【作者】 李瑞法；

【导师】 王静云；

【作者基本信息】 大连理工大学 ， 生物化工， 2011， 硕士

【摘要】 以Fe2+/Fe3+盐及氨水为起始原料、油酸做稳定剂,采用共沉淀法合成了粒径约为20nm的Fe304磁性纳米颗粒。通过添加少量盐为诱导剂的方法将表面油酸稳定的Fe304磁性纳米颗粒由水相萃入甲苯相中,之后采用配基交换法以硅烷偶联剂3-(异丁烯酰氧)丙基三甲氧基硅烷(MPS)对其表面进行双键功能修饰,使其表面带上大量可聚合双键。分别以苄基溴(BB)、碘甲烷(MI)及溴己烷(BH)三种不同的卤代烃对甲基丙烯酸二甲基氨基乙酯(DMAEMA)所含叔胺基团进行季铵盐化,将得到的三种季铵盐单体分别与表面双键功能化的Fe304磁性纳米颗粒在乙醇体系中进行两种引发剂浓度的自由基聚合,最终成功得到了三种不同的聚阳离子接枝的Fe304磁性微球(PQAC-Fe3O4)。各步反应后颗粒形貌及表面性质通过X射线衍射(XRD)、傅立叶红外(FT-IR)、动态光散射粒径分析(DLS)、透射电镜(TEM)、热重分析(TGA)等表征确定。采用动态接触法测定所合成PQAC-Fe3O4样品的抗菌活性,结果发现样品对大肠杆菌、金黄色葡萄球菌及白色假丝酵母菌均有很好的杀菌效果,10min即可达到90%以上的杀菌率,属于快速杀菌型抗菌剂；其杀菌效率表现出明显的浓度正相关性,这可能与抗菌颗粒浓度的升高增加了测试菌与颗粒间的接触机会有关。抗菌实验还表明三种测试菌对样品的敏感性不同,敏感性顺序依次为白色假丝酵母菌>金黄色葡萄球菌>大肠杆菌,原因可能与聚季铵盐的杀菌机理及不同菌种细胞壁结构的差异有关。此外,比较三种不同PQAC-Fe3O4样品的杀菌率可以发现,杀菌效果不仅与正电荷密度及疏水性有关,还受其在水中的分散性及聚合物链长的影响。由于具有良好的外磁场响应性,所合成的PQAC-Fe3O4颗粒可以方便的回收利用,重复利用性实验表明其抗菌活性耐久性好,经10次循环利用后对大肠杆菌的杀菌率仍可达95%以上。综上所述,成功合成了具有外磁场响应性的PQAC-Fe3O4抗菌颗粒,颗粒杀菌效果不仅与所接枝季铵盐基团的多少有关还与季铵盐取代基团有关。作为一种具有高效广谱杀菌性和良好循环利用性的新型可循环水不溶性抗菌剂,PQAC-Fe3O4在水处理等方面有很好的应用前景。更多还原

【Abstract】 magnetic nanoparticles with a diameter of 20nm were prepared by coprecipitation of Fe2+/Fe3+ in ammonia solutions and with oleic acid (OA) as the stabilizer. These magnetic nanoparticles were extracted into toluene from water by simply adding some salt as inducer, and then the Fe3O4 magnetic nanoparticles were functionalized with the silane coupling agent of 3-methacryloylpropyl trimethoxysilane (MPS) through ligand exchange method, which could provide double bonds on the surface of Fe3O4 nanoparticles.Three quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl bromide (BB), methyl iodide (MI) and bromohexane(BH), respectively. And then, the monomers were copolymerized with MPS on the surface of Fe3O4 magnetic nanoparticles by free radical polymerization in ethanol at two different concentration of initiator. Finally, three kinds of polymeric quaternary ammonium salts grafted Fe3O4 nanoparticles (PQAC-Fe3O4) were obtained. The morphology and surface composition of nanoparticles was characterized by XRD, FT-IR, DLS, TEM and TGA.The in vitro antimicrobial activity of the PQAC-Fe3O4 nanoparticles was evaluated against E. coli, S. aureus and C. albicans by the the shake-flask method, it was found that PQAC-Fe3O4 nanoparticles showed a wide spectrum of high efficient antibacterial activity, and the biocidal efficiency coulde be achieved 90% witin 10 minutes. The biocidal efficiency increased with the increasing concentration of the PQAC-Fe3O4 nanoparticles used, possibly due to the more opportunities for contact between the nanoparticles and the microorganisms. Compared to the other two tested microorganisms, the PQAC-Fe3O4 nanoparticles were less toxic to the gram-negative bacterium E. coli, it possibly due to the mechanism which the PQAC-Fe3O4 nanoparticles operated. In addition, it was found that the different antibacterial efficiency of the three synthesized PQAC-Fe3O4 was influenced not only by their positive charge density and hydrophobicity but also their dispersibility in water and the length of the polymeric quaternary ammonium salts. The antimicrobial activity of the PQAC-Fe3O4 nanoparticles which exhibited a response to an external magnetic field retained 95% biocidal efficiency against E. coli after 10 cycles of repeated test.In conclusion, high antibacterial efficiency of the PQAC-Fe3O4 nanoparticles which exhibited a response to an external magnetic field was attributed to not only the quaternary group density but also the substitent chain of the quaternary group. As one kind of biocides with high microbial activity and be resuability in water, the PQAC-Fe3O4 nanoparticles would be advantageous as a new type of insoluble antimicrobial agent in water treatment.更多还原