Correlation of Mn local structure and photoluminescence from CdS:Mn nanoparticles

摘要

The structure and luminescence properties of Mn~(2+) in CdS nanoparticles are studied. Electron paramagnetic resonance measurements show the existence of three distinct Mn~(2+) centers with different local structures in CdS nanocrystals: Mn ions substitutionally incorporated on Cd sites [Signal S_Ⅰ: g = 2.0025 and a hyperfine interaction constant A of 64.6 x 10~(-4) cm~(-1) (6.9 mT)], Mn located near the surface [Signal S_Ⅱ: g=2.0013 and A = 89 x 10~(-4) cm~(-1) (9.5 mT)], and a broad background signal (S_Ⅲ) correlated to interacting Mn ions or Mn clusters. Luminescence studies indicate that only substitutional ions located in the core of the nanocrystals contribute to the typical ~4T_1 to ~6A_1 (2.12 eV) emission. The colloidal preparation process of the nanoparticles allows selective incorporation of the Mn ions, i.e., core/shell doping of the nanoparticles. It shows that Mn located in the shell quenches the total luminescence via nonradiative processes.