Hydrothermal synthesis and photoluminescence investigation of NaY(MoO4)2:Eu3+ nanophosphor.

An intense red-emitting NaY(MoO4)2:Eu3+ nanophosphor was developed using a hydrothermal technique. A highly pure and single-phase NaY(MoO4)2:Eu3+ nanopowder was obtained after sintering the as-prepared sample at 800 degrees C. The crystal structure and photoluminescence properties of this double molybdate were investigated. X-ray diffraction analysis showed that the NaY(MoO4)2 nanoparticles have a scheelite-type tetragonal structure, without mixed phases. Rietveld analysis provided the atomic coordinates and Mo-O-rare-earth angles. The morphology of the molybdate precursor was controlled by adjusting the synthesis conditions. The pH was found to play a crucial role in the particle size and morphology distribution. The crystalline powder phosphor exhibited intense and efficient red emissions attributed to efficient energy-transfer from MoO4(2-) to Eu3+. The chromaticity coordinates (x,y) of the NaY(MoO4)2:Eu3+ phosphor sample correspond to (0.662, 0.337). The NaY(MoO4)2:Eu3+ powder exhibited a deep-red emission under near-ultraviolet (UV) excitation, indicating a promising red phosphor for white-light-emitting diodes based on near-UV light-emitting diodes.

Wide-band excited Y6(WMo)(0.5)O12:Eu red phosphor for white light emitting diode: structure evolution, photoluminescence properties, and energy transfer mechanisms involved.

Y6(WMo)(0.5)O12 activated with Eu(3+) ions was investigated as a red-emitting conversion phosphor for white light emitting diodes (WLEDs). The phosphors were synthesized by calcining a citrate-complexation precursor at different temperatures. The photoluminescence properties of the phosphors and the energy transfer mechanisms involved were studied as a function of structure evolution. It was found that the host lattices were crystallized in a cubic or a hexagonal phase depending on the synthesis conditions. Although all the phosphors showed intensive red emission under an excitation of near-UV or blue light due to energy transfer from the host lattices to Eu(3+) ions, the photoluminescence spectra and temporal decay features were found to vary significantly with the structure and crystallinity of the host lattice. The mechanisms of the energy transfer from the host lattices to Eu(3+) ions and energy quenching among Eu(3+) ions were discussed on the basis of structure evolution of the host lattice. Phosphors calcined at 800 and 1300 °C were suggested to be promising candidates for blue and near-UV light excited WLEDs, respectively.

Fabrication and characterization of graphene/poly(p-phenylenediamine) hybrids.

Graphene nanosheets functionalized with poly(p-phenylenediamine) (PPDA) were prepared via the in-situ chemical oxidative polymerization using potassium persulphate as a catalyst. Graphene nanosheets were previously prepared by chemical reduction of exfoliated graphite oxide. The structure and morphology of the composite material were characterized by FTIR, XPS, HRTEM, FESEM and XRD, while the thermal and electrical properties were measured by TGA and a four-probe method. FESEM and HRTEM observations indicated that the graphene sheets were encapsulated in the PPDA matrix. Furthermore, the nanocomposites exhibited improved conductivity and thermal stability as compared with pure PPDA.

Crystal growth and photoluminescence properties of Sm3+ doped CeO2 nanophosphors by solvothermal method.

The phosphor of CeO2 activated with the trivalent rare-earth Sm3+ ions were synthesized by using a solvothermal method. The CeO2:Sm3+ powders were finally obtained through calcination process sintered in the air at 800-1200 degrees C. The synthesized phosphors were characterized systematically by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and photoluminescence excitation spectra (PLE). The XRD and FE-SEM results reveal that the phosphor exhibit agglomerated spherical shape and with the increase of sintering temperature peaks become sharper and narrower and the crystal sizes also increase, respectively. The room temperature photoluminescence spectra of Sm3+ doped CeO2 powders were recorded on a PTI (Photon Technology International) flurimeter using a Xe-arc lamp with a power of 60 W. The emitted radiation was dominated by the orange light with the characteristic emission of Sm3+ from the transitions of 4G5/2 --> 6H5/2,7/2. The sharp emission properties show that the CeO2 has the potential to serve as a host material for rare-earth doped laser crystal and phosphor material.

Concentration enhanced upconversion luminescence in ZrO2:Ho3+, Yb3+ nanophosphors.

