Ion Transport At Nanopipettes And The Enhanced Performance Of Scanning Ion-conductance Microscopy

With the development of the times,the evolution of nanotechnology and technique has matured,and great progress has been made in the exploration of the nanoworld.As a powerful tool for studying nanostructures,nanopipettes play an irreplaceable role in the fields of biology,physics,chemistry and medicine.Quartz nanopipettes have become the most widely used nanoscale tools because of their advantages such as simple preparation,easy operation,high insulation and low leakage current.This paper aims to study the sub-nanometer sized nanopipettes and to improve the resolution of the scanning ion-conductance microscopy,to explore the potential properties of quartz nanopipettes,and to fully exert the advantages of scanning ion-conductance microscopy.Subnano-sized quartz pipettes can be prepared here and characterized by cyclic voltammetry and potentiostatic method,respectively.And the ratio 1:9(molar concentration)of tetrabutylammonium chloride to potassium chloride was used to verify the experimental phenomenon.In this experiment,ion flow obstruction phenomenon was observed.Due to lack of space and ions surrounded by water molecules,ions in the electrolyte cannot be smoothly introduced and output at the tip of nanopipette when the diameter of the tip is in the sub-nanometer scale,resulting in blocking of the ion current and a sudden drop in current.This process is dynamic and irregular.This is another important property of quartz nanopipettes,this quality is very similar to that of ion channels on bio-membrane.Therefore,the study of sub-nanometer sized nanopipettes is of great significance for understanding the working mechanism of biological ion channels.In terms of scanning ion-conductance microscopy,the spatial resolution of scanning imaging is mainly studied.By introducing an FPGA module,preparing quartz nanopipettes of 5~10 nm and changing the Z-axis moving step,the scanning system has been greatly optimized.By scanning ITO samples,Ruled Diffraction Gratings,and etched Hydrogen Silsesquioxane(HSQ)surfaces,the images with a resolution of up to 10 nm were obtained.A major breakthrough has been made in the spatial resolution of the scanning ion-conductance microscopy.