The Investigantion Of Transport Properties About The Water And Ion In The Nanotube

There are many kinds of biological channels in the biological metabolic metro such as aquaporin(AQP), potassium channel and so on. Over the years, researchers have made great achievements by sdudying these kinds of biological nanotube. Some researchers have been found that the permeation of water and ion will be affected by the construction of the biological channel and its residues. For example, the water molecules must automatically build up a single line before they go through the aquaporins. Because there is a narrow region and some residues in the middle of the biological nanotube. As the same time, these interesting phenomena of biological nanotube will be more concerning in the future and the related basic and applied research is ongoing It includes that using the molecular simulation researches the transportation of water and ion in the biological channel by the computer. Although, it is only basic research of simulation. In fact this kind of research is conductive to the development of nanotechnology. So we think that our work is helpful for the researching in the biological channel and the designing of nanoscale devices for transportation.The main work:Various types of research based on the carbon nanotube have began since 1991. Although the discovery of carbon nanotube is very late, its development could be described by the word "fast". Certainly it includes the research in the molecular simulation. The carbon nanotube could be treated as the alternative of biological channel as some of its transport properties are similar as biological channel. In this work, we use two models to research the transportation of water and ions in the nanotube.Firstly, It has been found that the narrow region in a water channel is responsible for gating or selectivity. However, the effect in the position of the narrow region on water transport is still not thoroughly understood. By using molecular dynamics simulations, we have found that the water flux through the nanotube (The type of the nanotube is (6,6). Its diameter and length are 8.1 A and 14.8 A respectively) will change significantly if the narrow location moves away from the middle region along the tube. Simulation results show that the flux reaches the maximum when the deformation occurs in the middle of the nanotube and decreases as the deformation location moves toward the ends of the nantoube. However the decrease of water flux is not mono tonic and the net flux gets the minimums near the ends about 2.5 A. These interesting phenomena can be explained by the water-water interactions and water-carbon interactions. This work may be helpful for people to research the relation between structure and the water permeation. And it may be also sensitive for people to design better nanodevice about permeation.Secondly, by using molecular simulation, we have studied transportation of ions (Na+,K+) through four kinds of nano slitpores with four different widths. We find that these nano slitpores constructed by two pieces of graphite display Na+-selectivity. When the width of the slitpore is equal to 8.8 A, the ion's transport ratio (Na+/K+) could reach six times. However, the selectivity will be weakened when the distance of the two pieces of graphite becomes larger. This kind of structure is very simple. Therefore, the special nano slitpores have wide potential application in ion separation and seawater desolation.