One‐Dimensional Arsenic Allotropes: Polymerization of Yellow Arsenic Inside Single‐Wall Carbon Nanotubes

Abstract

The pnictogen nanomaterials, including phosphorene and arsenene, display remarkable electronic and chemical properties. Yet, the structural diversity that these main group elements are capable of is still poorly explored. Here we fill single-wall carbon nanotubes with elemental arsenic from the vapor phase. Using electron microscopy, we find chains of highly reactive As4 molecules as well as two new one-dimensional allotropes of arsenic: a single-stranded zigzag chain and a double-stranded zigzag ladder. These linear structures are important intermediates between the gas-phase clusters of arsenic and the extended sheets of arsenene. Raman spectroscopy indicates weak electronic interaction between the arsenic and the nanotubes which implies that the formation of the new allotropes is driven primarily by the geometry of the confinement. The relative stabilities of the new arsenic structures are estimated computationally. Band-gap calculations predict that the insulating As4 chains become semiconducting, once converted to the zigzag ladder, and form a fully metallic allotrope of arsenic as the zigzag chain.

One-Dimensional Pnictogen Allotropes inside Single-Wall Carbon Nanotubes

“…However, the transition to the metallic zig-zag chain is expected to be insensitive to the choice of functional. 54 found to depend on SWCNT diameter. SWCNTs were successfully filled using red phosphorus, which may be more convenient than using white phosphorus, to yield predominately the new zigzag ladders.…”

“…The filling yields of m-P@CoMoCat and v-As@HiPCO were reported in our earlier studies. [53][54] Some of the highest filling yields were observed for elemental phosphorus using the melt filling technique and they were found to be relatively independent of the diameter of the SWCNTs. Filling with phosphorus from the vapor phase was successful as well and gave the single highest filling yield out of all experiments in the case of HiPCO tubes.…”

“…[43][44] Carbon nanotubes have been used as inert molds to prepare new one-dimensional allotropes of a range of elements including carbon in its various forms, [45][46][47] iodine, 48 sulphur, 49 selenium 50 , tellurium, 51 as well as the two pnictogens phosphorus [52][53] and arsenic. 54 In the case of phosphorus, fibrous chains with alternating P8 and P2 units have been identified inside large-diameter multiwall carbon nanotubes. 52 Single-stranded phosphorus zig-zag chains have been prepared in narrow single-wall carbon nanotubes (SWCNTs) by polymerizing encapsulated chains of P4 molecules.…”

Determination of the length of single-walled carbon nanotubes by scanning electron microscopy

“…Carbon nanotubes (CNTs) combine a myriad of excellent properties and are being explored for a wide variety of applications ranging from composite materials to the biomedical field, going through electronic devices. They are characterized by a large aspect ratio and hollow core which allows both their exohedral [ 1 , 2 ] and endohedral [ [3] , [4] , [5] , [6] ] functionalization, further expanding their range of application. CNTs of different lengths are desired depending on the targeted applications.…”

One-Dimensional Pnictogen Allotropes Inside Single-Wall Carbon Nanotubes

“…55 The single-stranded zig-zag chain has also recently been observed for arsenic inside SWCNTs which also forms double-stranded zig-zag ladders. 54 In addition to stabilizing new pnictogen nanostructures inside carbon nanotubes, they also provide environments stabilizing the highly reactive P4 and As4 molecules against the infamous spontaneous combustion with atmospheric oxygen to give the corresponding oxides. [53][54] Filling carbon nanotubes with antimony has been attempted as part of the arc-discharge preparation process.…”