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A series of single-phased Na 2 Ba 5.99- x (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ , x Mg 2+ and Na 2 Ba 5.99- y (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ , y Zn 2+ phosphors have been successfully prepared via the solid-state reaction. Structural refinement, luminescence property, color tuning and thermally stability were systematically investigated. The as-prepared Na 2 Ba 6 (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ phosphor showed broad excitation bands from 250 nm to 450 nm and presented wide emission bands under 365 nm excitation, which could be decomposed by Gaussian fitting into three peaks corresponding to different Eu luminous centers named Eu1, Eu2 and Eu3. By substituting Mg 2+ or Zn 2+ for Ba 2+ , the relative intensities of Eu1, Eu2 and Eu3 emission bands changed gradually. Combined with the variation tendencies of Ba O bond lengths by Rietveld refinement, the possible mechanism of the luminescence transformation of Eu 2+ ion was the preferential occupancy of Eu 2+ at different crystallographic sites. In addition, the introduction of Mg 2+ ion expressed more obvious improvement on the thermal quenching behaviors of Eu 2+ than Zn 2+ ion in this matrix. The emission intensities of Eu2 and Eu3 could be enhanced from 63.2% to 82.7% and 35.1%–46.8% at 373 K compared to the initial intensity when Mg 2+ concentration was 0.10. Generally, this work sheds some new lights on the design and structure explanation of preferential occupancy at different crystallographic sites in phosphors. [ABSTRACT FROM AUTHOR]

Monodisperse mono-concave microsphere/microflower/nanosheet GdBO 3 :Eu 3+ samples have been successfully synthesized via hydrothermal method using Gd 0.99 Eu 0.01 (OH) 3 nanorods as sacrificial precursors. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field scanning electron microscopy (FE-SEM) and fluorescence spectrometry were used to characterize the samples. The shape of these as-prepared GdBO 3 :Eu 3+ architectures can be tuned effectively by controlling the concentrations of NaOH (C NaOH ) of the precursor solution and the amounts of PEG (20000) surfactant. As a typical morphology, the possible formation mechanism for GdBO 3 :Eu 3+ monodisperse mono-concave microsphere was presented in detail. Under ultraviolet excitation, the as-obtained GdBO 3 :Eu 3+ samples showed strong characteristic orange and red emission of Eu 3+ . Compared with samples get by solid state reaction, the samples obtained by hydrothermal method possess higher red/orange (R/O) ratio attributed to 5 D 0 − 7 F 1 and 5 D 0 − 7 F 2 transitions. The influence of diversity morphology on the R/O ratio and emission intensity has been also investigated. This work sheds some light on the design of a well-defined complex structure, and the luminescent properties have potential applications in fluorescent lamps and field emission displays. [ABSTRACT FROM AUTHOR]

High-efficiency and thermal stability are two important factors of ideal microwave absorption materials (MAMs), which are becoming desired because of the more complex modern service environment. Herein, a novel quaternary magnetic core-shell-shell structure FeCo-Co@Fe 3 O 4 @SiO 2 (FCSF) has been fabricated by a facile and generic route. In this structure, the incipient oxidation temperature of magnetic core can be greatly increased from 523 K to 773 K by the Fe 3 O 4 /SiO 2 double shells, and the multiple magnetic heterointerfaces can generate electron transfer and spin-orbit interaction based on DFT calculations. The minimum reflection loss (RL min) and efficient absorption band (RL<−10 dB, f eff) of FCSF composites can reach up to −42.8 dB and 7.3 GHz with the thickness of 2 mm, due to the emerged electromagnetic loss mechanisms of interface polarization and exchange resonance. Moreover, owing to the optimized impedance matching and enhanced electromagnetic loss at elevated temperature, the RL min values of FCSF at 673 K and 773 K increase by 15.4% and 41.2% compared with that at 298 K, respectively. The results demonstrate that the FCSF composite can act as a promising candidate for high-efficiency MAMs in thermal environment, and the synthetic strategy of heterostructures in this work can also be applied to design other MAM systems. • A quaternary magnetic heterostructures FeCo-Co@Fe 3 O 4 @SiO 2 was synthesized. • Charge transfer and orbital interaction in magnetic heterointerface were verified. • The RL min and f eff of FCSF are −42.8 dB and 7.3 GHz at the thickness of 2 mm. • The RL min of FCSF at 773 K increase by 41.2% compared with that at 298 K. • The component and heterostructures cause the high-efficiency and thermal stable. [ABSTRACT FROM AUTHOR]

