Oriented Attachment of 2D Nanosheets: The Case of Few-Layer Bi2Se3

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.