The upconversion luminescence properties of ZrO2:Ho3+ and co-doped ZrO2:Ho3+, Yb3+ nanophosphors with various concentrations of Yb3+ ions were synthesized via a solvothermal reaction method. Our samples have a nearby spherical shape and an average crystal size was about 80 nm. For low concentrations of Yb3+ ion, the crystalline structure changed from tetragonal to monoclinic phase as the Yb3+ concentration increased to 3 mol% Yb3+ ions. As the Yb3+ concentration increased to above 5 mol%, ZrO2 nanophosphors displayed a very stable tetragonal phase. The sample shows a strong green (550 nm) and weak red (660 nm) and near infrared (757 nm) upconversion emission corresponding to the transitions of Ho3+:5F4/5S2 --> 5I8, 5F5 --> 5I8 and 5S2 --> 5I7, respectively. The energy transfer (ET) processes between the Ho3+ and Yb3+ ions and the involved mechanisms have been investigated. Experimental results suggest that two-photon upconversion processes are taking place under excitation by a 975 nm.

Fabrication of conducting poly(3-thiophene boronic acid)-grafted multi-walled carbon nanotubes by oxidative polymerization.

Composite materials of multi-walled carbon nanotubes (MWNTs) and a conducting polymer, poly(3-thiophene boronic acid) (PTBA) were prepared by in-situ oxidative polymerization of TBA in the presence of MWNTs and potassium dichromate. The MWNTs which were previously surface functionalized with acid chloride groups were reacted with TBA using a simple "chemical grafting" technique. It was observed that the nanotubes were dispersed uniformly in the pi-conjugated polymer matrix and entrapped by the polymer. The conductivity of the composites was higher than that of the pure polymer from a conventional four-probe technique, which indicates that the fabrication of MWNTs into the polymer matrix significantly improves the conductivity of the polymer due to the intrinsic properties of MWNTs.

Controlled fabrication and shape-dependent luminescence properties of hexagonal NaCeF4, NaCeF4:Tb3+ nanorods via polyol-mediated solvothermal route.

Hexagonal monodisperse NaCeF(4) and NaCeF(4):Tb(3+) nanorods have been successfully synthesized by a polyol-mediated solvothermal route with ethylene glycol (EG) as solvent. The crystalline phase, size, morphology, and luminescence properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra as well as dynamic decays. The experimental results indicate that the content of NH(4)F and NaNO(3) are crucial in controlling product morphology and size. Nanorods with different aspect ratios could be controllably obtained under settled conditions. Shape-dependent luminescence and energy transfer routes from Ce(3+) to Tb(3+) in NaCeF(4):Tb(3+) nanorods were observed by the modified local crystal field environment around rare earth ions. The 4f-5d transitions of Ce(3+) ions have much higher sensitivity to the anisotropic shape of samples than that of Tb(3+) ions.

Crystal structure, electronic structure, and optical and photoluminescence properties of Eu(III) ion-doped Lu6Mo(W)O12.

Lu(6)WO(12) and Lu(6)MoO(12) doped with Eu(3+) ions have been prepared by using a citrate complexation route, followed by calcination at different temperatures. The morphology, structure, and optical and photoluminescence properties of the compounds were studied as a function of calcination temperature. Both compositions undergo transitions from a cubic to a hexagonal phase when the calcination temperature increases. All the compositions have strong absorption of near-UV light and show intense red luminescence under a near-UV excitation, which is related to the transfer of energy from the host lattices to dopant Eu(3+) ions. Density functional theory calculations have also been performed. The calculation reveals that hexagonal Lu(6)WO(12) and Lu(6)MoO(12) are indirect bandgap materials, and the near-UV excitations are due to the electronic transitions from the O-2p orbitals to W-5d and Mo-4d orbitals, respectively. The lattice parameters and bandgap energies of hexagonal Lu(6)WO(12) and Lu(6)MoO(12) were determined.

Hydrothermal synthesis and optical properties of Eu(3+)-doped CaSnO3 nanocrystals.

In this paper, CaSnO3:Eu3+ nanocrystals were prepared by hydrothermal synthesis method. The influence of different molar ratio of Ca:Sn on structure of CaSnO3:Eu3+ was investigated by using X-ray powder diffraction (XRD). Well-crystallized and phase-pure CaSnO3:Eu3+ particles of approximately 90 nm in size can be readily obtained at 900 degrees C. Furthermore, photoluminescence characterization of the Eu(3+)-doped CaSnO3 nanocrystals was performed and discussed. The emission peak situated at 618 nm showing prominent and bright red light is due to the 5D0-7F2 electric dipole transition. The excellent luminescence properties make it possible as a good candidate for PDP application.

