磁性Fe3O4纳米材料由于具有的小粒径、超顺磁性等性质，再加上其毒副作用小，易于进行修饰，可以通过表面修饰连接上多种功能基团，从而其在生物学领域的独特应用备受关注。 本文首先用三价乙酰丙酮铁盐[即Fe(acac)3]在油酸和油胺存在下与1，2－十六烷二醇的高温液相反应制得了单分散Fe3O4磁性纳米粒子。后在室温下用生物相容性较好的带有2个羧基的聚乙二醇分子作为配体去置换原修饰于Fe3O4磁性纳米粒子表面的油酸分子，制得了新的水溶性磁性纳米粒子。并对其进行了相关表征，如透射电镜（TEM）、DLS粒径分析、热重分析（TG-DTA）以及傅立叶变换红外光谱（FT-IR）。表征结果显示带2个羧基的聚乙二醇分子无法将原Fe3O4磁性纳米粒子表面的油酸完全置换掉。并且，通过热重分析，体系中HOOC-PEG-COOH的质量分数为10.29%。同时，通过电感耦合等离子发射光谱（ICP-AES）与热重分析（TGA）测得Fe3O4纳米粒子表面活性基团羧基的理论含量，通过实际含量与理论含量的比值来间接确定纳米粒子表面组成。 本课题的研究工作对于评价纳米材料的表面修饰效果、纳米材料表面反应活性点的检测以及对后续生物蛋白的固定效率的研究都具有重要的指导意义。

Fe3O4 nanoparticles are emerging as “super star materials”in biological research world, based on their ultra-fine sizes, biocompatibility and superparamagnetic properties. In this Paper, we synthesized the monodisperse magnetite (Fe3O4) nanoparticles which are hydrophilic by the high-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)3，with 1,2-hexadecanediol in the presence of oleic acid and oleylamine. Then we used the HOOC-PEG-COOH(Mn=600) which is biocompatible as ligand to replace the oleic acid in room temperature( ligand exchange) and obtained the novel nanogels which is hydrophilic.The as-synthesized nanoparticles were characterized by TEM、TG-DTA andFT-IR. The results indicated that the PEG-diacid can replace the oleic acid partially. Then we research the surface structure of the Fe3O4 nanoparticles through electronic titration method in combination with the TEG and ICP-AES. This project involves the significant value in the evaluation of nano-materials, the detection of reaction point and the research of protein conjugation.