Single-Walled Carbon Nanotubes Acting as ControllableTransport Channels

Abstract

The motion and equilibrium distribution of water molecules adsorbedinside neutral and negatively charged single-walled carbon nanotubes(SWNTs) have been studied using molecular dynamics simulations (MDSs)at room temperature based on CHARMM (Chemistry at HARvard MolecularMechanics) potential parameters. We find that water molecules have aconspicuous electropism phenomenon and regular tubule patterns insideand outside the charged tube wall. The analyses of the motion behaviourof water molecules in the radial and axial directions show that bycharging the SWNT, the adsorption efficiency is greatly enhanced, andthe electric field produced by the charged SWNTs prevents watermolecules from flowing out of the nanotube. However, water moleculescan travel through the neutral SWNT in a fluctuating manner. Thisindicates that by electrically charging and uncharging the SWNTs, onecan control the adsorption and transport behaviour of polar moleculesin SWNTs for using as a stable storage medium or long transportchannels. The transport velocity can be tailored by changing the chargeon the SWNTs, which may have a further application as modulatabletransport channels.