PNNL

Abstract

We report the synthesis and luminescence decay kinetics of 1.2 nm Mn2+ doped ZnS nanoclusters grown in reverse micelles. The preparation method produces small particles with narrow size distribution and fluorescence bands near 400-450 nm and 585 nm. Time-dependent fluorscence decay measurements using picosecond, nanosecond and millisecond techniques reveal relaxation processes on all three time scales. In the doped sample the red emission detected at 600 nm exhibits an 1-2 ms decay in addition to faster decay with time constants on the order of hundreds of ps, a few ns and tens of us. While the slow decay is the same as that of bulk Mn2+ doped ZnS, the fast decays are present for both doped and undoped samples and are unique to nanocluster ZnS, which are attributed deep trap state emission. The blue luminescence near 400-450 nm is attributed to shallow trap state emission of ZnS. These results help to resolve the controversy in the literature regarding the lifetime of the Mn2+ emission in Mn-doped ZnS nanoparticles.