SingleWalled

Singlewalled describes structures composed of a single continuous layer that forms a hollow interior, in contrast to multiwalled structures that have two or more concentric layers. The term is used across materials science, chemistry, and nanotechnology to denote tubular or shell-like objects with a single wall.

The best-known example is single-walled carbon nanotubes (SWCNTs). Each nanotube consists of a single graphene sheet rolled into a cylinder, with typical diameters around 0.4 to 3 nanometers and lengths that can reach micrometers. The electronic properties depend on the chirality, described by a pair of integers (n, m); some configurations are metallic, others semiconducting. SWCNTs are notable for very high tensile strength and stiffness, along with exceptional thermal conductivity along their axis, making them attractive for composites and nanoelectronic applications.

Synthesis methods include arc discharge, laser ablation, and chemical vapor deposition. Because the wall is only one atom thick, SWCNT materials can contain defects or mixtures of metallic and semiconducting tubes, complicating purification and separation. Research efforts focus on controlling diameter and chirality, as well as scalable production and dispersion in matrices.

Applications span reinforced polymer and ceramic composites, nanoelectronic components, energy storage devices, and sensors. Limitations for widespread use include production cost, quality control, and the need for methods to purify and sort tubes by electronic type and structure.

Outside carbon, other single-walled nanotubes exist, such as boron nitride nanotubes, which illustrate how the single-wall concept extends to related materials with different properties. The term singlewalled can also describe vesicles or shells formed by a single layer in chemistry and biology, distinguishing them from multilayer counterparts.