe semiconductor quantum dots and the complex luminescent properties, particle morphology, and luminescent properties of CdSe quantum dots under reaction conditions for a long period of time change results from a more detailed research and analysis. The research results show that the reaction parameters affect the size, reaction time, and Cd: Se ratio parameter CdSe quantum dot size can be as important regulatory means. As the reaction time increases, the absorption and emission peaks of the CdSe quantum dots are moved towards the longwave direction, increasing the size of the quantum dots; under conditions of the same reaction time, Cd: Se ratio is smaller, then the larger the size of quantum dots. With the reaction time, the different Cd: Se first increases and then decreases trend than the quantum yield of the synthesis of quantum dots; Cd: Se ratio the smaller the quantum yield decline in the shorter reaction time. The study found that the peak phenomenon (Cd: Se = 1:2) emission spectra of CdSe quantum dot samples prepared in a long time, combined TEM results of analysis to determine the main reason of this phenomenon as follows: When prolonging the reaction time, enter to the grain growth of the ripening zone, some abnormal grains grow, resulting in the reaction system in the presence of different size distribution of the quantum dots. Abnormal grain growth process may: (1) with the reaction time increases, the system reduced monomer concentration, Ostwald ripening grains were small particles disappear into large particles. Part of the large particles, adhesion and agglomeration, size quickly grew up. Showed that the morphology control of CdSe quantum dots and luminescent properties associated regular TDPA ligand insulation treatment of Cd precursor solution conducive to columnar quantum dots; aspect ratio within columnar quantum The Dots performance better than spherical quantum dots. Fe 3 O 4 experimental results show that the synthesis of magnetic particles, the metal organic compounds of Fe (acac) 3 , 1,2-dodecane glycol, oleic acid, benzyl ether, ODA, the organic ligand and the presence of a solvent in the reaction can be obtained through the thermal decomposition conditions, good monodisperse the high crystallinity Fe 3 O 4 magnetic particles, the mean particle size of about 6-8nm; to display superparamagnetic, saturation magnetization at room temperature about 51.4emu / g. The the synthetic Fe two-step method 3 the O 4 / CdSe composite quantum dot research shows that by the Fe 3 the O 4 nano-magnetic particles as heterogeneous nucleation interface means for Growth of CdSe quantum dots, can get along with luminescence and magnetic properties of the quantum dots / magnetic particle complexes. Composite quantum dots with the excellent luminous performance: such as narrow emission peaks (the narrowest FWHM 28nm), the fluorescence quantum yield (without special passivation, up 27.8%), room temperature display superparamagnetic a saturation magnetization of about 0.92emu / g. Synthetic reaction conditions, and the HRTEM test results analysis, the Fe 3 O 4 / of CdSe composite quantum dots may exist two formation mechanism: A magnetic particles as heterogeneous nucleation interface formed by the total cell surface heterogeneity structure; another by Fe 3 O 4 and CdSe surface organic ligands interact to form a center for the Fe 3 O particles, the outer layer of CdSe quantum dots \By changing the reaction time and Cd: Se ratio of Fe 3 O 4 / luminescent properties of CdSe quantum dots multiphase study show that: with increasing reaction time, sample absorption emission peak moves to longer wavelengths, indicating that the growth time increased with the reaction CdSe quantum dots grow older; However, when its size grows to a certain extent, by lattice strain conditions will cease to grow up. In the same reaction under the conditions of time, to change the CD to: Se than Diphase quantum dots as fluorescent emission peak, but a great influence on the quantum yield of the product. CD in the present experimental design: Se ratio range, with Cd: SE ratio decreases, the sample continuously improve the quantum yield, the maximum quantum yield of approximately 27.8%. By different ligands of Fe 3 O 4 / CdSe quantum dots multiphase product of the synthesis and properties of that: using ODA as a surface ligand, can be obtained with excellent luminous performance composite quantum dots; while using TDPA as a ligand, the poor performance of the PL, this light-emitting significant performance differences may be related to the mechanism of ligands.
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