Triangular morphology of orthorhombic wurtzite (11-20) ZnSe nanoplatelets

Determine the mechanism that produces the triangular morphology observed experimentally in ZnSe nanoplatelets if these nanoplatelets are assumed to have a wurtzite (11-20)-oriented orthorhombic structure, since within that structural model the triangular shape is not explained.

Background

Experiments reported triangular ZnSe nanoplatelets only ~0.6 nm thick with hexagonal symmetry, and adsorption of cysteine-based ligands was observed. One possible structural model to enable binding of both ZnCl2 and cysteine is a nonpolar wurtzite surface with (11-20) orientation, which has an orthorhombic in-plane lattice.

However, an orthorhombic (11-20)-oriented wurtzite ZnSe nanoplatelet does not naturally explain the experimentally observed triangular shape, prompting the authors to explicitly note this unresolved issue. They subsequently propose a new hexagonal tr-ZnSe structure that better aligns with triangular morphology and adsorption behavior, but the origin of triangular shape remains unclear under the orthorhombic wurtzite assumption.