Assembly of Ring‐Shaped Phosphorus within Carbon Nanotube Nanoreactors

A phosphorus allotrope that has not been observed so far, ring‐shaped phosphorus consisting of alternate P 8 and P 2 structural units, has been assembled inside multi‐walled carbon nanotube nanoreactors with inner diameters of 5–8 nm by a chemical vapor transport and reaction of red phosphorus at 500 °C. The ring‐shaped nanostructures with surrounding graphene walls are stable under ambient conditions. The nanostructures were characterized by high‐resolution transmission electron microscopy, scanning transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, Raman scattering, attenuated total reflectance Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy.