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A Yb3+ free self-sensitized Er2WO6 phosphor has been synthesized via a solid-state reaction method. The phosphor material, Er2WO6, has a monoclinic crystal structure with space group P2/c (13). The deconvoluted high-resolution X-ray photoelectron spectra of all the core elements in the Er2WO6 phosphor material were explored. The highly resolved absorption peaks in the ultra-violet, visible and near-infra-red (NIR) regions of the diffuse reflectance spectrum were due to the Stark-splitting of the 4f energy levels of the Er3+ ions. Under 980 nm NIR laser excitation, the Er2WO6 phosphor showed an intense up-converted red emission at 677 nm due to the 4F9/2 → 4I15/2 transitions of the Er3+ ions. The cross-relaxation and resonance energy transfer process involved in the key intermediate 4F3/2 and 4F5/2 levels of the Er3+ and their role in generating red emissions were investigated. The laser pump power versus upconversion intensity plot showed a slope with an n value

This review provides a comprehensive discussion on the microwave-assisted synthesis of various materials for photoluminescence and photocatalytic applications. In the past decade, because of its ability to synthesize nanomaterials through faster, cleaner and more cost-effective routes compared to conventional heating, microwave techniques have gained significant importance for the synthesis of metal oxides, fluorides, sulphides, and quantum dots. Additionally, due to the uniqueness of its heating mechanism, the synthesis of materials in various nanostructured forms through microwave-assisted methods has been of great interest and is widely pursued. The materials thus synthesized have been applied as sensing elements in gas sensors, luminescent nanoprobes in bioimaging, materials in fuel cells and solar cells and as photocatalysts for water treatment and energy harvesting. This review describes and discusses their optical and photocatalytic performance in detail, emphasizing on the reaction parameters employed and the structural and morphological properties obtained.

Pr3+ doped BaMoO4 nano thin films have been deposited by pulsed laser deposition on a glass substrate using a Nd-YAG laser (λ = 266 nm). The thin phosphor films were deposited in an ultra-high vacuum at a substrate temperature of 400 °C at different oxygen partial pressures. The crystal structure, surface morphology, film thickness and composition were examined by X-ray diffraction patterns, scanning electron microscope and energy-dispersive X-ray spectroscopy, respectively. The binding energy of the core levels, chemical state, atomic fractions, depth profiling of the thin film were investigated by X-ray photo-electron spectroscopy. The photoluminescence excitation, emission spectra and energy transfer process involved in Pr3+ doped BaMoO4 thin films were analyzed. The color chromaticity co-ordinates, fluorescence decay time and the photometric properties of the as-deposited thin phosphor films were examined.

Self-assembled flowers of (Na0.5La0.5)MoO4:Eu3+ with many petals have been successfully synthesized by using the Ethylenediaminetetraacetic acid mediated hydrothermal route. X-ray diffraction patterns(XRD) indicated that (Na0.5La0.5)MoO4:Eu3+ crystallized into a scheelite tetragonal structure with the space group I41/a. A significant spectral blue shift was observed when the Eu3+ doping concentration increased from 2 mol% to 10 mol%. Upon 395 nm excitation, the flower-like (Na0.5La0.5)MoO4:Eu3+ structures showed a strong emission in the red region due to the characteristic 5D0 → 7F2 transition of Eu3+. The effect of doping content of Eu3+ (2, 4, 6, 8, 10 mol%) on the luminescence properties of (Na0.5La0.5)MoO4 have been reported. To check the color purity and emission quality of the phosphors, photometric parameters were investigated. The percentage of luminous efficiency of as-synthesized micro flowers was found to be 43%, which has the potential to be used in phosphor converted light emitting diodes (LED).

Eu3+ activated LiGd3(MoO4)5 phosphors were synthesized proficiently by simple sol gel method. Structural, morphological and luminescence characteristics of the phosphors were investigated in detail. The photo physical parameters and quantum efficiency values are studied by using Judd–Ofelt concepts. All the outcomes imply that LiGd3(MoO4)5:0.07Eu3+ phosphor may be a meritful candidate as red emitting component for white light emitting diodes applications.

