  Manganese (Mn)-doped ZnS nanocrystals (NCs) have been extensively explored
for optical applications with the advantages of low toxicity, large Stokes
shifts, and enhanced thermal and environmental stability. Although numerous
studies on Mn-doped ZnS dots, rods, and wires have been reported, the
literature related to Mn-doped ZnS nanoplatelets (ZnS:Mn NPLs) is scarce. Here,
we present the first example of direct doping of Mn2+ ions into ZnS NPLs via
the nucleation-doping strategy. The resulting ZnS:Mn NPLs exhibit Mn
luminescence, indicative for successful doping of the host ZnS NPLs with Mn2+
ions. The energy transfer from the ZnS NPLs to the Mn2+ ions was observed by
employing spectroscopic methods. Furthermore, the impact of the Mn
concentration on the optical properties of ZnS:Mn NPLs was systematically
investigated. As a result of Mn-Mn interaction, tunable Mn emission and
shortened photoluminescence (PL) lifetime decay were observed and rationalized
by means of electron paramagnetic resonance (EPR) and X-ray photoelectron
spectroscopy (XPS). Finally, we show that the initially low dopant PL quantum
yield (QY) of ZnS:Mn NPLs can be dramatically enhanced by passivating the
surface trap states of the samples. The presented synthetic strategy of ZnS:Mn
NPLs opens a new way to synthesize further doped systems of two-dimensional
(2D) NPLs.
