Synthesis and characterization of monodisperse spherical core-shell structured SiO2@Y3Al5O12 : Ce3+/Tb3+ phosphors for field emission displays

Nanocrystalline Y3Al5O12: Ce3+/Tb3+ ( average crystalline size 30 nm) phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by the sol-gel method, resulting in the formation of core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ particles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO2@Y3Al5O12: Ce3+/Tb3+ phosphor particles. The obtained core-shell structured phosphors consist of well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the Y3Al5O12:Ce3+/Tb3+ shells on the SiO2 cores ( average size about 500 nm, crystalline size about 30 nm) could be easily tailored by varying the number of deposition cycles (100 nm for four deposition cycles). Under the excitation of ultraviolet and low-voltage electron beams (1-3 kV), the core-shell SiO2@Y3Al5O12:Ce3+/ Tb3+ particles show strong yellow-green and green emission corresponding to the 5d-4f emission of Ce3+ and D-5(4)-F-7(J) ( J = 6, 5, 4, 3) emission of Tb3+, respectively.

Host-sensitized luminescence of Dy3+, Pr3+ , Tb3+ in polycrystalline CaIn2O4 for field emission displays

Caln(2)O(4):Dy3+/Pr3+/Tb3+ blue-white/green/green phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence (PL) and cathodoluminescencc (CL) spectra as well as lifetimes were utilized to characterize the samples. The XRD results reveal that the samples begin to crystallize at 800 degrees C 3-1 and pure CaIn2O4 phase can be obtained after annealing at 900 degrees C. The FE-SEM images indicate that the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ samples consist of spherical grains with size around 200-400nm. Under the excitation of ultraviolet light and low electron beams (1-5kV), the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ phosphors show the characteristic emissions of Dy3+ ((F9/2-H15/2)-F-4-H-6 and (F9/2-H13/2)-F-4-H-6 transitions, blue-white), Pr3+ ((P0-H4)-P-3-H-3, (D2-H4)-D-1-H-3 and (P1-H5)-P-3-H-3 transitions, green) and Tb3+ ((D4-F6,5,4,3)-D-5-F-7 transitions, green), respectively. All the luminescence is resulted from an efficient energy transfer from the CaIn2O4 host lattice to the doped Dy3+ ,Pr3+ and Tb3+ ions, and the corresponding luminescence mechanisms have been proposed.

Hydrothermal synthesis of SrCO3 : Eu3+/Tb3+ microneedles and their luminescence properties

SrCO3:Eu3+ /Tb3+ microneedles that grow along the a-axis were successfully prepared through a large-scale and facile hydrothermal method without any template and further annealing treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectra as well kinetic decays, were used to characterize the samples. The preferential growth along a-axis for SrCO3:Eu3+/Tb3+ microneedles has been proposed through analysis of the XRD patterns of samples obtained at different hydrothermal treatment time. Under ultraviolet excitation, the SrCO3:Eu3+ and SrCO3:Tb3+ microncedle samples show a strong red and green emission corresponding to the D-5(0)-F-7(j) (J = 1, 2, 3, 4) transitions of Eu3+ and the D-5(4)-(7) F-j (J = 6, 5, 4, 3) transitions of Tb3+, respectively, which have potential applications in lighting fields.

Luminescence properties of Y0.9-xGdxEu0.1Al3(BO3)(4) (0 <= x <= 0.9) phosphors prepared by spray pyrolysis process

Starting from metal nitrate aqueous solutions and H3BO3, Y0.9-xGdxEu0.1Al3(BO3)(4) (0 <= x <= 0.9) phosphors were synthesized by spray pyrolysis followed by annealing at high temperature. The obtained phosphor particles have spherical morphology with size in the range 0.5-2 mu m. Independent of the x values in Y0.9-xGdxEu0.1Al3(BO3)(4) (0 <= x <= 0.9) phosphors, the Eu3+ ion shows its characteristic D-5(0), (1)-F-7(J) (J = 0, 1, 2, 3, 4) transitions with D-5(0)-F-7(2) red emission (612 nm) as the most prominent group. The photoluminescence intensity of phosphors increases with the increase of x value in Y0.9-xGdxEu0.1Al3(BO3)(4) (0 <= x <= 0.9) due to an energy migration process like Gd3+-(Gd3+)(n)-Eu3+ that occurred in the host materials.

Synthesis and luminescent properties of europium (III) schiff base complexes covalently bonded to silica xerogels

A new kind of luminescent organic-inorganic hydrid material consisting of Eu(III)-schiff base complex covalently bonded to silica xerogel was synthesized via the sol-gel method using a Eu (N-propylene salicylimine ligand) complex modified with pendant triethoxysilane groups (Eu(III)(salenHSi)). The Eu(III)(salenHSi) complex is characterized by Fourier transform infrared (FT-IR) spectroscopy. Luminescent properties of the complex and the resulted hybrid silica xerogels have been investigated at room temperature.