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Octahedrally and tetrahedrally connected Mo-O complexes in two different crystal phases were comparatively investigated. The material Ba2YMoO6:Eu3+ exhibits the cubic perovskite structure for which the Mo-O groups are coordinated octahedrally, while BaY2(MoO4)4:Eu3+ has a monoclinic crystal phase for which the Mo-O complexes are connected tetrahedrally. The photoluminescence (PL) excitation spectra show that, the intensity, position and shape of the charge transfer (CT) transitions in the two different materials depended strongly on the surrounding environment. The PL emission properties of Ba2YMoO6:Eu3+ and BaY2(MoO4)4:Eu3+ phosphors as a function of various doping content of Eu3+ ions excited at different wavelengths were explored in detail. The critical concentration of Eu3+ and the critical distance between Eu3+ ions, as well as the concentration quenching effects were discussed. The absolute quantum yield for the monoclinic phase BaY2(MoO4)4:Eu3+ phosphor was about an order of magnitude higher than that of the cubic phase Ba2YMoO6:Eu3+ phosphor.

A series of Tm2−xWO6:xEr3+ (where x = 0.02–0.50 mol) phosphors were synthesized successfully by the solid-state reaction method. The powder X-ray diffraction patterns of the Tm2−xWO6:xEr3+ phosphors confirmed that the as-synthesized materials belonged to the monoclinic crystalline structure, which has a P2/c (13) space group. Due to a similar ionic size and valence state of the Er3+ ions, they can easily replace the Tm3+ in the Tm2WO6 crystal lattice. High-resolution X-ray photoelectron spectroscopy was used to explore the photoelectron binding energy and chemical state of all the elements. The XPS results confirmed that the W atom coordinated octahedrally to the oxygen atoms with its highest 6+ state in the Tm2WO6 material. The upconversion luminescence intensity at 657 nm [4F9/2→4I15/2 (Er3+)], when excited at 980 nm, was enhanced with higher magnitude when increasing the doping concentration from 0.02 mol to 0.20 mol of Er3+ ions. The dependence of the laser pump power with respect to the upconversion luminescence intensity depicts that the emission at 657 nm is due to a single-photon absorption process, and the possible reasons for the number of photons involved in the excitation of the emitting state, n ≤ 1 were discussed. The Commission Internationale del'Eclairage chromaticity coordinates and decay time measured for the Tm2WO6:Er3+ phosphors were investigated. Real-time latent-fingerprint detection using Tm2WO6:Er3+ upconversion phosphor without using Yb3+ ion showed an excellent marking agent for applications in forensic science and medical diagnostics.

Tetragonal phase CaGd2(MoO4)4:Eu3+ with ovoid like hierarchical structures were prepared via employing ethylene diamine tetra acetic acid (EDTA) using the hydrothermal route at 200 °C for 24 h. X-ray diffraction patterns and field emission scanning microscopy images were used to characterize the crystal structure, phase, morphology and size of the nano samples. X-ray photo electron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (Edax) confirmed the presence of elements in phosphor samples. The PL properties of the phosphors were studied thoroughly. The photophysical properties of the samples were examined by the Judd–Ofelt theory. The CIE coordinates of the prepared phosphor samples illustrate that red light emission can be realized from CaGd2(MoO4)4:Eu3+ phosphor and it coexists very close to NTSC standard values. All these results show that ovoid like CaGd2(MoO4)4:Eu3+ micro/nanophosphor is a promising material for display applications.

Highly crystalline RE2-xWO6:xLn3+ (RE, Ln = Er3+ and Tm3+, x = 0.02 to 0.50 mol.) phosphors were successfully synthesized by the solid-state reaction method. The cathodoluminescence (CL) properties of the RE2-xWO6:xLn3+ phosphors were studied in detail by changing the Ln3+ (Er, Tm) doping concentration, accelerating voltage and tuning the electron beam current. The CL spectra of the undoped Er2WO6 phosphor showed bright red emission due to the 4F9/2→4I15/2 (Er3+) transition, while Tm3+ doped Er2WO6 display the strong green emission due to 4S3/2→4I15/2 (Er3+) transitions. The Er3+ doped Tm2WO6 phosphor showed strong white light emission due to the combination of several bands in the CL spectra. The CL emission intensity of the phosphors linearly enhanced when the electron beam current was increased from 1.00 nA to 7.0 nA and no saturation emission was noted in this range. The Commission Internationale del’Eclairage chromaticity coordinates were measured for the RE2WO6:Ln3+ phosphors.

