Time-resolved luminescence of ZnS:Mn2+ nanocrystals

Recently, Yu and co-workers reported the observation of hot luminescence for Mn2+ in 3.6 nm ZnS nanocrystals, implying that the phonon relaxation rates in nanocrystals were ∼106 times lower than that in bulk materials. In order to verify this unexpected observation, we investigated the time-resolved spectroscopy of 4.5 nm ZnS:Mn2+ nanocrystals. Samples with two different Mn2+ concentrations were studied. In contradiction with the results reported by Yu and co-workers, no evidence of Mn2+ hot luminescence was found, regardless of the Mn2+ concentration, temperature (4.2–300 K), time delay (0.1–1000 μs), gate width (2–3000 μs), or excitation density (40–700 mJ/cm2).