A novel white-light-emitting phosphor Ca(9)Lu(PO(4))(7):Eu(2+),Mn(2+) has been prepared by solid-state reaction. The photoluminescence properties indicate that there is an efficient energy transfer from the Eu(2+) to Mn(2+) ions via a dipole-quadrupole reaction. The obtained phosphor exhibits a strong excitation band between 250 and 430 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Upon excitation of UV light, white light is realized by combining a broad blue-green emission band at 480 nm and a red emission band at 645 nm attributed to the Eu(2+) and Mn(2+) ions. The energy-transfer efficiency and critical distance were also calculated. Furthermore, the phosphors can generate lights from blue-green through white and eventually to red by properly tuning the relative ratio of the Eu(2+) to Mn(2+) ions through the principle of energy transfer. Preliminary studies showed that the phosphor might be promising as a single-phased white-light-emitting phosphor for a UV white-light LED.

A series of Eu(2+) and Eu(2+)/Tb(3+) activated novel Ba3LaNa(PO4)3F phosphors have been synthesized by traditional solid state reaction. Rietveld structure refinement of the obtained phosphor indicates that the Ba3LaNa(PO4)3F host contains three kinds of Ba sites. The photoluminescence properties exhibit that the obtained phosphors can be efficiently excited in the range from 320 to 430 nm, which matches perfectly with the commercial n-UV LED chips. The critical distance of the Eu(2+) ions in Ba3LaNa(PO4)3F:Eu(2+) is calculated and the energy quenching mechanism is proven to be dipole-dipole interaction. Tunable blue-green emitting Ba3LaNa(PO4)3F:Eu(2+),Tb(3+) phosphor has been obtained by co-doping Eu(2+) and Tb(3+) ions into the host and varying their relative ratios. Compared with the Tb(3+) singly doped phosphor, the codoped phosphors have more intense absorption in the n-UV range and stronger emission of the Tb(3+) ions, which are attributed to the effective energy transfer from the Eu(2+) to Tb(3+) ions. The energy transfer from the Eu(2+) to Tb(3+) ions is demonstrated to be a dipole-quadrupole mechanism by the Inokuti-Hirayama (I-H) model. The Eu(2+) and Tb(3+) activated phosphor may be good candidates for blue-green components in n-UV white LEDs.

Gd(2)O(2)S:Ln(3+) (Ln = Eu, Tb) submicrospheres were successfully prepared through a facile and mild solvothermal method followed by a subsequent heat treatment. X-ray diffraction (XRD) results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure hexagonal phase of Gd(2)O(2)S. The energy dispersive spectroscopy (EDS), element analysis, and FT-IR results show that the precursors are composed of the Gd, Eu, O, S, C, H, and N elements. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that these spheres are actually composed of randomly aggregated nanoparticles. The formation mechanism for the Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres has been proposed on an isotropic growth mechanism. Under ultraviolet excitation, Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres show red and green emission corresponding to the (5)D(0)→(7)F(2) transition of the Eu(3+) ions and the (5)D(4)→(7)F(5) transition of the Tb(3+) ions. Furthermore, this synthetic route may have potential applications for fabricating other lanthanide oxysulfides.

Well-dispersed, uniform Gd(2)O(3) hollow microspheres have been successfully fabricated via a urea-based homogeneous precipitation method in the presence of colloidal melamine formaldehyde (MF) microspheres as templates, followed by subsequent heat treatment. The main process was carried out under aqueous conditions without any organic solvents, surfactants, or etching agents. The as-obtained Gd(2)O(3) microspheres with a spherical shape and hollow structure are uniform in size and distribution, and the thickness of the shell is about 200 nm. The lanthanide ion (Ln(3+))-doped Gd(2)O(3) hollow microspheres exhibit bright down- and upconversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which might find potential applications in fields such as drug delivery or biological labeling because of their excellent dispersing and luminescence properties. Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.

In this paper, the color point tuning of Y 3 Al 5 O 12 : Ce 3+ phosphor has been realized by the incorporation of Mn 2+ -Si 4+ . The Mn 2+ ions occupy the dodecahedral crystallographic Y 3+ site, while the Si 4+ ions substitute the tetrahedral Al 3+ crystallographic site in the obtained powder. Under 450 nm excitation, the YAG : Ce 3+ ,Mn 2+ ,Si 4+ samples exhibit the typical yellowish-green emission band of the Ce 3+ ions, as well as an orange emission band of the Mn 2+ ions. Furthermore, the intensity ratio of the orange/yellowish-green band can be enhanced through the increase of Mn 2+ -Si 4+ content. The intense orange emission band of the Mn 2+ ions is attributed to the effective energy transfer from the Ce 3+ to Mn 2+ ions, which has been justified through the luminescence spectra and the fluorescence decay dynamics. The related mechanism was demonstrated to be the electric dipole-quadrupole interaction based on the Inokuti-Hirayama theoretical model, and critical distance is calculated to be 8.6A by the spectral overlap method.

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Novel one-dimensional terbium 1,3,5-benzenetricarboxylate nanobelts have been synthesized on a large scale through direct precipitation in solution phase without the assistance of any surfactant, catalyst, or template. The as-obtained nanobelts present crystallinity in spite of the moderate reaction conditions, exhibiting 1D helical strands and a 3D network framework. The influence of the reaction temperature, concentration, molar ratio of reactants, and solvent on the belt-like nanostructure has been discussed in detail. A possible mechanism based on the crystal structure of the compound is proposed to account for the formation of the nanobelts. A detailed investigation of the photoluminescence of Tb(1,3,5-BTC)(H 2 O)$3H 2 O nanobelts indicates that the optical properties of these phosphors are dependent on their size. More interestingly, the luminescence color of the Tb(1,3,5-BTC)(H 2 O)$3H 2 O:Eu 3+ nanobelts can be easily tuned from green to green-yellow, yellow, orange and red-orange due to the energy transfer from the Tb 3+ to Eu 3+ ions by changing the doping concentration of activator ions.

A series of single-component Sr 3 Lu(PO 4 ) 3 :Eu 2+ ,Mn 2+ phosphors were successfully synthesized by solid-state reaction, and their photoluminescence properties were investigated. The Sr 3 Lu(PO 4 ) 3 :Eu 2+ ,Mn 2+ phosphor system was efficiently excited at wavelength ranging from 250 to 420 nm, which is well-matched with ultraviolet (UV) light-emitting diode (LED) chips. As a result of fine-tuning of the emission composition of the Eu 2+ and Mn 2+ ions, warm white light emission can be realized by combining the emission of Eu 2+ and Mn 2+ in a single host lattice under UV light excitation. Efficient resonant energy transfer from the Eu 2+ to Mn 2+ ions was demonstrated to be a dipoleÀquadrupole mechanism in such system, and the energy transfer efficiency increases with an increase in the Mn 2+ doping content, which was confirmed by the luminescence spectra and fluorescence decay curves. In addition, the energy transfer efficiency and critical distance were also calculated. The results indicate that the developed phosphor can be used as a potential white-light-emitting phosphor for white LEDs.