A simple and self-energetic mechano-chemical reaction has been used for the synthesis of crystalline La2(MoO4)3:Eu3+ nano-phosphors at low temperature. X-ray diffraction patterns indicated that La2(MoO4)3:Eu3+ crystallized into a scheelite tetragonal structure with the space group I41/a. Input accelerating voltage and beam current depended cathodoluminescence (CL) properties of La2(MoO4)3:Eu3+ phosphors have been investigated. Under e-beam irradiation, the La2(MoO4)3:Eu3+ phosphor exhibited intense red emission at 615 nm due to the electric dipole transitions of the Eu3+ ions. The concentration dependent doping effect of Eu3+ (0.01–0.20 mol.) on the CL properties of La2(MoO4)3:Eu3+ have been reported. The red phosphor La2(MoO4)3:Eu3+ material could be considered as a candidate for solid-state lighting applications.

The Sm3+- doped Ca0.5La(MoO4)2 were successfully synthesized by the solid state reaction method. Indexed powder X-Ray diffraction pattern suggests the scheelite tetragonal crystal structure. Surface Morphology of the sample shows polyhedral morphology and the average particle size estimated from SEM image is 5.5 µm. The energy dispersive X-ray analysis confirms the existence of Ca, La, Mo, O, and Sm elements. The room temperature photoluminescence (PL) emission spectra of Sm3+- doped Ca0.5La(MoO4)2 with various concentrations upon 404 nm excitation were recorded. The PL emission spectra show three intense emission peaks at 565, 600 and 647 nm were owing to the f–f electronic transitions of 4f electrons of Sm3+ attributed to the transitions 4G5/2→6H5/2, 4G5/2→6H7/2 and 4G5/2→6H9/2 respectively. Among them, bright orange-red visible emission is obtained due to 4G5/2→6H9/2 transition. The decay time and color chromaticity co-ordinates were estimated. From the obtained results, the prepared powder phosphor Ca0.5La(MoO4)2:Sm3+ stands as a suitable candidate for the display and solid state lighting applications.

Microstructures of Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr(3+) co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications.

Herein, we report on rare-earth (RE) activated Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, Dy, Yb/Er, Yb/Ho, and Yb/Tm) phosphors synthesized using a surfactant-mediated hydrothermal route. Timedependent experiments were performed, and the morphological evolution of the phosphors was studied. From prepared powder samples of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu and Yb/Er), nano-sized thin phosphor films were grown using pulsed laser deposition (PLD). The surface topography of the as-grown thin phosphor films was analyzed. The asprepared phosphors were characterized by structural and optical studies. The powder phosphor exhibited bi pyramid-like micro-architectures. Structural studies indicated that Ca0.5Y1-x(MoO4)2 possesses the scheelite tetragonal crystal structure. The down-conversion luminescence of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, and Dy) as powder phosphors and Eu3+ doped Ca0.5Y1-x(MoO4)2 thin phosphor film were studied. Upon irradiation with a 980 nm laser, the Ca0.5Y1-x(MoO4)2: xRE3+ (RE = Yb/Er, Yb/Ho, and Yb/Tm) powder phosphors and Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Yb/Er) thin phosphor film showed intense up-converted visible emissions in green, yellow, and blue regions. The fluorescence decay time and color co-ordinates were determined for all synthesized phosphors. From the obtained results, the prepared powder and thin film phosphors are suggested to be suitable candidates for display and electro-luminescence applications.

