Novel Eu3+-Doped Glasses in the MoO3-WO3-La2O3-B2O3 System: Preparation, Structure and Photoluminescent Properties

Novel multicomponent glasses with nominal compositions of (50-x)MoO3:xWO3:25La2O3:25B2O3, x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu2O3 were prepared using a conventional melt-quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. The optical properties of the glasses were investigated by UV-vis absorption spectroscopy and a determination of the refractive index. Physical parameters such as density, molar volume, oxygen molar volume and oxygen packing density were determined. The glasses are characterized by a high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO4)2- and (WO4)2- units providing Raman bands of around 317 cm-1, 341-352 cm-1, 832-820 cm-1 and 928-935 cm-1. At the same time, with the replacement of MoO3 with WO3 some fraction of WO6 octahedra are produced, the number of which increases with the increasing WO3 content. A strong red emission from the 5D0 level of Eu3+ ions was registered under near-UV (397 nm) excitation using the 7F0 → 5L6 transition of Eu3+. Photoluminescence (PL) emission gradually increases with increasing WO3 content, evidencing that WO3 is a more appropriate component than MoO3. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. All findings suggest that the investigated glasses are potential candidates for red light-emitting phosphors.

Structural, photoluminescence and energy transfer investigations of novel Dy3+ → Sm3+ co-doped NaCaPO4 phosphors for white-light-emitting diode applications

In this study, Dy3+-doped and Dy3+/Sm3+ co-doped NaCaPO4 white-emitting polycrystalline phosphor samples were synthesized using a solid-state reaction method. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL) analysis. The phase purity characterization and crystal structural analysis were done using the Rietveld refinement-based FullProf Suite software. The Rietveld refinement result confirms single-phase formation for both Sm3+ and Dy3+/Sm3+ co-doped NaCaPO4 samples with an orthorhombic structure and with a monotonic change in lattice parameters with doping. The PL studies of the Dy3+-doped samples revealed two emission bands. However, at 352 nm, the Dy3+/Sm3+-co-doped samples revealed distinctive emission bands for both ions. The emission peaks at 480 nm (blue) and 573 nm (yellow) are related to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions; however, the emission peaks at 600 nm and 647 nm are attributed to the 4G5/2 → 6H7/2 and 4G5/2 → 6H7/2 transitions of Sm3+ ions. The intensity of the Dy3+ emissions decreased as the Sm3+ levels increased but the emission intensity of the Sm3+ ions increased. The co-doping of Sm3+ ions in Dy3+-doped phosphors results in unique characteristics due to the energy transfer (ET) from Dy3+ → Sm3+ ions. The effectiveness of this ET from Dy3+ → Sm3+ ions is positively correlated with the dopant amounts of the Sm3+ ions. The interaction mechanisms have been identified as dipole-dipole based on Dexter's energy transfer and Readfield's approaches. All decay curves can be adequately fitted via bi-exponential functions, suggesting the movement of energy between Dy3+ → Sm3+ ions. Temperature-dependent PL measurements and CIE color coordinate analysis reveal excellent luminescent properties, making these Dy3+/Sm3+ co-doped phosphors advantageous for white light-emitting diode (WLED) technologies.

Impact of Structural Changes on Energy Transfer in the Anion-Engineered Re3+:Y2O3 Through Low-Temperature Synthesis Approach

Anion engineering has proven to be an effective strategy to tailor the physical and chemical properties of metal oxides by modifying their existing crystal structures. In this work, a low-temperature synthesis for rare earth (RE)-doped Y2O2SO4 and Y2O2S was developed via annealing of Y(OH)3 intermediates in the presence of elemental sulfur in a sealed tube, followed by a controlled reduction step. The crystal structure patterns (X-ray diffraction) and optical spectra (UV-IR) of Y2O2SO4, Y2O2S, and crystalline Y2O3 were collected throughout the treatment steps to correlate the structural transformations (via thermogravimetric analysis) with the optical properties. Local and long-range crystallinities were characterized by using X-ray and optical spectroscopy approaches. Systematic shifts in the Eu3+ excitation and emission peaks were observed as a function of SO42- and S2- concentrations resulting from a crystal evolution from cubic (Y2O3) to trigonal (Y2O2S) and monoclinic (Y2O2SO4), which can modify the local hybridization of sensitizer dopants (i.e., Ce3+). Ultimately, Tb3+ and Tb3+/Ce3+ doping was employed in these hosts (Y2O2SO4, Y2O2S, and Y2O3) to understand energy transfer between sensitizer and activator ions, which showed significant enhancement for the monoclinic sulfate structure.

