Search

Full spectrum white LED plant growth light sources are suitable for use in conditions requiring a high color rendering index. In addition to red and blue light, green light was shown to have a positive impact on plant growth in earlier studies. In this work, a series of Sm3+ doped ZnWO 4 phosphors was prepared using the high-temperature solid-state reaction method. Li+ serves as a charge compensator to reduce lattice defects caused by non-equivalent isomorphism. XRD measurements and Rietveld refinement were used to investigate the phase composition and structural properties of the samples. The luminescent properties of the samples were tested using a fluorescence spectrophotometer. The Li + introduction can significantly improve the energy transfer from the matrix to Sm3+ and the luminescence intensity of Sm 3+ . In addition, this phenomenon was explained with non-equivalent isomorphism and the charge density difference diagram. The LED lamp was prepared using ZnWO 4 : 0.004Sm3+, 0.004Li + phosphor and LED chip. The emitted full spectrum light can match well with the absorption spectrum of plant pigments. The color rendering index of the LED lamp is greater than 91. And the comparative experiment of plant cultivation shows that the prepared LED plant lamp has good effects. The dependence of luminescence properties of ZnWO 4 : 0.004Sm3+, 0.004Li+ phosphor on temperature was determined. Based on fluorescence intensity ratio (FIR) technology, the maximum S aMAX and S rMAX are 52 % K−1 at 453 K and 9.31 % K−1 at 303 K, respectively. As the temperature increases, the chromaticity shift (Δ s) value is 0.254. The benefits of the ZnWO 4 : 0.004Sm3+, 0.004Li+ phosphor are the straightforward synthesis process, low cost, pure phase, full spectrum, high color rendering index, tunable red-to-blue ratio, and temperature monitoring function. Therefore, this phosphor is an ideal material in plant growth and optical temperature measurement. [ABSTRACT FROM AUTHOR]

Novel Pr 3+ , Ho 3+ , and Er 3+ single-doped Ca X Sr Y Ba 1−X−Y WO 4 phosphors were successfully prepared via a facile hydrothermal method. The hydrothermal process was conducted in aqueous condition without the use of any organic solvent, surfactant, or catalyst. The effects of doping-host composition and RE 3+ doping concentration on the emission intensity were investigated to optimize the luminescent properties of Ca X Sr Y Ba 1−X−Y WO 4 :RE 3+ phosphors. Experimental results demonstrate that the morphologies of the products vary gradually and regularly with the change of the host composition, in which the anisotropic growth played a key role. Moreover, the down-conversion emissions of Pr 3+ , Ho 3+ , and Er 3+ in Ca X Sr Y Ba 1−X−Y WO 4 host were successfully realized. After optimizing the luminescent properties, Ca 0.4 Sr 0.6 WO 4 :0.01Pr 3+ , Ca 0.8 Sr 0.2 WO 4 :0.01Ho 3+ , and Ca 0.6 Sr 0.4 WO 4 :0.005Er 3+ exhibited optimal luminescent property, with orange, yellowish-green, and green emissions, respectively. [ABSTRACT FROM AUTHOR]

Dy 3+ and Eu 3+ codoped KSr 4 (BO 3 ) 3 phosphors were successfully synthesized by solid-state reaction process. Under near-ultraviolet (near-UV) excitation, individual Dy 3+ or Eu 3+ ion activated sample exhibits characteristic emissions in their respective regions. In KSr 4 (BO 3 ) 3 :Dy 3+ , x Eu 3+ phosphors, the energy transfer from Dy 3+ to Eu 3+ was revealed to be resonant type by dipole–dipole mechanism. And the critical distance R Dy–Eu was calculated to be 13.95 Å. The energy transfer efficiency of KSr 4 (BO 3 ) 3 :Dy 3+ , x Eu 3+ reached about 20% when the concentration of Eu 3+ was 0.035. Moreover, the emitting colors of Dy 3+ and Eu 3+ codoped samples can be adjusted from the edge of white area to warm white via tuning the activator (Eu 3+ ) doped concentration. More significantly, the chromaticity coordinates (0.334, 0.351) of KSr 4 (BO 3 ) 3 :0.005Dy 3+ , 0.015Eu 3+ sample are extremely adjacent to standard white light (0.33, 0.33). The quantum efficiency of the KSr 4 (BO 3 ) 3 :0.005Dy 3+ , 0.015Eu 3+ phosphor with 389 nm excitation is found to be 42%, demonstrating that the obtained single-component white-emitting phosphor exhibits potential applications for solid state lighting. [ABSTRACT FROM AUTHOR]

Abstract: Tetragonal CaMoO4 and CaMoO4:Eu3+ with various novel three-dimensional (3D) hierarchical architectures were successfully synthesized via a facile, efficient sonochemistry process in the absence of any surfactant or template. XRD, EDS, FE-SEM, and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that morphology modulation could be easily realized by changing pH value of the precursor. The pH value of the precursor not only affected the substructures of the hierarchical structures, but also determined the size distributions of the final products. The formation mechanism for different hierarchical architectures was proposed on the basis of time-dependent experiments. The luminescence spectra showed that CaMoO4:Eu3+ phosphors can be effectively excited by the near ultraviolet (UV) (396nm) and blue (466nm) light, and exhibited strong red emission around 615nm, which was attributed to the Eu3+ 5D0→7F2 transition. Compared with Y2O3:Eu3+ phosphor, CaMoO4:Eu3+ is much more stable, efficient and suitable, therefore, this phosphors could be a promising red component for possible applications in the field of LEDs. [Copyright &y& Elsevier]

