Distinct interface behaviors of Ni(II) on graphene oxide and oxidized carbon nanotubes triggered by different topological aggregations
Distinct interface behaviors of Ni(II) on graphene oxide and oxidized carbon nanotubes triggered by different topological aggregations
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不同拓扑聚集引发的Ni(II)在氧化石墨烯和氧化碳纳米管上的独特界面行为
DOI：
10.1039/c7nr07966d
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发表时间：
2018
期刊：
影响因子：
6.7
通讯作者：
Wang Dongqi
中科院分区：
文献类型：
--
作者：
Liang Jianjun;Li Ping;Zhao Xiaolan;Liu Ziyi;Fan Qiaohui;Li Zhan;Li Jiaxing;Wang Dongqi
虽然碳纳米管可以被描述为无缝卷曲的石墨烯纳米片，但二维氧化石墨烯（GO）和一维氧化碳纳米管（OCNT）具有不同的命运和环境风险，例如沉积、降解和细胞毒性。特别是，共存的重金属离子（HM）触发这两个碳衍生物的不同形态的转变。此外，这些形态转变可以改变这两种材料上的HM的界面行为。在这项研究中，GO和OCNTs的形态变化和Ni（II）的界面行为的差异进行了探索，通过这两个典型的碳材料的内在微观结构的变化。批实验表明，Ni（II）吸附在GO急剧下降，增加离子强度，而它几乎是独立的OCNTs上的离子强度。这种现象归因于GO片在较高Na+浓度下的聚集和缠结，导致GO表面积和吸附位点数量的减少。同时，OCNTs的缠绕聚集仍然保证了吸附位点的裸露。首次观察到Ni 2+离子即使在碱性条件下也作为内球络合物在GO上持续存在，其中在OCNT上确定了Ni（OH）2（s）相。这可能是由于GO的快速聚集将Ni ~（2+）固定在中间层中，抑制了Ni（OH）_2的成核。GO聚集体的稳定层状结构难以剥离，导致随着Ni（II）负载的增加，从GO中释放的Ni（II）减少。对于OCNTs，裸Ni 2+离子可以容易且有效地释放。这些发现对于评估纳米材料和HM在水生环境中的流动性、转化和细胞毒性至关重要。
Although carbon nanotubes can be described as a seamlessly curled graphene nanosheet, two-dimensional graphene oxide (GO) and one-dimensional oxidized carbon nanotubes (OCNTs) have different fates and environmental risks, such as deposition, degradation and cytotoxicity. In particular, coexisting heavy metal ions (HMs) trigger distinct morphological transformations of both of these carbon derivatives. In addition, these morphological transformations can change the interface behaviors of HMs on both of these materials. In this study, the differences in the morphological changes of GO and OCNTs and the interface behaviors of Ni(II) were explored via the intrinsically microscopic structural changes of both of these typical carbon materials. Batch experiments revealed that Ni(II) sorption on GO drastically decreased with increasing ionic strength, while it was almost independent of ionic strength on the OCNTs. This phenomenon is attributed to the aggregation and wrinkling of GO sheets at higher Na+ concentrations, resulting in a decrease in the GO surface area and number of sorption sites. Meanwhile, the intertwining aggregations of OCNTs still ensured that the sorption sites were naked. For the first time, Ni2+ ions were observed to persist as inner-sphere complexes on GO even under alkaline conditions, where the.Ni(OH)2(s) phase was determined on the OCNTs. This could be attributed to the fact that the fast aggregation of GO, which fixed Ni2+ ions into the interlayers, inhibited the nucleation of Ni(OH)2. Stable layered structures of GO aggregations were difficult to exfoliate, leading to a decreased release of Ni(II) from GO with increasing Ni(II) loading. For the OCNTs, naked Ni2+ ions could be easily and effectively released. These findings are critical to assess the mobility, transformation and cytotoxicity of nanomaterials and HMs in aquatic environments.