Color-tunable and white-emitting Pr3+ and Tb3+ co-doped La 2 Ti 2 O 7 phosphors were prepared via a molten salt method. The as-synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflection spectra (DRS), photoluminescence spectra (PL), fluorescence decay curves and temperature-dependent photoluminescence spectra in detail. The La 2 Ti 2 O 7 :Pr3+, Tb3+ phosphors are uniform square-like nanobelt and the band gap of La 2 Ti 2 O 7 host is calculated to be 3.83 eV by DRS. Under 296 nm wavelength UV excitation, the La 2 Ti 2 O 7 :Pr3+ compounds show strong red emission with peaking at 612 nm. Four typical emission lines of Tb3+ ions are observed from the region of 480–650 nm in La 2 Ti 2 O 7 :Tb3+ phosphors, and the strongest green emission peak is located at 545 nm. What's more, the emission color of La 2 Ti 2 O 7 :0.001Pr3+, 0.010 Tb3+ can be tuned from white (0.3274, 0.3379) to pink (0.4777, 0.2890) upon the excitation from 290 to 348 nm and the emission color of La 2 Ti 2 O 7 :0.001Pr3+, x Tb3+ can be also tuned from white to green by changing the concentration of Tb3+. The La 2 Ti 2 O 7 :Pr3+, Tb3+ phosphors have the poor temperature dependence, resulting from the value of Δ R (the displacement between parabolas of the intervalence charge transfer states and ground states) for Tb3+ and Pr3+ both are larger. The results indicate that La 2 Ti 2 O 7 :Pr3+, Tb3+ phosphors could be a promising tunable and white light emission phosphor. Image 1 • The La 2 Ti 2 O 7 : Pr3+/Tb3+ nanostrips were successfully prepared by molten salt method. • Multi-color luminescence evolution was achieved. • A new single-phased white light emission was realized through Pr3+/Tb3+-codoping. [ABSTRACT FROM AUTHOR]

Abstract Exploring the process of structure evolution and mechanism of controllable luminescence in the solid solution phosphors is meaningful but still challenging. Herein, new solid solution phosphors of Ca 9 Al 1- x Y x (PO 4) 7 :Eu2+ were selected as examples to address the challenging via the construction of bi-directional relationships between structure evolution and photoluminescence property. In Ca 9 Al 1- x Y x (PO 4) 7 , the structure evolution caused the redistribution of Eu2+ in the multiple cationic sites, accompanied by the changes of emission color from blue (0.1828, 0.1192) to cyan (0.1723, 0.3305), which were investigated by Gaussian fitting, decay time, and bond energy theory. Conversely, the Gaussian fitting peaks displayed different blue or red shifts in the process of structure evolution, which could reversely reflect the specific changes of bond lengths in each cationic site and were helpful for exhaustive understanding the process of structure evolution in Ca 9 Al 1- x Y x (PO 4) 7. Besides, the thermal stability behaviors of Ca 8.95 Al 1- x Y x (PO 4) 7 :0.05Eu2+ exhibited that the decline rate of low energy bands were faster than that of high energy bands due to the thermally active phonon-assisted effect. The constructed bi-directional relationships pave a feasible way to investigate the variations of structure evolution and emission properties, which will be helpful for the design of new kinds of phosphors. Graphical abstract Image 1 Highlights • Bi-directional relationships between structure evolution and luminescence were built. • The structure evolution caused the redistribution of Eu2+ in various cationic sites. • The delicate information of structure was analyzed by the shifts of emission peaks. • The changes of thermal stabilities were detected and analyzed. [ABSTRACT FROM AUTHOR]

