International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
J Am Chem Soc. 2015 Mar 4;137(8):2844-7. doi: 10.1021/jacs.5b00317. Epub 2015 Feb 20.
The surface charge of various anionic unilamellar nanosheets, such as graphene oxide (GO), Ti0.87O2(0.52-), and Ca2Nb3O10(-) nanosheets, has been successfully modified to be positive by interaction with polycations while maintaining a monodispersed state. A dilute anionic nanosheet suspension was slowly added dropwise into an aqueous solution of high molecular weight polycations, which attach on the surface of the anionic nanosheets via electrostatic interaction. Surface modification and transformation to positively charged nanosheets were confirmed by various characterizations including atomic force microscopy and zeta potential measurements. Because the sizes of the polycations used are much larger than the nanosheets, the polymer chains may run off the nanosheet edges and fold to the fronts of the nanosheets, which could be a reason for the continued dispersion of the modified nanosheets in the suspension. By slowly adding a suspension of polycation-modified nanosheets and pristine anionic nanosheet dropwise into water under suitable conditions, a superlatticelike heteroassembly can be readily produced. Characterizations including transmission electron microscopy and X-ray diffraction measurements provide evidence for the formation of the alternately stacked structures. This approach enables the combination of various pairs of anionic nanosheets with different functionalities, providing a new opportunity for the creation of unique bulk-scale functional materials and their applications.
各种阴离子型单层纳米片（如氧化石墨烯（GO）、Ti0.87O2(0.52-) 和 Ca2Nb3O10(-) 纳米片）的表面电荷通过与聚阳离子相互作用成功地被修饰为正电性，同时保持单分散状态。将稀释的阴离子纳米片悬浮液缓慢逐滴加入高分子量聚阳离子的水溶液中，聚阳离子通过静电相互作用附着在阴离子纳米片的表面。通过原子力显微镜和 zeta 电位测量等各种特性分析证实了表面修饰和转化为带正电荷的纳米片。由于所使用的聚阳离子的尺寸远远大于纳米片，因此聚合物链可能会从纳米片边缘滑出并折叠到纳米片的前面，这可能是修饰后的纳米片在悬浮液中继续分散的原因。通过在适当的条件下将聚阳离子修饰的纳米片和原始阴离子纳米片的悬浮液缓慢逐滴加入水中，可以很容易地制备出超晶格样的杂组装体。透射电子显微镜和 X 射线衍射测量等特性分析提供了形成交替堆叠结构的证据。这种方法能够将具有不同功能的各种阴离子型纳米片组合在一起，为创造独特的块状功能材料及其应用提供了新的机会。