Comparative investigations of Eu3+ activated Ba(Y0.67Mo0.33)O3 and BaMoO4 red phosphors, that were successfully prepared by a high temperature solid-state reaction method, were done. The synthesized Ba(Y0.67Mo0.33)O3:Eu3+ phosphor materials possessed a cubic phase structure belonging to a Pm3m space group when the Mo6+ ions coordinated octahedrally. The phosphor BaMoO4:Eu3+ exhibited a scheelite tetragonal phase structure that categories under the space group I41/a when the Mo6+ ions coordinated tetrahedrally. The intense phonon absorption lines detected in the Fourier transform infrared spectra depicted that for the cubic phase the F2(ν4) vibrations were dominant and for the tetragonal phase the F2(ν3) vibrations were active. High resolution X-ray photoelectron spectroscopy analysis indicated that the Mo atoms were coordinated octahedrally with two different oxidation states in the cubic phase Ba(Y0.67Mo0.33)O3 lattice and tetrahedrally with the highest oxidation state in the BaMoO4:Eu3+ lattice. The photoluminescence (PL) excitation spectrum confirmed that the position of the charge transfer band and intraconfigurational f-f transitions of Eu3+ strongly depended on the coordination of Mo6+ ions in the octahedral and/or tetrahedral symmetry. The PL emission spectra for the Eu3+ activated phosphors showed intense red emission with a high asymmetry ratio when the phosphors were excited with blue light. The critical concentration of Eu3+ as dopants in Ba(Y0.67Mo0.33)O3 and BaMoO4 was found to be 0.06 mol and later concentration quenching effect occurred in the solid-solutions. The decay profiles for the major 5D0→7F2 transition of the Eu3+ ion doped phosphors were measured. The Judd–Ofelt theory has been used to investigate the photophysical properties and quantum efficiencies of the prepared phosphors. Further, to elucidate the purity and quality of the red light emitted color, the photometric properties such as correlated color temperature, color rendering index, chromaticity coordinates and luminous efficacy of optical radiation were calculated and compared for the two different solid solutions.

A series of Eu3+ activated BaY2(MoO4)4 reddish-orange emitting phosphors was successfully synthesized by changing the doping concentrations of Eu3+ ions using a solid-state reaction route. All the reflections obtained in the powder X-ray diffraction analysis signposted that the as-prepared phosphors belonged to the monoclinic phase with the C2/c space group. Narrow scan X-ray photoelectron spectroscopy analysis suggested that the molybdenum ions were connected tetrahedrally to oxygen with its maximum 6+ valance state and yttrium atoms with 3+ state in the BaY2(MoO4)4:Eu3+ material. The influence of doping concentration of Eu3+ ions on the cathodoluminescence (CL) properties of BaY2(MoO4)4 was explored with respect to various accelerating voltages and filament currents. The penetration depth of the electrons into the phosphors has been estimated as a function of accelerating voltage. The phosphor showed no saturation current or saturation voltage in the ranges that were explored. The CL spectra revealed that reddish-orange emission was witnessed when the phosphor material was stimulated under e− beam excitation due to the 5D0→7F2 transition of the Eu3+ ions. The as-prepared phosphor material exhibited intense and strong CL emission lines with better International Commission on Illumination (CIE) chromaticity coordinates and higher colour purity and can be considered to be utilize in field emission display device applications.

In this article, we have investigated the down-conversion luminescence properties of Ca0.5La(MoO4)2 doped with trivalent Pr3+ (substitute for La3+ site) and codoped with Mn2+ (substitute for Ca2+ site). The powder X-ray diffraction patterns confirm that the single crystalline phosphor powders belong to the scheelite-type tetragonal crystal structure. The photoluminescence (PL) excitation spectra of Ca0.5La(MoO4)2:Pr3+ exhibits a charge transfer band centered at 276 nm along with three intense sharp absorption bands identified at 449, 475, and 488 nm which are attributed to the f–f electronic transitions of 3H 4 (1) → 3P2, 3H 4 (1) → 3P1, 3H 4 (1) → 3P0 of Pr3+, respectively. Upon optical excitation, the depopulation of excited 3P0 level into the 3F2 lower levels of Pr3+ is governed by radiative transfer of energy, as a result, high intense red emission peak was observed at 647 nm. The change in PL emission intensity as a function of Pr3+ concentrations, Mn2+ concentrations, and different excitation wavelengths have been investigated in detail. Further, the codoping of alkali metal chlorides MCl (M = Na, K, Li) into the Ca0.5La(MoO4)2:Pr3+ phosphor greatly improves the luminescence intensity of the transition 3P0 → 3F2 which can be explained by charge compensation effect. To ensure the colour richness and quality of its emission, the photometric parameters were estimated using spectral energy distribution functions of Ca0.5La(MoO4)2:Pr3+. The luminous efficacy of radiation for NaCl codoped Ca0.5La(MoO4)2:Pr3+ phosphor was estimated to be 154 lm/W and the percentage of luminous efficiency is 23 %.