Enhanced luminescence of gadolinium niobates by Bi3+ doping for field emission displays

Blue emitting GdNbO4: Bi3+ powder phosphors for field emission displays were prepared by a solid state reaction. Both photoluminescence and cathodoluminescence properties of the materials were investigated. GdNbO4 itself shows only a very weak luminescence in the blue spectral region. By doping Bi3+ in GdNbO4, the luminescence intensity was improved greatly. The emission spectrum of the GdNbO4: Bi3+ consists of a broad band with maximum at 445 nm (lifetime = 0.74 mu s; CIE chromaticity coordinates: x = 0.1519 and y = 0. 1196) for both UV and low voltage (1-7 kV) cathode ray excitation. In GdNbO4:Bi3+ phosphors, the energy transfer from NbO43- to activator Bi3+ occurred.

Sol-gel deposition and luminescence properties of LiYF4 : Tb3+ thin films

Tb3+-doped LiYF4 films were deposited on quartz glass by a simple sol-gel method. X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), photoluminescence spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 300 degrees C and fully crystallized at 400 degrees C. AFM and FESEM images of singly coated LiY0.95Tb0.05F4 annealed at 400 degrees C indicated that the film is uniform and crack-free films with average grain size of 90 nm, root mean square roughness of 11 nm and thickness of 120 nm. The doped Tb3+ ions showed its characteristic emission in crystalline LiYF4 films, i.e., D-5(3), F--7(4)J (J = 6, 5, 4, 3) emissions. The optimum doping concentration of the Tb3+ was determined to be 5.0 mol% of Y3+ in LiYF4 films.

A method to collect an infrared spectrum in solution

Herein we report a new method to collect a qualified infrared spectrum of a solute in solution by two solvent cells with different thickness during background single-beam spectrum scanning. By collecting the background spectrum with two cells (two stages), we successfully achieved accurate solvent compensation between a sample and a reference, namely, the solvent amounts in the sample and background measurements could become congruent. Therefore, the solvent bands were thoroughly suppressed in the infrared spectrum and a qualified spectrum of the solute was obtained.

The luminescence of CaYBO4 : RE3+ (RE=Eu, Gd, Tb, Ce) in VUV-visible region

Phosphors CaYBO4:RE3+ (RE = Eu, Gd, Tb, Ce) were synthesized with the method of solid-state reaction at high temperature, and their vacuum ultraviolet (VUV)-visible luminescent properties in VUV-visible region were studied at 20 K. In CaYBO4, it is confirmed that there are two types of lattice sites that can be substituted by rare-earth ions. The host excitation and emission peaks of undoped CaYBO4 are very weak, which locate at about 175 and 350-360nm, respectively. The existence of Gd3+ can efficiently enhance the utilization of host absorption energy and result in a strong emission line at 314 nm. In CaYBO4, Eu3+ has typical red emission with the strongest peak at 610 nm; Tb3+ shows characteristic green emission, of which the maximum emission peak is located at 542 nm. The charge transfer band of CaYBO4:Eu3+ was observed at 228 nm; the co-doping of Gd3+ and Eu3+ can obviously sensitize the red emission of Eu3+. The fluorescent spectra of CaYBO4:Ce3+ is very weak due to photoionization; the co-addition of Ce3+-Tb3+ can obviously quench the luminescence of Tb3+.

Near infrared light-emitting diodes based on composites of near infrared dye, CdSe/CdS quantum dots and polymer

Near infrared (NIR) light emitting diodes employing composites of an IR fluorescent dye, CdSe/CdScore/shell semiconductor quantum dots and poly( N-vinylcarbazole) (PVK) have been demonstrated. The device, with a configuration of indium-tin-oxide (ITO)//PEDOT:PSS//PVK:NIR Dye:CdSe/CdS//Al, had a turn-on voltage of 7 V, emitted the NIR light with a maximum at 890 nm and the irradiance intensity of 96 mu W. The electroluminescence efficiency of 0.02% was achieved at a current density of 13 mA cm(-2).

Synthesis and luminescence properties of nanocrystalline Gd2O3 : Eu3+ by combustion process

The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 45, and 23 run for the precursor and samples annealed at 600, 700 and 800 degrees C, respectively, which coincided with the results from TEM images. The emission intensity, host absorption and charge transfer band intensity increased with increasing the temperature. The slightly broad emission peak at 610 nm for smaller particles can be observed. The ratio of host absorption to O-2-Eu3+ charge transfer band of smaller nanoparticles is much stronger compared with that for larger nanoparticles, furthermore, the luminescence lifetimes of nanoparticles increased with increasing particles size. The effects of doping concentration of Eu3+ on luminescence lifetimes and intensities were also discussed. The samples exhibited a higher quenching concentration of Eu3+, and luminescence lifetimes of nanoparticles are related to annealing temperature of samples and the doping concentration of Eu3+ ions.

Organic photovoltaic cells with near infrared absorption spectrum

Organic photovoltaic cells with a strong absorption spectrum in the near infrared region were fabricated with the structure of indium tin oxide (ITO)/zinc phthalocynine (ZnPc)/lead phthalocynine (PbPc)/C-60/Al. PbPc has a broad and strong absorption, while the organic films of PbPc/C-60 showed an additional new absorption peak at 900 nm. The absorption in the near infrared region can harvest more photons to invert into photocurrent. Moreover, the introduction of ZnPc thin layer between ITO and PbPc further improved the new absorption peak and the collection of hole carriers at the electrode ITO, which increased the power conversion efficiencies to 1.95% and short-circuit current density to 9.1 mA/cm(2) under AM 1.5 solar spectrum.