3D Metallic Ti@Ni0.85 Se with Triple Hierarchy as High-Efficiency Electrocatalyst for Overall Water Splitting.

In this study, Ti@Ni0.85 Se electrodes with a triple hierarchy architecture were designed, and their applications in electrocatalytic water splitting were studied. The 3D electrode is comprised of three types of structures including the bottom square Ti mesh structure as the conductive substrate, a vertical and uniform Ni0.85 Se nanosheet arrays structure in the intermediate section, and the topmost Ni0.85 Se flower structure. This triple hierarchy architecture is binder-free, conductive, and has a particular feature of enlarged surface areas, exposing more active sites, promoting mass- and charge-transfer, and accelerating dissipation of gases generated during water electrolysis. Moreover, DFT calculations confirmed that the Ni0.85 Se possesses metallic character, which further promotes the charge transfer of the electrocatalyst. Benefiting from this special structure and metallic character, the electrode displays a superior activity of 10 mA cm-2 at 120 mV hydrogen evolution reaction overpotential and 30 mA cm-2 at 270 mV oxygen evolution reaction overpotential. By using this electrode as a bifunctional electrocatalyst, an alkali electrolyzer affords a water splitting current of 10 mA cm-2 at a cell voltage of 1.66 V.

Two-step synthesis of hole structure bastnasite (RECO3F RE = Ce, La, Pr, Nd) sub-microcrystals with tunable luminescence properties.

A two-step synthetic route using RE(OH)CO3 colloid spheres as the sacrificial template was designed to prepare monodisperse, pure bastnasite (RECO3F: RE = Ce, La, Pr, Nd) with a hole structure for the first time. A variety of morphologies, including jujube core-like, stacked nanoblocks, and stacked nanosheets were obtained through changing the ratio of reactants. The phase, structure, shapes, and photoluminescence properties of samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The CeCO3F:Ln3+ (Ln = Tb, Eu, Dy) phosphors give green, yellow and blue emission, respectively, due to the f-f transitions of Ln3+ ions. Furthermore, the energy transfer from Ce3+ to Dy3+ and Tb3+ was described in detail.

A novel color-tunable phosphor, Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) sub-microcrystals: structure, luminescence and energy transfer properties.

Ln3+-Doped fluorides are economical and highly efficient luminescent materials, which play a crucial role in LEDs, biolabeling, and sensors. Therefore, Na5Gd9F32:Ln3+ sub-microspheres with tunable multicolor emissions were successfully synthesized via a simple water bath method employing colloidal Gd(OH)CO3 spheres as precursors. Samples were characterized by XRD, SEM, TEM, EDS and PL. It was found that the hydrolysis of BF4- ions had a dynamic effect on the retention of the morphology of the product owing to the mild reaction environment caused by the low hydrolysis rate of BF4- ions. Upon excitation by ultraviolet light, the Na5Gd9F32:Ln3+ (Ln = Eu, Tb, Dy, Sm, Ho) phosphors underwent characteristic f-f transitions and gave rise to red, green, green, yellow, and pale green emissions, respectively. Moreover, various emission colors could be obtained by using different excitation wavelengths and adjusting the Eu3+/Tb3+ molar ratio owing to energy transfer between Tb3+ and Eu3+ ions in the Na5Gd9F32 host. The energy transfer mechanism was demonstrated to be a dipole-dipole interaction. The multicolor luminescent phosphors with a certain dopant concentration based on a single host and excitation wavelength may have potential applications in the field of lighting displays.

Facile synthesis and color-tunable properties of monodisperse ß-NaYF4:Ln3+ (Ln = Eu, Tb, Tm, Sm, Ho) microtubes.

In this study, monodisperse and uniform ß-NaYF4 hexagonal microtubes were successfully synthesized via a simple hydrothermal method without any organic surfactants, employing Y(OH)CO3 colloid spheres as precursors. The possible formation mechanism was studied on the basis of a series of time-dependent control experiments and its intrinsic crystal structure. The integrated emission intensity of ß-NaYF4:0.05Tb3+ is almost 1.78 times stronger than that of α-NaYF4:0.05Tb3+. In addition, the photoluminescence properties of ß-NaYF4:Ln3+ (Ln = Eu, Tb, Tm, Sm, Ho) were studied in detail, and it was found that the photoluminescence color of ß-NaYF4:0.03Tm3+ phosphor was close to the standard blue light (0.14, 0.08). Moreover, by co-doping the Tb3+ and Eu3+ ions into the ß-NaYF4 host, multicolor tunable emissions were obtained due to the efficient energy transfer from Tb3+ to Eu3+ at 368 nm excitation. These merits demonstrate that this material may find potential application in color display fields.

