# A Comprehensive Review on Filled Carbon Nanotubes: Synthesis, Properties and Applications

## TL;DR

This review explores how carbon nanotubes can be filled with various materials to create new hybrid materials with unique properties and applications.

## Contribution

The paper provides a comprehensive overview of filling methods and applications of filled carbon nanotubes, emphasizing their potential in solving societal challenges.

## Key findings

- Filled CNTs exhibit tailored optical, electronic, catalytic, and mechanical properties due to nanoscale confinement.
- Encapsulation in CNTs influences chemical reactivity, phase stability, and quantum phenomena of the encapsulated materials.
- Filled CNTs have promising applications in biomedicine, energy storage, gas separation, and nanoelectronics.

## Abstract

Carbon nanotubes (CNTs) have emerged as one of the most
exciting
families of carbon nanomaterials. Their hollow tubular architecture,
with a nanometric inner cavity, not only defines their distinct physical
and chemical behavior but also enables the encapsulation of a wide
range of materials, including inorganic and organic compounds. This
encapsulation capability allows CNTs to function as nanocontainers,
protective hosts, and confined reaction vessels, leading to novel
hybrid materials with tailored optical, electronic, catalytic, and
mechanical properties. In this review, we provide a comprehensive
overview of the methodologies employed for filling CNTs, including in situ and ex situ approaches. We critically
examined the diverse range of materials encapsulated within CNTs,
highlighting how confinement at the nanoscale influences their chemical
reactivity, phase stability, and emergent quantum phenomena. Special
attention is given to the wide range of applications of filled CNTs
in addressing societal challenges. These include biomedicine, catalysis,
energy storage, gas separation, filtration membranes, sensing technologies,
and nanoelectronics. Beyond revisiting the current state-of-the-art,
this review offers a critical discussion of future directions and
challenges in this field.