Hi Eugenio: In my experience, nanoparticles tend to become perfect crystals because the strain energy per atom in the cluster is too large to support a dopant which severely distorts the structure. It is possible that a dopant like Er is simply expelled from the nanoparticle. In the bulk, there are more mechanisms for relaxing the strain and, more importantly, there are many more atoms available over which to spread the strain energy.

From the bond distances you quote, the Er may indeed be on the surface. Did you notice any change in the spectrum as a function of time?

Cheers, Carlo On Tue, 3 Feb 2009, Eugenio Otal wrote:

Hi everybody, thanks for your time, knowledge and pacience. The first shell is can be fitted by 2 sub shells with this composition: n_first_1 = 2.4702860 r = 1.782161 n_first_2 = 9.2476950 r = 2.342539 This is really far from Zn in ZnO, is closer to Er(OH)3, with 8 between 2.40 and 2.43 and ErOOH presents 7 neighbors between 2.26 and 2.45, with something like 2 sub-shells. Er2O3 has two sites with octahedral simmetry, one is perfectly Oh and the other distorted with 2.21 to 2.36 for Er-O. I chequed the doping element incorporation and found that what I suppose to be 1% is in fact 0.6% (by ICP quantification) the incorporation is less I though. Maybe that is the reason to do not find call parameters change. What kind of difference could I find between nanoparticles and bulk for incorporation? Cheers, euG

-- Carlo U. Segre -- Professor of Physics Associate Dean for Special Projects, Graduate College Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://www.iit.edu/~segre segre@debian.org