Preparation And Characterization Of Fluorescent Magnetic Nanocomposites

With the rapid development of nanotechnology,a single nanoparticle can not meet the needs of biomedical science any more.Magnetic fluorescent nanocomposite has the properties of magnetism and fluorescence and has solved the problem of the separation of single fluorescent marker after labeling cells.So,it is expected to have an excellent performance in cross-cutting areas of biology,medicine,and chemistry.Consequently,the combination of fluorescent quantum dots and nanomagnetic materials has important practical significance.Among them,the selection of fluorescent material and its connection with magnetic materials have become the focus of the study.Compared with the traditional semiconductor quantum dots,the carbon quantum dots（CQDs）have high fluorescence intensity and stability,and it is also naturally biocompatible and environmental friendly,which can be widely used in the field of life science.In this paper,the preparation and optimization of CQDs were investigated.Besides,Fe₃O₄ magnetic nanoparticle was prepared and modified.Then it was connected with CdSe and CQDs under the function of adsorption,hydrogen bond and bonding connection,respectively.Finally,two kinds of magnetic fluorescent nanocomposites were obtained and the products were characterized.（1）CQDs were prepared through oil bath and autoclave equipment.The properties of CQDs were compared from three aspects of infrared structure,fluorescent intensity and stability.The results showed that CQDs prepared through autoclave equipment were better.Amino modification of the CQDs.The influence of types,addition amount,addition order of nitrogen sources,reaction temperature and reaction time on the fluorescence properties were researched.Through characterization tests by fluorescence microscopy and transimission electron microscopy,it indicated that CQDs and the aminated CQDs had good dispersion,excellent luminescence properties,uniform particle size.The study also proved that the aminated CQDs had better luminescence and higher quantum yields,which makes it has a wider range of applications.（2）Fe₃O₄ were modified by alendronate and Tris.CdSe was modified by 3-mercapto propionic acid so a large number of careboxyl groups were introducted on the surface of quantum dots.In this study,3-mercapto propionic acid can be used as coupling agent and protective agent to react with the modified Fe₃O₄ particles.Then the magnetic fluorescent bi-functional material Fe₃O₄/Alendronate@CdSe and Fe₃O₄/Alendronate/Tris@CdSe were synthesized.After various types of characterization,the results showed that Fe₃O₄/Alendronate@CdSe and Fe₃O₄/Alendronate/Tris@CdSe have good dispersion and excellent magnetic.However,influenced by the quenching effect of Fe₃O₄,the fluorescence intensity and fluorescence quantum yields were at a low level,and it still needs to be further improved.（3）Fe₃O₄ was coated by chitosan（CS）and then connected with carbon quantum dots through the shaking table reaction.Fluorescent magnetic bi-functional material Fe₃O₄/CS@CQDs were successfully prepared.Combined with fluorescence microscope,TEM,VSM and other characterization methods,we found that the nano-composites have favourable relative fluorescence intensity,magnetic responsiveness,uniform particle size and good dispersion.The magnetic nanocomposite material of CQDs have no toxicity and high biocompatibility,which can replace the magnetic nanocomposite material of semiconductor quantum dots and be applied in the field of life science,such as medicine separation,visualization,targeted therapy and so on.（4）Fe₃O₄ were modified by poly dopamine（PDA）.PDA can not only introduce amino groups to improve its dispersion and biocompatibility,but also connect Fe₃O₄ nanoparticles with CQDs as a coupling agent for the first time.The non-toxic magnetic nano material Fe₃O₄/ P DA@C Q Ds was then prepared.The nanocomposites were characterized by FTIR,XRD,TEM,VSM,fluorescence spectrophotometer and fluorescence microscope.The results showed that Fe₃O₄/PDA@CQDs had uniform particle size,good dispersion,excellent fluorescence performance and magnetic induction.This magnetic nanocomposite material of the CQDs can replace the magnetic nanocomposite material of semiconductor quantum dots and be applied in the field of biology,material science,medical and so on.