Transition-metal trichalcogenides (TMTs) of the type MX₃ usually form chain-like structures, with the chains weakly bound together by van der Waals interactions. These materials have been well-studied in the bulk, and there are also some examples of TMTs isolated in few- or single-chain forms.

Alex Zettl, University of California, Berkeley, and Lawrence Berkeley National Laboratory, CA, USA, and colleagues have synthesized three previously unknown MX₃-type compounds—NbTe₃, VTe₃, and TiTe₃—using nanoconfined growth within multiwalled carbon nanotubes (MWCNTs). The team sealed the respective transition-metal powder (Nb, V, or Ti) together with tellurium and commercially available end-opened MWCNTs under vacuum in a quartz ampule. The reaction mixture was then heated to 520–625 °C for several days.

The products were characterized using transmission electron microscopy (TEM) and atomic-resolution scanning transmission electron microscopy (STEM). The team found that the desired MTe₃ compounds can be isolated in forms from many chains, to few chains (between two and four), and down to single-chain samples, depending on the cavity diameter of the MWCNTs. The nanotubes protect and stabilize the chain-like structures of the MTe₃ products, and thus, make their synthesis possible.

• Stabilization of NbTe₃, VTe₃, and TiTe₃ via Nanotube Encapsulation,
  Scott Stonemeyer, Jeffrey D. Cain, Sehoon Oh, Amin Azizi, Malik Elasha, Markus Thiel, Chengyu Song, Peter Ercius, Marvin L. Cohen, Alex Zettl,
  J. Am. Chem. Soc. 2020.
  https://doi.org/10.1021/jacs.0c10175