单锥形纳米孔道离子输运研究

发布时间：2018-08-13 09:01

【摘要】：单锥形纳米孔道由于具有对称性破缺和表面电荷特性而表现出整流效应,因此在离子分离、电能供应、化学阀等领域具有重要的潜在应用价值。深入研究纳米孔道中的电学特性及纳米孔道修饰方法,对于理解纳米尺度下的离子输运特性和改进锥形纳米孔道应用性能具有重要的意义。本文基于兰州交叉学科重离子微束装置的单离子辐照技术,用单个离子辐照PET薄膜样品,通过化学蚀刻单离子径迹的方法成功制备出了单锥形纳米孔道,并测量了多种电解质溶液在单锥形纳米孔道中的离子输运特性。研究发现,在KCl、NaCl、LiCl、MgCl_2、CaCl_2五种不同的溶液中均可以观测到单锥形纳米孔道的整流效应,并且整流系数都随溶液浓度增加呈现先增大后减小的趋势;相比于一价电解质溶液,二价电解质溶液中整流系数在较低浓度下就能达到最大值。对此我们提出了单锥形纳米孔道内的离子输运模型,该模型考虑了溶液浓度、施加电压以及离子富集引起纳米孔内的势阱的变化,成功解释了观察到的实验现象。为了对整流效应有更深入的理解,我们进一步对单锥形纳米孔道的离子选择性进行了研究。我们设计实验实现了单锥形纳米孔道内离子的单向输运测试,通过阴阳离子电流大小可以确定单锥形纳米孔道的阴阳离子选择性。我们发现PET单锥形纳米孔道在多价阳离子溶液中浸泡会使其表面由负电荷态转变为正电荷态,进而导致其由阳离子选择性转变为阴离子选择性。我们继续研究了多价阳离子使单锥形纳米孔道表面电荷反转的过程,发现其表面电荷反转主要是由于多价阳离子在孔壁上的吸附,并且受到电解质溶液浓度的影响。数据显示,三价离子溶液中的电荷反转浓度小于二价离子,而一价离子溶液中未观测到表面电荷反转。
[Abstract]:Single conical nanochannels exhibit rectifying effects due to their symmetry breaking and surface charge characteristics, so they have important potential applications in the fields of ion separation, power supply, chemical valves and so on. It is of great significance to study the electrical properties and the modification methods of nanorods in order to understand the ion transport characteristics in nanoscale and improve the application performance of conical nanochannels. Based on the single ion irradiation technique of Lanzhou interdiscipline heavy ion microbeam device, single conical nanorods were successfully prepared by chemical etching of single ion track in PET thin film samples irradiated by single ion. The ionic transport characteristics of various electrolyte solutions in a single conical nano-channel have been measured. It is found that the rectifying effect of single conical nano-channel can be observed in five different solutions of KCl-NaCl-LiCl-MgCl-2CaCl2, and the rectifying coefficient increases first and then decreases with the increase of solution concentration, compared with the monovalent electrolyte solution, The rectifying coefficient in bivalent electrolyte solution can reach the maximum at lower concentration. In this paper, we present an ion transport model in a single conical nano-channel. The model takes into account the changes of the potential trap in the nano-pore caused by solution concentration, applied voltage and ion enrichment, and explains the observed experimental phenomena successfully. In order to better understand the rectifying effect, we have further studied the ion selectivity of single conical nano-channels. The unidirectional transport test of ions in a single conical nano-channel has been carried out. The anion selectivity of a single conical nano-channel can be determined by the current of anion and anion. We find that immersion of PET mono-conical nano-channels in polyvalent cationic solution can change the surface of PET from negative charge state to positive charge state, which leads to the conversion from cationic selectivity to anionic selectivity. We continue to study the charge reversal process of polyvalent cations on the surface of mono-conical nano-channels. It is found that the surface charge inversion is mainly due to the adsorption of polyvalent cations on the pore wall and is affected by the concentration of electrolyte solution. The data show that the concentration of charge inversion in trivalent ion solution is lower than that in divalent ion solution, but no surface charge inversion is observed in monovalent ion solution.
【学位授予单位】：中国科学院大学(中国科学院近代物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1

【参考文献】