ABSTRACT
Novel green-red color-tunable Ca8(Mg,Mn)Tb(PO4)7:Eu2+ phosphors have been synthesized via the traditional solid-state method. Since Tb3+/Mn2+ ions are the parent ions in the lattice, the structural confinement occurs when the sensitizer Eu2+ is introduced into the Ca8(Mg,Mn)Tb(PO4)7:Eu2+ structure. The distance from Eu2+ to Tb3+/Mn2+ is confined in the 5 Å range, which induces a highly efficient energy transfer process. At Eu2+ 350 nm excitation, Ca8MgTb(PO4)7:Eu2+ shows dominant Tb3+ green emission with almost-vanished Eu2+ emission. Red emission is clearly observed as Mn2+ ions doping into Ca8MgTb(PO4)7:Eu2+, and color-tuning from green to red is realized by varying the Mn2+ contents. Eu2+-Tb3+-Mn2+ cascade energy transfer process is in effect due to short Eu2+-Tb3+/Mn2+ and Tb3+-Mn2+ distances, which is verified by PL and decay variations. Meanwhile, the Ca8(Mg,Mn)Tb(PO4)7:Eu2+ phosphor indicates good thermal stability and maintained the 45% emission level at 150 °C, which demonstrates their potential applications in white light LEDs.
ABSTRACT
Calcium carbonate, as the main inorganic component of human bones and teeth, has good biocompatibility and bioactivity and finds increasing applications in the field of bone drug carriers. In this study, hollow calcium carbonate microspheres were synthesized by a water hydrothermal method using folic acid as a template. Before drug loading, the prepared calcium carbonate microspheres were subjected to aminidation, carboxylation, and vinylenimine modification. The hollow calcium carbonate microspheres loaded with doxorubicin hydrochloride (DOX) were further incorporated with light-emitting carbon quantum dots(CQDs) and hyaluronic acid (HA). The result showed that the drug loading capacity in the as-prepared calcium carbonate was 179.064 mg/g. In the simulated solutions of cellular metabolism containing various concentrations of reduced glutathione(GSH), the sustained release of DOX was confirmed qualitatively by the luminescence of the CQDs. The DOX release rate was measured quantitively by UV absorption spectra. The highest release rate reached 85.99% in a simulated solution of 0.005 mol/L GSH solution, and the release rate could vary intelligently with the concentration.
ABSTRACT
The Ce3+/Tb3+/Mn2+ activated color-tunable phosphors Sr9LiMg(PO4)7 (SLMP) were prepared by solid-state reaction with post-annealing treatment. The structural, static and time-resolved luminescent properties are studied in detail. XRD pattern showed the pure trigonal phase of Sr9LiMg(PO4)7 at an annealing temperature of 1300 °C. Ce3+-doped SLMP phosphor exhibits near-ultraviolet emission with peak-wavelength at 380 nm. Efficient Ce3+-Tb3+/Mn2+ energy transfer process is demonstrated by luminescence spectrum and luminescence lifetimes of as-prepared samples. The emitting-color of SLMP: Ce3+/Tb3+/Mn2+ was tunable through changing Ce3+/Tb3+/Mn2+ ratio. Emission peak intensity of SLMP: Ce3+, Tb3+ phosphor shows good thermal stability with rising temperature. These results suggest its great potential as luminescent materials with good performance for UV-excitable applications.
ABSTRACT
Bi(3+)/Tb(3+), Eu(3+) co-doped Li6Gd(BO3)3 (LGBO) phosphors were synthesized via a traditional solid-state method. Phase purity was investigated using X-ray diffraction, absorption strength of the phosphors were investigated by UV-vis absorption spectra, and the photoluminescence properties of the phosphors were studied systematically. Results showed that the emission intensity of Bi(3+), Eu(3+) co-doped LBOG was 2.76 times higher than that of Eu(3+)-doped LGBO irradiated at 275 nm, thereby implying the possibility of energy transfer from Bi(3+) to Eu(3+). The excitation spectra of Tb(3+), Eu(3+) co-doped LGBO phosphors are broader in comparison with single-doped phosphors and show tunable colors from green to yellow to orange-red when the ratio of Tb(3+) to Eu(3+) is adjusted These results demonstrate that LGBO:Tb(3+), Eu(3+) phosphors have potential use in light-emitting diodes.
Subject(s)
Color , Energy Transfer/radiation effects , Lanthanoid Series Elements/chemistry , Lighting/methods , Luminescent Measurements/methods , Colorimetry/methods , Dose-Response Relationship, Radiation , Materials Testing , Radiation DosageABSTRACT
A series of novel color-tunable phosphors of Ce(3+), Tb(3+)-codoped Li6Gd(BO3)3 was synthesized through a classic solid-state reaction. The color of these phosphors changes from blue to green by adjusting the ratio of Ce(3+) to Tb(3+). The photoluminescence properties of the synthesized phosphors were investigated, and several major emission bands that belong to Ce(3+) and Tb(3+) ions were irradiated with near ultraviolet light. Moreover, the energy transfer mechanism between Ce(3+) and Tb(3+) in Li6Gd(BO3)3 was explored. The photoluminescence decay curves were performed to validate the energy transfer. The analysis demonstrated that the energy transfer from Ce(3+) to Tb(3+) arose from dipole-dipole interaction with a critical distance of approximately 17.6 Å.