Characterization and biological prospects of various calcined temperature-V2O5 nanoparticles synthesized by Citrus hystrix fruit extract

In this study, a simple green synthesis of vanadium pentoxide nanoparticles (VNPs) was prepared by the extract of Kaffir lime fruit (Citrus hystrix) as a green reducing and stabilizing agent, along with the investigation of calcination temperature was carried out at 450 and 550 °C. It was affirmed that, at higher temperature (550 °C), the VNPs possessed a high degree crystalline following the construction of (001) lattice diffraction within an increase in crystalline size from 47.12 to 53.51 nm, although the band gap of the materials at 450 °C was lower than that of the VNPs-550 (2.53 versus 2.66 eV, respectively). Besides, the materials were assessed for the potential bioactivities toward antibacterial, antifungal, DNA cleavage, anti-inflammatory, and hemolytic performances. As a result, the antibacterial activity, with minimal inhalation concentration (MIC) < 6.25 μg/mL for both strains, and fungicidal one of the materials depicted the dose-dependent effects. Once, both VNPs exhibited the noticeable efficacy of the DNA microbial damage, meanwhile, the outstanding anti-inflammatory agent was involved with the IC50 of 123.636 and 227.706 μg/mL, accounting for VNPs-450 and VNPs-550, respectively. Furthermore, this study also demonstrated the hemolytic potential of the VNPs materials. These consequences declare the prospects of the VNPs as the smart and alternative material from the green procedure in biomedicine.

Directional Electrosynthesis of Adipic Acid and Cyclohexanone by Controlling the Active Sites on NiOOH

Dicarboxylic acids and cyclic ketones, such as adipic acid (AA) and cyclohexanone (CHN), are essential compounds for the chemical industry. Although their production by electrosynthesis using electricity is considered one of the most promising strategies, the application of such processes has been hampered by a lack of efficient catalysts as well as a lack of understanding of the mechanism. Herein, a series of monolithic msig/ea-NiOOH-Ni(OH)2/NF were prepared by means of self-dissolution of metal matrix components, interface growth, and electrochemical activation (denoted as msig/ea). The as-synthesized catalysts have three-dimensional cuboid-like structures formed by interconnecting nanosheets composed of NiOOH. By theoretically guided regulation of the amounts of Ni3+ and oxygen vacancies (OV), a 96.5% yield of CHN from cyclohexanol (CHA) dehydrogenation and a 93.6% yield of AA from CHN oxidation were achieved. A combined experimental and theoretical study demonstrates that CHA dehydrogenation and CHN oxidation were promoted by the formation of Ni3+ and the peroxide species (*OOH) on OV. This work provides a promising approach for directional electrosynthesis of high-purity chemicals with in-depth mechanistic insights.

Understanding the excited state dynamics and redox behavior of highly luminescent and electrochemically active Eu(III)-DES complex

Deep eutectic solvents (DES) are considered a novel class of environmentally benign molecular solvents that are considered as potential solvents for nuclear fuel reprocessing, material recycling, and many other technological applications in both research and industry. However, there is a complete dearth of understanding pertaining to the behavior of metal ions in DES. Herein, we have investigated the speciation, complexation behavior, photochemistry, and redox properties and tried to obtain insight into the chemical aspects of the europium ion in DES (synthesized from heptyltriphenylphosphonium bromide and decanoic acid). The same has been probed using time-resolved photoluminescence (TRPL), cyclic voltammetry (CV), synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations. TRPL indicated the stabilization of europium in the +3 oxidation state, favoring the potential of the Eu(III)-DES complex to emit red light under near UV excitation and the existence of inefficient energy transfer between DES and Eu3+. EXAFS analysis revealed the presence of Eu-O and Eu-Br, which represent the local surroundings of Eu3+ in the Eu(III)-DES complex. TRPL measurement has also suggested two distinct local environments of europium ions in the complex. DFT calculations supported the EXAFS findings, confirming that the Eu(III)-DES structure involves not only the oxygen atom of decanoic acid but also the oxygen atoms from the nitrate ions, contributing to the local coordination of Eu(III). Electrochemical studies demonstrated that the redox reaction of Eu(III)/Eu(II) in DES displays quasi-reversible behavior. The reaction rate was observed to increase with higher temperatures. The findings of this study can contribute to the understanding of the fundamental properties and potential applications of this luminescent and electrochemically active complex and pave the way for further studies and the development of novel materials with enhanced luminescent and electrochemical properties.

