Quantum mazes: luminescent labyrinthine semiconductor nanocrystals having a narrow emission spectrum.

We exploit the polytypism of group II–VI semiconductors and the long-range dipolar interactions typical of CdSe nanoparticle formation to modulate the geometrical structure and the optical emission properties of novel branched CdSe nanocrystals through shape-dependent quantum confinement effects. X-ray diffraction confirms that these materials incorporate crystalline domains of cubic zinc-blende and hexagonal wurtzite within a polycrystalline growth form whose geometry can be controlled by varying thermodynamic conditions. In particular, labyrinthine-shaped nanoparticles of tunable dimensions are reproducibly synthesized based on a heterogeneous reaction between cadmium acetate in a solution in hexadecylamine and trioctylphosphine with Se as a solid precursor at a relatively low temperature (110 °C). The resulting highly branched CdSe structures resemble labyrinthine patterns observed in magnetic fluids and superconductors films in magnetic fields, and in lipid films and other materials where strong dipol...