Sr Site Research Articles

RETRACTED: Oxygen vacancy induced high specific capacitance in Sr2CoSbO6

Sr2CoSbO6, a double perovskite compound known to have oxide ion vacancies, is not well explored for its electrical properties. In the present article, we study the effect of the aliovalent doping of Na+ at Sr site in Sr2CoSbO6 on their electrochemical performance. The X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) techniques confirm the phase formation and reveal particle-like morphologies for all the samples. The cyclic voltammetry study reveals the specific capacitance increases with increasing Na concentration and a specific capacitance value of 228 F/g is obtained for the maximum dopant composition. Excellent cycling stability of 92% of initial capacitance retention even after 2000 continuous cycles at a high scan rate of 100 mVs-1 in an aqueous 1 M KOH electrolyte solution and a 98% of coulombic efficiency at a current density of 1 A/g is observed. These values suggest that the Na doped Sr2CoSbO6 can find application as supercapacitors material.

Multiband transport enables thermoelectric enhancements in the SrMg2Bi2 compound

A small energy offset (ΔE < 0.2 eV) between Γ(pxy) and Γ(pz) band orbitals in AB2X2 Zintl compounds enables the realization of band alignment for an increased band degeneracy as well as an enhanced electronic performance. The SrMg2Bi2 Zintl compound has been theoretically illustrated to have a small ΔE, suggesting an approximately inherent convergence of two band orbitals. Therefore, this work is devoted to the revelation of the thermoelectric potential of the SrMg2Bi2 Zintl compound in a broad Hall carrier concentration of 0.3–5 × 1019 cm−3 by Ag-doping at the Sr site. The electrical transport properties can be well predicted by the single parabolic band model with acoustic phonon scattering, which reveals a multi-band transporting behavior in the heavily doped samples due to Fermi level deepening, leading to a significant zT-enhancement. In terms of the model, a peak zT of up to 1.0 is achievable by assuming the amorphous minimum lattice thermal conductivity, which demonstrates this compound as a promising thermoelectric material.

Sorption of Sr on montmorillonite clays: Theoretical and experimental study

Montmorillonite is a clay mineral widely used to remove pollutants from wastewater. The Sr sorption on montmorillonite was analyzed combining an experimental - theoretical approach. Sr sorption on natural and synthetic Na-montmorillonite was studied, characterizing the materials before and after Sr incorporation by X-ray diffraction and Zeta potential. The total specific surface area was also determined. Besides, ab-initio calculations were performed in order to investigate the sorption stability of the clay. The effect of the hydration of Sr atoms and the influence of the van der Waals interaction were evaluated. The experimental results indicated that Sr was sorbed on both, external and internal surfaces and that the total specific surface area seems to be relevant for the sorption process. The increasing in the interlayer space by Sr incorporation was associated with the cationic exchange, the hydration of the Sr atom and the relative humidity. Nuclear magnetic resonance parameters were calculated and compared with the experimental chemical shift and electric field gradient. The calculated Sr-chemical shift corresponds to the range for atomic coordination n = 6. Since there is no experimental data available for the principal component of the electric field gradient at Sr site, the obtained theoretical value stands as a prediction.

Eu2+ Doping Concentration-Induced Site-Selective Occupation and Photoluminescence Tuning in KSrScSi2O7:Eu2+ Phosphor.

Regulation of Eu2+ dopants in different cation sites of solid-state materials is of great significance for designing multicolor phosphors for light-emitting diodes (LEDs). Herein, we report the selective occupation of Eu2+ for multiple cationic sites in KSrScSi2O7, and the tunable photoluminescence from blue to cyan is realized through Eu2+ doping concentration-dependent crystal-site engineering. Eu2+ preferably occupies the K and Sr sites in KSrScSi2O7 at a low doping concentration, resulting in a 440 nm blue emission. As the Eu2+ concentration increases, a new Eu2+ substitution pathway is triggered, that is, Eu2+ enters the Sc site, leading to the red-shifted emission spectra from 440 to 485 nm. The doping mechanism and photoluminescence properties are corroborated by structural analysis, optical spectroscopy study, and density functional theory calculations. The optical properties of the as-fabricated white LEDs are studied, which demonstrates that these phosphors can be applied to full-spectrum phosphor-converted LEDs. This study provides a new design strategy to guide the development of multicolor Eu2+-doped oxide phosphors for lighting applications.

