The quest for the ideal inorganic scintillator

The Ce3+, Mn2+-codoped calcium fluorapatite [Ca5(PO4)3F, 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˙− 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˙− 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.

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

Highly uniform and well-dispersed CaF(2) hollow spheres with tunable particle size (300-930 nm) have been synthesized by a facile hydrothermal process. Their shells are composed of numerous nanocrystals (about 40 nm in diameter). The morphology and size of the CaF(2) products are strongly dependent on experimental parameters such as reaction time, pH value, and organic additives. The size of the CaF(2) hollow spheres can be controlled from 300 to 930 nm by adjusting the pH value. Nitrogen adsorption-desorption measurements suggest that mesopores (av 24.6 nm) exist in these hollow spheres. In addition, Ce(3+)/Tb(3+)-codoped CaF(2) hollow spheres can be prepared similarly, and show efficient energy transfer from Ce(3+) to Tb(3+) and strong green photoluminescence of Tb(3+) (541 nm, (5)D(4)-->(7)F(5) transition of Tb(3+), the highest quantum efficiency reaches 77%). The monodisperse CaF(2):Ce(3+)/Tb(3+) hollow spheres also have desirable properties as drug carriers. Ibuprofen-loaded CaF(2):Ce(3+)/Tb(3+) samples still show green luminescence of Tb(3+) under UV irradiation, and the emission intensity of Tb(3+) in the drug-carrier system varies with the released amount of ibuprofen, so that drug release can be easily tracked and monitored by means of the change in luminescence intensity. The formation mechanism and luminescent and drug-release properties were studied in detail.

Facile and controllable synthesis of monodisperse CaF2 and CaF2:Ce3+/Tb3+ hollow spheres as efficient luminescent materials and smart drug carriers.

Scintillation and optical stimulated luminescence of Ce-doped CaF2

Uniform and well-dispersed SrF2 hierarchical microspheres have been successfully synthesized by a facile and friendly hydrothermal method. The experimental results indicate that such 3D hierarchical SrF2 microspheres with size about 1 μm are assembled by numerous nanocrystals (about 100 nm). Nitrogen adsorption−desorption measurement suggests that mesopores exist in these hierarchical microarchitectures. The formation process of the hierarchical SrF2 microspheres and luminescence properties of SrF2:Ln3+ (Ln = Ce, Tb, Yb, Er) microspheres have been investigated in detail. It is found that reaction time and trisodium citrate play a key role in forming the hierarchical microspheres. In addition, the lanthanide ions (Ln3+)-doped SrF2 hierarchical microspheres show strong green (Ln3+ = Ce3+, Tb3+) photoluminescence with 45% quantum efficiency and cathodoluminescence centered at 542 nm corresponding to the 5D4 → 7F5 transition of Tb3+ under excitation of ultraviolet light and low-voltage electron beam, respecti...

Mesoporous SrF2 and SrF2:Ln3+ (Ln = Ce, Tb, Yb, Er) Hierarchical Microspheres: Hydrothermal Synthesis, Growing Mechanism, and Luminescent Properties

Control of optical properties of YAG crystals by thermal annealing

Luminescence of heavily Ce-doped alkaline-earth fluorides

Spectral-kinetic characteristics of Pr3+ luminescence in LiLuF4 host upon excitation in the UV–VUV range

Luminescent and structural properties of M1-xCexF2+x (M=Ca, Sr, Ba, 0.15<x<0.35) single crystals were studied. It was found that the solid solutions have fluorite crystal structure with the lattice constant noticeably different from that of MF2 crystal. A partial deficiency in the fluorine positions as well as excessive fluorine in interstitial sites was revealed. Crystal lattice modification does not strongly affect the basic absorption and emission properties as compared with weakly Ce-doped MF2. The spectral-kinetic parameters of solid solutions luminescence are similar to those of Ce3+ ion in perturbed site in CeF3 lattice. Low light yield of mixed compounds is connected with the small Stokes shift and reabsorption. The probable model of perturbed Ce3+ center in M1-xCexF2+x crystals assumes the presence of interstitial fluorine in the nearest or next nearest neighborhood of the cerium ion.

Luminescence of Heavily Ce-Doped Alkaline-Earth Fluorides

ZnSe(Te) scintillating layers were produced by the physical vapor deposition technique. Structure and scintillation properties of the layers were investigated. Specially treated ZnSe(Te) layers exhibit the strong luminescent band at 640 nm under X-ray excitation.

V. Nesterkina

Papers

Control of optical properties of YAG crystals by thermal annealing

Luminescence of heavily Ce-doped alkaline-earth fluorides

Spectral-kinetic characteristics of Pr3+ luminescence in LiLuF4 host upon excitation in the UV–VUV range

Luminescence of Heavily Ce-Doped Alkaline-Earth Fluorides

Vacuum Deposited ZnSe(Te) Scintillating Layers