A novel optical temperature sensor and energy transfer properties based on Tb3+/Sm3+ codoped SrY2(MoO4)4 phosphors

A series of SrY2(MoO4)4 phosphors doped and co-doped with Tb3+/Sm3+ ions was synthesized to develop new optical temperature sensor materials. The structures, morphologies, and luminescent characteristics of these phosphors were thoroughly investigated. Luminescence spectra of mono-doped SrY2(MoO4)4 phosphors were measured under the excitation at 375 and 403 nm corresponding to direct excitation of Tb3+ and Sm3+, respectively. The characteristic luminescence bands corresponding to electronic transitions of terbium and samarium ions were detected and investigated for different dopant concentrations. The emission spectrum of the Tb3+/Sm3+ co-doped sample exhibited a total of five distinct emission peaks, indicating an energy transfer from Tb3+ to Sm3+ ions. The energy transfer efficiency from Tb3+ ions to Sm3+ ions was investigated in detail. At elevated temperatures, Tb3+ and Sm3+ exhibited distinct thermal sensitivities in their emission and excitation spectra, leading to evident thermochromic behavior. The fluorescence intensity ratio (FIR) was utilized with dual center to evaluate the temperature sensitivity of SrY2(MoO4)4:Tb3+/Sm3+ phosphors. The temperature sensing mechanism relied on the emission band intensity ratios of the 4G5/2 → 6H5/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H7/2 transitions of Sm3+ in conjunction with the 5D5/2 → 7F5/2 transitions of Tb3+. This approach demonstrated high thermal sensitivity values, reaching up to 0.9% K-1. The studied nanoparticles exhibited sub-degree thermal resolution, making them suitable candidates for precise temperature-sensing applications.

Network Structure and Luminescent Properties of ZnO-B2O3-Bi2O3-WO3:Eu3+ Glasses

In this study, we investigated the influence of Bi2O3 and WO3 on both structure and optical properties of 50ZnO:(49 - x)B2O3:1Bi2O3:xWO3; x = 1, 5, 10 glasses doped with 0.5 mol% Eu2O3. IR spectroscopy revealed the presence of trigonal BØ3 units connecting superstructural groups, [BØ2O]- metaborate groups, tetrahedral BØ4- units in superstructural groupings (Ø = bridging oxygen atom), borate triangles with nonbridging oxygen atoms, [WO4]2- tetrahedral, and octahedral WO6 species. Neutron diffraction experimental data were simulated by reverse Monte Carlo modeling. The atomic distances and coordination numbers were established, confirming the short-range order found by IR spectra. The synthesized glasses were characterized by red emission at 612 nm. All findings suggest that Eu3+ doped zinc borate glasses containing both WO3 and Bi2O3 have the potential to serve as a substitute for red phosphor with high color purity.

Low-temperature in situ preparation of Eu3+/Tb3+-doped CaMoO4/SrMoO4 nanoparticle thin films and their application in anti-counterfeiting

Rare earth-doped metal oxide thin films exhibit remarkable potential for application in anti-counterfeiting, owing to their exceptional fluorescent properties. However, the existing fabrication techniques for these rare earth-doped luminescent thin films are predominantly complex and necessitate high-temperature conditions. In light of this issue, we present a low-temperature method for in situ fabrication of luminescent Ca1-xMoO4:Eux3+ and Sr1-xMoO4:Tbx3+ nanocrystal thin films by a solution deposition process. The developed method has the advantages of simple operation, rapid and low-temperature synthesis. The optimal chemical compositions of molybdate-based luminescent films are Ca0.90MoO4:Eu0.103+ and Sr0.90MoO4:Tb0.103+. Moreover, we evaluate the practical feasibility of luminescent nanoparticle films in the field of anti-counterfeiting by combining the unique fluorescent properties of rare earth ions and designing customized fluorescent patterns.

