Coating of Silica Nanolayers on Carbon Nanofibers via the Precursor Accumulation Method
Coating of Silica Nanolayers on Carbon Nanofibers via the Precursor Accumulation Method
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DOI：
10.1021/acs.langmuir.0c00083
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发表时间：
2020-03-24
期刊：
影响因子：
3.9
通讯作者：
Kurokawa, Hideki
中科院分区：
文献类型：
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作者：
Ogihara, Hitoshi;Usui, Norihiro;Kurokawa, Hideki
纳米碳的表面改性，例如，通过涂覆氧化物纳米层，是一个重要的研究课题，因为改性的纳米碳的物理化学性质的急剧变化。在纳米碳上产生这些氧化物纳米层涂层的一种简单方法是前体累积（PA）技术，其需要以下步骤：（1）将前体溶液逐滴添加到纳米碳粉末上;（2）干燥溶剂，将累积的前体留在纳米碳表面上;和（3）前体在空气中的水解或分解导致在纳米碳上形成氧化物纳米层。在这项研究中，正硅酸乙酯（TEOS）被用作前体的碳纳米纤维（CNFs）上的涂层二氧化硅纳米层。TEOS是如此稳定，以至于它在原始CNF的表面上几乎不经历水解。通过H2SO 4/HNO 3处理CNF，在CNF表面引入酸性官能团。由于酸处理后的CNF表面聚集的酸性官能团催化TEOS的水解，通过PA包覆在CNF表面成功地合成了二氧化硅纳米层。扫描透射电子显微镜表明，二氧化硅层的厚度约为几个纳米。二氧化硅纳米层的孔径分布分析表明存在3-5 nm的纳米孔。TEOS分子可以通过纳米孔进入官能团;因此，形成的二氧化硅纳米层的数量随着PA涂层的数量而增加。最后，我们比较了PA涂层与传统的溶胶-凝胶和原子层沉积技术。
Surface modification of nanocarbons, for example, by coating with oxide nanolayers, is a research topic of significant interest because of the drastic changes in the physicochemical properties of the modified nanocarbons. One simple method of creating these oxide nanolayer coatings on nanocarbons is the precursor accumulation (PA) technique, which entails the following: (1) a precursor solution is added dropwise onto nanocarbon powder; (2) the solvent is dried, leaving the accumulated precursor on the nanocarbon surface; and (3) hydrolysis or decomposition of the precursor in air leads to the formation of oxide nanolayers on the nanocarbons. In this study, tetraethoxysilane (TEOS) was used as a precursor for coating silica nanolayers onto carbon nanofibers (CNFs). TEOS is so stable that it hardly undergoes hydrolysis on the surface of pristine CNFs. By treating CNFs with H2SO4/HNO3, acidic functional groups were introduced onto the CNF surfaces. Silica nanolayers were successfully synthesized on these acid-treated CNFs via PA coating because the acidic functional groups catalyzed the hydrolysis of TEOS accumulated on the CNF surfaces. Scanning transmission electron microscopy indicated that the thickness of silica layer is approximately several nanometers. Pore size distribution analysis for the silica nanolayer suggested the presence of nanopores with 3-5 nm. The TEOS molecules could have accessed the functional groups through the nanopore; therefore, the number of silica nanolayers formed increased with the number of PA coatings. Finally, we compared the PA coating with conventional sol-gel and atomic layer deposition techniques.