Surface oxygen vacancy induced solar light activity enhancement of a CdWO4/Bi2O2CO3 core-shell heterostructure photocatalyst.

A CdWO4/Bi2O2CO3 core-shell heterostructure photocatalyst was fabricated via a facile two-step hydrothermal process. Flower-like Bi2O2CO3 was synthesized and functioned as the cores on which CdWO4 nanorods were coated as the shells. Photoluminescence (PL) spectra and electron paramagnetic resonance (EPR) demonstrate that the CdWO4/Bi2O2CO3 core-shell heterostructure photocatalyst possesses a large amount of oxygen vacancies, which induce defect levels in the band gap and help to broaden light absorption. The photocatalyst exhibits enhanced photocatalytic activity for Rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and colorless contaminant phenol degradation under solar light irradiation. The heterostructured CdWO4/Bi2O2CO3 core-shell photocatalyst shows drastically enhanced photocatalytic properties compared to the pure CdWO4 and Bi2O2CO3. This remarkable enhancement is attributed to the following three factors: (1) the presence of oxygen vacancies induces defect levels in the band gap and increases the visible light absorption; (2) intimate interfacial interactions derived from the core-shell heterostructure; and (3) the formation of the n-n junction between the CdWO4 and Bi2O2CO3. The mechanism is further explored by analyzing its heterostructure and determining the role of active radicals. The construction of high-performance photocatalysts with oxygen vacancies and core-shell heterostructures has great potential for degradation of refractory contaminants in water with solar light irradiation.

Morphology-controllable synthesis of LaOF:Ln(3+) (Ln=Eu, Tb) crystals with multicolor luminescence properties.

In this paper, well defined LaOF crystals with multiform morphologies were first prepared via the urea-based precipitation method followed by a heat treatment. The morphologies of the LaOF samples, including nanospheres and nanorods, can be easily modulated by changing the fluorine sources. XRD, FT-IR, SEM, TEM, and emission spectra were used to characterize the prepared samples. Under ultraviolet excitation, the LaOF:Ln(3+) nanospheres display the characteristic f-f transitions of Ln(3+) (Ln=Eu, Tb) ions and give bright red, and green emissions, respectively. Furthermore, by codoping the Tb(3+) and Eu(3+) ions into LaOF host and varying the doping concentration of the Eu(3+) ions, multicolor tunable emissions have been obtained under the irradiation of 379nm. These results show this material may have potential applications in field-emission displays.

A novel synthetic route towards monodisperse LaOF:Ln³âº (Ln = Eu, Tb) hollow spheres with multicolor luminescence properties.

In this study, monodisperse and uniform LaOF hollow spheres were successfully synthesized through a novel facile synthetic route employing a La(OH)CO3 sphere as a sacrificial template followed by a subsequent calcination process. The structure, morphology, formation process, and luminescence properties were well investigated using various techniques. The possible formation mechanism of evolution from the La(OH)CO3 spheres to the LaCO3F precursor, and to the final LaOF hollow spheres can be attributed to the Kirkendall effect and the decomposition of the LaCO3F precursor. Under ultraviolet excitation, the LaOF:Ln(3+) (Ln = Eu,Tb) hollow spheres show their characteristic f-f emissions and exhibit red, green emissions, respectively. Moreover, by codoping the Tb(3+) and Eu(3+) ions into the LaOF host and tuning their relative concentration ratio, multicolor tunable emissions are obtained due to the efficient energy transfer from Tb(3+) to Eu(3+) at 378 nm excitation. This material may find potential application in color display fields.

Highly bright multicolour emission through energy migration in core/shell nanotubes.