Thermally stable and color-tunable bi-activated (Dy3+/Eu3+) alkaline earth metasilicate phosphor for luminescent devices

A solid-state reaction methodology has been adopted to synthesize Dy³⁺ (dysprosium)/Eu³⁺ (europium) co-activated Na₄Ca₄Si₆O₁₈ (NCMS) phosphors. The structural, morphological, and luminescence characteristics of the prepared materials have been investigated. The phase purity of the material was confirmed by X-ray diffraction (XRD) by comparing the diffraction peaks with the JCPDS standard pattern (JCPDS card no. 75-1687). The photoluminescence (PL) spectra of NCMS phosphors activated with Dy³⁺ and co-activated with Dy³⁺ (sensitizer)/Eu³⁺ (activator) ions were investigated. The as-prepared NCMS phosphors co-activated with Dy³⁺/Eu³⁺ ions were excited with near-ultraviolet light (λ_ex = 348 nm) and showed the utmost energy transfer of up to 97.80% from sensitizer to activator. Dexter and Reisfeld's approximation specifically confirms that the energy transfer from sensitizer to activator was through electric dipole-dipole interactions. The Dy³⁺-activated NCMS phosphor showed an illumination shift from yellow to red by varying the Eu³⁺ ion concentration and colour tunability is also observed by altering the excitation energy. The emission intensity was sustained up to 92.21% at 423 K (∼150 °C), indicating an excellent thermal stability of the bi-activated NCMS phosphor. The Dy³⁺/Eu³⁺ co-doped NCMS phosphors display excellent thermal stability with flexible color tunability to emerge as promising contenders in the field of lighting and display technologies.

Low temperature-synthesized MgAl2 O4 :Eu3+ nanophosphors and their structural validations using density functional theory: photoluminescence, photocatalytic, and electrochemical properties for multifunctional applications

A low temperature-assisted and oxalyl dihydrazide fuel-induced combustion synthesized series of uncalcined MgAl2 O4 :Eu3+ nanophosphors showed an average crystallite size of ~20 nm, and bandgap energy (Eg ) of 4.50-5.15 eV, and were validated using density functional theory and found to match closely with the experimental values. The photoluminescence characteristic emission peaks of Eu3+ ions were recorded between 480 and 680 nm. The nanophosphors excited at 392 nm showed f-f transitions assigned as 5 D0 →7 FJ (J = 0, 1, 2, and 3). The optimized MgAl2 O4 phosphors had Commission Internationale de l'Eclairage coordinates in the red region, a correlated colour temperature of 2060 K, and a colour purity of 98.83%. The estimated luminescence quantum efficiency ( η ) was observed to be ~63% using Judd-Ofelt analysis. Electrochemical and photocatalytic performance were explored and indicated its multifunctional applications. Therefore, MgAl2 O4 :Eu3+ nanophosphors could be used for the fabrication of light-emitting diodes, industrial dye degradation, and as electrodes for supercapacitor applications.

Synthesis, photoluminescence, Judd-Ofelt analysis, and thermal stability studies of Dy3+-doped BaLa2ZnO5 phosphors for solid-state lighting applications

Here, we report a series of white-emitting Ba(La_2-x Dy _x )ZnO₅ (x = 0-7 mol%) phosphors synthesized via a high-temperature solid-state reaction. The synthesized phosphor's phase purity and tetragonal crystal structure were confirmed by an X-ray powder diffraction (XRPD) pattern. The wide bandgap characteristic feature was assessed through reflectance spectra, and the estimated bandgap was found to be 4.70 eV. Besides analyzing the effect of doping on the surface morphology, the distribution of ions on the surface was observed through the secondary ion mass spectroscopy technique. The synthesized phosphor was found to display bluish (486 nm) and yellowish (576 nm) bands in the emission spectra under the excitation of 325 nm and 352 nm, which together are responsible for producing the white luminescence. The analysis of Judd-Ofelt parameters indicates the symmetric nature of Dy³⁺ substitution in the present host. The thermal stability of the phosphor was assessed by varying the temperature up to 403 K, and it was found that the synthesized phosphor possesses improved thermal stability with an activation energy of 0.29 eV. The photometric evaluations of the present phosphor revealed the CIE coordinates around the near-white regime (0.3448, 0.3836), along with the color-correlated temperature value of 5102 K. All research on this luminescent material's unique features points to the possibility of using it to fabricate white-light-emitting devices for solid-state lighting applications.

