SWCNTs

Single-walled carbon nanotubes (SWCNTs) are cylindrical nanostructures formed from a single layer of carbon atoms rolled into a seamless tube. They have diameters typically around 0.4 to 2 nanometers and can reach micrometers in length. The electronic behavior depends on the tube’s chirality, described by a pair of integers (n,m) that define how the graphene sheet is rolled. Depending on (n,m), SWCNTs can be metallic or semiconducting; their band gap, when present, scales roughly inversely with diameter. The discovery of SWCNTs is credited to Sumio Iijima in 1993.

SWCNTs are produced by several methods, including arc discharge, laser ablation, and chemical vapor deposition (CVD) using transition-metal catalysts. Post-synthesis purification is often required to remove amorphous carbon and metal residues, and separation techniques can enrich samples for specific diameters or chiralities. Functionalization strategies include covalent bonding to introduce solubility or compatibility with matrices, and noncovalent approaches using supramolecular interactions or polymers.

In terms of properties, SWCNTs exhibit exceptional mechanical strength and stiffness, with high Young’s modulus and tensile strength along the tube axis. Thermal conductivity along the axis is among the highest observed in materials at room temperature. Electrically, metallic SWCNTs conduct with minimal resistance, while semiconducting tubes can form field-effect transistors; the electrical performance is highly sensitive to chirality, diameter, and defects. Environmental and health considerations, handling safety, and lifecycle impacts are active research areas.

Applications span nanoelectronics (transistors and interconnects), sensors, energy storage (supercapacitors, electrodes), and composites that gain strength and electrical conductivity. Control over chirality and scalable, selective processing remain key challenges for widespread deployment.