Two series of ZnWO 4 : RE3+, Li+ (RE = Sm, Eu) phosphors were prepared using the facile solid-state reaction sintering at 800 °C. Its structural properties were investigated by XRD and Rietveld refinement method. The luminescence properties of the phosphors were studied, and they can be used in the white light-emitting diodes (wLEDs). Li+ was introduced into phosphors as a charge compensation agent. The influence of Li+ on the phase and luminescent properties was studied. The Vienna Ab-initio Simulation Package (VASP) software was employed to calculate the charge density differences. It is shown that the ZnWO 4 : Sm3+, Li+ phosphor has potential application in the plant growth LEDs. Image 1 • Two series of ZnWO 4 : Sm3+ or Eu3+ phosphors were prepared by solid state method. • The broad excitation peak around 305 nm perfectly matches the AlGaN semiconductor. • Emission color can be turned from white to red by adjusting concentration of RE3+. • Two white phosphors (ZnWO 4 : 0.004Sm3+, Li+; ZnWO 4 : 0.002Eu3+, Li+) were obtained. • Sm3+ doped ZnWO 4 phosphor has potential application in plant growth LEDs. [ABSTRACT FROM AUTHOR]

A series of YBO 3 :Ln 3+ (Ln = Eu, Tb) phosphors have been successfully synthesized for the first time via a simple solution-based hydrothermal method using Y(OH)CO 3 :Ln 3+ (Ln = Eu, Tb) colloid spheres and Na 2 B 4 O 7 ·10H 2 O as the precursors. The as-prepared phosphors present uniform ellipsoid-like morphology and have a diameter of about 2.5 μm. FTIR confirms the formation of vaterite-type YBO 3 can be synthesized by this method. The molar ratio of Y/B plays an important role in controlling the product morphology. The possible formation mechanism for the ellipsoid-like microcrystals was proposed on the basis of a series of time-dependent experiments. Even in such a simple solution-based hydrothermal reaction system, the formation of YBO 3 microcrystals went through complex crystallization and crystal growth processes: a small amount of random shaped particles served as precursors for the crystals initially formed which continuously grew into large flower-like YBO 3 , the excess borax resulted in the dissolution of flower-like YBO 3 and the formation of new YBO 3 particles. Moreover, there exists characteristic luminescence of Eu 3+ and Tb 3+ individually when doping them in the YBO 3 host. The quenching concentration of YBO 3 :Eu 3+ and YBO 3 :Tb 3+ is 25% and 20%, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract A series of ZnWO 4 : Eu3+, M+ (Li, Na, K) phosphors were prepared using a facile solid-state reaction method. After the different alkali metals introduction, emission spectra have changed obviously. The color of the emitting light can be tuned from greenish blue to white and finally to the red via co-doping different alkali metals. Highlights • A series of ZnWO 4 : Eu3+, M+ phosphors were prepared by solid-state reaction. • The broad excitation peak from 280 to 315 nm matches perfectly AlGaN based LED. • The emission spectra change obviously when the alkalis co-doped into the host. • Emitting light colors can be tuned from greenish blue to white finally to the red. Abstract A series of ZnWO 4 :Eu3+, M+ (Li, Na, K) phosphors were prepared using a facile solid-state reaction method by sintering at 800 °C. The XRD patterns of the phosphors indicate that the Eu3+ and M+ ions have successfully been introduced into the ZnWO 4 lattice. Their luminescent properties have been studied. The broad excitation peak from 280 to 315 nm by monitoring emission at 616 nm perfectly matches the wavelength range of deep UV LED based on AlGaN semiconductor. When the doping concentration of Eu3+ exceeds 2% in the ZnWO 4 : Eu3+, the luminescence intensity of Eu3+ gradually decreases due to the formation of impurity Eu 2 (WO) 4. The alkali metals are added into the ZnWO 4 as a charge compensator. After the introduction of alkali metals, emission spectra have changed obviously. The addition of Li+ can effectively promote the energy transfer from WO 4 2− to Eu3+. The Commission Internationale de L'Eclairage (CIE) chromaticity color coordinates are calculated. The color of the emitting light can be tuned from greenish blue to white and finally to the red via co-doping different alkali metals. [ABSTRACT FROM AUTHOR]