Screening loaded perovskite oxygen carriers for chemical looping steam methane reforming

Chemical looping steam methane reforming (CL-SMR) is a novel process that produce syngas and hydrogen by using solid oxygen carriers to react with methane. The selection of oxygen carriers is a key problem in the development of CL-SMR. This study screened the perovskites with different A (La, Sr) site elements, different B (Co, Fe) site elements, and different loaded materials (CeO2, ZrO2, Al2O3 and SiO2). The results showed that La in A site presented higher hydrogen production, Fe in B site could help keep the H2/CO ratio of the syngas at about 2, and CeO2 loading could achieve highest H2 purity. Thus, LaFeO3-CeO2 was screened as the optimal oxygen carrier. When WHSV was 11.79 h−1, the CO selectivity of LaFeO3-CeO2 was over 98%, H2/CO ratio of syngas was 2, and H2 purity was about 95%. The sample could recover its original crystalline phases after cyclic reactions. CeO2 could not only provide lattice oxygen for syngas production in POM stage, but also enhance the H2 production in RS stage. Furthermore, although a slight agglomeration of the sample occurred during high temperature reactions, LaFeO3-CeO2 exhibited stable reaction performance during 10 CL-SMR cycles.

Regulation of Local Site Structures to Stabilize Mixed-Valence Eu2+/3+ under a Reducing Atmosphere for Multicolor Photoluminescence.

Co-doping mixed-valence Eu2+/3+ in a single-phase phosphor is an efficient method to realize the emission color regulation, which holds great potential for anticounterfeiting and ratiometric temperature sensing. Here, the mixed-valence Eu-doped Sr1.95+xLi1-xSi1-xAlxO4F (0 ≤ x ≤ 0.25) phosphors were designed and prepared under a reducing atmosphere. The correlation of local phase structures and luminescence properties was discussed. Replacing Si4+-Li+ ion pairs with Al3+-Sr2+ ion pairs compresses the Sr sites occupied by Eu2+, and it stabilizes Eu3+ in a reducing atmosphere and leads to the coexistence of Eu2+ and Eu3+ in single-phase Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu (0 ≤ x ≤ 0.25) phosphors. Based on the wavelength-dependent luminescence color behaviors of Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors, the fluorescent anticounterfeit papers/patterns containing Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors were the same as ordinary paper under ambient conditions. However, the hidden colors or images can be read out with green-orange luminescence under 365/300 nm light excitation. Benefiting from the diverse thermal response emission behaviors of Eu2+ (530 nm) and Eu3+ (703 nm), Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors exhibit temperature sensing performances, with the maximum absolute and relative sensitivity being 0.0294 K-1 at 573 K and 0.83% K-1 at 348 K. More importantly, Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors showed excellent stability in humid, acid, and alkali environments, which contributed to applying mixed-valence Eu2+/3+-doped Sr1.95+xLi1-xSi1-xAlxO4F to the fields of multicolor anticounterfeiting and noncontact optical thermometry.

Enhancement of the thermoelectric properties of Zintl phase SrMg2Bi2 by Na-doping.

Due to their low lattice thermal conductivity and manipulable electronic properties, AB2X2 Zintl phases have been widely studied for thermoelectric applications. This has motivated numerous efforts to focus on the exploration of novel AB2X2 Zintl thermoelectrics. In this study, SrMg2Bi2 was systematically investigated to reveal its potential for thermoelectric application. Pristine SrMg2Bi2 exhibits an intrinsic p-type semiconducting behavior. The Hall carrier concentration (nH) was efficiently increased to ∼9 × 1019 cm-3 by Na-substitution at the Sr site. The increased nH leads to enhanced electrical conductivity, but reduced Seebeck coefficient. Moreover, Na doping effectively decreased the thermal conductivity because of the intensified scattering from defects and lattice distortion. Thus, the zT of the Na-doped SrMg2Bi2 can reach 0.44 and be extremely higher than that of the pristine one. The well-known single parabolic band (SPB) model estimated that the increase in Nv and m* through doping boosts the electrical conductivity. This work sheds light on the discovery of new prospective thermoelectric materials and demonstrates that Bi-based p-type AB2X2 Zintl phases can achieve high thermoelectric performance.

