Highly uniform and monodisperse beta-NaYF4 : Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: Hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu(3+) (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to D-5(0-3) -> F-7(J) (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively.

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.

Synthesis, structure, photoluminescence, and electroluminescence properties of a new dysprosium complex

A new dysprosium complex Dy(PM)(3)(TP)(2) [where PM = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone and TP = triphenyl phosphine oxide] was synthesized, and its single-crystal structure was also studied. Its photophysical properties were studied by absorption spectra, emission spectra, fluorescence quantum efficiency, and decay time of the f-f transition of the Dy3+ ion. In addition, the antenna effect was introduced to discuss the energy transfer mechanism between the ligand and the central Dy3+ ion. Finally, a series of devices with various structures was fabricated to investigate the electroluminescence (EL) performances of Dy(PM)(3)(TP)(2). The best device with the structure ITO/CuPc 15 nm/Dy complex 70 nm/BCP 20 nm/AlQ 30 nm/LiF 1 nm/Al 100 nm exhibits a maximum brightness of 524 cd/m(2), a current efficiency of 0.73 cd/A, and a power efficiency of 0.16 lm/W, which means that a great improvement in the performances of the device was obtained as compared to the results reported in published literature. Being identical to the PL spectrum, the EL spectrum of the complex also shows characteristic emissions of the Dy3+ ion, which consist of a yellow band at 572 nm and a blue emission band at 480 nm corresponding to the F-4(9/2)-H-6(13/2) and F-4(9/2)-H-6(15/2) transition of the Dy3+ ion, respectively. Consequently, an appropriate tuning of the blue/yellow intensity ratio can be presumed to accomplish a white luminescent emission.

Long-lasting properties of rare earth-doped Y2O2S phosphors

The aim of this presentation is to report a new result of afterglow materials. The Y2OS: Ln(3+) (Ln = Sm, Tm) phosphors show bright reddish orange and orange-yellow colors when excited by UV or visible light. The main spectroscopic characterizations of Sin(3+) and Tin(3+) in yttrium oxysulfide and their long-lasting phosphorescence were measured and discussed in this presentation. Their long-lasting phosphorescence can be seen by the naked eyes clearly for about one hour in the dark room after the Irradiation light sources were removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize these long-lasting phosphorescence phosphors. The results of XRD indicate that the products synthesized through the flux fusion method tinder 1050 degreesC, for 6 It have a good crystallization without any detectable amount of impurity phase. Both the PL spectra and luminance decay results reveal that these phosphors have efficient luminescent and good long-lasting properties. We believe that the experimental data gathered in our present work will be. useful in finding some new long-lasting phosphors with different colors.

Tunable photoluminescent and cathodoluminescent properties of ZnO and ZnO : Zn phosphors

ZnO and ZnO: Zn powder phosphors were prepared by the polyol-method followed by annealing in air and reducing gas, respectively. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectra (XPS), electron paramagnetic resonance (EPR), and photoluminescence (PL) and cathodoluminescence ( CL) spectra, respectively. The results indicate that all samples are in agreement with the hexagonal structure of the ZnO phase and the particle sizes are in the range of 1-2 mu m. The PL and CL spectra of ZnO powders annealed at 950 degrees C in air consist of a weak ultraviolet emission band ( similar to 390 nm) and a broad emission band centered at about 527 nm, exhibiting yellow emission color to the naked eyes. When the sample was reduced at the temperatures from 500 to 1050 degrees C, the yellow emission decreased gradually and disappeared completely at 800 degrees C, whereas the ultraviolet emission band became the strongest. Above this temperature, the green emission ( similar to 500 nm) appeared and increased with increasing of reducing temperatures.

Polyimides derived from 3,3 '-bis(N-aminophthalimide)

A novel diamine, 3,3'-bis(N-aminophthalimide) (BAPI), was prepared from 3,3'-bis(N-phenylphthalimide). Its structure was determined via IR, H-1 NMR, N-15 NMR, elemental analysis, and single-crystal X-ray diffraction analysis. A series of homo- and copolyimides were synthesized by a conventional one-step method in p-chlorophenol. The characteristic IR absorption bands of hydrazine-based imide groups were near 1780, 1750, 1350, 1100, and 730 cm(-1). The polymers showed good solubility in polar aprotic solvents and phenols at room temperature. The temperatures of 5% weight loss (T-5%) of the polyimides ranged from 495 to 530 degrees C in air. DMTA analyses indicated that the glass-transition temperatures (Tgs) of the polyimides were in the range 371-432 degrees C. These polymers had cutoff wavelengths between 350 and 400 nm. The polyimide films of 6FDA/BAPI and 4,4'-HQPDA/BAPI were colorless; other films were pale yellow or yellow.

