Self-assembled Nanocapsules in Water: A Molecular Mechanism Study

TL;DR

This study investigates the self-assembly of open-ended carbon nanotubes into stable nanocapsules in water, exploring their formation, stability, and electric field responsiveness through molecular dynamics simulations.

Contribution

It reveals a novel self-assembly mechanism for nanocapsules and demonstrates their electric field controllability, advancing nanomaterial design for biomedical and nano-reactor applications.

Findings

Nanocapsules form via coaxial self-assembly of CNTs with different diameters.

Nanocapsules are stable in water under ambient conditions.

Electric fields can open nanocapsules by inducing polarization.

Abstract

The self-assembly mechanism of one-end-open carbon nanotubes (CNTs) suspended in an aqueous solution was studied by molecular dynamics simulations. It was shown that two one-end-open CNTs with different diameters can coaxially self-assemble into a nanocapsule. The nanocapsules formed were stable in aqueous solution under ambient conditions, and the pressure inside the nanocapsule was much higher than the ambient pressure due to the van der Waals interactions between two parts of the nanocapsule. The effect of the normalized radius difference, normalized inter-tube distance and aspect ratio of the CNT pairs were systematically explored. The electric field response of nanocapsules was studied with ab initio molecular dynamics simulations, which shows that nanocapsules can be opened by applying an external electric field, due to the polarization of carbon atoms. This discovery not only sheds light on a simple yet robust nanocapsule self-assembly mechanism, but also underpins potential innovations in drug delivery, nano-reactors, etc.