| In recent years,Ionic Liquids（ILs）have attracted much attention as a new type of organic solvent due to their excellent properties such as extremely low volatility,high conductivity,low melting point,wide electrochemical window,thermal stability,and tunability.ILs have been widely used in various fields,such as environmental,energy,materials,chemical physics,life sciences,and aerospace technology.However,in many applications,ILs are usually limited to the microscale and nanoscale,especially in nanoconfined environments where the physicochemical properties of ILs are different significantly from those in the bulk phase.Currently,the understanding and application of ILs properties at the microscale and nanoscale are not completely clear.Therefore,this thesis presents an in-depth study of ion transport behavior in ILs/water solution system using quartz nanopipette.This study provides important guidance and practical application value for understanding the physicochemical properties of ILs in nanoconfined and designing new sensors such as single-molecule detection and nucleic acid sequencing.This study combined experiments and COMSOL simulation to investigate ionic current rectification phenomenon and diffusion characteristics in ILs/water solution system and provide theoretical explanations for the ionic current behaviors of this system.The main research content are as follows:The quartz nanopipette-based ILs/water solution system were constructed at the microscale and nanoscale,and the ionic current behaviors of the system were studied to explain and reveal the intrinsic mechanism of ionic current behaviors.（1）The effect of different nanopipette and micropipette on ionic current behavior in ILs/water solution system was studied.The results showed that the system exhibited significant ionic current rectification in nanopipettes but not in micropipettes.The diffusion current in the microscale and nanoscale pores were negative,but the current-time curve of the nanopipette showed the fluctuating behavior after applying a bias voltage,while no fluctuation was observed for the micropipette.（2）The effect of KCl electrolyte concentration on ionic current behaviors of the ILs/water solution system was studied.The results showed that significant ionic current rectification was observed in the system under different concentrations of KCl solution.The strength of ionic current rectification in the system increased with increasing KCl electrolyte concentration,which was opposite to the results obtained from traditional water solution systems.（3）The effect of ILs species on ionic current behaviors of the ILs/water solution system was studied.The strength of ionic current rectification for different ILs was[Bmim][BF4]>[Bmim][PF6]>[Bmim][N（CN）2],and the magnitude of diffusion current was[Bmim][N（CN）2]>[Bmim][BF4]>[Bmim][PF6].The model of the ILs/water solution system was constructed using the finite element analysis software COMSOL Multiphysics to further reveal the ionic current behaviors of the system.（1）The potential distribution,space charge density distribution,ionic concentration distribution,ionic flux distribution,and the distribution of the electric field along the axis of symmetry of the ILs/water solution system were studied and analyzed in detail.（2）Based on the constructed model,the current-voltage curves at the microscale and nanoscale were obtained by integrating the current density,and compared with the experimentally measured current-voltage curve,and was analyzed and explained in detail.This thesis aims to conduct effective research on the ionic current behaviors of ILs/water solution systems through the combination of experiments and simulations,providing theoretical guidance for the application of this system in fields such as molecular detection,ion sensors,and chemical analysis. |
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