Broadband UV-Excitation and Red/Far-Red Emission Materials for Plant Growth: Tunable Spectrum Conversion in Eu3+,Mn4+ Co-doped LaAl0.7Ga0.3O3 Phosphors

Broadband ultraviolet (UV) excitation and red/far-red emission phosphors can effectively convert solar spectrum to enhance photosynthesis and promote morphogenesis in plants. Based on the above application requirements, Eu³⁺ single-doped LaAl_1-yGa_yO₃ solid solutions and Eu³⁺,Mn⁴⁺ codoped LaAl_0.7Ga_0.3O₃ phosphors were designed and synthesized in this work. The LaAl_0.7Ga_0.3O₃:0.05Eu³⁺ (LAG:Eu³⁺) phosphor exhibits a strong charge transfer band (CTB) excitation and characteristic ⁵D₀ → ⁷F₂ transition red emission (619 nm), which is very similar to the luminescence properties of Eu³⁺-organic ligand compound (EuL₃). Rietveld refinement studies further revealed that the cation substitution disturbs the site symmetry. The optimal Eu³⁺, Mn⁴⁺ co-doped LaAl_0.7Ga_0.3O₃ (LAG:Eu,Mn) phosphor possesses a dual-band excitation spectrum in broadband ultraviolet (UVA, UVB) area and a dual-band emission spectrum within red/far-red area. Under the sunlight radiation, the real-time spectrum of luminous laminated glasses fabricated by coating the LAG:Eu,Mn phosphor shows the percentage of radiant intensity in the red/far-red region significantly increases, suggesting that the phosphor can be a promising candidate for solar spectral conversion in plant cultivation. We believe this work provides a new idea for developing novel broadband ultraviolet excitation and red/far-red emission phosphors.

Enhanced emission intensity in (Li+/Ca2+/Bi3+) ions co-doped NaLa(MoO4)2: Dy3+phosphors and their Judd-Ofelt analysis for WLEDs applications

In the present study, we have synthesized a series of Dy3+ ion doped NaLa(MoO4)2phosphors by the conventional solid-state method at 750 °C for 4h. All the compounds were crystallized in the tetragonal scheelite type structure with space group (I41/a, No.88). The morphology and functional group were confirmed by the field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared(FTIR)spectroscopy. Upon near-Ultraviolet (n-UV) excitation, the PL spectra exhibit the two characteristic emissions of Dy3+ ions, blue (4F9/2→6H15/2) at 487 nm and yellow (4F9/2→6H13/2) at 574nm respectively. The optimum concentration of Dy3+ionis 3 mol% and then quenching occurred due to multipolar interaction. Further, enhanced the emission intensity by co-doping with monovalent (Li+), divalent (Ca2+) and trivalent (Bi3+) ions. Among them, Li+ ion co-doped samples are shown maximum intensity (50 times) more than Dy3+ doped phosphors as relaxation of parity restriction of electric dipole transition because of local distortion of crystal field around the Dy3+ ions. In addition, by incorporation of Eu3+ ions into NaLa(MoO4)2:Dy3+system, tuned the emission color from white to red, owing to energy transfer from Dy3+ to Eu3+ ions. The intensity parameters (Ω2, Ω4) and radiative properties such as transition probabilities (AT), radiative lifetime (rad), and branching ratio were calculated using the Judd-Ofelt theory. CIE color coordinates, CCT values indicates that these phosphors exhibit an excellent white emission. The determined radiative properties, CIE and CCT results revealed that the Dy3+-activated NaLa(MoO4)2phosphors are potential materials for developing white LEDs, and optoelectronic device fabrications.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications

The article reports the successful fabrication of Eu³⁺-doped WO₃ thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO₃:Eu³⁺ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu³⁺ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO₃, but for all the films', micro-Raman spectra detected bands related to WO₃ monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu³⁺-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu³⁺-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu³⁺ ions, besides the band edge emission of WO₃. With an enhancement of the Eu³⁺ content, the concentration quenching process of the Eu³⁺ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu³⁺ ion concentration.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

The high thermal stability of white emitting phosphor Mg2 Y2 Al2 Si2 O12 :Dy3+ , Eu3+ , La3+ /Lu3+ for white LEDs

