Water Layering and Orientation Modulate Lanthanide Hydration in Carbon Nanotubes
- 1Department of Biosystems and Agricultural Engineering
- 2University of Kentucky
- 3Department of Chemical and Materials Engineering
Abstract
Nanoscale confinement can reorganize water molecules and alter ionic hydration, offering a potential route to separating chemically similar ions. We use molecular dynamics simulations with the MACE-MH-1 foundation machine-learning interatomic potential to investigate the hydration of eight trivalent lanthanide ions (Ln 3+ : La 3+ , Pr 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Tm 3+ , and Lu 3+ ) in carbon nanotubes (CNTs) with diameters of 1.09–1.49 nm. We first evaluate MACE-MH-1 for Ln 3+ hydration in bulk solution. The OMOL model of MACE-MH-1 reproduces the reported Ln–O distances and coordination-number trends and is therefore used for the CNT simulations. The hydration factor, which measures first-shell orientational order, varies nonmonotonically with CNT diameter and reaches a minimum in CNT(9,9), which also accommodates the most first-shell water molecules. This minimum coincides with the emergence of a central water population and reflects two combined effects: difference in preferred orientation between first-shell and surrounding water molecules and increased hydrogen-bond coupling between them. However, different Ln 3+ ions respond similarly to confinement, suggesting that CNT confinement alone may offer limited selectivity for their separation.
Related
- Orientation tomography of lanthanide-doped nanoprobes by polarization-resolved micro-spectroscopy
- Intermolecular and Interfacial Origins of Layering in a Near-Isotropic Organic Glass Former
- Reference Conventions and Structure Types, Rather Than 4f Occupancy, Shape Lanthanide Errors in Universal Machine-Learning Interatomic Potentials
- How the Energy Gaps between Partners Rules ns-Scale Sensitization and Back-Energy Transfer in Lanthanide(III) Complexes?
- Reconciling visible emission intensity and ON/OFF commutation ratio in photochromic lanthanide complexes of europium(III) and samarium(III).
BibTeX
@misc{zhang2026water,
title = {{Water Layering and Orientation Modulate Lanthanide Hydration in Carbon Nanotubes}},
author = {Kailong Zhang and Jian Shi and Qing Shao},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009104/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009104/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Water Layering and Orientation Modulate Lanthanide Hydration in Carbon Nanotubes
AU - Kailong Zhang
AU - Jian Shi
AU - Qing Shao
PY - 2026
DA - 2026/09/20
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009104/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009104/v1
AB - Nanoscale confinement can reorganize water molecules and alter ionic hydration, offering a potential route to separating chemically similar ions. We use molecular dynamics simulations with the MACE-MH-1 foundation machine-learning interatomic potential to investigate the hydration of eight trivalent lanthanide ions (Ln 3+ : La 3+ , Pr 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Tm 3+ , and Lu 3+ ) in carbon nanotubes (CNTs) with diameters of 1.09–1.49 nm. We first evaluate MACE-MH-1 for Ln 3+ hydration in bulk solution. The OMOL model of MACE-MH-1 reproduces the reported Ln–O distances and coordination-number trends and is therefore used for the CNT simulations. The hydration factor, which measures first-shell orientational order, varies nonmonotonically with CNT diameter and reaches a minimum in CNT(9,9), which also accommodates the most first-shell water molecules. This minimum coincides with the emergence of a central water population and reflects two combined effects: difference in preferred orientation between first-shell and surrounding water molecules and increased hydrogen-bond coupling between them. However, different Ln 3+ ions respond similarly to confinement, suggesting that CNT confinement alone may offer limited selectivity for their separation.
ER -