Synthesis and Characterization Core

碳工程纳米材料(CENMs)是一种新的相对论材料(Kroto，1985；Lijima，1991)，尽管利用CENMs独特性质的研究进展迅速，但对其毒理学的了解才刚刚发展。在日益发展的纳米技术领域，对纳米颗粒进行表征以确定毒理学研究的因果性质一直是争议的来源，并且已经公布了一些“最小表征数据集”的清单(Oberdorster等人，2005年；Power等人，2006年；NCI，2009年)。RTI研究人员发现的一个未被认识到的令人困惑的问题是商业CENM中的随机内毒素污染(Esch等人，2010年)。第二个令人困惑的问题是，CENMS可能会保留纯化过程中使用的溶剂，这可能会影响毒理学研究的结果(Spohn et 因此，必须仔细选择CENMS的提纯方法，并测定测试材料的挥发性含量。 由于石墨烯衍生的CENM是由碳原子在蒸气状态下组装而成的，因此等离子体弧放电、激光烧蚀和化学气相沉积(CVD)等方法是主要的合成方法。这些过程提供了COO以及其他多面体碳部分(例如富勒烯)、多芳香族化合物、无定形碳和碳(Hou，2008)。COO是一种定义明确的有机分子，在有机溶剂中具有一定的溶解性，分离和表征COO相对简单(见第4节，初步研究/进展报告)。CVD法制备的多壁碳纳米管具有更高的缺陷发生率，它涉及催化剂辅助碳氢化合物的分解和金属催化剂上的生长。污染物是金属，它们可能存在于多壁碳纳米管中，也可能存在于多面体碳副产品、芳香烃或无定形碳中。另一方面，从电弧放电中获得的多壁碳纳米管被认为是相对纯净的(Henstridge，2008)。RTI的方法是使用内部研究规模的等离子弧放电方法(见第4节，初步研究/进展报告)，该方法在过去4年中一直被使用，向大学和政府的研究人员提供表征良好的、统一标记为060、MWCNT和单壁碳纳米管(SWCNT)的纯碳-14。这种方法还消除了任何工艺或环境污染的可能性。根据我们的经验，我们的合成过程是可重复的，碳-14标记材料和未标记材料的物理和化学特性是相同的。我们对商用060和MWCNT(Esch等人，2010；Levine等人，2010)进行了表征研究，发现我们合成的材料具有类似的物理特性。

Carbon engineered nanomaterials (CENMs) are relativity new (Kroto, 1985; lijima, 1991), and despite the fast-advancing research that utilizes the unique properties of CENMs, understanding of their toxicology is only now developing. The characterization of nanoparticles to identify the causal properties for toxicology studies has been a source of controversy in the growing nanotechnology field, and a number of lists of the "minimum characterization data set" have been published (Oberdorster et al., 2005; Powers et al., 2006; NCI, 2009). An unrecognized and confounding problem discovered by RTI researchers is random endotoxin contamination in commercial CENMs (Esch et al., 2010). A second confounding problem is that the CENMs may retain solvents used during purification, which may influence ttie outcomes of toxicology studies (Spohn et al,, 2009), Therefore, the method of purification ofthe CENMs must be carefully selected and the volatile content ofthe test material determined. Since the graphene-derived CENMs are formed by the assembly of carbon atoms in the vapor state, methods such as plasma arc discharge, laser ablation, and chemical vapor deposition (CVD) are the main synthetic approaches. These procedures afford COO, as well as other polyhedral carbon moieties (e.g., fullerenes), polyaromafic compounds, amorphous carbon, and carbon (Hou, 2008). Isolation and characterization of COO as a well-defined organic molecule with some solubility in organic solvents is relatively simple (see Section 4, Preliminary Studies/Progress Report). MWCNTs derived from CVD, which involves catalyst-assisted decomposition of hydrocarbons and growth over metal catalysts, have a higher incidence of defects than those produced by arc discharge. Contaminants are metals, which may be within the MWCNTs or within polyhedral carbon byproducts, aromafic hydrocarbons, or amorphous carbon. On the other hand, MWCNTs obtained from arc discharge are considered to be relatively pure (Henstridge, 2008). RTI's approach is to use an in-house research-scale plasma arc discharge method (see Section 4, Preliminary Studies/Progress Report) that has been used for the past 4 years to provide well-characterized, pure carbon-14 uniformly labeled 060, MWCNT, and single-walled carbon nanotubes (SWCNT) to researchers in universities and government. This approach also eliminates any possibility of process or environmental contamination. It has been our experience that our synthetic procedure is reproducible and that the physical and chemical characterisfics are identical for the carbon-14 labeled and unlabeled materials. We have conducted characterization studies of commercial 060 and MWCNT (Esch et al., 2010; Levine et al., 2010) and found that our synthesized materials have comparable physical characteristics.