Abstract
Developing growth schemes for functional two-dimensional (2D) nanomaterials is of much interest, especially because synthetic conditions are often correlated with physical properties such as optical absorbance. Bi2Se3 is an interesting material because of its transition from a narrow gap semiconductor, for the thinnest structures, to a topological insulator, when the structures are at least six quintuple molecular layers (QLs), and its appealing photothermal, thermoelectric, and optical properties. Here, we developed a controlled colloidal synthesis based on oriented attachment to produce Bi2Se3 nanoplatelets with varying thicknesses. The synthesis scheme also enables the facile doping of the structures without noticeable intercalation. The variation in optical properties confirmed the higher concentration of charge carriers at the edge of the structures, which is due in this system to Se deficiency and low crystallinity. This research opens a way to tune the composition and thickness of nanostructured 2D Bi2Se3, an important functional material.
Highlights
Research on nanostructured two-dimensional (2D) materials confined to few-layer and monolayer thicknesses has expanded dramatically since the discovery of graphene and transitionmetal dichalcogenides
There is a great deal of interest in producing structures of a few layers of Bi2Se3 in the range of 2−8 quintuple layers (QLs) to study the properties of the thin platelets around the transition thickness from a topological insulator.[19−21] In addition, the photothermal properties are appealing for forming hybrid structures where the higher temperature may be used for promoting catalytic reactions
The particles appeared to be uniform in the conventional transmission electron microscopy (TEM)
Summary
Research on nanostructured two-dimensional (2D) materials confined to few-layer and monolayer thicknesses has expanded dramatically since the discovery of graphene and transitionmetal dichalcogenides. The nanosheets were isolated by adding a trioctylphosphine (TOP)−ethanol mixture to remove any unreacted selenium and centrifuged at 4000 rpm for 4 min. This purification process was repeated one more time. In a 20 mL vial, elemental selenium powder (118 mg, 1.5 mmol) was added to a solution of ODE (1 mL) and OLA (100 μL) under vigorous stirring. The nanosheets were isolated by adding a TOP−ethanol mixture to remove any unreacted selenium and centrifuged at 4000 rpm for 4 min. The 7−8 QL Bi2Se3 nanosheets were prepared by the above procedure except for the use of a mixture of OLA (1 mL) and ODE (13 mL) for the Bi precursor
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