Abstract The Dy3+ or/and Sm3+ doped LiLa(WO 4) 2 phosphors are synthesized by a facile solid state reaction method. The phase and luminescence properties of the phosphors are investigated. The powder X-ray diffraction (XRD) results show that the phosphor has a tetragonal phase crystal structure. The quenching concentration of single doped Dy3+ and Sm3+ in the LiLa(WO 4) 2 are determined to be 6% and 3%, respectively. Under the excitation of 404 nm, warm white light is obtained in the co-doped phosphors. With the concentration of Sm3+ increasing, the correlated color temperature (CCT) gradually decreases from 3090 to 2453 K. Two kinds of energy transfer may exist at the same time. The overlap between the emission spectrum of Dy3+ and the excitation spectrum of Sm3+ reveals that the energy of Dy3+ can transfer to Sm3+ via radiation. Another way of energy transfer, that is non-radiative energy transfer, is attributed to the excited state of Dy3+ (4F 9/2) slightly higher than that of Sm3+ (4I 19/2). The calculation results show that non-radiative energy transfer process from Dy3+ to Sm3+ ions is predominated by quadrupole–quadrupole interaction. Graphical abstract Image Highlights • Dy3+ or/and Sm3+ doped phosphor powders are synthesized using a facile solid-state reaction. • The quenching concentration of single doped Dy3+ and Sm3+ in the LiLa(WO 4) 2 are determined to be 6% and 3%, respectively. • The warm white light is obtained in the co-doped phosphors LiLa(WO 4) 2: 0.06Dy3+, ySm3+. • The mechanism of energy transfer from Dy3+ to Sm3+ are discussed. [ABSTRACT FROM AUTHOR]

A series of Tm 3+ and Dy 3+ codoped BaWO 4 phosphors with tunable shapes were controllably synthesized by a facile solvothermal method. The effects of ratio of ethylene glycol (EG) and water on the morphologies of BaWO 4 structures are systematically studied. It was discovered that the reason for these morphological changes is based on the reaction speed of the kinetic control, which relates to the strong chelating abilities of ethylene glycol. And when the solvent is pure ethylene glycol, the peanut-like BaWO 4 :Dy 3+ has the strongest emission intensity. Moreover, the emission color of the phosphors varied from blue (0.232, 0.180) to white (0.268, 0.250) by controlling Dy 3+ ions content with a fixed Tm 3+ concentration. The energy transfer mechanism was investigated in detail. With increasing the doped concentration of Dy 3+ ions, the energy transfer efficiency of BaWO 4 :0.005Tm 3+ ,yDy 3+ increased gradually and reached as high as 63% when the Dy 3+ doped concentration is 0.03. The critical distance R C calculated by the spectral overlap method is about 19.93 Å, and it is in good agreement with that obtained using the concentration quenching method (19.70 Å), indicating that the electric dipole-dipole interaction is the main energy transfer mechanism for BaWO 4 :Tm 3+ ,Dy 3+ phosphors. [ABSTRACT FROM AUTHOR]

In the presence of polyethylene glycol (PEG), we first investigate a facile hydrothermal process to fabricate CdMoO 4 :Tb 3+ green phosphor. The morphology and size of the products can be controlled by simply tuning the PEG amounts and the reaction time. The XRD results show that the CdMoO 4 :Tb 3+ can be indexed to CdMoO 4 phase. FE-SEM results revealed that the pure CdMoO 4 was a sphere with a diameter of about 2.6 μm. The photoluminescence (PL) properties of CdMoO 4 :Tb 3+ phosphors indicated energy transfer from MoO 4 2 - groups to Tb 3+ . PL spectra indicated the phosphors emitted green light centered at 544 nm under ultraviolet excitation. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating about the properties of molybdate materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] OmimPF6 acts not only as a reactant but also as a morphology-directing agent was introduced to prepare uniform LuF3 nanocrystals. [•] Morphology and size-controlled synthesis of rare earth doped LuF3 for the first time, different shapes of the orthorhombic LuF3 nanocrystals were obtained in this research. [•] The effect of different sizes and morphologies on luminescence properties has also been discussed. [•] This study provides more alternatives of rare earth fluorides that exhibit strong characteristic emission, and further complements the exploration of Lu-based nanomaterials, which may have unique properties that the Y/Ln-based nanoparticles do not possess and may serve as versatile luminescent phosphors for further application. [ABSTRACT FROM AUTHOR]

A series of Dy3+ doped CaWO 4 phosphors was successfully synthesized via the facile high temperature solid state method. The phase purity and effect of different valence isomorphism on cell parameters were fully evaluated by XRD analysis. When divalent Ca2+ is replaced by trivalent Dy3+, the local electric field is distorted, which has an obvious influence on the lattice. The introduction of Li+ aggravates the degree of lattice distortion. The excitation spectra of CaWO 4 : Dy3+ and CaWO 4 : Dy3+, Li+ have the same shapes, but they are some different in intensity. The emission spectra show that the co-doping of Li+ can reduce the luminescence intensity at 575 nm, and many phosphors emit white light by adjusting the Dy3+ doping concentration. The density of states (DOS) and charge difference plots of phosphors were studied by first-principles calculation. The calculated results show that the band gap decrease gradually on doping. [Display omitted] • A series of Dy3+ doped CaWO 4 phosphors were prepared by facile solid state method. • The introduction of Li+ aggravates the degree of lattice distortion. • Many phosphors emit white light by adjusting the Dy3+ doping concentration. • The theoretical calculation study of CaWO 4 : Dy3+ phosphor was carried out. [ABSTRACT FROM AUTHOR]