Bi selectively doped SrTiO3-x nanosheets enhance photocatalytic CO2 reduction under visible light

Converting CO2 into chemical energy by using solar energy is an environmental strategy to achieve carbon neutrality. In this paper, two dimensionality (2D) SrTiO3-x nanosheets with oxygen vacancies were synthesized successfully. Oxygen vacancies will generate defect levels in the band structure of SrTiO3-x. So, SrTiO3-x nanosheets have good photocatalytic CO2 reduction performance under visible light. In order to further improve its photocatalytic efficiency, Bi was used to dope Sr site and Ti site in SrTiO3-x nanosheets respectively. It is found that Sr site is the adsorption site of CO2 molecules. When Bi replaced Sr, CO2 adsorption on the surface of SrTiO3-x nanosheets was weakened. When Bi replaced Ti, there has no effect on CO2 adsorption. Due to the synergistic effect of Bi doping, oxygen vacancies, and Sr active site, the 1.0% Bi-doped Ti site in SrTiO3-x (1.0% Bi-Ti-STO) had the best photocatalytic performance under visible light (λ ≥ 420 nm). CO and CH4 yields were 5.58 umol/g/h and 0.36 umol/g/h. Photocatalytic CO2 reduction path has always been the focus of exploration. The in-situ FTIR spectrum proved the step of photocatalytic CO2 reduction and COO– and COOH are important intermediates in the photocatalytic CO2 reaction.

Role of oxygen vacancies and Sr sites in SrCo0.8Fe0.2O3 perovskite on efficient activation of peroxymonosulfate towards the degradation of aqueous organic pollutants

Metal-based perovskite oxides have contributed significantly to the advanced oxidation processes (AOPs) due to their diverse active sites and excellent compositional/structural flexibility. In this study, we specially designed a perovskite oxide with abundant oxygen vacancies, SrCo 0.8 Fe 0.2 O 3 (SCF), and firstly applied it as a catalyst in peroxymonosulfate (PMS) activation towards organic pollutants degradation. The result revealed that the prepared SCF catalyst exhibited excellent performance on organic compounds degradation. Besides, SCF showed much better activity than La 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3 (LSCF) in terms of reaction rate and stability for the degradation of the organic compounds. Based on the analysis of scanning electron microscope, transmission electron microscope, X-ray diffraction, N 2 adsorption–desorption, X-ray photoelectron spectroscopy and electron paramagnetic resonance, it was confirmed that the perovskite catalysts with high content of Sr doping at A-site could effectively create a defect-rich surface and optimize its physicochemical properties, which was responsible for the excellent heterogeneous catalytic activity of SCF. SCF can generate three highly active species: 1 O 2 , SO − 4 ∙ and ∙OH in PMS activation, revealing the degradation process of organic compounds was a coupled multiple active species in both radical and nonradical pathway. Moreover, it was mainly in a radical pathway in the degradation through PMS activation on SCF and SO − 4 ∙ radicals produced were the dominant species in SCF/PMS system. This study demonstrated that perovskite-type catalysts could enrich OVs efficiently by doping strategy and regulate the PMS activation towards sulfate radical-based AOPs.

Synergetic modulation of surface alkali and oxygen vacancy over SrTiO3 for the CO2 photodissociation

Photochemical conversion of CO2 into solar fuels is one of the promising strategies to reducing the CO2 emission and developing a sustainable carbon economy. For the more efficient utilization of solar spectrum, several approaches were adopted to pursue the visible-light-driven SrTiO3. Herein, oxygen vacancy was introduced over the commercial SrTiO3 (SrTiO3−x ) via the NaBH4 thermal treatment, to extend the light absorption and promote the CO2 adsorption over SrTiO3. Due to the mid-gap states resulted from the oxygen deficiency, combined with the intrinsic energy level of SrTiO3, the SrTiO3−x catalyst exhibited excellent CO productivity (4.1 μmolˑg−1ˑh−1) and stability from the CO2 photodissociation under the visible-light irradiation (λ > 400 nm). Then, surface alkalization over SrTiO3−x (OH-SrTiO3−x ) was carried out to further enhance the CO2 adsorption/activation over the surface base sites and provide the OH ions as hole acceptor, the surface alkali OH connected with Sr site of SrTiO3 could also weaken the Sr–O bonding thus facilitate the regeneration of surface oxygen vacancy under the light illumination, thus resulting in 1.5 times higher CO productivity additionally. This study demonstrates that the synergetic modulation of alkali OH and oxygen vacancy over SrTiO3 could largely promote the CO2 photodissociation activity.