Two birds with one stone: Ratiometric sensing platform overcoming cross-interference for multiple-scenario detection and accurate discrimination of tetracycline analogs

Environmental pollution caused by tetracycline antibiotics (TCs) is a major concern for public health worldwide. Trace detection and reliable discrimination of tetracycline and its analogs are consequently essential to determine the distribution characteristics of various tetracycline family members. Here, a dual-response sensor was constructed by integrating the fluorescence emission of fluorescein isothiocyanate (FITC) doped SiO2 and Eu3+. A portable Lab-on-Paper device is further fabricated through probe immobilization, which allows convenient visual detection of tetracycline using a smartphone. In addition, for the coexistence of multiple tetracycline analogs, dimensionality reduction via principal component analysis is applied to the spectra, realizing accurate differentiation of the four most widely used tetracycline analogs (tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DOX)). The dual-response nanoplatform enabled a wide-gamut color variation crossing from green to red, with limit of detection (LOD) of 2.9 nM and 89.8 nM for spectrometer- and paper-based sensors, respectively. Analytical performance was examined in multiple real samples, including food, environmental, and biological settings, confirming robust environmental adaptability and resistance. Compared to previous TC sensors, this method has several notable improvements, including improved ecological safety, accessibility, reproducibility, practicality, and anti-cross-interference capacity. These results highlight the potential of the proposed "two birds with one stone" strategy, providing an integrated methodology for synchronous quantitative detection and derivative identification toward environmental contaminants.

An Ultrafast and Room-Temperature Strategy for Kilogram-Scale Synthesis of Sub-5 nm Eu3+ -doped CaMO4 Nanocrystals with a Photoluminescence Quantum Yield Exceeding 85

Rare earth-doped metal oxide nanocrystals have a high potential in display, lighting, and bio-imaging, owing to their excellent emission efficiency, superior chemical, and thermal stability. However, the photoluminescence quantum yields (PLQYs) of rare earth-doped metal oxide nanocrystals have been reported to be much lower than those of the corresponding bulk phosphors, group II-VI, and halide-based perovskite quantum dots because of their poor crystallinity and high-concentration surface defects. Here, an ultrafast and room-temperature strategy for the kilogram-scale synthesis of sub-5 nm Eu3+ -doped CaMoO4 nanocrystals is presented, and this reaction can be finished in 1 min under ambient conditions. The absolute PLQYs for sub-5 nm Eu3+ -doped CaMoO4 nanocrystals can reach over 85%, which are comparable to those of the corresponding bulk phosphors prepared by the high-temperature solid state reaction. Moreover, the as-produced nanocrystals exhibit a superior thermal stability and their emission intensity unexpectedly increases after sintering at 600 °C for 2 h in air. 1.9 kg of Eu3+ -doped CaMoO4 nanocrystals with a PLQY of 85.1% can be obtained in single reaction.

CdSe-Decorated Flowerlike CaMoO4 Microspheres with Enhanced Hydrogen Production Activity

Photocatalytic hydrogen production technology from water is a more effective and promising method to solve energy and environmental crises. In this work, flowerlike CaMoO₄ microspheres were successfully synthesized by an ultrasonic precipitation method and modified with variable concentrations of CdSe NCs. CdSe/CaMoO₄ microspheres showed increased light absorption ability, larger relative surface area, lower electrochemical impedance, and longer fluorescence lifetime. The photocatalytic hydrogen production rate of CdSe/CaMoO₄ microspheres could reach up to 10 162.33 μmol g^-1 h^-1. The constructed type-I heterostructure improved the separation of photogenerated electrons and inhibited the rapid recombination of photogenerated electrons and holes, thus enhancing the photocatalytic hydrogen production performance. CdSe/CaMoO₄ with high hydrogen production activity would be an efficient photocatalyst for hydrogen production applications.