Ca0.5La(MoO4)2:Ln3+ phosphors, where Ln = 4, 8, 12, 16, and 20 mol% of Eu, Tb, or Dy, were successfully synthesized by a conventional solid-state reaction method at 900 °C for 3 h. The Ca0.5La(MoO4)2:Ln3+ phosphors exhibit a scheelite tetragonal crystal structure belonging to the I41/a space group. The strong absorption bands seen in Fourier transform infrared (FTIR) spectra confirm that F2(ν3) modes of vibration are IR active. The photoluminescence(PL) spectra reveal that, under optical excitation, the as-synthesized phosphors show high intensity narrow emission bands in the red (615 nm), and green (545 nm), and yellow (570 nm) regions for samples doped with Eu3+, Tb3+, and Dy3+ ions, respectively. The critical concentrations of Eu3+, Tb3+, and Dy3+ as dopants in Ca0.5La(MoO4)2 were found to be 16, 12 and 12 mol%, respectively. Thereafter, concentration quenching effect occurred in the solid solutions. The fluorescence decay times for the major transitions of 5D0 → 7F2, 5D4 → 7F5, and 4F9/2 → 6H13/2 were estimated for different doping concentrations of Eu3+, Tb3+, and Dy3+ in Ca0.5La(MoO4)2, respectively. To determine the color purity and emission quality of the phosphor, photometric parameters such as color chromaticity coordinates, color correlated temperature (CCT), color rendering index (CRI), and luminous efficacy of radiation (LER) were estimated using the spectral energy distribution functions of the Ca0.5La(MoO4)2:Ln3+ phosphors.

For the first time, we report the successful synthesis of novel nanoparticle-sheathed bipyramid-like and almond-like Fe0.5R0.5(MoO4)1.5:Ln3+ (R = Gd3+, La3+), (Ln = Eu, Tb, Dy) 3D hierarchical microstructures through a simple disodium ethylenediaminetetraacetic acid (Na2EDTA) facilitated hydrothermal method. Interestingly, time-dependent experiments confirm that the assembly-disassembly process is responsible for the formation of self-aggregated 3D architectures via Ostwald ripening phenomena. The resultant products are characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and magnetic measurements. The growth and formation mechanisms of the self-assembled 3D micro structures are discussed in detail. To confirm the presence of all the elements in the microstructure, the energy loss induced by the K, L shell electron ionization is observed in order to map the Fe, Gd, Mo, O, and Eu components. The photo luminescence properties of Fe0.5R0.5(MoO4)1.5 doped with Eu3+, Tb3+, Dy3+ are investigated. The room temperature and low temperature magnetic properties suggest that the interaction between the local-fields introduced by the magnetic Fe3+ ions and the R3+ (La, Gd) ions in the dodecahedral sites determine the magnetism in Fe0.5R0.5(MoO4)1.5:Eu3+. This work provides a new approach to synthesizing the novel Fe0.5R0.5(MoO4)1.5:Ln3+ for bi-functional magnetic and luminescence applications.

Scheelite type Ca0.5Y(1−x)(MoO4)2:xRE3+ (RE = Pr, Sm, Eu, Tb, Dy) phosphors were successfully synthesized by the conventional solid-state reaction method. The as prepared phosphors were characterized by means of X-ray diffraction, scanning electron microscopy and photoluminescence. The results reveal that the obtained powder phosphors possess scheelite structure with tetragonal symmetry with a space group of I41/a. The photoluminescence excitation and emission spectra of Ca0.5Y(1−x)(MoO4)2:xRE3+ (RE = Pr, Sm, Eu, Tb, Dy) microstructures were investigated in detail. Upon UV or blue excitation, Ca0.5Y(1−x)(MoO4)2:xRE3+ (RE = Pr, Sm, Eu, Tb, Dy) show bright red, orange, red, green and yellow emissions respectively. To confirm the color richness, color chromaticity coordinates of RE3+ doped Ca0.5Y(1−x)(MoO4)2 microstructures were estimated. In addition to that, it is observed that there is an enhanced luminescence red emission is achieved by means of adding the alkali chloride to the Ca0.5Y(1−x)(MoO4)2:Pr3+ phosphor. The results suggest that the obtained powder phosphors are promising phosphor candidates for solid state lighting applications.

