Single Quasi-1D Chains of Sb₂Se₃ Encapsulated within Carbon Nanotubes

Abstract

The realization of stable monolayers from 2D van der Waals (vdW) solids has fueled the search for exfoliable crystals with even lower dimensionalities. To this end, 1D and quasi-1D (q-1D) vdW crystals comprising weakly bound subnanometer-thick chains have been discovered and demonstrated to exhibit nascent physics in the bulk. Although established micromechanical and liquid-phase exfoliation methods have been applied to access single isolated chains from bulk crystals, interchain vdW interactions with nonequivalent strengths have greatly hindered the ability to achieve uniform single isolated chains. Here, we report that encapsulation of the model q-1D vdW crystal, Sb 2 Se 3 , within single-walled carbon nanotubes (CNTs) circumvents the relatively stronger c-axis vdW interactions between the chains and allows for the isolation of single chains with structural integrity. High-resolution transmission electron microscopy and selected area electron diffraction studies of the Sb 2 Se 3 @CNT heterostructure revealed that the structure of the [Sb 4 Se 6 ] n chain is preserved, enabling us to systematically probe the size-dependent properties of Sb 2 Se 3 from the bulk down to a single chain. We show that ensembles of the [Sb 4 Se 6 ] n chains within CNTs display Raman confinement effects and an emergent band-like absorption onset around 600 nm, suggesting a strong blue shift of the near-infrared band gap of Sb 2 Se 3 into the visible range upon encapsulation. First-principles density functional theory calculations further provided qualitative insight into the structures and interactions that could manifest in the Sb 2 Se 3 @CNT heterostructure. Spatial visualization of the calculated electron density difference map of the heterostructure indicated a minimal degree of electron donation from the host CNT to the guest [Sb 4 Se 6 ] n chain. Altogether, this model system demonstrates that 1D and q-1D vdW crystals with strongly anisotropic vdW interactions can be precisely studied by encapsulation within CNTs with suitable diameters, thereby opening opportunities in understanding dimension-dependent properties of a plethora of emergent vdW solids at or approaching the subnanometer regime.

Encapsulation of crystalline and amorphous Sb2S3 within carbon and boron nitride nanotubes

“…23 We, however, did not observe any apparent difference between empty and filled SWCNTs in the region we surveyed, with only broadband CNT absorbance visible. This contrasts with our work on Sb 2 Se 3 @SWCNT, where we saw the onset of a distinct edge in the heterostructure not present in empty SWCNTs 72 and is likely due to the lower absorption coefficient of Sb 2 S 3 compared to Sb 2 Se 3 . 31 From these measurements, it became clear that the observation of confined optical properties of Sb 2 S 3 down to the single chain regime in encapsulated heterostructures requires a transparent nanotube as a host material.…”

“…1B). As we saw previously with our work on Sb 2 Se 3 , 72 this method of confinement within SWCNTs accessed ultrathin nanowires of Sb 2 S 3 within nanotubes of fewer than 2 nm, meaning that only 1–2 covalent chains with 1.04 nm distance between terminal sulfur atoms could occupy a given nanotube.…”

Functionalization and Structural Evolution of Conducting Quasi-One-Dimensional Chevrel-Type Telluride Nanocrystals

“…Beyond materials in two dimensions, the search for well-defined solid-state materials with even lower dimensionalities has led to the rediscovery of one-dimensional (1D) crystals with chain-like building blocks, whose cross sections approach the subnanometer regime. − Of these, 1D crystals that display metallic and semimetallic characteristics have gained recent attention owing to their potential to harness unusual charge density waves, superconductivity, and topologically insulating states. From a materials discovery standpoint, the inherent susceptibility of 1D metals and semimetals toward Peierls distortion-induced phase transition hinders the realization and isolation of these phases, especially approaching the atomic scale. , This renewed interest in solid-state 1D and quasi-1D (q-1D) materials with subnanometer building blocks has motivated recent efforts to understand the structure and physical properties of a family of molybdenum-based Chevrel-like q-1D ionic lattices. − These q-1D lattices are characterized by anionic metal-chalcogenide (M-Ch) infinite chains that are separated or intercalated by monovalent cations (A) with an A 2 Mo 6 Ch 6 (where A = Li, Na, K, Rb, Cs, In, Tl; Ch = S, Se, Te) stoichiometry.…”

GaSI: A Wide-Gap Non-centrosymmetric Helical Crystal

“…The case of the Sn(Br/I)P crystals suggests that the propagation of crystallographic screw axes along the long-axis of weakly bound chains leads to helical structures. ,,, Encouragingly, the immense interest in exfoliable 1D crystals has sparked the search for classes of inorganic crystals with sub-nanometer-thick chains held by vdW interactions. − Thus, the identification of screw axis symmetry within emergent 1D vdW crystal classes led to our discovery of helical motifs in III–VI–VII 1D vdW crystals (III = Al, Ga, In; VI = S, Se, Te; VII = Cl, Br, I). ,,,,− We found that crystals in this class manifest tetrahelical motifs along chains held by vdW interactions. ,,,− For example, InSeI is a semiconductor consisting of periodic helical chains defined by a 4 1 screw axis and shows highly temperature-sensitive bandgaps in the visible range (Figure S1). ,,,− Substitution of Ga atoms to the In site led to GaSeI, which is the first freestanding inorganic tetrahelix that is an approximate Boerdjik–Coxeter (B–C) helix .…”