Formation of nickel clusters wrapped in carbon cages: towards new endohedral metallofullerene synthesis

TL;DR

This paper introduces a novel electron irradiation method within high-resolution transmission electron microscopy to synthesize nickel endohedral metallofullerenes inside carbon nanotubes, enabling new nanoobject creation and in situ mechanism study.

Contribution

It presents a new synthesis approach for nickel EMFs using electron irradiation in AC-HRTEM, expanding the variety of accessible EMFs and allowing in situ structural analysis.

Findings

Successful synthesis of nickel EMFs inside carbon nanotubes.

In situ observation of structural transformations during synthesis.

Molecular dynamics simulations support experimental results.

Abstract

In spite of the high potential of endohedral metallofullerenes (EMFs) for application in biology, medicine and molecular electronics and recent efforts in EMF synthesis, the variety of EMFs accessible by conventional synthetic methods remains limited and does not include, for example, EMFs of late transition metals. We propose a method in which EMF formation is initiated by electron irradiation in aberration-corrected high-resolution transmission electron spectroscopy (AC-HRTEM) of a metal cluster surrounded by amorphous carbon inside a carbon nanotube serving as a nano-reactor and apply this method for synthesis of nickel EMFs. The use of ACHRTEM makes it possible not only to synthesize new, previously unattainable nanoobjects but also to study in situ the mechanism of structural transformations. Molecular dynamics simulations using the state-of-the-art approach for modeling the effect of electron irradiation are performed to rationalise the experimental observations and to link the observed processes with conditions of bulk EMF synthesis.