Harada Takumi, Suzuki Yasutaka, Nakato Teruyuki, Breu Josef, Kawamata Jun
Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8512, Japan.
Department of Applied Chemistry, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata, Kitakyushu, Fukuoka 804-8550, Japan.
Langmuir. 2024 Apr 30;40(17):9189-9196. doi: 10.1021/acs.langmuir.4c00560. Epub 2024 Apr 18.
Inorganic nanotubes have attracted much attention due to their unique physicochemical properties. Nanotubes can be prepared by scrolling exfoliated nanosheets under ambient conditions. However, how the nanosheet scrolled in its colloidal state has not been experimentally visualized. In this paper, we directly observed the scrolling process of nanosheets upon adsorption of organic cations. Exfoliated flat nanosheets of niobate and clay in aqueous colloids were found to scroll by adding organic cations, such as exfoliation reagents, to the colloids. Employment of cationic stilbazolium dye enabled in situ observation of the dye adsorption and scrolling by optical microscopy based on changes in color and morphology of the nanosheets. The scrolling was promoted for nanosheets adsorbed with a stilbazolium dye with a longer alkyl chain, suggesting that the interaction between the hydrophobic parts of the dye cations is the driving force of the scrolling. This finding should encourage research on the formation of nanotubes from nanosheets and also provides important guidelines for the selection of appropriate exfoliation reagents when exfoliating nanosheets from layered crystals.
无机纳米管因其独特的物理化学性质而备受关注。纳米管可以在环境条件下通过卷曲剥离的纳米片来制备。然而，处于胶体状态的纳米片是如何卷曲的尚未通过实验观察到。在本文中，我们直接观察了有机阳离子吸附时纳米片的卷曲过程。发现在水胶体中加入有机阳离子（如剥离试剂）时，铌酸盐和粘土的剥离扁平纳米片会卷曲。使用阳离子二苯乙烯基苯并噻唑染料能够基于纳米片颜色和形态的变化，通过光学显微镜对染料吸附和卷曲过程进行原位观察。对于吸附有较长烷基链二苯乙烯基苯并噻唑染料的纳米片，卷曲过程得到促进，这表明染料阳离子疏水部分之间的相互作用是卷曲的驱动力。这一发现应会推动关于从纳米片形成纳米管的研究，也为从层状晶体剥离纳米片时选择合适的剥离试剂提供重要指导。
