1 research outputs found
Single Quasi-1D Chains of Sb<sub>2</sub>Se<sub>3</sub> Encapsulated within Carbon Nanotubes
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, Sb2Se3, 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 Sb2Se3@CNT heterostructure revealed that the structure of
the [Sb4Se6]n chain
is preserved, enabling us to systematically probe the size-dependent
properties of Sb2Se3 from the bulk down to a
single chain. We show that ensembles of the [Sb4Se6]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 Sb2Se3 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 Sb2Se3@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 [Sb4Se6]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