Fabricated Flexible Composite for a UV-LED Color Filter and Anti-Counterfeiting Application of Calcium Molybdate Phosphor Synthesized at Room Temperature

Crystalline CaMoO₄ and rare-earth-doped CaMoO₄:RE³⁺ (RE = Tb, Eu) phosphors were synthesized at room temperature using a co-precipitation method. The crystal structure of the synthesized powder was a tetragonal structure with a main diffraction peak (112) phase. When CaMoO₄ was excited at 295 nm, it showed a central peak of 498 nm and light emission in a wide range of 420 to 700 nm. Rare-earth-ion-doped CaMoO₄:Tb³⁺ was excited at 288 nm and a green light emission was observed at 544 nm, and CaMoO₄:Eu³⁺ was excited at 292 nm and a red light emission was observed at 613 nm. To take advantage of the light-emitting characteristics, a flexible composite was manufactured and a color filter that could be used for UV-LEDs was manufactured. In addition, it was suggested that an ink that could be checked only by UV light could be produced and applied to banknotes so as to prevent counterfeiting.

Morphology-oxygen evolution activity relationship of iridium(iv) oxide nanomaterials

This work demonstrated shape tuning of IrO2 nanoparticles to nanocube and nanorods in molten salt and demonstrated the exemplary performance of IrO2 nanorods as an electrocatalyst for oxygen evolution reaction even surpassing commercial IrO2.

Single crystals of undoped Li2WO4 and Li2W1-0.0125Mo0.0125O4: formation enthalpies, heat capacity in the temperature range 320-997 K

The Li₂WO₄ single crystal was first grown by applying the Czochralski technique with weight control and low-temperature-gradients. A single crystal of Li₂WO₄ is one of the perspective materials for researching rare events. The heat capacity for a Li₂W_1-0.0125Mo_0.0125O₄ single crystal has been determined by DSC calorimetry in the temperature range 320-997 K for the first time. No anomalies in the heat capacity associated with phase transitions were found. The standard formation enthalpy for the Li₂WO₄ single crystal was studied using reaction calorimetry. It has been shown that the relation of standard formation enthalpies for Li₂W_1-xMo_xO₄ (x = 0.15-0) with function (1-x)W + xMo are close to linear, which allows one to predict the thermodynamic properties for single crystals with isotopes Li₂W¹⁸⁶_1-0.0125Mo¹⁰⁰_0.0125O₄ and Li₂W¹⁸⁶O₄. It was shown that single crystals with isotopes are more thermodynamically stable than without isotopes.

White light emission from co-doped La2Hf2O7 nanoparticles with suppressed host → Eu3+ energy transfer via a U6+ co-dopant

This work highlights white light emission from La₂Hf₂O₇:Eu³⁺ nanoparticles assisted by uranium co-doping to restrict energy transfer from the host oxygen vacancy to the Eu³⁺ dopant.

A dual-response ratiometric fluorescent sensor by europium-doped CdTe quantum dots for visual and colorimetric detection of tetracycline

Residues in animal food and drinking water caused by the abuse of antibiotics lead to cell resistance and many chronic diseases in the human body. Therefore, it has become an inevitable trend to develop a fast, easy-to-use, on-site/real-time visualization method for the detection of antibiotics. Herein, we report a dual-response ratiometric fluorescence sensor which is fabricated by chelating europium ions (Eu³⁺) onto cadmium telluride quantum dots (CdTe QDs) for real-time and visible detection of tetracycline (TC). With the TC addition, the fluorescence of probe can be seen by the naked eye, from green to yellow and finally to red, exhibiting a dosage-sensitive and broad-chromatic detection strategy for TC. The fluorescence intensity ratio of I₆₁₆/I₅₁₂ of Eu/CdTe QDs sensor displays a good linear relation to TC concentrations in the range of 0-80 μM with a limit of detection (LOD) of 2.2 nM. In addition, the sensor can visually detect 200 nM TC in actual samples, which is lower than the maximum residue limit (MRL) of the safety standard. The methodology reported here opens a window toward the real applications of fluorescent and shows the wide applicability in pursuing the concepts simple, rapid, visual, and real-time for food safety and environmental protection.