Tetragonal phase (Na 0.5 La 0.5 )MoO 4 :RE 3+ (RE = Eu, Tb, Dy) with almond like hierarchical structures assembled from nanosheets building blocks were successfully synthesized by employing disodium ethylenediaminetetraacetic acid (Na 2 EDTA) using hydrothermal route at 200 °C for 24 h. Field emission scanning electron microscope, transmission electron microscope, and X-ray diffraction patterns were used to characterize the morphology, size, and crystal structure with good resolution. The sequestering agent EDTA acts as quadridentate ligand coordinated with metal ions [Na + , La 3+ /RE 3+ ] facilitating the formation of self-organized 3D networks. The growth mechanism for the formation of almond like nanostructures is explicated in four paths: dissolution, adsorption, in situ transformation in acidic and basic media and the effective collision. Photoluminescence excitation and emission spectra reveals a spectral blue shift which was observed in the nanosamples towards shorter wavelengths compared with the bulk sample. Upon UV irradiation, both bulk and nanostructure show strong luminescence in the red region due to the 5 D 0 → 7 F 2 transition in Eu 3+ . Also, Tb 3+ and Dy 3+ doped (Na 0.5 La 0.5 )MoO 4 phosphor exhibit green and yellow luminescence due to the transitions 5 D 4 → 7 F 5 and 4 F 9/2 → 6 H 13/2 , respectively. Color richness and fluorescence decay times for major emission lines in Eu 3+ , Tb 3+ , and Dy 3+ , that were determined to be x = 0.593, y = 0.326, τ = 0.417 ms; x = 0.228, y = 0.619, τ = 0.411 ms; x = 0.3851, y = 0.4334, τ = 0.403 ms, respectively. The as-synthesized nanophosphor exhibits weak ferromagnetic hysteresis with significant remnant magnetization (1.84E −4 emu/gm) at room temperature in comparison with bulk sample. The above results suggesting these materials can serve as excellent luminescence markers which being controlled by external magnetic field.

Highly uniform and self-assembled spheroid-like microstructures of Na0.5La0.5MoO4:Eu3+ were successfully synthesized by hexamine assisted hydrothermal route at 180 °C for 24 hours with neutral pH (7~8). Scanning electron microscope, X-ray diffraction pattern and energy dispersive X-ray analysis were used to characterize the morphology, crystal structure, size, and elements of the particles. It is found that, the particle size was well-controlled by increasing the molar concentration of the chelating agent hexamine. While, irradiating at 395 nm UV light, the emission spectra of micro-spheres shows remarkable characteristic dominance of red emission which is attributed to the transition 5D07F2. Furthermore, the synthesized homogeneous and well-crystallized Na0.5La0.5MoO4:Eu3+ microstructures will serve as an excellent phosphor candidate to produce high-quality luminescence for display devices in future.Keywords: Hydrothermal route, hexamine, self-assembly, photoluminescence

Correction for ‘Synthesis and up/down conversion luminescence properties of Na0.5R0.5MoO4:Ln3+ (R3+ = La, Gd), (Ln3+ = Eu, Tb, Dy, Yb/Er) thin phosphor films grown by pulsed laser deposition technique’ by Rajagopalan Krishnan et al., RSC Adv., 2014, 4, 64258–64266.

Novel bi-pyramid-like (Na0.5Gd0.5)MoO4:Ln3+ (Ln = Eu, Tb, Dy, Yb/Er, Yb/Ho, and Yb/Tm) hierarchical microstructures are synthesized via the EDTA-aided hydrothermal route. Time-dependent experiments were carried out and the morphological evolution was discussed, which signposted that the present method corresponded to a typical Ostwald ripening process for the formation of bi-pyramid-like structures. Elemental mapping analysis confirms the incorporation and uniform distribution of all the elements. Phase purity and crystal structure of the as-synthesized phosphor were analyzed by the X-ray diffraction (XRD) technique. Fourier transform infrared spectroscopy (FTIR) results confirm that for scheelite tetragonal symmetry, F2 (ν3) modes of vibrations are IR active. (Na0.5Gd0.5)MoO4 was demonstrated to be a good host material for down- and up-conversion luminescence, which were strongly dependent on the hydrothermal reaction time interval. The down-conversion luminescence properties of (Na0.5Gd0.5)MoO4 doped with Eu3+, Tb3+, Dy3+ were studied. Under 980 nm NIR excitation intense up-converted visible emissions were observed in (Na0.5Gd0.5)MoO4:Yb3+/Ln3+ (Ln = Er, Tm, and Ho), which shows green (2H11/2 → 4I15/2 of Er3+ at 525 nm), blue (1G4 → 3H6 of Tm3+ at 474 nm), and yellow (5S2 → 5I8 and 5F5 → 5I8 of Ho3+ at 541 nm and 660 nm, respectively) luminescence. Also, Yb3+/Er3+-doped samples exhibit luminescence in the near infrared (combination of Er3+/Yb3+ at 977 nm, Er3+ at 1530 nm) region. The energy transfer process, fluorescence decay time, and colour coordinates were analyzed for both down- and up-conversion luminescence. Further, the magnetic properties of (Na0.5Gd0.5)MoO4:Ln3+ (Ln = Eu and Yb/Er) as-prepared bi-pyramid-like structure exhibit typical paramagnetic behavior.