Luminescence characteristics of Pr3+ ion doped CaTiO3 nanopowder phosphors synthesized by solvothermal method.

In display applications, each displays technique needs different phosphors according to its applications. So, in this paper, nano-sized red emitting CaTiO3:Pr3+ powder phosphors were prepared by solvothermal reaction method. The phase purity and the structure of the phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM). The particles show the spherical morphology, which indicates the good luminescent characteristics. The luminescent properties of CaTiO3:Pr3+ powder phosphors have been carried out by the measurement of their phototluminescence (PL) and phototluminescence excitation (PLE) spectra. The PL spectra shows the strong red emission due to 1D2 --> 3H4 transition. The emissions of intra-4f transitions from the excited states (1D2) to the ground state (3H4) of Pr3+ are mainly observed around from 612 to 618 nm. The effect of the Pr3+ concentration on their photoluminescent properties was investigated extensively. These luminescent powders are expected to find potential applications such as optical display systems.

Preparation of properties of SWNT/graphene oxide type flexible transparent conductive films.

Single walled carbon nanotube (SWNT)/graphene oxide (GO) hybrid films were prepared by a facile bar coating method on a polyethylene terephthalate substrate using a mixed solution of SWCNTs and GO. An acryl type polymer was employed as a dispersion agent to obtain SWCNT and GO suspension in ethyl alcohol. The SWCNT/GO hybrid films were highly transparent and electrically conductive, showing 80% transmittance and 1.8 x 10(3) ohm/sq surface resistance. The surface resistance of the SWCNT/GO film could be further improved to 750 ohm/sq by hydrazine vapor reduction.

Synthesis and luminescence properties behavior of Eu(3+)-doped nanocrystalline and bulk GdVO4 phosphors by high-energy ball milling and solid state reaction.

Europium-doped nanosized-GdVO4:Eu3+ powders and bulk GdVO4:Eu3+ powders were synthesized using a planetary ball mill and conventional solid state reaction method, respectively. The effects of the grain size on the crystallinity, morphology, structure and luminescence spectra were investigated by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy (PL). The room temperature PL spectra of the GdVO4:Eu3+ nanophosphors showed four emission bands at 611, 615, 619 and 595 nm. The bands at 611, 615 and 619 nm were assigned to the 5D0 --> 7F2 transition of the EU3+ ion when excited with 312 nm light.

Structure, charge transfer bands and photoluminescence of nanocrystals tetragonal and monoclinic ZrO2:Eu.

Eu(3+)-doped tetragonal and monoclinic ZrO2 (called t-ZrO2:Eu and m-ZrO2:Eu, respectively) nanoparticles were prepared using the Pechini sol-gel process. The samples were characterized via X-ray diffraction (XRD) and field-emission-scanning electron microscopy (FE-SEM), and with photoluminescence spectra. The influences of the Eu3+ concentration and the fired temperature on the crystal phase composition of the tetragonal and monoclinic ZrO2:Eu were reported. The typical interesting photoluminescence (PL) properties of the t-ZrO2:Eu and m-ZrO2:Eu nanoparticles were presented. In the t-ZrO2:Eu and m-ZrO2:Eu, the main emission peaks were at 607 and 615 nm, respectively, both of which originated from the 5D0-7F2 transition. The excitation band of the t-ZrO2:Eu powder with a lower Eu3+ doping concentration that was obtained at a low temperature (450 degrees C) consisted of a broad band of 230-500 nm. Both broad excitation bands in the t-ZrO2:Eu and m-ZrO2:Eu were ascribed to the O(2-) - Eu3+ charge transfer (CT) transition. The reason was discussed based on the relationship between the CT energy and its crystal structure. The CT energy of m-ZrO2:Eu is higher than that of t-ZrO2:Eu. A detailed chemical bond analysis was performed to explore the CT energy difference between t-ZrO2: Eu and m-ZrO2:Eu.

Luminescent properties of SrZnO2:Tb3+ hybrid thin film phosphors grown by pulsed laser deposition.

