High-Quality Boron Nitride Nanoribbons: Unzipping during Nanotube Synthesis

摘要

Boron nitride nanoribbons (BNNRs) are strips of thin BN sheets with widths on the nanometer scale. BNNRs have unique edge states and width-related properties. First-principle calculations reveal that the bandgaps of zigzag BNNRs relate to nanoribbon width and are tunable by external electric fields and different levels of edge hydrogenation. Though bulk hexagonal boron nitride (hBN) crystals are electrically insulating, BNNRs can be made half-metallic through edge hydrogenation, fluorination, and oxygen func-tionalization. Intriguing edge magnetism has also been proposed in BNNRs. An experimental study has shown that BNNRs are much more electrically conductive than boron nitride nanotubes (BNNTs). BNNRs are chemically more reactive than bulk BN owing to the high number of unsaturated edge atoms, which makes them ideal gas-sensing materials. Compared to BN nanotubes and nanosheets, BNNRs could be better composite fillers for improved mechanical enhancement because of stronger interface bindings between BNNR edges and matrix. Therefore, BNNRs are of great interest for nanoscale electronic, spintronic, optoelectronic, sensor, and composite applications. All of these applications require BNNRs in large amounts and high quality. However, the synthesis of nanoribbons is quite challenging. BNNRs have been produced by unzipping BNNTs by postsynthesis treatment, that is, plasma etching and alkali metal intercalation, similar to the methods proposed for the production of graphene nanoribbons (GNRs). However, the yield of the current BNNR production is low.