Molecular Dynamics Simulation And Experimental Studies On Ion Current Rectification And C60 Transport In Nanochannels

The size effect is obvious in the nanochannel and some unique properties would appear which can not be observed in macro channels,such as ion current rectification or molecular detection.A deep understanding to the fluid transport properties under the nano scale is a important foundation for the development of micro/nano fluidic devices,the main researches of this paper are as follows:(1)Ion transport in a confined conical nanochannel with high solution concentration has been investigated using molecular dynamics simulation.Results indicate that the ion current rectification appears in a confined conical nanopore while without the overlap of electrical doulbe layer.Similar to in low solution concentration,the ion current rectification in high solution concentration can be influenced by both the solution concentration and the surface charge properties.With solution congcentration increasing,a maximum of rectification ratio can be obtained.This phenomenon is attributed to the competion result that the changing of binding energy along axial arised from the confined geometry will intensify the ion axial asymetric concentration plarizaton while the decreasing length of electriczal doulbe layer will weaken concentration plarizaton,which is different from that in low solution concentration.(2)The effect of C60 molecular with different charge densities through the nanochannel on ion current with different solution concentrations has been investigated using molecular dynamics simulation.Results indicate that the ion axial velocity in the nanochannel would decrease when the C60 molecular through the nanochannel because the electroosmotic flow are affected by C60 and the counterion will not be attracted into the nanochannel when the C60 molecular has no charge,so the vias current would be smaller than the reference current.The number of the counterion which attracted into the channel by the C60 molecular to maintain electrical neutrality of the nanochannel and the axial velocity of the ions would increase with the addition of the charge density of the C60 molecular,so the vias current would also increase.The effect of the increased number of the counterion and the decreased axial velocity which both caused by the charged C60 on the electroosmotic flow make the cross phenomenon between the vias current and reference current.(3)For the need of the detection of the nanochannel ionic current in nanofluidic technology,a test bench for detecting the nano-channel ionic current has been set up,and verifing the ion current rectification in the conical nanopore.