Intense red-emitting phosphor Na0.5La0.5−xMoO4:xEu3+ (x = 0.02, 0.04, 0.06, 0.08, 0.10 mol of Eu3+) was prepared at 900 °C for 3 h using conventional solid-state reaction method. Crystal structure and phase purity of the phosphor were identified using X-ray diffraction analysis. The morphology and composition of the materials were examined by scanning electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy, respectively. The diffuse reflectance spectra of Na0.5La0.5−xMoO4:xEu3+ showing a significant shift in the band gap (0.14 eV) was observed due to increase in doping concentration of Eu3+. Photoluminescence and decay time (τ) study on Na0.5La0.5−xMoO4:xEu3+ showed strong red emission upon UV illumination, and this implied potential application in the field of luminescent displays.

Orthorhombic Gd2(MoO4)3:Eu3+ nanosized particles with complex 3D self-assembled superstructures (dumbbell) were successfully synthesized by a hydrothermal method in ethyleneiamine tetra-acetic acid (EDTA) mediated processes. The pH value, reaction time, temperature, ando molybdenum source have crucial influence on the growth mechanism, shape evolution, and nanostructures. In the hydrothermal process, EDTA not only acts as a chelating reagent to facilitate the formation of Gd2(MoO4)3:Eu3+, but also acts as a surface capping agent to adhere to the newly created surface and to promote the crystal splitting. Comprehensive structural, morphological studies like X-ray diffraction, scanning and transmission electron microscopy were employed to characterize the as synthesized nanostructures. Photoluminescence studies on Gd2(MoO4)3:Eu3+ showed strong red emission upon UV illumination, and this implied potential application in the field of luminescent nano ceramics.

The nanostructured NaGd(MoO4)2:Pr3+ phosphor was rapidly synthesized at room temperature by mechanochemically assisted solid state meta-thesis reaction method. The as-synthesized nanophosphor possess scheelite tetragonal crystal structure with space group I41/a. Photoluminescent studies revealed that under the excitation of blue light (448 nm), a strong emission in the red region was observed at 647 nm due to the transition from populated 3P0 level to the 3F3 lower level of Pr3+ ions. The nanostructured NaGd(MoO4)2:Pr3+ material could serve as excellent red phosphor candidate for solid state lighting applications.

Red-emitting Eu3+-doped indium gallium zinc oxide (IGZO) transparent thin films were fabricated using sol–gel method under UV (254-nm irradiation) in nitrogen atmosphere (inside the glove box) and thermally annealed at 500°C for 1 h. Structure, morphology, composition, and optical properties of the materials were examined using X-ray diffraction analysis, scanning electron microscope, X-ray photoelectron spectroscopy, and photoluminescence, respectively.

Correction for ‘Up/down conversion luminescence properties of (Na0.5Gd0.5)MoO4:Ln3+ (Ln = Eu, Tb, Dy, Yb/Er, Yb/Tm, and Yb/Ho) microstructures: synthesis, morphology, structural and magnetic investigation’ by Rajagopalan Krishnan et al., New J. Chem., 2014, 38, 3480–3491.

Correction for ‘Synthesis and up/down conversion luminescence properties of Na0.5R0.5MoO4:Ln3+ (R3+ = La, Gd), (Ln3+ = Eu, Tb, Dy, Yb/Er) thin phosphor films grown by pulsed laser deposition technique’ by Rajagopalan Krishnan et al., RSC Adv., 2014, 4, 64258–64266.