The electronic structure, surface properties, and in situ N2O decomposition of mechanochemically synthesised LaMnO3

The use of mechanochemistry to prepare catalytic materials is of significant interest; it offers an environmentally beneficial, solvent-free, route and produces highly complex structures of mixed amorphous and crystalline phases. This study reports on the effect of milling atmosphere, either air or argon, on mechanochemically prepared LaMnO3 and the catalytic performance towards N2O decomposition (deN2O). In this work, high energy resolution fluorescence detection (HERFD), X-ray absorption near edge structure (XANES), X-ray emission, and X-ray photoelectron spectroscopy (XPS) have been used to probe the electronic structural properties of the mechanochemically prepared materials. Moreover, in situ studies using near ambient pressure (NAP)-XPS, to follow the materials during catalysis, and high pressure energy dispersive EXAFS studies, to mimic the preparation conditions, have also been performed. The studies show that there are clear differences between the air and argon milled samples, with the most pronounced changes observed using NAP-XPS. The XPS results find increased levels of active adsorbed oxygen species, linked to the presence of surface oxide vacancies, for the sample prepared in argon. Furthermore, the argon milled LaMnO3 shows improved catalytic activity towards deN2O at lower temperatures compared to the air milled and sol-gel synthesised LaMnO3. Assessing this improved catalytic behaviour during deN2O of argon milled LaMnO3 by in situ NAP-XPS suggests increased interaction of N2O at room temperature within the O 1s region. This study further demonstrates the complexity of mechanochemically prepared materials and through careful choice of characterisation methods how their properties can be understood.

Understanding the mechanochemical synthesis of the perovskite LaMnO3 and its catalytic behaviour

Mechanochemistry offers a solventless, 'waste free' route to preparing metal oxide catalysts, however, there is limited information on the chemical steps involved. In this work, the perovskite LaMnO₃ has been successfully synthesized via mechanochemistry from metal oxide powders, La₂O₃ and Mn₂O₃, at room temperature, using a planetary ball mill. Separate ex situ'time slices' were taken during the milling procedure to provide insights into the underlying chemistry. The crystalline material was assessed using XRD, which identified 100% perovskite phase after 3 h of milling. Conversely, characterization by X-ray absorption spectroscopy (XAS) at both the Mn K-edge and La L₃-edge provides a very different picture. The XAS data shows that there are significant structural alterations as early as 30 min of milling, with the La precursor dispersed over Mn₂O₃. Increasing milling time then allows for mechanical activation of both precursors and the formation of powdered LaMnO₃, with no calcination step required. The XAS highlights that there is a significant amount of amorphous, oxygen deficient, content even when XRD has identified 100% perovskite phase. The samples were tested for the decomposition of the environmental pollutant N₂O; at a milling time of 3 h, the LaMnO₃ catalyst displays a much early onset production of N₂ compared to a traditional sol-gel synthesized LaMnO₃, resulting from increased oxygen deficiency at the surface, confirmed by XPS and STEM-EELS. This is an encouraging sign that mechanochemical routes can be harnessed to provide a sustainable route to preparing mixed metal oxide catalysts with enhanced catalytic performance.

Role of alkali charge compensation in the luminescence of CaWO4:Nd3+ and SrWO4:Nd3+ Scheelites

The present work demonstrates the distinct role of alkali metal ion charge compensators on the luminescence of NIR-emitting Nd³⁺ Scheelite. The unit cell dimensions of the host lattice and excitation wavelength play a very important role.

Probing emission and defects in BaWxMo1–xO4 solid solutions: achieving color tunable luminescence by W/Mo ratio and size manipulation

This work highlights the size, structure, and composition manipulation for designing color-tunable phosphors based on doped scheelite micro- and nanocrystals.

Traditional salt-in-water electrolyte vs. water-in-salt electrolyte with binary metal oxide for symmetric supercapacitors: capacitive vs. faradaic

The electrochemical energy storage of lithium and sodium ions from aqueous solutions in binary metal oxides is of great interest for renewable energy storage applications. Binary metal oxides are of interest for aqueous energy storage due to their better structural stability and electronic conductivity and tunability of redox potentials. They have also been widely studied as novel electrodes for supercapacitors. The interactions between water and lithium/sodium ions, and water and binary metal oxide surface determine the electrochemical reactions and their long-term stability. Our results indicate that the aqueous sodium electrolyte has a stronger influence on the capacitance and cycling stability of the binary (Ca and Mo) metal oxide electrode than its lithium cousin. The symmetric cell in a two-electrode configuration was assembled with the proposed binary metal oxide, which shows an average discharge voltage of 1.2 V, delivering a specific capacitance of 72 F g-1 at a specific energy density of 32 W h kg-1 based on the total mass of the active materials. The development of highly concentrated aqueous electrolytes such as the "water-in-salt" electrolyte showed a larger electrochemical (voltage) window with enhanced storage capacitance for increasing the salt concentrations has also been discussed.

