Variations in the 5D0 → 7F0–4 transitions of Eu3+ and white light emissions in Ag–Eu exchanged zeolite-Y

摘要

The variations in the ~(5) D _(0) → ~(7) F _( J ( J =0–2)) transitions of Eu ~(3+) in the 580–630 nm range can reveal the exchanged-ion distribution within the zeolite pores for Ag–Eu exchanged zeolite-Y. A laser could excite more Eu ~(3+) ions at symmetric sites (SI, SU) in the cages deep inside the zeolite besides activating those at the shallow surface. Significantly, the ~(5) D _(0) → ~(7) F _(4) transition of Eu ~(3+) at 696 nm can be selectively modulated and enhanced by laser beam compared to xenon light according to the intensity ratio and decay-lifetime ratio of ~(5) D _(0) → ~(7) F _(4) to ~(5) D _(0) → ~(7) F _(2) transitions, which could be ascribed to the dynamic coupling effect on Eu ~(3+) for the polarization of Eu ~(3+) -coordinated chemical environment induced by laser. Both transitions are determined by the odd-rank static electric field parameters of Eu ~(3+) site according to the point charge model, but the ~(5) D _(0) → ~(7) F _(4) transition is further influenced by the polarizability of chemical environment around Eu ~(3+) following the covalent bond model. Such strengthened effect may be partially relevant to the electronegativity of the zeolite framework. White light emission is achieved in these composites for excitation of both the 266 nm xenon lamp and laser, while the latter shows better tuning behaviors. The Ag–Eu codoped zeolite composites have potential applications in white light illumination.