Hello, you can use the J-O theory for nanoparticles only doped Eu3+ by using the emission spectrum

see for example : NewJ.Chem., 2014, 38, 1129

Thanks Prof. Kamel Damak. But until now,  almost papers only study on Eu3+ by using the emission spectra. I have a question for me, why ? Can you give me any ideas ?

If you can take absorption spectra for nanoparticles, which is possible if you mix your nanoparticles with epoxy and dried or using some other methods, you can prepare pallet. However, you have to correct for the refractive index.  

If you are interested calculating JO parameter using absorption spectra, There are possible methods to prepare nanoparticles samples for absorption (O.D.) measurements.

Thanks Ivan I.Leonidov. But my powder samples were doped with Tm3+ and Er3+.Until now, I did not find any papers to report J-O of  Tm, Er-codoped powder samples.

Hello, Bui The Huy.

It is quite hard to have a quantitative estimation of the absorbance from the diffuse reflectance exactly because it is difficult to estimate the penetration depth (which is also wavelength-dependent). It is safer to apply the theory on the emission spectra, but you should be sure of the relative intensity of the observed transitions. To do so, you need to correct your curves with respect to the response of the detector and to the optics you use in your luminescence setup. This might not be an easy task, but if doing so and applying the JO theory you are able to simulate correctly the position of most of the transitions that you observe, then it means you're on the right way.

I would like to add few considerations on the JO theory that you should consider.

As far as I know, the JO theory is used to determine the electric dipole transitions between 4f levels of a single rare earth ion in a certain crystal field. If you have a second rare earth ion next to your rare earth or crystal defects (like those that compensate the different ionic radius and electronic valence) whose energy is in resonance with a transition of the rare earth, the transition rates will be modified and you cannot apply the JO theory safely. I do not know how Er and Tm behave in othosilicate, but it is probable that more than one active site exist. Also in this case, the JO theory cannot be applied because it is very difficult to deconvolute the Stark components of the 4f levels of the two sites.

I hope this can help.

Hello, Matteo Balestrieri

Thank you very much for your help. The factors are mentioned are all right and I also think that. But anyway I will try on Tm-doped, Er-doped and Tm,Er-codoped orthorsilicate. I hope we can compare and learn little from it :)

One more, thank you very much

You could try using the Kubelka-Munk function to produce an estimate of absorption spectra using the DRS. If you canot measure the length of your samples, you should make it very thick, infinitely long in relative to the wavelength you test in UV-Vis to be exact. That way the scattering coefficient is constant and Kubelka-Munk function can be applied. Having the absorption spectra I hope you can fit it for Judd-Ofelt theory to find their JO parameters.

Hi, Leow

The layer sample is think, which was performed. But it is difficult because the boundary between the particles alway exist. It will effect to the result of diffusion reflectance. Anyway thank you for your guide.