Current Understanding of Water Properties inside Carbon Nanotubes

Chatzichristos, Aris; Hassan, Jamal

doi:10.3390/nano12010174

Cited by 34 publications

(34 citation statements)

References 211 publications

(509 reference statements)

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“…Comparison with other systems exhibiting sub-diffusion. It is interesting to note some striking similarities of this system with water inside hydrophobic carbon nanotubes (CNTs) 49 . In narrow CNTs (d < 1.0 nm) water is found to diffuse as a single file by a very large number of studies, both theoretical [27][28][29] and experimental 17,18 .…”

Section: Resultsmentioning

confidence: 94%

Dynamic molecular ordering in multiphasic nanoconfined ionic liquids detected with time-resolved diffusion NMR

et al. 2023

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Molecular motion in nanosized channels can be highly complicated. For example, water molecules in ultranarrow hydrophobic nanopores move rapidly and coherently in a single file, whereas by increasing the pore size they organize into coaxial tubes, displaying stratified diffusion. Interestingly, an analogous complex motion is predicted in viscous charged fluids, such as room temperature ionic liquids (RTILs) confined in nanoporous carbon or silica; however, experimental evidence is still pending. Here, by combining 1H NMR diffusion experiments in different relaxation windows with molecular dynamics simulations, we show that the imidazolium-based RTIL [BMIM]+[TCM]−, entrapped in the MCM-41 silica nanopores, exhibits an intricate dynamic molecular ordering; adsorbed RTIL molecules form a fluctuating charged layer near the pore walls, while in the bulk pore space they diffuse discretely in coaxial tubular shells, with molecular mean square displacement following a nearly ∼τ0.5 time dependence, characteristic of single file diffusion.

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Section: Resultsmentioning

confidence: 94%

Dynamic molecular ordering in multiphasic nanoconfined ionic liquids detected with time-resolved diffusion NMR

et al. 2023

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“…For instance, it was recently discovered that diffusion-osmotic transport is crucial to the ion diffusion process across nanofluidic channels, relevant in the osmotic energy conversion. − This requires detailed understanding about the transport properties of water across nanotubes. Both experimental − and simulation − studies have suggested that the diffusion of water inside a cylindrical nanotube can be significantly different from the bulk. Diffusivity of water through a narrow carbon nanotube (CNT) was reported to be lower than bulk .…”

Section: Introductionmentioning

confidence: 99%

What Is the Viscosity of Liquid Water Confined in a Hydrophobic Nanotube? Estimation Using a Novel Approach

Khan

Daschakraborty

2023

J. Phys. Chem. C

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Computation of the shear viscosity (η) of liquid water under nanoconfinement is a daunting task, albeit crucial in different areas related to nanofluidics. The viscosity of bulk water is computed using the Green–Kubo formula or Stokes–Einstein (SE) relation. However, these relations are less useful in the case of water confined in a cylindrical nanotube since the stress tensors are asymmetric and the SE relation breaks down. Using a novel method, based on the translational Jump-corrected Confined Stokes–Einstein (JCSE) relation that takes into account the breakdown of the SE relation, we compute the viscosity of water inside some hydrophobic carbon nanotubes (CNTs) in a wide range of temperatures including the supercooled regime. The viscosity of water in narrow CNT(10,10) is seen to be surprisingly higher compared to bulk water at the same thermodynamic condition. This contradicts the usual notion and the past theoretical observations suggesting significantly low viscosity of water inside hydrophobic CNTs.

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“…Research on the diffusion of water molecules in artificial water channels is of interest to many researchers because it can lead to new designs of synthetic channels with similar performance to biological water channels. In recent years, water in carbon nanotubes (CNTs) has been studied extensively using different experimental techniques [ 12 , 13 ] and molecular dynamics simulations [ 14 ]. These methods extracted valuable information, such as the temperature dependence of water diffusion in nanohydrophobic confinements, which is of great interest in many applications.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bond Dynamics and Phase Transitions of Water inside Carbon Nanotubes

2023

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Water dynamics in nanochannels are altered by confinement, particularly in small carbon nanotubes (CNTs). However, the mechanisms behind these effects remain unclear. To address these issues, we carried out extensive molecular dynamics (MD) simulations to investigate the structure and dynamics of water inside CNTs of different sizes (length of 20 nm and diameters vary from 0.8 nm to 5.0 nm) at different temperatures (from 200 K to 420 K). The radial density profile of water inside CNTs shows a single peak near the CNT walls for small nanotubes. For CNTs with larger sizes, water molecules are arranged into coaxial tubular sheets, the number of which increases with the CNT size. Subdiffusive behavior is observed for ultranarrow CNTs with diameters of 0.8 nm and 1 nm. As the size of CNTs increases, Fickian diffusion becomes evident. The hydrogen bond correlation function of water inside CNT decays slower than in bulk water, and the decay rate decreases as we increase the diameter of the CNTs. In large CNTs, the hydrogen bond lifetime of the innermost layer is shorter than the other layers and depends on temperature. Additional analysis of our results reveals that water molecules along the CNT axis show a non-Arrhenius to Arrhenius diffusion crossover. In general, the diffusion transition temperature is higher than that of bulk water, but it depends on the size of the CNT.

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Current Understanding of Water Properties inside Carbon Nanotubes

Cited by 34 publications

References 211 publications

Dynamic molecular ordering in multiphasic nanoconfined ionic liquids detected with time-resolved diffusion NMR

Dynamic molecular ordering in multiphasic nanoconfined ionic liquids detected with time-resolved diffusion NMR

What Is the Viscosity of Liquid Water Confined in a Hydrophobic Nanotube? Estimation Using a Novel Approach

Hydrogen Bond Dynamics and Phase Transitions of Water inside Carbon Nanotubes

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