Luminescence properties, centroid shift and energy transfer of Ce3+ in aqueous chloride solutions

Abstract

This paper focuses upon three themes: all related to aqueous cerium chloride solutions.First, the features in the absorption spectra of CeCl3 solutions do not shift noticeably with concentration and are at similar energies to bands in the solid-state absorption spectrum of Ce(H2O)93+, with the exception of the weak band at 297nm which is due to Ce(H2O)83+. The broad emission band in solution is only due to [Ce(H2O)83+]⁎ and the emission quenches at concentrations >0.06M. Bands in the excitation spectra of aqueous CeCl3 solutions apparently change position with increasing concentration, due to absorption by Ce(H2O)93+ which does not contribute to emission. At concentrations above 1M, there is total extinction of incident radiation for wavelengths shorter than 310nm.Second, this system is chosen to illustrate the revised calculation of centroid shift, by taking into account the vibronic nature of spectral features, in contrast with the pure electronic transition of the free ion. Similar calculations are applicable to other Ce3+ systems.Thirdly, excitation spectra are employed to demonstrate the energy transfer occurring from Ce3+ to Tb3+ and Eu3+ in aqueous chloride solutions, which is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution.