High-Quality Manganese-Doped ZnSe Nanocrystals

We demonstrate high-quality, highly fluorescent, ZnSe colloidal nanocrystals (or quantum dots) that are doped with paramagnetic Mn 2+ impurities. We present luminescence, magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) measurements to confirm that the Mn impurities are embedded inside the nanocrystal. Optical measurements show that by exciting the nanocrystal, efficient emission from Mn is obtained, with a quantum yield of 22% at 295 K and 75% below 50 K (relative to Stilbene 420). MCD spectra reveal an experimental Zeeman splitting in the first excited state that is large (28 meV at 2.5 T), depends on doping concentration, and saturates at modest fields. In the low field limit, the magnitude of the effective g factor is 430 times larger than in undoped nanocrystals. EPR experiments exhibit a six-line spectrum with a hyperfine splitting of 60.4 × 10 -4 cm -1, consistent with Mn substituted at Zn sites in the cubic ZnSe lattice.