石墨包裹纳米铁晶粒的纯化及表面改质程序之初步研究

Preliminary Study on the Purification and Surface Modification Procedures of Graphite Encapsulated Iron Nanoparticles

摘要: 石墨包裹纳米金属晶粒(Graphite Encapsulated Metal nanoparticles, GEM)是一种在1993年偶然间发现的新超威复合材料，外层由吸附效果佳的多片石墨层所组成，内核则包裹有纳米金属晶粒，而由于铁、钴和镍等铁磁性金属具有催化碳变为石墨的能力，故以合成石墨包裹纳米铁磁性金属晶粒的研究最为普遍。本研究系以石墨包裹纳米铁晶粒(FeGEM)做为主要研究材料，针对该材料的合成纯化步骤及表面改质程序，进行操作条件的分析改良，成功发现使用盐酸进行FeGEM颗粒的酸溶纯化步骤可降低产物中氧化物杂质的产生，并可保留最佳包裹良率；而利用硝酸进行升温回流程序，则可以在较低的升温条件(80℃)下达到改质FeGEM表面特性的目的，使颗粒表面由亲油性转变为亲水性，且可稳定悬浮于去离子水或乙醇等极性溶剂中24小时以上，有效解决颗粒容易团聚的缺点，大幅提升FeGEM的应用潜力。

Abstract: The novel ultrafine material of graphite encapsulated metal (GEM) nanaoparticles was first dis-covered in 1993. The outer shells of GEM material are composed of graphitic layers with superior adsorbing property and the inner core is composed of nanocrystalline metal. Due to the excellent catalytic ability of ferromagnetic metal to transform carbon to graphite, the researches about synthesizing graphite encapsulated ferromagnetic metal nanoparticles are most common. In this study, we focused on the purification and surface modification procedures of FeGEM. It is found that the purification steps with hydrochloric acid can reduce the impurities of oxides and preserve high percentage of well-encapsulated nanoparticles. We also found that after the purification, the following refluxing procedure with nitric acid under 80˚C can modify the surface of FeGEM nanoparticles from hydrophobicity to hydrophilicity and maintain the suspension of FeGEM in water or ethanol for more than 24 h. The modification processes not only overcome the agglomeration problem of FeGEM nanoparticles but also enhance the potential applications of the material.