Novel green-light-emitting Tb(3+)-doped SrZnO2 phosphor thin films were grown via the pulsed-laser-deposition technique. The films were grown at various substrate temperatures and oxygen pressures. The crystallinity and surface morphology of the films were investigated via X-ray diffraction (XRD) and atomic-force microscopy (AFM), respectively. The luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. The thin films showed a green emission radiated by the transitions from the 5D4 excited states to the 7FJ (J = 3-6) ground states of the Tb3+ ions found under ultraviolet excitation with a 272 nm wavelength. The crystallinity, surface morphology, and photoluminescence spectra of thin-film phosphors were found to be highly dependent on the deposition conditions, particularly the substrate temperature and oxygen pressure. The surface roughness and photoluminescence intensity of the films showed similar behaviors as a function of the substrate temperature and oxygen pressure.

Bifunctional application of La3BWO9:Bi3+,Sm3+ phosphors with strong orange-red emission and sensitive temperature sensing properties.

Through a solid-phase reaction technique, Sm3+ and Bi3+ co-doped La3BWO9 phosphors with high emission intensity and sensitive temperature sensing properties have been successfully synthesized. Based on XRD Rietveld refinement, the optimized crystal structure was used as the original model to calculate the band structure and partial density of states (PDOS) by density functional theory (DFT) calculations. The luminescence characteristics of Sm3+ and Bi3+ co-doped La3BWO9 phosphors were measured and analyzed. In addition, the optimal doping concentrations of Sm3+ and Bi3+ were investigated. The luminescence properties of Sm3+ doped phosphors were optimized by introducing Bi3+ ions. Efficient energy transfer from Bi3+ to Sm3+ ions was observed in La3BWO9:Sm3+, Bi3+ phosphors. An optical temperature sensor with high sensitivity was designed based on the different thermal quenching properties of Sm3+ and Bi3+ ions. In the temperature range of 293-498 K, the optimum absolute sensitivity (Sa) and maximum relative sensitivity (Sr) were 2.88 %K-1 and 1.32 %K-1, respectively. These results indicated that the prepared La3BWO9:Bi3+, Sm3+ phosphors have wide application prospects as solid state lighting materials and optical temperature sensors.

Facile Fabrication of MnCo2O4/NiO Flower-Like Nanostructure Composites with Improved Energy Storage Capacity for High-Performance Supercapacitors.

Over the past few decades, the application of new novel materials in energy storage system has seen excellent development. We report a novel MnCo2O4/NiO nanostructure prepared by a simplistic chemical bath deposition method and employed it as a binder free electrode in the supercapacitor. The synergistic attraction from a high density of active sites, better transportation of ion diffusion and super-most electrical transportation, which deliver boost electrochemical activities. X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy have been used to investigate the crystallinity, morphology, and elemental composition of the as-synthesized precursors, respectively. Cyclic voltammetry, galvanostatic charge/discharge, and electron impedance spectroscopy have been employed to investigate the electrochemical properties. The unique nanoparticle structures delivered additional well-organized pathways for the swift mobility of electrons and ions. The as-prepared binder-free MnCo2O4/NiO nanocomposite electrode has a high specific capacity of 453.3 C g-1 at 1 Ag-1, and an excellent cycling reliability of 91.89 percent even after 4000 cycles, which are significantly higher than bare MnCo2O4 and NiO electrodes. Finally, these results disclose that the as-fabricated MnCo2O4/NiO electrode could be a favored-like electrode material holds substantial potential and supreme option for efficient supercapacitor and their energy storage-related applications.

Infrared excited Er3+/Yb3+ codoped NaLaMgWO6 phosphors with intense green up-conversion luminescence and excellent temperature sensing performance.

The Er3+/Yb3+-codoped NaLaMgWO6 phosphors were synthesized via a traditional high-temperature solid-state reaction method. The temperature sensing performance was thoroughly investigated by studying the temperature-dependent up-conversion (UC) emission intensity ratio in the range of 293-533 K. A remarkable enhancement of green UC emission, as well as enhanced temperature sensitivity, were observed by increasing the Yb3+ concentration. The maximum absolute sensor sensitivity was 2.29% K-1 at 533 K. When the pump power of the 980 nm laser increased from 200 to 1000 mW, a slightly elevated temperature from 293-307 K was achieved in the compounds. Using the prepared phosphors and a 940 nm NIR chip, a green-emitting LED device was developed to confirm the applicability of our prepared phosphors for solid-state lighting. As a temperature probe, the prepared phosphor detected that the temperature increased from 286 K to 315 K when the drive current was increased from 90 mA to 300 mA. These results suggest that the Er3+/Yb3+-codoped NaLaMgWO6 phosphors have a potential application in solid-state lighting and optical thermometry.

