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 P₈and P₂structural 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.