A series of Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ , Eu³⁺ were prepared by the solid-state method, and the phosphor can emit white light by tuning the ratio of Dy³⁺ /Eu³⁺ . The effects of La³⁺ /Lu³⁺ on the structure and luminescent properties of Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ , Eu³⁺ were explored. Under the influence of bond length and twist, the luminescent intensity of the materials increased first and then decreased under the excitation of ultraviolet light. The lattice distortion of the trivalent cation La³⁺ substituted Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ and Eu³⁺ phosphors are reduced, the symmetry of polyhedron occupied by the luminescent center is improved, and the thermal stability of the luminescent center is improved to a certain extent. The white light emitting diodes (LEDs) were fabricated by combining the 370 nm LED chip and Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ , Eu³⁺ , La³⁺ (Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ , Eu³⁺ , Lu³⁺ ) phosphor. The results show that Mg₂ Y₂ Al₂ Si₂ O₁₂ :Dy³⁺ , Eu³⁺ , La³⁺ /Lu³⁺ may be potential application in the region of white light emitting diodes.

Luminescence and energy transfer of warm white-emitting phosphor Mg2Y2Al2Si2O12:Dy3+,Eu3+ for white LEDs

A series of Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors were synthesized by the solid-state method. The luminescent properties and crystal structures of the Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors were analyzed. The XRD results show that the synthesized Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors are of pure phase. Mg2Y2Al2Si2O12:Dy3+ can emit blue and yellow light under 367 nm light excitation; when doped with Eu3+, there is an obvious energy transfer from Dy3+ to Eu3+, and warm white light can be realized by adjusting the concentrations of Dy3+ and Eu3+ in Mg2Y2Al2Si2O12. A warm white LED device was fabricated by combining Mg2Y1.88Al2Si2O12:0.05Dy3+,0.07Eu3+ and a UV LED chip (370 nm) under a voltage of 3.2 V and current of 5 mA, the characteristics of the white LED being CIE = (0.4071, 0.3944), CCT = 3500 K and CRI = 91.3.

Asparagine modified downconversion NaGdF4:Dy3+/Tb3+ nanophosphor for selective and sensitive detection of Cu(ii) ion

Pure NaGdF4, NaGdF4:Dy3+, and Dy3+/Tb3+ co-doped NaGdF4 nanoparticles with different concentrations of Tb3+ (ranging from 3 to 20 mol%) were prepared via hydrothermal method.

A novel green emitting NaGdF4:Dy3+,Ho3+ phosphor with tunable photoluminescence

Dy³⁺,Ho³⁺ co-doped β-NaGdF₄ nanomaterials emitted different shades of green light, which varies from the light blue area towards the blue-green area and ultimately to the green area with the increase of Ho³⁺ ions.

Neutralizing the Charge Imbalance Problem in Eu3+-Activated BaAl2O4 Nanophosphors: Theoretical Insights and Experimental Validation Considering K+ Codoping

In recent years, rare-earth-doped nanophosphors have attracted great attention in the field of luminescent materials for advanced solid-state lighting and high-resolution display applications. However, the low efficiency of concurrent red phosphors creates a major bottleneck for easy commercialization of these devices. In this work, intense red-light-emitting K⁺-codoped BaAl₂O₄:Eu³⁺ nanophosphors having an average crystallite size of 54 nm were synthesized via a modified sol-gel method. The derived nanophosphors exhibit strong red emission produced by the ⁵D₀ → ⁷F _J (J = 0, 1, 2, 3, 4) transitions of Eu³⁺ upon UV and low-voltage electron beam excitation. Comparative photoluminescence (PL) analysis is executed for Eu³⁺-activated and K⁺-coactivated BaAl₂O₄:Eu³⁺ nanophosphors, demonstrating remarkable enhancement in PL intensity as well as thermal stability due to K⁺ codoping. The origin of this PL enhancement is also analyzed from first-principles calculations using density functional theory. Achievement of charge compensation with the addition of a K⁺ coactivator plays an important role in increasing the radiative lifetime and color purity of the codoped nanophosphors. Obtained results substantially approve the promising prospects of this nanophosphor in the promptly growing field of solid-state lighting and field emission display devices.

Role of Dy3+ → Sm3+ energy transfer in the tuning of warm to cold white light emission in Dy3+/Sm3+ co-doped Lu3Ga5O12 nano-garnets

Nano-crystalline lutetium gallium garnets co-doped with Dy³⁺ and Sm³⁺ ions have been synthesized via a sol–gel method and their structural, morphological and luminescence properties have been characterized.