Preferential occupancy of Eu3+ and energy transfer in Eu3+ doped Sr2V2O7, Sr9Gd(VO4)7 and Sr2V2O7/Sr9Gd(VO4)7 phosphors.

The vanadate-based phosphors Sr2V2O7:Eu3+ (SV:Eu3+), Sr9Gd(VO4)7:Eu3+ (SGV:Eu3+) and Sr9Gd(VO4)7/Sr2V2O7:Eu3+ (SGV/SV:Eu3+) were obtained by solid-state reaction. The bond-energy method was used to investigate the site occupancy preference of Eu3+ based on the bond valence model. By comparing the change of bond energy when the Eu3+ ions are incorporated into the different Sr, V or Gd sites, we observed that Eu3+ doped in SV, SGV or SV/SGV would preferentially occupy the smaller energy variation sites, i.e., Sr4, Gd and Gd sites, respectively. The crystal structures of SGV and SV, the photoluminescence properties of SGV:Eu3+, SV, SGV/SV and SGV/SV:Eu, as well as their possible energy transfer mechanisms are proposed. Interesting tunable colours (including warm-white emission) of SGV/SV:Eu3+ can be obtained through changing the concentration of Eu3+ or changing the relative quantities of SGV to SV by increasing the calcination temperature. Its excitation bands consist of two types of O2- → V5+ charge transfer (CT) bands with the peaks at about 325 and 350 nm respectively, as well as f-f transitions of Eu3+. The obtained warm-white emission consists of a broad photoluminescence band centred at about 530 nm, which originates from the O2- → V5+ CT of SV, and a sharp characteristic spectrum (5D0-7F2) at about 615 and 621 nm.

Dual-Mode Manipulating Multicenter Photoluminescence in a Single-Phased Ba9Lu2Si6O24:Bi3+, Eu3+ Phosphor to Realize White Light/Tunable Emissions.

A Bi3+ and Eu3+ ion co-doped Ba9Lu2Si6O24 single-phased phosphor was synthesized successfully via a conventional high-temperature solid-state reaction. X-ray diffraction, crystal structure analysis, diffuse reflectance and luminescent spectra, quantum efficiency measurements, and thermal stability analysis were applied to investigate the phase, structure, luminescent and thermal stability properties. From the analyses of the crystal structure and luminescent spectra, we observed four discernible Bi3+ luminescent centers with peaks at ~363.3, ~403.1, ~437.7, and ~494.5 nm. Moreover, due to the complex energy transfer processes among these Bi3+ centers, their relative emission intensity tightly depended on the incident excitation wavelength. Interestingly, the as-prepared phosphor could generate warm white light/tunable emission by changing the concentration of Eu3+ ions or adjusting the excitation wavelength. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed via an electric dipole-dipole interaction, the energy transfer efficiencies [Formula: see text] from Bi3+ to Eu3+ were 50.84% and 40.17% monitoring at 410 and 485 nm, respectively. The internal quantum efficiency of the optimized Ba9Lu2Si6O24:Bi3+, Eu3+ phosphor was calculated to be 42.6%. In addition, the configurational coordinate model was carried out to explain the energy decrease of the phonon-electron coupling effect.

Synthesis and Photoluminescent Properties of Nanorod Bundle Ln4O(OH)9NO3:Eu(Ln = Y, Lu) Prepared by Hydrothermal Method.

Well-crystallized nanorod bundles Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) have been successfully prepared by hydrothermal method. The crystalline phase, size and optical properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), infrared (IR) spectrograph and photoluminescent (PL) spectra. Site occupations of Eu3+ in crystals Ln4O(OH)9NO3:Eu(Ln = Y, Lu) were discussed based on excitation spectra and the empirical relationship formula between the charge transfer (CT) energy and the environmental factor. The emission spectra exhibited that the strongest emission peaks with an excitation wavelength of 395 nm were at 617 and 626 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, both of which come from 5D0-7F2 transition of the Eu3+ ions. The broad excitation peaks at about 254 and 255 nm were found when monitored at 617 and 628 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, which were due to O-Eu CT transition. Based on the dielectric theory of complex crystal, the CT bands at about 254 and 255 nm in Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) were assigned to the transition of O-Eu at Ln3(Ln = Y, Lu) site, from which we can conclude that Eu3+ ions occupied the site of Ln3(Ln = Y, Lu) in crystal Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu). It put forward a new route to investigate site occupation of luminescent center ions in rare earth doped complex inorganic luminescence materials.