Enhanced crystallinity and photoluminescence properties of Yb2+ doped SrSi2O2N2 phosphor for image storage applications

A series of Yb2+ and Dy3+ doped SrSi2O2N2 phosphors with enhanced crystallinity and photoluminescence properties have been successfully synthesized by two-step method using Sr2SiO4 as precursor. It is clearly indicated from XRD results that Yb2+ ions can substitute Sr sites in SrSi2O2N2 crystal and exhibit pure phase and well-crystalline in comparison with the samples prepared by traditional solid-state reaction. The excessive amount of Si3N4 in the reactants promoted the formation of pure SrSi2O2N2 phosphors phase. SrSi2O2N2: Yb2+ phosphors show emission band at 583 nm and the broad excitation peaks located at 308 nm, 384 nm and 447 nm, covering the emission wavelength of NUV and blue chips. Compared with the sample prepared by traditional one-step solid-state reaction method, a dramatic enhancement of photoluminescence emission intensity (∼1.75 times) can be observed for SrSi2O2N2: 0.01 Yb2+ phosphor synthesized by two-step method. Due to the concentration quenching, the luminescence intensity reaches the maximum when doping concentration of Yb2+ ions is 1 mol%, which is identified as the electric dipole-electric dipole interaction. Notably, Yb2+ and Dy3+ co-doped SrSi2O2N2 phosphors with pure phase exhibit a unique thermal-stimulated luminescence property under NUV excitation, indicating the potential application in optical information storage. Furthermore, the mechanism of thermal-stimulated luminescence has been proposed.

The Electrical and Thermal Transport Properties of La-Doped SrTiO3 with Sc2O3 Composite.

Donor-doped strontium titanate (SrTiO3) is one of the most promising n-type oxide thermoelectric materials. Routine doping of La at Sr site can change the charge scattering mechanism, and meanwhile can significantly increase the power factor in the temperature range of 423–773 K. In addition, the introduction of Sc partially substitutes Sr, thus further increasing the electron concentration and optimizing the electrical transport properties. Moreover, the excess Sc in the form of Sc2O3 composite suppresses multifrequency phonon transport, leading to low thermal conductivity of κ = 3.78 W·m−1·K−1 at 773 K for sample Sr0.88La0.06Sc0.06TiO3 with the highest doping content. Thus, the thermoelectric performance of SrTiO3 can be significantly enhanced by synergistic optimization of electrical transport and thermal transport properties via cation doping and composite engineering.

Isotherm and Kinetic Modeling of Strontium Adsorption on Graphene Oxide.

In this study, graphene oxide (GO) was synthesized using Hummers method. The synthesized GO was characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The analyses confirmed the presence of oxygen functional groups (C=O and C-O-C) on the GO surface. These oxygen functional groups act as active sites in the adsorption Sr (II). The BET analysis revealed the surface area of GO of 232 m2/g with a pore volume of 0.40 cm3/g. The synthesized GO was used as an adsorbent for removing Sr (II) from aqueous solutions. The adsorption equilibrium and kinetic results were consistent with the Langmuir isotherm model and the pseudo-second-order kinetic model. A maximum strontium adsorption capacity of 131.4 mg/g was achieved. The results show that the GO has an excellent adsorption capability for removing Sr (II) from aqueous solutions and potential use in wastewater treatment applications.

Synthesis and structure of calumetite-like SrCu4(OH)8Cl2⋅3.5H2O

AbstractThe synthesis and structure of the title compound, 1, is presented, refined using Rietveld against powder X-ray diffraction data. 1 crystallises dominantly in a pseudotetragonal C-centred orthorhombic lattice with dimensions a = 6.6791(6) Å, b = 15.5006(6) Å, c = 6.6811(6) Å and V = 691.70(10) Å3. The structural model proposed here refined by Rietveld is Sr0.928(8)Cu4(OH)8Cl2⋅3.60(21)H2O in space group Cmcm (63), with Z = 2. The chemistry and diffraction pattern of 1 are similar to that for the known Ca analogue, calumetite. The copper sites are arranged with square planar coordination at ¼ and ¾ height and are bonded to four (protonated) oxygens at an average of 1.966 Å (effective coordination of 3.82 Å). The more distant Cl sites (at Cu−Cl = 3.190(6) Å) complete the heavily Jahn–Teller distorted Cu[(OH)4,Cl2] polyhedra. The ½-occupied Sr sites are 8 coordinated to four protonated oxygens shared with the Cu-layer (at 2 × 2.438(8) Å, 2 × 2.566(15) Å) and by 4 bonds to the proposed water sites (Sr−Ow = 2.760(9) Å). The structure of 1 is predisposed towards defects, based on a notional tetragonal, P4/nmm, substructure with asub ≈ a1, csub = b½ dimensions. Average diffraction models have been further elaborated in order to resolve additional peaks (and peak-shapes) using DIFFaX+.