White light emitting MgAl2O4:Dy3+,Eu3+ nanophosphor for multifunctional applications

An efficient energy transfer from Dy³⁺ to Eu³⁺ in MgAl₂O₄ offers white light emission and self-referencing thermal behaviour.

Soft X-ray activated NaYF4:Gd/Tb scintillating nanorods for in vivo dual-modal X-ray/X-ray-induced optical bioimaging

Lanthanide (Ln) nanocrystals using soft X-ray as an excitation source have received significant research interest due to the advantages of unlimited penetration depth of X-ray light. In this study, we demonstrated an efficient scintillator based on NaYF₄:Gd nanorods (denoted as NRs) doped with different contents of terbium (Tb) ions for optical bioimaging under X-ray irradiation. The experimental results showed that the emission intensity was correlated to the doping contents of Tb³⁺, and the largest emission intensity was achieved by doping 15% Tb under excitation by soft X-ray light. In addition, the emission intensity of the as-prepared NRs can be significantly improved by increasing the excitation power and irradiation times of the X-ray. Owing to the efficient X-ray-induced emission, these NRs were successfully used as probes for X-ray-induced optical bioimaging with high sensitivity. In addition, the dual-modal X-ray imaging and X-ray induced optical bioimaging were performed on a mouse, which indicated that the NRs were promising dual-modal bioprobes. Therefore, the X-ray activation nature of the designed NRs makes them promising probes for biomedicine and X-ray-induced photodynamic therapy (PDT) applications owing to the unlimited penetration depth of X-ray excitation source and absence of autofluorescence.

Controlled synthesis of lanthanide-doped Gd2O2S nanocrystals with novel excitation-dependent multicolor emissions

Developing multicolor-emitting materials has significant value in many research fields such as displays, bioimaging, and information storage. The widely adopted strategies to realize multicolor emission are tuning the material composition, phase, and size. Herein, the emission color was continuously controlled from yellow to pink by simply changing the excitation wavelength from 254 nm to 365 nm for Tb³⁺/Eu³⁺ co-doped Gd₂O₂S NCs. The Gd₂O₂S NCs with different morphologies, including nanoplate with various sizes and flower-like, were successfully prepared by seed-mediated, Na⁺/Y³⁺ co-doped, and S concentration-tuned methods. The results indicated that Na⁺ ions greatly promote the growth of Gd₂O₂S NCs and Y³⁺ ions have an impact on their shape. Moreover, the PL intensity of the 2%Eu-doped flower-like Na/Y:Gd₂O₂S (F-NYG) NCs decreased by about 24.7%, 6.8%, and 5.1% under 254 nm, 316 nm, and 348 nm excitation, respectively; this is due to less non-radiative relaxation paths above the excited state of Eu³⁺:⁵D₀ at longer excitation wavelength, which result in a decreased degree of the PL intensity reduction.

Synthesis of Sr2Si5N8:Ce3+ phosphors for white LEDs via an efficient chemical vapor deposition [corrected]

Novel chemical vapor deposition (CVD) process was successfully developed for the growth of Sr₂Si₅N₈:Ce³⁺ phosphors with elevated luminescent properties. Metallic strontium was used as a vapor source for producing Sr₃N₂ vapor to react with Si₃N₄ powder via a homogeneous gas-solid reaction. The phosphors prepared via the CVD process showed high crystallinity, homogeneous particle size ranging from 8 to 10 μm, and high luminescence properties. In contrast, the phosphors prepared via the conventional solid-state reaction process exhibited relative low crystallinity, non-uniform particle size in the range of 0.5–5 μm and relatively lower luminescent properties than the phosphors synthesized via the CVD process. Upon the blue light excitation, Sr_2−xCe_xSi₅N₈ phosphors exhibited a broad yellow band. A red shift of the emission band from 535 to 556 nm was observed with the increment in the doping amount of Ce³⁺ ions from x = 0.02 to x = 0.10. The maximum emission was observed at x = 0.06, and the external and internal quantum efficiencies were calculated to be 51% and 71%, respectively. Furthermore, the CVD derived optimum Sr_1.94Ce_0.06Si₅N₈ phosphor exhibited sufficient thermal stability for blue-LEDs and the activation energy was calculated to be 0.33 eV. The results demonstrate a potential synthesis process for nitride phosphors suitable for light emitting diodes.