Phase evolution in calcium molybdate nanoparticles as a function of synthesis temperature and its electrochemical effect on energy storage

The design of a suitable electrode is an essential and fundamental research challenge in the field of electrochemical energy storage because the electronic structures and morphologies determine the surface redox reactions. Calcium molybdate (CaMoO₄) was synthesized by a combustion route at 300 °C and 500 °C. We describe new findings on the behaviour of CaMoO₄ and evaluate the influence of crystallinity on energy storage performance. A wide range of characterization techniques was used to obtain detailed information about the physical and morphological characteristics of CaMoO₄. The characterization results enable the phase evolution as a function of the electrode synthesis temperature to be understood. The crystallinity of the materials was found to increase with increasing temperature but with no second phases observed. Molecular dynamics simulation of electronic structures correlated well with the experimental findings. These results show that to enable faster energy storage and release for a given surface area, amorphous CaMoO₄ is required, while larger energy storage can be obtained by using crystalline CaMoO₄. CaMoO₄ has been evaluated as a cathode material in classical lithium-ion batteries recently. However, determining the surface properties in a sodium-ion system experimentally, combined with computational modelling to understand the results has not been reported. The superior electrochemical properties of crystalline CaMoO₄ are attributed to its morphology providing enhanced Na⁺ ion diffusivity and electron transport. However, the presence of carbon in amorphous CaMoO₄ resulted in excellent rate capability, suitable for supercapacitor applications.

Correlating Structure and Luminescence Properties of Undoped and Eu3+-Doped La2Hf2O7 Nanoparticles Prepared with Different Coprecipitating pH Values through Experimental and Theoretical Studies

Understanding the structure-property relationship and optimizing properties of phosphors for use in lighting and scintillation fields is an important materials challenge. In this work, we investigated the effects of the pH value of the coprecipitating solution adjusted by the concentration of NH₄OH(aq) on the structure and optical properties of the obtained La₂Hf₂O₇ nanoparticles (NPs). The obtained NPs stabilize in the ideal pyrochlore structure, but the extent of ordering increased with an increase in the pH value used. The NPs prepared at pH = 12.1 displayed the best optical performance owing to the balance of the crystallinity, agglomeration, and surface defects. On the basis of density functional theory (DFT) calculations, the origin of violet-blue emission in undoped La₂Hf₂O₇ NPs was attributed to defect states in the electronic band gap arising due to oxygen defects. For the La₂Hf₂O₇:Eu³⁺ NPs, the Eu³⁺ dopants possess low symmetry and their occupancy is more favorable at the LaO₈ site. DFT calculations further justify the complete host-to-dopant energy transfer and origin of the most intense red emission observed experimentally. Understanding the interplay of the experimental and theoretical results thus is a very useful general approach for improving the efficiency of luminescent materials.

CaMoO4 nanosheet arrays for efficient and durable water oxidation electrocatalysis under alkaline conditions

It is highly desirable to design and develop earth-abundant electrocatalysts for efficient and durable oxygen evolution reaction (OER) under alkaline conditions. In this communication, we demonstrate the development of CaMoO4 nanosheet arrays on nickel foam (CaMoO4/NF) as a durable high-performance non-noble-metal electrocatalyst for the OER. CaMoO4/NF shows high catalytic activity and needs an overpotential of only 345 mV to attain a geometrical catalytic current density of 50 mA cm-2 in 1.0 M KOH. Notably, it also shows high long-term electrochemical durability for at least 25 h.

Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β-Ca2SiO4: Probing Local Site and Structure

The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca₂SiO₄ (from here on C₂S) particle from Pechini (C₂SP) and hydrothermal (C₂SH) methods, and its luminescence variance upon doping with Eu²⁺ and Eu³⁺ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu³⁺-O^2- distance in Eu³⁺ doped C₂SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO₄^4- tetrahedra in C₂SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C₂SP to C₂SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd-Ofelt analysis. The concentration quenching and site-occupancy of Eu³⁺ ions in two nonequivalent sites of C₂S were discussed. The charge state and concentration of europium ions in C₂SP and C₂SH were determined using X-ray photoelectron spectroscopy measurements. The C₂S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C₂SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C₂S and thereby improves the applications in optical and biomedical areas and cement hydration.

