报告时间：2017年12月15日13:00-14:00
报告地点：近代物理系210会议室
报告人：  石国升副研究员（上海应用物理研究所 ）
报告题目：Hydrated ion-π interactions and their relative applications
报告摘要：Carbon-based nano-materials widely exist and have attracted wide attentions. Most of them such as graphene, graphene oxides (GOs), and carbon nanotubes (CNTs) contain many aromatic rings structures, which are hexagonal carbon rings rich in π electrons. On the other hand, solutions with ions are also widely exists. Early in 1980’s, the interactions of the hexagonal carbon rings with ions were proposed, namely ion-π interactions. The ion-π interactions are greatly reduced by the hydration of cations and thus the cation-π interactions of ions in solutions have been usually neglected. In this talk, I will show that, due to the polycyclic aromatic rings structure which includes more π electrons, the cation-π interactions of ions in solutions are still strong enough and play important roles in the systems with aqueous ions solutions and carbon-based materials.
It has long been expected that the CNT can be used as an excellent seawater desalination membrane because of its experimentally confirmed ultrafast pure water flow and theoretically predicted ion rejection. However, there is insufficient experimental evidence of adequate salt rejection for desalination before 2015. We explain this difficulty by showing the blockage of CNTs by hydrated cations because of the hydrated cation-π interactions of cations in solutions with aromatic rings in CNTs [1]. We further proposed that this ion blocking can be prevented while maintaining a fast water flow rate by functionalizing the CNT entrance with saturated groups for narrow CNT, which has been confirmed very recently [2].
GO membranes have shown potential in a variety of applications including water desalination and purification, gas and ion separation, biosensors and lithium-based batteries. However, it is very difficult to fix the interlayer spacing to a length scale comparable to hydrated ions. This challenge hinders potential applications of GO membranes. We experimentally demonstrate the cationic control of interlayer spacing of GO membranes with precision as small as 1 Å using ions themselves [3]. First-principles calculations and ultraviolet (UV) absorption spectral experiments reveal that the key interaction is the hydrated cation-π interaction which stabilizes the ions between two graphene sheets, fixing the interlayer spacing between according the lengths of the hydrated ions.

[1] J. Liu, G. Shi*, et al., Phys. Rev. Lett. 115, 164502 (2015).
[2] R. H. Tunuguntla, et al., Science 357, 792 (2017).
[3] L. Chen#, G. Shi#(equal contributors), et al., Nature 550, 380 (2017).

报告人简介：http://water.sinap.cas.cn/cn/yjtd/201312/t20131230_150593.html