Abstract Novel single-phased and emission-tunable layered Bi 4 Ti 3 O 12 :Pr3+ nanosheets have been successfully synthesized via molten salt method. The as-prepared samples were characterized by X-ray diffraction and scanning electron microscopy to investigate their crystalline phases and morphologies. Furthermore, we explored the photoluminescence properties of the Bi 4 Ti 3 O 12 :Pr3+ phosphors, while the cross-relaxation processes between 1D 2 , 3P 0 emitting states and the Pr3+–Ti4+ intervalence charge transfer state, color tuning and thermally stability were discussed in detail. Besides, the emission hue of Bi 4 Ti 3 O 12 :Pr3+ could be adjusted from white-light (0.3059, 0.2731) to yellow (0.5167, 0.4792) by tuning the excitation wavelength, in which the ratio of 3P 0 →3H 4 and 1D 2 →3H 4 was changed. In addition, the increases in temperatures led to the cooperative effects of thermal-quenching behavior and the cross-relaxation processes, thus resulting in the significant decrease of 3P 0 →3H 4 emission in comparison to the 1D 2 →3H 4 emission. The results suggested that the Bi 4 Ti 3 O 12 :Pr3+ is an effective color-tuning phosphor. Graphical abstract Image 1 Highlights • The regular sheet-like Bi 4 Ti 3 O 12 :Pr3+ phosphors were successfully prepared by molten salt method. • The phosphors show color tuning emissions form near white to yellow. • The thermal stability of the 1D 2 emission is obviously better than that of 3P 0. [ABSTRACT FROM AUTHOR]

Ferromagnetic metal/alloy particles are widely used in the field of electromagnetic wave absorption. Doping is an effective means of modulating the electromagnetic properties of magnetic metals and alloys. In this study, (Fe 3 Co 7) 1−x Ru x nanoparticles with different Ru doping contents are prepared using a polyvinylpyrrolidone (PVP)-assisted liquid-phase reduction process. First-principles calculations reveal that strong electron-orbit hybridization occurs between Ru-4 d and Fe/Co-3 d owing to the strong spin-orbit coupling effect of Ru-4 d orbital electrons. This generates a space charge distribution and carries a magnetic moment of 1.80 hbar/2. The use of Ru doping results in a reduction in FeCo alloy particle size from 1.5 µm to 200 nm, slight decrease in the saturation magnetization from 179 to 152 emu/g, and increase in the electrical conductivity from 2.79 × 10-4 to 6.62 × 10-4 S·cm-1. The dielectric and magnetic loss values vary from 0.22 to 0.95 and 0.06–0.37, respectively, in the 2–18 GHz frequency range. Ru doping-induced dipole polarization relaxation, exchange resonance, and increased conductivity loss are the primary reasons for the enhanced electromagnetic loss of the material. When the level of Ru doping x reaches 0.10, the minimum reflection loss (RL min) increases from − 21.5 to − 41.9 dB. Thus, (Fe 3 Co 7) 1−x Ru x is a promising material for electromagnetic loss due to its tunable composition, size, conductivity, magnetic properties, and excellent electromagnetic loss capability. • The doped Ru caused intense d - d electron interaction between Ru and Fe/Co atoms. • Electron transmission and enhanced magnetism within Ru/FeCo alloy have been proved. • The doping of Ru reduces the particle size of FeCo alloy from 1.5 µm to 200 nm. • The conductivity increased by 137 %, reaching the maximum of 6.62 × 10-4 S·cm-1. • The dielectric loss and magnetic loss increase from 0.22 to 0.95 and 0.06–0.37. [ABSTRACT FROM AUTHOR]