Thermal annealing effects on La2Hf2O7:Eu3+ nanoparticles: a curious case study of structural evolution and site-specific photo- and radio-luminescence

High temperature annealed La₂Hf₂O₇:Eu³⁺ nanoparticles favor tunneling of Eu³⁺ to symmetric sites showing orange emission, whereas low temperature annealed samples favor red emission.

Self-assembled hierarchical architecture of tetragonal AgLa(MoO4)2 crystals: hydrothermal synthesis, morphology evolution and luminescence properties

Tetragonal AgLa(MoO₄)₂ microcrystals with novel discal hierarchical architectures were successfully synthesized via a one-step hydrothermal route.

Red and green colors emitting spherical-shaped calcium molybdate nanophosphors for enhanced latent fingerprint detection

We report the synthesis of spherical-shaped rare-earth (Eu³⁺ and Tb³⁺) ions doped CaMoO₄ nanoparticles in double solvents (IPA and H₂O) with the help of autoclave. The X-ray diffraction patterns well match with the standard values and confirm the crystallization in a tetragonal phase with an I4₁/a (88) space group. The luminescence spectra exhibit the strong red and green emissions from Eu³⁺ and Tb³⁺ ions doped samples, respectively. The X-ray photoelectron spectroscopy results show the oxidation states of all the elements present in the sample. The temperature-dependent luminescence spectra reveal the stability of Eu³⁺ and Tb³⁺ ions doped samples. The red- and green-emitting Eu³⁺ and Tb³⁺ ions doped CaMoO₄ samples were used for detection and enhancement of latent fingerprints which are the common evidences found at crime scenes. The enhanced latent fingerprints obtained on different surfaces have high contrast with low background interference. The minute details of the fingerprint which are useful for individualization are clearly observed with the help of these nanopowders.

Multicolor Tuning in Room-Temperature Self-Activated Ca2 Nb2 O7 Submicroplates by Lanthanide Doping

Self-activated phosphors are capable of generating optical emissions from the internal ion groups of host lattice before externally introducing luminescent ions. However, numerous self-activated phosphors only show luminescence at low temperature due to the thermally activated energy migration among ion groups at room temperature, severely confining their application conditions. In this letter, we propose a strategy to converting the low-temperature luminescence to a room-temperature one through changing the synthesis conditions to induce structural distortions and thus to limit energy migration. Room-temperature self-activated luminescence of Ca₂ Nb₂ O₇ was accordingly achieved in submicroplates synthesized using the sol-gel method. By further coupling the blue broadband emission from Ca₂ Nb₂ O₇ submicroplates with the characteristic luminescence of Ln³⁺ (Pr³⁺ , Sm³⁺ , and Dy³⁺ ) dopants, multicolor emissions were successively tuned through adjusting the concentration of Ln³⁺ . Our results are expected to expand the scope of designing room-temperature self-activated phosphors and tuning multicolor emission.

Crystal structure of Ba2(La0.727Ba0.182M0.091)MO6 (M = Nb, Sb, Bi): symmetry nuance identified in photoluminescence and IR spectroscopy studies

