Molecular dynamics study on the field effect ion transport in carbon nanotube

Kang, Jeong Won; Byun, Ki Ryang; Lee, Ju Yul; Kong, Sun Cheol; Choi, Young‐Wan; Hwang, Ho Jung

doi:10.1016/j.physe.2004.06.040

“…Molecular simulation techniques are invaluable for unveiling the physical mechanisms responsible for these, and other, interesting experimental results. For example, Kang et al [24] investigated the importance of thermal fluctuations in determining the flux of potassium ions through (5,5) carbon nanotubes under external fields and Kotsalis et al [25] studied the flow of liquid-vapor water mixtures through carbon nanotubes using non-equilibrium molecular dynamics. They found that the flowing water is characterized by a slip length that increases as the radius of the nanotube increases.…”

Section: Introductionmentioning

confidence: 99%

Water self-diffusion through narrow oxygenated carbon nanotubes

Striolo¹

2007

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The hydrophobic interior of carbon nanotubes, which is reminiscent of ion channels in cellular membranes, has inspired scientific research directed towards the production of, for example, membranes for water desalination, drug-delivery devices, and nanosyringes. To develop these technologies it is crucial to understand and predict the equilibrium and transport properties of confined water. We present here a series of molecular dynamics simulation results conducted to understand the extent to which the presence of a few oxygenated active sites, modeled as carbonyls, affects the transport properties of confined water. The model for the carbon nanotube is not intended to be realistic. Its only purpose is to allow us to understand the effect of a few oxygenated sites on the transport properties of water confined in a narrow cylindrical pore, which is otherwise hydrophobic. At low hydration levels we found little, if any, water diffusion. The diffusion, which appears to be of the Fickian type for sufficiently large hydration levels, becomes faster as the number of confined water molecules increases, reaches a maximum, and slows as water fills the carbon nanotubes. We explain our findings on the basis of two collective motion mechanisms observed from the analysis of sequences of simulation snapshots. We term the two mechanisms ‘cluster-breakage’ and ‘cluster-libration’ mechanisms. We observe that the cluster-breakage mechanism produces longer displacements for the confined water molecules than the cluster-libration one, but deactivates as water fills the carbon nanotube. From a practical point of view, our results are particularly important for two reasons: (1) at low hydration levels the presence of only eight carbonyl groups can prevent the diffusion of water through (8, 8) carbon nanotubes; and (2) the extremely fast self-diffusion coefficients observed for water within narrow carbon nanotubes are significantly decreased in the presence of only a few oxygenated active sites. These results are relevant, for example, for the design of water-desalination membranes.

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“…Ions can easily permeate CNT when external forcing is applied. According to MD simulation of electric field driven potassium ion transport in (5,5) CNT (Kang, Byun et al 2004), K + ions can enter CNT much faster when driven by external force field than driven by thermal fluctuations at equilibrium. This finding implies an application of data storage device via controllable gate ion transport in CNT.…”

Section: Ionic Liquid Transportmentioning

confidence: 99%

“…It has potential of recovery of the alum in a high purity in a single-step process and reuse of it in the same plant or elsewhere as a coagulant. Also, the CNT based devises designed for ionic liquid transport and selectivity have potential applications in energy generation such as fuel cells, chemical nanoreactors, nanosensors and unipolar ionic field-effect transistors (Daiguji, Yang et al 2004;Kang, Byun et al 2004), since the high surface-to-volume ratio in CNT leads to ion separation via a transport mechanism governed by surface charges. While chapter 2 and 3 have discussed the progress and basic understandings of water and gas transport phenomena inside CNT, this chapter focuses on introductions of the MD simulation theories associated with ionic liquids inside CNT.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Carbon Nanotube Nanofluidics

Shadmehr,

Tang

2011

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“…It has potential of recovery of the alum in a high purity in a single-step process and reuse of it in the same plant or elsewhere as a coagulant. Also, the CNT based devises designed for ionic liquid transport and selectivity have potential applications in energy generation such as fuel cells, chemical nanoreactors, nanosensors and unipolar ionic field-effect transistors (Daiguji, Yang et al 2004;Kang, Byun et al 2004), since the high surface-to-volume ratio in CNT leads to ion separation via a transport mechanism governed by surface charges. While chapter 2 and 3 have discussed the progress and basic understandings of water and gas transport phenomena inside CNT, this chapter focuses on introductions of the MD simulation theories associated with ionic liquids inside CNT.…”

Section: Introduction and Overviewmentioning

confidence: 99%