Formation and Distinctive Decay Times of Surface- and Lattice-Bound Mn²⁺ Impurity Luminescence in ZnS Nanoparticles

Abstract

The Mn 2+ impurity luminescence decay of Mn 2+ -doped ZnS nanoparticles has been clearly distinguished from ZnS host emission decay by measuring transient absorption and emission kinetic profiles in the picosecond-millisecond time domain. The Mn 2+ luminescence for the doped sample shows two decay components of 0.18 and 2 ms. The fast one is attributed to surface-bound Mn 2+ impurities and the slow one to lattice-bound Mn 2+ impurities. In comparison, the slowest component of ZnS host emission decays within 20 ns. Moreover, excitation-energy transfer from ZnS host to Mn 2+ impurity is also measured to occur on the time scale of 700 ps.

Optical and Dynamic Properties of Undoped and Doped Semiconductor Nanostructures

“…The difference in lifetimes on all time scales was attributed to a mechanism of energy transfer from host to dopant either mediated by trap states and another without (directly from the bandedge states). From these results the energy transfer possibly occurs on a time scale of tens to hundreds of ps which appears to be shorter than that reported in a study of ZnS:Mn by Chung where they found a rise time for the Mn 2+ luminescence of 700 ps [228].…”

“…However, subsequent studies have shown that the Mn 2+ PL lifetime in ZnS nanoparticles is the same as the bulk (1.8 ms) [225][226][227][228]. In our study of the PL kinetics of ZnS:Mn nanoparticles monitored at 580 nm, we observed a slow 1.8 ms decay that is similar to the Mn 2+ emission lifetime in bulk ZnS as well as fast ns and µs decays that are also present in undoped ZnS particles and thereby attributed to trap state emission [227], as shown in Figure 9.…”

Doped Semiconductor Nanocrystals: Synthesis, Characterization, Physical Properties, and Applications

“…6 A 1 transition of the Mn 2þ . Subsequent reports helped to substantiate the interpretation of fast decay from traps and slow decay from Mn 2þ , and have additionally reported the observation of a fast Mn 2þ emission decay associated with surface-exposed Mn 2þ ions (37). The absence of an enormous enhancement in radiative decay rates in the nanocrystals can also be verified by electronic absorption spectroscopy.…”

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

“…[39] Because the lifetime of a Mn ion emission is of the order of milliseconds, [40] further excitation of a nanocrystal with one of the Mn ions already at its excited state is possible under excitation light with a sufficiently high intensity. [39] In this case, Equation (1) no longer applies, because "n" in Equation (1) has changed (note that "n" is www.chemeurj.org the number of Mn ions in their ground state).…”