COLL 400 |
| Pedro Gonzalez, Subra Muralidharan, and Subodh Dutta. Department of Chemistry, Western Michigan University, Kalamazoo, MI 49008 |
| We have proposed a theoretical model to explain the apparent multiple exponential decay of the long-lived emission line at 590 nm of Mn doped Zinc sulphide quantum dots. The emission of ZnS:Mn(II) at 590 nm has been ascribed to the 4T1-6A1 transition characteristic of Mn occupying Zn positions in the ZnS crystal. Mn dipole-dipole interactions contribute to relax the spin selection rule of this forbidden transition, which lead to non-zero transition probabilities and finite lifetimes. The dispersion in the distances among Mn(II) ions inside the quantum dot lattice accounts for the variability in the dipole-dipole interaction and indeed, it is responsible for dispersion in the kinetics of the decay of the 590 nm luminescence emission. We have derived a mathematical model based on a normal distribution of Mn-Mn distances and the radial dependence of the decay constant. The model fits very well the decay curve of the 590 nm emission line of ZnS:Mn(II) nanoparticles for a wide range of Mn doping (1 - 35% mol). Additionally, this model can explain the reduction in lifetimes with the decrease of the particle size and the increase in the amount of Mn doping. The more relevant aspects of this model will be discussed and a comparison with the traditional multiple exponential decay will be addressed.
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Nanoscience and Nanotechnology
8:30 AM-11:45 AM, Wednesday, March 31, 2004 Marriott -- Orange County 5, Oral
Division of Colloid and Surface Chemistry |