Preparation of Cobalt doped Bi₂Se₃ nano-topological insulators

Magnetically doped topological insulator samples, namely Co–Bi₂Se₃, were prepared at the nanoscale using a combined organic–inorganic hot-injection technique. In such a one-pot synthesis method, the nanoparticle sizes were tuned by varying the time at which the nanoparticles are drawn from the reaction flask. Highly crystalline, spherical, and dispersive ultra-small nanoparticles were imaged by High Resolution Transmission Electron Microscopy. It was shown that deviations from the spherical shapes and reduced crystallinity occur for samples taken at longer reaction times, however, with slight enlargement of the average particle sizes. The Infrared spectra taken for all samples showed two well-defined peaks located at 414 and 438 cm⁻¹ which were assigned to Bi₂Se₃ stretching modes. A strong red-shift in the UV–visible absorption spectra for samples taken at different reaction times was also observed. The present system provides the zero-dimensional analogy to the rapidly progressing field of 3D topological insulators doped with magnetic materials.