We demonstrate the
preparation of mesoscale semiconductor (II–VI)
nanoplatelets (NPLs) for the first time using colloidal seeded growth.
These nanoplatelets are quantum-confined and atomically precise but
grown to a length scale compatible with conventional optical imaging
and microscopic manipulation (even reaching >1 μm2) offering an opportunity to bridge the application space between
nanocrystals and two-dimensional (2D) materials. Using CdTe as a model
system, we develop a seeded growth procedure, show the parameters
that control extension, and apply them to a variety of thicknesses
and compositions. In situ spectroscopy demonstrates that addition
onto the nanoplatelet seeds is not continuous and likely occurs through
ripening. Finally, we use correlative optical and electron microscopy
to demonstrate that at large sizes, photoluminescence (PL) mapping
of the entire structure can be resolved including spatial inhomogeneities.
Overall, these results show that nanoplatelets can be compared to
2D semiconductors while maintaining the advantages of scalable colloidal
synthesis, thickness tunability, and solution processability.