Lianchun Zou

White light-emitting properties of NaGdF4 nanotubes through Tb3+, Eu3+ doping

White light-emitting NaGdF4 phosphor samples based on efficient energy transfer between Tb3+ and Eu3+ were synthesized via a conventional hydrothermal reaction process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra and lifetime measurement were performed to characterize the samples. The energy transfer process between Tb3+ and Eu3+ was demonstrated to be a resonant type via a dipole–dipole interaction mechanism. Furthermore, for NaGdF4:Tb3+,Eu3+, white light emission can be realized in the single-phase NaGdF4 host by reasonably adjusting the relative doping concentrations of Tb3+ and Eu3+ under ultraviolet excitation. Due to their excellent PL properties and good CIE chromaticity coordinates, the as-prepared Tb3+, Eu3+ co-doped NaGdF4 nanocrystalline phosphors have potential application in field-emitting displays.

Hydrothermal synthesis, characterization, and color-tunable luminescence properties of Bi2MoO6:Eu3+ phosphors

In this paper, Bi2MoO6:Eu3+ phosphors were successfully synthesized via a facile, efficient hydrothermal synthesis process followed by a further calcination treatment without using any surfactants. The samples were analyzed by XRD, UV-vis absorption spectroscopy, photoluminescence (PL) and decay curve measurements. XRD patterns reveal that all the diffraction peaks could be indexed to well-crystallized orthorhombic structures. UV-visible diffuse reflection spectra of the prepared Bi2MoO6 and Bi2MoO6:Eu3+ indicate that they had absorption in the UV-light region. The luminescence spectra showed that Bi2MoO6:Eu3+ phosphors can be effectively excited by UV light (328 nm), and exhibited strong red emission around 613 nm attributed to the Eu3+ 5D0 → 7F2 transition. Effects of Eu3+ concentration on lattice constants and PL were presented.

Self-assembled 3D sphere-like SrMoO4 and SrMoO4:Ln3+ (Ln = Eu, Sm, Tb, Dy) microarchitectures: Facile sonochemical synthesis and optical properties

Three-dimensional (3D) well-defined SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures of obvious sphere-like shape have been successfully synthesized using a large-scale and facile sonochemical route without using any catalysts or templates. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of SrMoO4 and external factor, namely the ultrasonic time and the pH value, are responsible for the ultimate shape evolutions of the product. The possible formation mechanism for the product is presented. Additionally, the PL properties of SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures were investigated in detail. The Ln(3+) ions doped SrMoO4 samples exhibit respective bright red-orange, yellow, green and white light of Eu(3+), Sm(3+), Tb(3+) and Dy(3+) under ultraviolet excitation, and have potential application in the field of color display. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating about the properties of molybdate materials.

Morphology control and multicolor-tunable luminescence of YOF:Ln3+ (Ln = Eu, Tb, Dy, Tm) nano-/microcrystals

YOF:Ln3+ (Ln = Eu, Tb, Dy, Tm) nano-/microcrystals with high uniformity, monodispersity and a variety of well-defined morphologies, such as submicro spheres, ellipsoids, nanorods, microspindles and spindle nanorod bundles, have been successfully synthesized via a urea based homogeneous precipitation method followed by a heat-treatment process. The influence of pH values, fluoride sources and reaction time on the sizes and morphologies of the as-prepared precursor was systematically investigated and discussed. The possible formation mechanism for the precursor has been presented. Upon ultraviolet excitation, the YOF:Ln3+ (Ln = Eu, Tb, Dy, Tm) submicro spheres show their characteristic f–f emissions and give red, green, yellow, and blue emission, respectively. Moreover, a novel single-phased and near-UV-pumped white-light-emitting phosphor YOF:Tm3+,Dy3+ was also successfully fabricated by singly varying the doping content of Dy3+ with a fixed Tm3+ content through the principle of energy transfer. This merit of multicolor emissions in the visible region endows materials of this kind with potential application in field-emission display devices and white light-emitting diodes.

Formation mechanism and optical properties of CdMoO4 and CdMoO4:Ln3+ (Ln = Pr, Sm, Eu, Dy, Ho and Er) microspheres synthesized via a facile sonochemical route

In the present work, large-scale uniform CdMoO4 and CdMoO4:Ln3+ (Ln = Pr, Sm, Eu, Dy, Ho, Er) microspheres have been successfully synthesized via a facile sonochemical route. XRD, FE-SEM, EDS, the Brunauer–Emmett–Teller (BET) surface area, and photoluminescence (PL) spectra were used to characterize the samples. The results show that the CdMoO4:Ln3+ can be directly indexed to the tetragonal CdMoO4 phase with high purity. The influence of the reaction time and reactants on the size and shapes of the CdMoO4 microspheres has been studied, and the results revealed that the ultrasonication time and reactants play a crucial role in determining the final morphologies of the samples. Additionally, the PL properties of the CdMoO4 and CdMoO4:Ln3+ (Ln = Pr, Sm, Eu, Dy, Ho and Er) microspheres were investigated in detail. It can be seen that the CdMoO4:Pr3+, Sm3+, Eu3+, Dy3+, Ho3+ and Er3+ samples are located in the red, yellow, red, white, yellow and green regions, respectively. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating the properties of molybdate materials.

Size‐tailored synthesis and luminescent properties of three‐dimensional BaMoO4, BaMoO4:Eu3+ micron‐octahedrons and micron‐flowers via sonochemical route

Almost monodisperse three-dimensional (3D) BaMoO4, BaMoO4 :Eu(3+) micron-octahedrons and micron-flowers were successfully prepared via a large-scale and facile sonochemical route without using any catalysts or templates. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersion X-ray (EDS), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy were employed to characterize the as-obtained products. It was found that size modulation could be easily realized by changing the concentrations of reactants and the pH value of precursors. The formation mechanism for micron-octahedrons and micron-flowers was proposed on the basis of time-dependent experiments. Using excitation wavelengths of 396 or 466 nm for BaMoO4 :Eu(3+) phosphors, an intense emission line at 614 nm was observed. These phosphors might be promising components with possible application in the fields of near UV- and blue-excited white light-emitting diodes. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating the properties of molybdate materials.

A facile route to the controlled synthesis of β-NaLuF4:Ln3+ (Ln = Eu, Tb, Dy, Sm, Tm, Ho) phosphors and their tunable luminescence properties

Highly uniform and monodisperse β-NaLuF4:Ln3+ (Ln = Eu, Tb, Dy, Sm, Tm, Ho) hexagonal prisms have been synthesized via a facile two-step hydrothermal method without any organic surfactants. The structures, morphologies and luminescence properties of the samples were investigated through XRD, SEM, and PL spectra. Furthermore, the shapes and sizes of the products can be further manipulated through adjusting the pH values of initial solutions. Upon excitation at 368 nm, the β-NaLuF4:Tb3+ phosphors exhibit the strongest green emission at pH = 9.0. Moreover, the photoluminescence properties of β-NaLuF4:Ln3+ were studied in detail, and it was found that the photoluminescence color of the β-NaLuF4:0.03Tm3+ phosphor was close to standard blue light (0.14, 0.08). Under 356 nm irradiation, multicolour emission from blue to sapphire and then to pale green has been achieved from the Tm3+/Dy3+ co-doped β-NaLuF4 samples. The energy transfer process from Tm3+ to Dy3+ was studied and was demonstrated to be an electric dipole–dipole interaction mechanism. It is obvious that the β-NaLuF4 phosphors may have potential applications in the field of full-color displays.