High Pressure in Boron Nitride Nanotubes for Kirigami Nanoribbon Elaboration

Abstract

Cutting and folding 2D systems is one of the explored paths to tune physical and chemical properties in atomic thick matter. Contrarily to graphene, boron nitride 1 (BN) nanoribbons are difficult to obtain and their folded structures have not been yet reported. Here we show that pressure application in multiwall boron nitride nanotubes leads to different types of tube internal organizations including BN nanoribbon formation and folds. The new observed tube-structures are associated to the breaking of a number of the internal tubes leading either to non-organized structures in the form of internal tube alveoli or in an organized stacking of folded h-BN nanoribbons. Irreversible changes in the morphology of multiwall BN nanotubes (MWBNNTs) take place from ∼7 GPa and morphologically modified tubes could be observed up to pressures of at least 49 GPa. The here used experimental probes included high resolution transmission microscopy, electron tomography and Raman spectroscopy. Atomistic modelling was also performed showing the formation of pinch structures along the tubes which favour pressure induced bond-breaking and hybridization changes and confirming the folded structure. Both experiments and modelling show that tube polygonization is a prominent characteristic of MWBNNTs even at ambient pressure. Overall, the pressure evolution of MWBNNTs strongly differs from their carbon analogues. The high mechanical stability of BN tube geometry is of interest for composite based structural materials. On the other side, the availability of h-BN nanoribbons and folded structures opens new prospects to produce physically modified BN properties.

Electronic Structure of Folded Hexagonal Boron Nitride

“…We now turn to discuss the detailed structure of folded h-BN monolayers which are modeled here by collapsed SWBNNT in order to avoid the presence of any dangling bond. Collapsed BN nanotubes also have interest in themselves having been directly observed by transmission electron microscopy. − As for carbon nanotubes, SWBNNTs have a critical diameter, above which their circular section collapses to a dogbone-like shape consisting of a central flat region with two side cavities. The collapse occurs when the central attractive interlayer van der Waals interactions overcome the strain-induced energetic cost associated with localizing the tube curvature at the edge cavities; in the case of SWBNNTs, we have obtained a critical diameter for this transformation of ∼3.05 nm (smaller than 5.14–5.16 nm for SWCNTs obtained using a similar method, due to the higher interlayer binding in BN than graphite).…”

“…The collapse occurs when the central attractive interlayer van der Waals interactions overcome the strain-induced energetic cost associated with localizing the tube curvature at the edge cavities; in the case of SWBNNTs, we have obtained a critical diameter for this transformation of ∼3.05 nm (smaller than 5.14−5.16 nm for SWCNTs obtained using a similar method, 46 due to the higher interlayer binding in BN than graphite). Here, we considered both the cases of armchair folds, modeled by a collapsed (26,26) armchair SWBNNT (Figure 2a The optimized armchair fold presents a central flat region with an AA′-stacking having an interlayer spacing of 0.32 nm. The side cavities have a diameter of 0.54 nm, almost identical to the diameter of a circular (4, 4) nanotube.…”

“…Folded regions are very easily encountered in a number of BN-based bulk and nanostructured materials. For instance, folds have been directly observed by transmission electron microscopy in flakes obtained by chemical exfoliated or chemical vapor deposition − and, in bulk crystals, at the early stages of the hexagonal to cubic transformation. − Furthermore, zigzag edges in BN bilayers reconstruct by forming out-of-plane bonds, leading to lobe structures. , Similar smooth edge-folded h-BN also occurs in collapsed single-walled boron nitride nanotubes (SWBNNTs), composed of two edge cavities linked via a central flat region similar to bilayer h-BN. , A large fraction of folded BN nanostructures including a significant number of collapsed nanotubes can be obtained through plasma synthesis or the post-synthesis application of high pressures. , Whereas folds are very common in h-BN and their role in defining the ultimate optical properties of defective BN materials has been experimentally proved, their ground-state electronic structure has not yet been described. In this work, we present first-principles atomistic calculations of folded h-BN layers.…”

Kirigami‐Inspired Biodesign for Applications in Healthcare

“…Staggered linear and Y-shape cuts (15 mm and 5 mm) [60] Photoactive silk fibroin Photolithography Staggered linear cuts (25 µm), branched Y-shape cuts, saddles, chevrons [37] Graphite electrodes on polyimide sheet Laser cutting Staggered linear cuts (over 3 cm) [61] Gold nanofilms Dual-beam focused ion beam (FIB)/SEM Arcs and 3D microdomes (sub-50-nm) [27] Gold traces embedded in thin-film Parylene C Oxygen plasma etching Serpentine cuts [62] Mono-layer MoS 2 on PDMS Molding and plasma etching Linear patterns, pyramids, out-of-plane springs with alternating C-shapes [35] PMMA-PI composite Wet etching and laser cutting 2D hierarchical designs [63] PEO-PAA composite Blade cutting Curved patterns, linear cuts [64] Multiwalled boron nitride nanotubes Pressure-induced Folded nanoribbon internal structures/pleats [65] PLA-PEDOT:PSS Laser cutting Y-shape cuts [24] Hydrogel films-carboxyl-Zr 4+ metal coordination complexes Photolithography Custom papercut designs, woven-like alternating vertical/horizontal lines [30] Graphene sandwiched between polyimide sheets Photolithography and reactive ion etching Mesh (islands connected by kirigami bridges) [66] Liquid crystal elastomer Two-photon polymerization (2PP) Linear cuts, hinged squares, [67] PET encapsulated in PDMS Laser cutting Graded kirigami (10 mm segments of increasing void area) [68] PVDF-TrFE composite (ZnO nanoparticles and MWCNTs)…”

“…[ 67 ] Pressure application in multiwalled boron nitride nanotubes led to different types of folded nanoribbons in the form internal tube alveoli and organized stacking of folded nanoribbon structures, which could be designed for applications in optoelectronic devices and mechanically reinforced materials. [ 65 ]…”