Broad near-ultraviolet and blue excitation band induced dazzling red emissions in Eu3+-activated Gd2MoO6 phosphors for white light-emitting diodes

A series of Eu³⁺-activated Gd₂MoO₆ phosphors were synthesized via a citric acid-assisted sol–gel route.

Site selective substitution and its influence on photoluminescence properties of Sr0.8Li0.2Ti0.8Nb0.2O3:Eu3+ phosphors

Effects of substitution of Eu³⁺ ions at Sr²⁺ sites and simultaneously at Sr²⁺ and Ti⁴⁺ sites on the luminescence properties of lithium niobate incorporated strontium titanate.

Gd(OH)3 with multiform morphologies and MRI contrast agent properties by different solvents

The morphology of Gd(OH)₃ is changed from nanorods to microrods, nanoparticles and nanoplates by different solvents, which affects the MRI signal intensity.

An efficient green-emitting Ba5Si2O6Cl6:Eu2+ phosphor for white-light LED application

The present paper reports a new phosphor material for WLED application with high CRI, low CCT and high colour stability.

Facile microwave synthesis of ScPO4·2H2O flowerlike superstructures: morphology control, electronic structure and multicolor tunable luminescent properties

ScP0₄·2H₂O flowerlike superstructures constructed by well-aligned nanorods were prepared and multicolor tunable emission including white light emission was realized by adjusting the relative doping concentration.

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours

Excitation-dependent emission colour tuning in single host lattice phosphors by local symmetry changes due to reorganization of highly strained oxygen.

Synthesis and Behavior of Cetyltrimethyl Ammonium Bromide Stabilized Zn1+xSnO3+x (0 ≤ x ≤1) Nano-Crystallites

We report synthesis of cetyltrimethyl ammonium bromide (CTAB) stabilized Zn_1+xSnO_3+x (0 ≤ x ≤1) nano-crystallites by facile cost-effective wet chemistry route. The X-ray diffraction patterns of as-synthesized powders at the Zn/Sn ratio of 1 exhibited formation of ZnSn(OH)₆. Increasing the Zn/Sn ratio further resulted in the precipitation of an additional phase corresponding to Zn(OH)₂. The decomposition of these powders at 650°C for 3h led to the formation of the orthorhombic phase of ZnSnO₃ and tetragonal SnO₂-type phase of Zn₂SnO₄ at the Zn/Sn ratio of 1 and 2, respectively, with the formation of their mixed phases at intermediate compositions, i.e., at Zn/Sn ratio of 1.25, 1.50 and 1.75, respectively. The lattice parameters of orthorhombic and tetragonal phases were a ~ 3.6203 Å, b ~ 4.2646 Å and c ~ 12.8291Å (for ZnSnO₃) and a = b ~ 5.0136 Å and c ~ 3.3055Å (for Zn₂SnO₄). The transmission electron micrographs revealed the formation of nano-crystallites with aspect ratio ~ 2; the length and thickness being 24, 13 nm (for ZnSnO₃) and 47, 22 nm (for Zn₂SnO₄), respectively. The estimated direct bandgap values for the ZnSnO₃ and Zn₂SnO₄ were found to be 4.21 eV and 4.12 eV, respectively. The ac conductivity values at room temperature (at 10 kHz) for the ZnSnO₃ and Zn₂SnO₄ samples were 8.02 × 10⁻⁸ Ω^-1 cm^-1 and 6.77 × 10⁻⁸ Ω^-1 cm^-1, respectively. The relative permittivity was found to increase with increase in temperature, the room temperature values being 14.24 and 25.22 for the samples ZnSnO₃ and Zn₂SnO₄, respectively. Both the samples, i.e., ZnSnO₃ and Zn₂SnO₄, exhibited low values of loss tangent up to 300 K, the room temperature values being 0.89 and 0.72, respectively. A dye-sensitized solar cell has been fabricated using the optimized sample of zinc stannate photo-anode, i.e., Zn₂SnO₄. The cyclic voltammetry revealed oxidation and reduction around 0.40 V (current density ~ 11.1 mA/cm²) and 0.57 V (current density– 11.7 mA/cm²) for Zn₂SnO₄ photo-anode in presence of light.