Abstract
We report on a hydrothermal synthesis of hexagonal ultra-thin Bi2Se3 platelets, which was performed without any organic reactants. The synthesis resulted in the particles with a surface, clean of any organic adsorbents, which was confirmed with a high-resolution transmission electron microscopy, zeta-potential measurements and thermogravimetric measurements coupled with a mass spectroscopy. Due to the absence of the adsorbed organic layer on the Bi2Se3 platelet surface, we were able to measure their inherent surface and optical properties. So far this has not been possible as it has been believed that such hexagonal Bi2Se3 platelets can only be prepared by a solvothermal synthesis, for which it was unable to avoid the organic surface layer. Here we explain the mechanism behind the successful hydrothermal synthesis and show a striking difference in zeta potential behaviour and UV-vis absorption characteristics caused by the adsorbed layer. The surface of the hydrothermally synthesized Bi2Se3 platelets was so clean to enable the occurrence of the localized surface plasmon resonance due to the bulk and topological surface electronic states.
Highlights
Topological insulators (TI) are a novel class of materials that recently have been intensively studied due to their attractive electron properties that result from metallic, linearly dispersing, spin-polarized surface states, widely known as topological surface states (TSS)
Despite a successful preparation of a variety of Bi2Se3 nanostructures with well-defined morphologies, there are no reports on a successful synthesis of the shape-specific product with only the hexagonal Bi2Se3 platelets, using the hydrothermal method, that would allow avoiding the presence of organic adsorbents
The solvothermal synthesis is the most exploited one[21,22,24,25,26,27,29]. The disadvantage of this method is the use of organic reactants, which tend to adsorb on the surface of the particles, as it was demonstrated in this work
Summary
Topological insulators (TI) are a novel class of materials that recently have been intensively studied due to their attractive electron properties that result from metallic, linearly dispersing, spin-polarized surface states, widely known as topological surface states (TSS). The TI have a bulk band gap but, opposite to ordinary insulators, possess TSS on their surfaces that are robust to non-magnetic impurities and disorder because of the combined effect of time-reversal symmetry and spin-momentum locking[1,2,3] These peculiar properties make the TI as very promising materials for novel applications like quantum computing[4,5,6], THz detectors[7,8], plasmonics[9,10,11], spintronics[3,12,13], and for medical diagnostics and treatment[14,15]. Despite a successful preparation of a variety of Bi2Se3 nanostructures with well-defined morphologies, there are no reports on a successful synthesis of the shape-specific product with only the hexagonal Bi2Se3 platelets, using the hydrothermal method, that would allow avoiding the presence of organic adsorbents. The difference in the surface and optical properties compared to the surfaces with the adsorbed amorphous layer is striking
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