Excitation Induced Tunable Emission in Ce³⁺/Eu³⁺Codoped BiPO₄Nanophosphors

Abstract

Ce3+, Eu3+ions singly doped, and Ce3+/Eu3+codoped bismuth phosphate (BiPO4) nanophosphors were synthesized by a simple precipitation method and their structural, morphological, and photoluminescence properties were investigated. The structural and morphological analysis confirms the pure hexagonal crystal structure of the synthesized nanophosphors. From the Fourier transform infrared (FTIR) spectra various absorption bands respective to functional groups such as PO4 and phonon vibrations including the bending modes of the PO4units are identified. The Ce3+doped nanophosphors show spectrally broad luminescence in the blue (centred at 459 nm) wavelength region under the direct optical excitation of Ce3+at 417 nm. For Eu3+doped nanophosphors, five emission bands have been observed with 394 nm excitation wavelength. Among them, 595 nm has shown bright yellowish-orange emission. These results demonstrate that by appropriately tuning the excitation wavelength of these codoped nanophosphors the emission color in the visible region (blue and orange) can be flexibly controlled in a single sample without varying its chemical composition and size. The mechanism for this excitation energy dependent tunable emission is explained on the basis of nonenergy transfer (ET) occurring among Ce3+/Eu3+dopant ions.

Photoluminescence studies of Ce3+ ion‐doped BiPO4 phosphor and its photocatalytic activity

“…The excitation spectrum was recorded by monitoring the emission wavelength at 471 nm. The spectrum consists of two maxima at 370 and 417 nm which correspond to 2 F 5/2 → 5d transitions of Ce 3+ ion 31–33 …”

Synthesis of GAGG:Ce3+ powder for ceramics using mechanochemical and solution combustion methods

“…Although there are several options available, cerium III (Ce 3+ ) is commonly viewed as the most suitable activator to obtain fast‐decaying intense luminescence . It is well known that the electron in the 4f ground state of the Ce 3+ dopant can be photoexcited to the 5d levels . These 5d levels are further split into energy levels, where the splitting patterns are determined by the chemical environment and symmetry of the host matrix around the Ce 3+ ions.…”

“…The excited Ce 3+ ion then nonradiatively relaxes to the lowest‐energy crystal‐field level of the 5d state. From this position, it decays radiatively to the 2 F 7/2 and 2 F 5/2 4f multiplets of Ce 3+ …”

“…40 It is well known that the electron in the 4f ground state of the Ce 3+ dopant can be photoexcited to the 5d levels. 41,42 These 5d levels are further split into energy levels, where the splitting patterns are determined by the chemical environment and symmetry of the host matrix around the Ce 3+ ions. Direct excitation of Ce 3+ occurs through parity allowed absorptions.…”

“…From this position, it decays radiatively to the 2 F 7/2 and 2 F 5/2 4f multiplets of Ce 3+ . 41,[43][44][45] Due to the high crystal field at the dodecahedral rareearth site, the 5d states of the Ce 3+ are considerably split and shifted to a lower energy in garnet oxide hosts. 6 The 5d electron feels a strong crystal field because it is not very well shielded, resulting in a cubic field splitting of the 5d state usually larger than 10 000 cm À1 .…”