Recently, the concept of dimensionality, and the engineering of materials’ structure and properties via changes in dimensionality, has emerged as an additional degree of freedom within the processing-structure-property relationship intrinsic to traditional materials science. To this end, the isolation of single atomic-planes (e.g. graphene and the transition metal dichalcogenides) and chains (e.g. transition metal trichalcogenides, TMTs) from quasi-low-dimensional materials has been extremely fruitful. The archetypal quasi-1D materials family is the TMTs, commonly termed MX3 compounds, with M a transition metal and X a chalcogen. Typically, 1D MX3 chains are weakly coupled by interchain vdW interactions to form coherent, but highly anisotropic, three-dimensional crystals. The bulk synthesis and properties of the TMTs has been well explored and they are canonical examples of superconductors and charge density wave materials. This structural motif is common across a range of M and X atoms (e.g. NbSe3, HfTe3, TaS3), but not all M and X combinations are stable. Here, we demonstrate the successful synthesis of three previously unreported MX3 TMT compounds: NbTe3, VTe3, and TiTe3. This is accomplished through nano-confined growth within the cavity of multi-walled carbon nanotubes (MWCNTs). Depending upon the inner diameter of the encapsulating MWCNTs, specimens ranging from many chains, to few chains (2-4), and even single chain, can be isolated and studied. The MWCNT sheath stabilizes the chainlike morphology, enabling synthesis and characterization with transmission electron microscopy (TEM) and aberration-corrected scanning transmission electron microscopy (STEM). It is found that few-chain specimens of the new TMTs can exhibit a coordinated interchain spiraling, while the single-chain limit exhibits a trigonal anti-prismatic (TAP) rocking distortion, which we experimentally resolve for the first time here. First principles calculations give insight into the integral role that the encapsulating CNT plays in stabilization and provide information regarding the electronic structure of the new materials.

Stabilization of NbTe3, VTe3, and TiTe3 via nanotube encapsulation

ACS Spring Meeting 2021

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