Single-Walled Carbon Nanotubes (SWCNTs) are cylindrical nanostructures composed of a single layer of carbon atoms arranged in a hexagonal lattice, rolled into a seamless tube. As one of the most fascinating allotropes of carbon, SWCNTs possess exceptional mechanical, electrical, and thermal properties that make them a cornerstone in the field of nanotechnology.

Structural Features

SWCNTs are typically 0.4 to 3 nanometers in diameter, with lengths that can extend up to several micrometers or even millimeters. Their unique one-dimensional structure gives rise to properties that differ significantly from other carbon forms such as graphite, graphene, and fullerenes.

They can be categorized based on their chirality (the angle at which the graphene sheet is rolled):

• Armchair (n=n) – Metallic behavior

• Zigzag (n,0) – Can be semiconducting or metallic

• Chiral (n≠m) – Generally semiconducting

  
  

Exceptional Properties

• Electrical Conductivity: Depending on their structure, SWCNTs can behave as metals or semiconductors, making them highly desirable for nanoelectronic devices.

• Mechanical Strength: SWCNTs exhibit a tensile strength over 50 times greater than steel, with a much lower density.

• Thermal Conductivity: They can efficiently dissipate heat, with thermal conductivities exceeding that of diamond along the tube axis.

• Flexibility and Elasticity: Despite their rigidity, SWCNTs are highly flexible and can return to their original shape after deformation.

  
  

Key Applications

Electronics and Semiconductors: SWCNTs are investigated for use in field-effect transistors (FETs), sensors, and interconnects due to their ability to carry high current densities and function at nanoscale dimensions.

Composite Materials: They enhance the strength, thermal stability, and electrical conductivity of polymers and metals when used as reinforcing fillers in composites.

Energy Storage and Conversion: SWCNTs are used in electrodes for lithium-ion batteries, supercapacitors, and fuel cells, owing to their high surface area and conductive properties.

Biomedical Applications: Their biocompatibility and ability to penetrate cells make SWCNTs candidates for drug delivery, biosensing, and imaging applications.

Transparent Conductive Films: SWCNTs are being used to develop flexible, lightweight, and transparent conductive films for touchscreens, solar cells, and wearable electronics.

Challenges and Future Directions

Despite their immense potential, several challenges hinder the widespread commercialization of SWCNTs:

• Purity and Selectivity: Producing SWCNTs with specific chirality and minimal defects is difficult.

• Scalability: Large-scale, cost-effective, and consistent manufacturing methods are still under development.

• Toxicity and Environmental Impact: The long-term health effects and environmental persistence of SWCNTs are not fully understood, prompting ongoing research into safe handling and disposal.