Flexible manipulations of morphology and composition have been considered as an art to achieve excellent microwave absorption performance for absorbers derived from metal-organic frameworks (MOFs). In this work, a strategy combining ligand-exchange induced hollow engineering and high-temperature one-step sulfuration has been proposed to fabricate the Co 9 S 8 /Co@N, S dual-doped carbon-based absorbers with tailored solid, yolk-shelled and entirely hollow polyhedral morphologies. The progressive hollow engineering not only enables composition control in the sulfuration process, but also endows the proposed absorbers with superior microwave absorption capacity due to the enhanced conductivity loss and Maxwell-Wagner polarization as well as optimized impedance matching. The yolk-shelled Co 9 S 8 /Co@N, S dual-doped carbon-based composite achieves a broad effective absorption bandwidth of 5.13 GHz at 1.88 mm with 20 wt% loading and realizes a minimum microwave loss of − 51.78 dB @ 11.63 GHz with 2.37 mm. This work reveals that the joint strategy of ligand-exchange induced hollow engineering and gas-solid reactive thermal process is an effective path to construct high-efficient lightweight multi-interfacial microwave absorbers for addressing the electromagnetic pollutions. [Display omitted] • Ligand-exchange etching facilitates tailored cavity structure in MOF-derived MAMs. • Progressive hollow engineering enables composition control in sulfuration process. • Proposed yolk-shelled absorber achieves an EAB of 5.13 GHz with 20 wt% filling. • Synergy of attenuation and impedance matching realizes superior EM absorption. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) BiOCl x Br 1- x ( x = 0–1) solid solutions nanostructures with compositional tunability were successfully synthesized via a one-step glycol-assisted hydrothermal process in the presence of cationic polyacrylamide (C-PAM) and cetyltrimethylammonium bromide (CTAB). The prepared samples displayed hierarchical flower-like microspheres with rich in specific surface area and appropriate pore size, providing suitable pathways for transportation and separation of photogenerated electrons and holes. The controllable ratio of Cl − and Br − led to the decrease in the optical bandgap, thus increasing the absorption of visible light range. The solid solutions delivered remarkable adsorption capacity and photocatalytic activity in comparison with pure BiOCl, BiOBr and P25 (TiO 2 nanoparticles) in the photodegradation of methyl orange (MO) aqueous solution under visible light irradiation, and the degradation rate reached the maximum at x = 0.5 and decreased gradually with x moving away from 0.5. The BiOCl 0.5 Br 0.5 sample displayed high photostability under repeated visible light irradiation, which is especially important for its practical application. Based on the above findings, the reasonable formation mechanism and the main active species of the samples were also discussed in detail. [ABSTRACT FROM AUTHOR]

In the present study, uniform foursquare BiOCl nanosheets with highly exposed {001} facets were facilely synthesized via a simple, fast and mild hydrothermal route using cationic polyacrylamide (C-PAM) as both chlorine source and surfactant. The as-prepared BiOCl samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) to investigate their crystalline phases, morphologies and composition. N 2 adsorption/desorption measurement was conducted to determine the surface area and pore volume of the samples while zeta potential was measured to investigate their surface properties. It was revealed that the experimental parameters such as reaction temperature, time and the amount of additives (e.g., sodium hydroxide, C-PAM and sodium citrate) played vital roles in the formation of BiOCl nanosheets. The band gap of the typical-synthesized BiOCl nanosheets was estimated to be 3.33 eV from the UV–Vis diffuse reflectance spectrum (DRS). The photoluminescence (PL) emission spectrum of the BiOCl nanosheets could be fitted to Gaussian distribution with three emission bands centered at 404.9, 447.6 and 530.6 nm, respectively. Photocatalytic experiments were carried out by degrading the organic dyemethyl orange (MO), indicating the high catalytic activity of the BiOCl samples. [ABSTRACT FROM AUTHOR]

Designing nanocomposite with multi-level interfaces is an effective approach to improving the microwave absorbing capability of materials. In this study, the urchin-like multiple core-shelled Co/CoS 2 @NC@MoS 2 composites (CCM) are designed and fabricated by high-temperature pyrolysis and solvothermal process, where the structure and phase composition are affected by the migration of Co. Abundant interfaces in the multiple core-shelled structures favor the polarization relaxation loss, defects of MoS 2 and nitrogen doping carbon (NC) matrix induce the dipole orientation polarization loss. The CCM composite exhibits excellent microwave absorption with the strongest reflection loss (RL) of − 43.9 dB. Meanwhile, the broadest effective absorption bandwidth (EAB, RL<−10 dB) is 4.4 GHz with a thickness of 1.5 mm. Besides, with the thickness of 1.0–3.5 mm, all peaks of RL min < −20 dB (99 % absorptivity). It is believed that this work can provide an effective strategy for the design of tunable multi-interface nanostructures to regulate microwave absorption. • The urchin-like multiple core-shelled Co/CoS 2 @NC@MoS 2 composites (CCM) are fabricated. • The reactivity of Co under the pyrolysis temperature could affect the structure and phase composition. • The intrinsic loss of CCM is dominated by the polarization relaxation loss. • The effective absorption bandwidth is 4.4 GHz with a thickness of 1.5 mm. [ABSTRACT FROM AUTHOR]