Tunable luminescence in Ce3+, Mn2+-codoped calcium fluorapatite through combining emissions and modulation of excitation: a novel strategy to white light emission

The Ce3+, Mn2+-codoped calcium fluorapatite [Ca-5(PO4)(3)F, FAP] nanorods were prepared by a simple hydrothermal method. SEM and TEM images indicate that the FAP : Ce3+, Mn2+ sample consists of nanorods with lengths around 30-70 nm and diameters around 20 nm, respectively. The as-obtained FAP nanorods show an intense bright blue emission (centered at 432 nm, lifetime 7.5 ns) arising from CO2 center dot- radical impurities in the crystal lattice under UV light irradiation. In addition, codoped with Ce3+ and Mn2+, the as-synthesized FAP : Ce3+, Mn2+ sample shows the tunable luminescence from blue to white to yellow by the variation of excitation UV light. The emission spectra of the as-synthesized FAP : Ce3+, Mn2+ sample show three broad bands, which are associated with the CO2 center dot- radical impurities (blue emission), Ce3+ ions (ultraviolet emission), and Mn2+ ions (yellow emission), respectively. The coexistence of three broad emissions results in the bright white light directly under suitable excitation wavelength. The combination emissions of impurities and metal activator ions may provide a novel strategy to obtain white light and tunable luminescence.