By Josh Perry, Editor
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For the first time, scientists at University College London (U.K.) created individual, flexible, 2-D nanoribbons of crystalline phosphorene, the phosphorous equivalent of graphene and a material that scientists predict will have exciting properties to enhance electronics and fast-charging battery technology.

Individual phosphorene nanoribbons. (Watts et al./UCL)

Two-dimensional phosphorene was first isolated in 2014, according to a report from UCL, and there has been various predictions about how the material could benefit a variety of applications. This is the first time that individual nanoribbons have been created, with UCL researchers using crystals of black phosphorous and lithium ions.

“While nanoribbons have been made from several materials such as graphene, the phosphorene nanoribbons produced here have a greater range of widths, heights, lengths and aspect ratios,” the article noted. “Moreover, they can be produced at scale in a liquid that could then be used to apply them in volume at low cost for applications.”

The nanoribbons were one atom high, 4-50 nanometers wide, and up to 75 micrometers long. Researchers visualized the ribbons and saw that in areas where more than one layer of phosphorene exists there are “seamless steps” between the layers and each one has unique electrical properties.

“The nanoribbons are formed by mixing black phosphorus with lithium ions dissolved in liquid ammonia at -50°C,” the article explained. “After 24 hours, the ammonia is removed and replaced with an organic solvent which makes a solution of nanoribbons of mixed sizes.”

The research was recently published in Nature. The abstract stated:

“Phosphorene is a mono-elemental, two-dimensional (2D) substance with outstanding, highly directional properties and a bandgap that depends on the number of layers of the material. Nanoribbons, meanwhile, combine the flexibility and unidirectional properties of one-dimensional nanomaterials, the high surface area of 2D nanomaterials and the electron-confinement and edge effects of both. The structures of nanoribbons can thus lead to exceptional control over electronic band structure, the emergence of novel phenomena and unique architectures for applications.

“Phosphorene’s intrinsically anisotropic structure has motivated numerous theoretical calculations of phosphorene nanoribbons (PNRs), predicting extraordinary properties. So far, however, discrete PNRs have not been produced. Here we present a method for creating quantities of high-quality, individual PNRs by ionic scissoring of macroscopic black phosphorus crystals.

“This top–down process results in stable liquid dispersions of PNRs with typical widths of 4–50 nm, predominantly single-layer thickness, measured lengths of up to 75 μm and aspect ratios of up to 1,000. The nanoribbons are atomically flat single crystals, aligned exclusively in the zigzag crystallographic orientation. The ribbons have remarkably uniform widths along their entire lengths and are extremely flexible.

“These properties—together with the ease of downstream manipulation via liquid-phase methods—should enable the search for predicted exotic states, and an array of applications in which PNRs have been predicted to offer transformative advantages. These applications range from thermoelectric devices to high-capacity fast-charging batteries and integrated high-speed electronic circuits.”