A one-third lanthanum deficiency was created in Ba₂LaM⁵⁺O₆ compounds (LaM compounds) to form Ba₂La_2/3M⁵⁺O_5.5 compounds (La2/3M compounds) for M = Nb, Sb, and Bi. The compounds were prepared by a gel-combustion method using citric acid as a fuel. All the compounds were characterized by powder X-ray diffraction (XRD). The XRD analysis showed that the space group of the La2/3M compounds remains the same for the Bi and Sb samples when compared to the reported LaM compounds, except for the Nb sample. La2/3Nb and La2/3Sb adopt a rhombohedral structure with the space group R3[combining macron], whereas La2/3Bi adopts a monoclinic structure with the space group I2/m. As the positron annihilation spectroscopy (PALS) technique is sensitive to cation deficiency, it was used to detect the presence of cation vacancies in the samples, which are formed due to the decrease in the lanthanum concentration. The PALS analyses indicated that the absence of cation deficiency in the La2/3M compounds is similar to that observed in the LaM compound. Thus, the crystal structure of the La2/3M compound was modeled, such that the cation deficiency at the La site is filled by Ba²⁺ and M⁵⁺ ions, and the crystal structure formula is given as Ba₂(La_0.727Ba_0.182M_0.091)MO₆. This model was confirmed by Rietveld refinement of the XRD data. The emission spectra of Eu³⁺ showed a strong dependence on its local site symmetry in the host material, in which it is being doped and this can be used as a spectroscopic probe for detecting any differences in the symmetry. Comparison of the local symmetry around La³⁺ cation was studied using photoluminescence (PL) by doping 2 atom% Eu³⁺ in LaM and La2/3M compounds. Infrared spectroscopy (IRS) analyses were also carried out for LaM and La2/3M compounds. There was complete agreement between the PL and IRS results and they were also in concordance with the predicted crystal structure model. Interestingly in these La2/3M compounds, the equilibrium structure prefers large Ba²⁺ ion to occupy the octahedral B-site rather than forming an octahedral vacancy at that site, making these perovskite compounds rare and novel in their class.

Hydrothermal synthesis, characterization and luminescence properties of CaGd2(MoO4)4:Eu3+ ovoid like structures

Red light emission from CaGd₂(MoO₄)₄:0.06Eu³⁺ phosphor by EDTA assisted hydrothermal route at 200 °C for 24 h.

Facile hydrothermal synthesis and pulsed laser deposition of Ca0.5Y1−x(WO4)2:xEu3+ phosphors: investigations on the luminescence, Judd–Ofelt analysis and charge compensation mechanism

PL emission spectra of Ca_0.5Y_1−x(WO₄)₂:xEu³⁺ for powder and thin film phosphors, and PL spectra of Ca_0.5Y_1−x(WO₄)₂:xEu³⁺ co-doped with alkali metal ions.

Energy transfer dynamics and time resolved photoluminescence in BaWO4:Eu3+ nanophosphors synthesized by mechanical activation

Red purity and high quantum efficiency of BaWO₄:Eu³⁺ projects it as a new red phosphor for application in white LEDs.

Why host to dopant energy transfer is absent in the MgAl2O4:Eu3+ spinel? And exploring Eu3+ site distribution and local symmetry through its photoluminescence: interplay of experiment and theory

Local site occupancy of Eu³⁺ in combustion synthesized MgAl₂O₄ spinel and host → Eu³⁺ energy transfer dynamics is investigated using photoluminescence and DFT calculations.

Defects induced changes in the electronic structures of MgO and their correlation with the optical properties: a special case of electron–hole recombination from the conduction band

Defect induced tunable emission in MgO is investigated using photoluminescence and DFT calculations.

Effect of co-doping of alkali metal ions on Ca0.5RE1−x(MoO4)2:xEu3+ (RE = Y, La) phosphors with enhanced luminescence properties

Illustration of elemental mapping and PL emission spectra of the phosphors, Ca_0.5RE_1−x(MoO₄)₂:Eu³⁺,M⁺ (RE = Y, La; M = Li, K and Na).

Experimental and theoretical approach to account for green luminescence from Gd2Zr2O7 pyrochlore: exploring the site occupancy and origin of host-dopant energy transfer in Gd2Zr2O7:Eu3+

Origin of green emission in undoped Gd₂Zr₂O₇ and photophysical characteristics such as local site and energy transfer dynamics of Gd₂Zr₂O₇:Eu³⁺ is investigated using PL and DFT calculations.

Eu3+ local site analysis and emission characteristics of novel Nd2Zr2O7:Eu phosphor: insight into the effect of europium concentration on its photoluminescence properties

New Color tunable Nd₂Zr₂O₇:Eu³⁺ (0–5 mol%) phosphor was synthesized using gel-combustion and its photophysical characteristics such as energy transfer, point group symmetry and Judd–Ofelt parameter were investigated using time resolved photoluminescence.

Luminescence of undoped and Eu3+ doped nanocrystalline SrWO4 scheelite: time resolved fluorescence complimented by DFT and positron annihilation spectroscopic studies

Effect of annealing temperature on photophysical characteristics of pure and SrWO₄:Eu³⁺ nanoparticles were investigated and the changes observed correlated with density function theory (DFT) and positron annihilation lifetime spectroscopy (PALS).