Distribution of Ce in orthophosphate Sr3(PO4)2

The distribution of Ce in orthophosphate Sr3(PO4)2 was investigated by the combined single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) analyses. Sr3(PO4)2:Ce3+ compounds with two different Sr sites (3a and 6c sites) were synthesized using the solid-state reaction method. Single-crystal XRD analysis confirmed the location of Ce at the 3a site along with the corresponding vacancy or coexisting Li at the 6c site. Additionally, the Ce K-edge EXAFS analysis supported the occupancy of Ce3+ at the 3a site rather than at the 6c site.

High magnetic coercive field in Ca‐Al‐Cr substituted strontium hexaferrite

The structural and magnetic properties of Sr0.67Ca0.33Fe9Al3−xCrxO19 submicrometric powders with substitution levels ranging from x = 0 up to x = 3, prepared by sol-gel synthesis method, have been investigated. The powders were characterized by high resolution synchrotron X-ray diffraction, scanning electron microscopy, powder neutron diffraction and MPMS-SQUID magnetometer. The structural analysis shows that upon Ca-substitution of SrFe12O19 at the Sr site and Al–Cr at the Fe sites, the magnetoplumbite structure is preserved, even for large levels of substitutions. The X-ray powder diffraction peak broadening and Williamson-Hall plots analyses indicate an increase of crystallites size and relaxation of the microstrain with increasing amounts of Chromium. The magnetic hysteresis loops reveal high coercivity fields at room temperature, with the highest value of HC = 1125 kA/m (1.41 T) obtained for Sr0.67Ca0.33Fe9Al2.5Cr0.5O19 powder interesting to develop free-Rare Earth high coercivity magnets. The saturation magnetization and remanence values increase monotonically with increasing Cr content while the switching field decreases. The structural Rietveld refinement of combined X-ray/neutron diffraction data shows the affinity of Al3+ and Cr3+ cations to migrate mainly towards (2a) Fe-Oh2 and (12k) Fe-Oh3 sites and only minor amounts is found on the (4f1) Fe-Oh1 octahedral sites. The structural observations corroborate the magnetic properties, demonstrating a correlation between the structure and magnetic properties in Ca–Al–Cr substituted strontium hexaferrite. The role of the particle size to maximize the coercivity properties is discussed.

Manipulation of hole and band for thermoelectric enhancements in SrCd2Sb2 Zintl compound

Exploration of novel thermoelectric materials is of great significance for thermoelectric development. AB2X2 Zintl compounds with rich chemical constitute, have been frequently demonstrated as promising thermoelectric materials because of their low lattice thermal conductivity and tunable band structure. This motivates the current work to focus on the experimental evaluation of thermoelectric potential on SrCd2Sb2, a new member of Zintl compounds. Na-substitution at Sr site leads to an effective increase in Hall carrier concentration from ~ 2.6 × 1018 to ~ 1.1 × 1020 cm−3, enabling a well estimation of transport properties by a single parabolic band (SPB) model with acoustic scattering. This reveals a multi-band transporting behavior in SrCd2Sb2 thermoelectrics with heavy-doping or elevated-temperature, ensuring a 150%-improvement in thermoelectric figure of merit (zT). On the basis of model, a peak zT of ~ 1.4 is achievable by minimizing lattice thermal conductivity, which not only demonstrates this compound as a promising thermoelectric material, but also provides a guidance for further advancements.

Rapid Synthesis of Red‐Emitting Sr2Sc0.5Ga1.5O5:Eu2+ Phosphors and the Tunable Photoluminescence Via Sr/Ba Substitution

AbstractDiscovering new Eu2+‐doped red‐emitting phosphors in oxide‐based materials is a challenge for white light‐emitting diode (WLED) applications. Herein, a highly efficient high‐frequency induction heating method is employed to rapidly prepare the red‐emitting Sr2Sc0.5Ga1.5O5:Eu2+ phosphors peaking at 614 nm and exhibiting a high photoluminescence quantum yield of 78.4% under the excitation of 440 nm. The structural and spectral analyses suggest that Eu2+ ions tend to enter the [Sc1/Ga1O6] and [Ga2O6] polyhedrons with small coordination numbers, leading to the broadband red emission originated from large crystal field splitting of Eu2+ 5d level. The chemical substitution of Ba in the Sr site enhances the thermal stability and helps to the photoluminescence tuning from 614 to 728 nm in SrBaSc0.5Ga1.5O5:Eu2+. The WLED device fabricated by blending the red Sr1.7Ba0.3Sc0.5Ga1.5O5:Eu2+ and yellow Y3(Al, Ga)5O12:Ce3+ phosphors shows a high color‐rendering index (Ra = 91.1), and low color‐correlated temperature (CCT = 4750 K). This study aims to provide a new synthesis method and design principle for guiding the development of Eu2+‐doped oxide‐based red phosphors with low preparation cost; moreover, the photoluminescence tuning strategy via cation substitutions is essential to achieve tunable emission, even the near‐infrared luminescence.