Tuning of emission: Synthesis, structure and photophysical properties of imidazole, oxazole and thiazole-based iridium (III) complexes

Three new iridium (III) complexes with two cyclometalated (CN)-N-boolean AND ligands (imidazole, oxazole and thiazole-based, respectively) and one acetylacetone (acac) ancillary ligand have been synthesized and fully characterized. The structure of the thiazole-based complex has been determined by single crystal X-ray diffraction analysis. The Ir center was located in a distorted octahedral environment by three chelating ligands with the N-N in the trans and C-C in the cis configuration. By changing the hetero-atom of (CN)-N-boolean AND ligands the order S, O and N, a marked and systematic hypsochromic shift of the maximum emission peak of the complexes was realized. The imidazole-based complex emits at a wavelength of 500 nm, which is in the blue to green region. The tuning of emission wavelengths is consistent with the variation of the energy gap estimated front electrochemistry results. An electroluminescent device using the thiazole-based complex as a dopant in the emitting layer has been fabricated. A highly efficient yellow emission with a maximum luminous efficiency of 9.8 cd/A at a current density of 24.2 mA/cm(2) and a maximum brightness of 7985 cd/m(2) at 19.6 V has been achieved.

Fabrication and luminescence properties of Y2SiWO8 : Dy3+ phosphors via sol-gel process

(YSiWO8)-Si-2:Dy3+ phosphors were prepared through a sol-gel process. XRD and photoluminespectra were used to characterize the resulting phosphors. The results indicated that the phosphors crystallized completely at 1000 degrees C. In Y2SiWO8:Dy3+ phosphors, the Dy3+ showed its characteristic yellow emission at 483nm (F-4(9/2)-H-6(5/2)) and 575nm (F-4(9/2)-H-6(13/2)) upon excitation into 275nm.

Synthesis, characterization, photoluminescent and electroluminescent properties of new conjugated 2,2 '-(arylenedivinylene)bis-8-substituted quinolines

A series of new PPV oligomers containing 8-substituted quinoline, 2,2'-(arylenedivinylene) bis-8-quinoline derivatives, were designed and synthesized via a Knoevenagel condensation reaction of quinaldine, 8-hydroxy-or 8-methoxy-quinaldine with aromatic dialdehydes. These PPV oligomers were characterized by H-1 and C-13-NMR, X-ray diffraction, elemental analysis, UV-visible and fluorescence spectroscopies. The X-ray diffraction investigation showed that there are intermolecular pi...pi interactions in the solid state in 1 and 3. The optical and photoluminescent properties study demonstrated that the emission color of the resulting materials varies from blue to yellow and is dependent on the substituents (pi-donor and pi-acceptor groups) on both sides of the conjugated molecules and the aromatic core in the middle of the conjugated backbones. The electroluminescent devices using compounds 1-4 as the emitters and electron-transporting layers were fabricated with the structure ITO/NPB/emitter/LiF/Al. The best device performance with the maximum brightness of 5530 cd m(-2) and the luminous efficiency of 2.4 cd A(-1) is achieved by using compound 4, with intramolecular charge transfer character, as the emitter; these values represent a more than 5-fold improvement in brightness and efficiency compared to compound 3 without methoxy groups on the phenyl rings.

Luminescence of the compounds Y0.5-xLi1.5VO4 :(Dy3+,Eu3+)

In this paper for the first time the compounds Y0.5-xLi1.5VO4:(Dy3+, Eu3+),(YLV:Dy,Eu) (0.01yellow and the red emission from the F-4(9/2)-H-6(15/2) (474.2-484.2 nm) transitions and F-4(9/2)-H-6(13/2) (568-576.4 nm) transitions of Dy3+ and the D-5(0)-F-7(2) (608-619.2 nm) transitions of Eu3+, respectively, are very strong in multiwavelength.