Full-color emitting crystal engineered Sr3Al1−xSixO4+xF1−x: Eu2+/3+ oxyfluorides for developing bendable lighting composites

A series of full-color emitting Eu2+/Eu3+-coexisted Sr2.9Al1−xSixO4+xF1−x: 0.1Eu2+/3+ (SASixOF: Eu2+/3+) oxyfluorides were synthesized by annealing the solid precursors in oxygen-deficient atmosphere. The structural changes in Sr3AlO4F (SAOF) owing to the Si4+ ions’ doping were visualized from the Rietveld refinement analysis. The substitution of Si4+ ions in Al sites contracted the AlO4 tetrahedra and could enlarge the Sr sites, and enabled the suitable occupation of Eu2+ ions in the Sr1 sites. Eventually, the X-ray photoelectron spectroscopy studies confirmed the valence conversion of europium ions from its trivalent to the divalent state owing to the Si4+ ions doping in SAOF: Eu2+/3+. Photoluminescence studies of SASixOF: Eu2+/3+ showed a bluish emission band at 482 nm for the 4f-5d transition of Eu2+ ions along with several sharp peaks above 550 nm owing to the intra f-f transition of Eu3+ ions. Increasing the Si4+ ions’ concentration subsequently, enhanced the Eu3+ to Eu2+ conversion rate decreased their emission intensity ratio, owing to which the emission color chromaticity was also tuned from orange-red (CIE: 0.48, 0.29) to nearly white (CIE: 0.30, 0.26) and eventually to the bluish region (CIE: 0.18, 0.23). The nearly white light-emitting composition SASi0.03OF: Eu2+/3+ and the intense bluish light-emitting optimum SASi0.06OF: Eu2+/3+ phosphors were further chosen for fabricating flexible composites based on phosphor and castor oil (CO). At 150 °C, the composite showed almost double emission than the phosphor powders owing to the thermal encapsulation of the powders provided by the CO matrix. The obtained composite started to degrade at a temperature as high as 300 °C. Therefore, the composite made with near white emitting SASi0.03OF: Eu2+/3+ phosphor was integrated with a 372 near UV-LED which showed intense cool white emission with the CIE of (0.29, 0.33), CCT of 7562 K, and CRI of 89. The above studies broadly suggested the adaptability of the obtained composites for flexible lighting applications.

Photocatalytic and photoelectrocatalytic properties of Eu(III)-doped perovskite SrTiO3 nanoparticles with dopant level approaches

Eu(III) ion dopant exhibits unique luminescence depending on the local dopant environment in a host matrix. In the present study, Eu(III)-doped strontium titanate (SrTiO3) nanoparticles were synthesized and their catalytic activities were demonstrated to examine the roles of dopants in photocatalytic CO2 reduction, photocatalytic organic pollutant degradation and photoelectrocatalytic oxygen evolution reaction. The fundamental properties were characterized by X-ray diffraction crystallography, scanning electron microscopy, high resolution transmission electron microscopy, UV–visible absorption, Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). CO2 reduction products were observed to be mainly methanol, CO and CH4 with minor C2 compounds. Photocatalytic dye degradation showed the order of methyl orange < rhodamine B < methylene blue. The catalytic performances were found to be dependent on the Eu doping levels. Photoelectrocatalytic activities were tested by linear sweep voltammetry under 395 nm light which corresponds to the direct 5L6 ← 7F0 transition of Eu(III). Consequently, undoped SrTiO3 showed the highest enhancement in current density. Eu(III) ion was appeared to be initially doped in Sr(II) site confirmed by photoluminescence and XPS profiles. Ti(IV) oxidation state was also impacted by Eu(III) doping. The various tests demonstrated that Eu(III)-dopant could be a very useful probe for the elucidation of local environmental site and the dopant-role on catalytic activities.