This paper describes a simple and environmentally-friendly approach that allowed for the facile synthesis of a gadolinium-based core/shell/shell nanotube structure with a set of lanthanide ions incorporated into separated layers. In addition, by the rational design of a core/shell structure we systematically investigated the luminescence properties of different lanthanide ions in NaGdF4 host, and efficient down-conversion emission can be realized through gadolinium sublattice-mediated energy migration. The Gd(3+) ions play an intermediate role in this process. By changing the doped lanthanide ions, we generated multicolour emissions from the luminescent Ln(3+) centers via energy transfer of Ce(3+)→Gd(3+)→Ln(3+) and Ce(3+)→Ln(3+) (Ln = Eu, Tb, Dy and Sm) in separated layers. Due to the strong absorption of ultraviolet (UV) irradiation by Ce(3+) ions, the luminescence efficiency could be enhanced after doping Ce(3+) ions in the shell. In NaGdF4:5% Eu(3+)@NaGdF4@NaGdF4:5% Ce(3+) core/shell/shell nanotubes, with increasing the NaGdF4 interlayer thickness, a gradual decrease in emission intensity was observed for the Eu(3+) activator.

Size-tailored synthesis and luminescent properties of three-dimensional BaMoO4 , BaMoO4 :Eu(3+) micron-octahedrons and micron-flowers via sonochemical route.

Almost monodisperse three-dimensional (3D) BaMoO4, BaMoO4 :Eu(3+) micron-octahedrons and micron-flowers were successfully prepared via a large-scale and facile sonochemical route without using any catalysts or templates. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersion X-ray (EDS), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy were employed to characterize the as-obtained products. It was found that size modulation could be easily realized by changing the concentrations of reactants and the pH value of precursors. The formation mechanism for micron-octahedrons and micron-flowers was proposed on the basis of time-dependent experiments. Using excitation wavelengths of 396 or 466 nm for BaMoO4 :Eu(3+) phosphors, an intense emission line at 614 nm was observed. These phosphors might be promising components with possible application in the fields of near UV- and blue-excited white light-emitting diodes. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating the properties of molybdate materials.

Self-assembled 3D sphere-like SrMoO4 and SrMoO4:Ln3+ (Ln=Eu, Sm, Tb, Dy) microarchitectures: facile sonochemical synthesis and optical properties.

Three-dimensional (3D) well-defined SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures of obvious sphere-like shape have been successfully synthesized using a large-scale and facile sonochemical route without using any catalysts or templates. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of SrMoO4 and external factor, namely the ultrasonic time and the pH value, are responsible for the ultimate shape evolutions of the product. The possible formation mechanism for the product is presented. Additionally, the PL properties of SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures were investigated in detail. The Ln(3+) ions doped SrMoO4 samples exhibit respective bright red-orange, yellow, green and white light of Eu(3+), Sm(3+), Tb(3+) and Dy(3+) under ultraviolet excitation, and have potential application in the field of color display. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating about the properties of molybdate materials.

Photoluminescence properties and energy transfer in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8) phosphors for potential application in ultraviolet white light-emitting diodes.

Sr(3) MgSi(2) O(8) :Ce(3+) , Dy(3+) phosphors were prepared by a solid-state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce(3+) ions (403 nm) but also as a band due to Dy(3+) ions (480, 575 nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8)phosphors, and the co-doping of Ce(3+) could enhance the emission intensity of Dy(3+) to a certain extent by transferring its energy to Dy(3+) . The Ce(3+) /Dy(3+) energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94 MgSi2 O8 :0.01Ce(3+) , 0.05Dy(3+) phosphors, the fluorescence lifetime of Dy(3+) (from 3.35 to 27.59 ns) is increased whereas that of Ce(3+) is greatly decreased (from 43.59 to 13.55 ns), and this provides indirect evidence of the Ce(3+) to Dy(3+) energy transfer. The varied emitted color of Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) phosphors from blue to white were achieved by altering the concentration ratio of Ce(3+) and Dy(3+) . These results indicate Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) may be as a candidate phosphor for white light-emitting diodes.

New secoiridoid glycosides from the roots of Picrorhiza scrophulariiflora.

Three new secoiridoid glycosides, named picrogentiosides A (1), B (2) and C (3), have been isolated from the underground parts of Picrorhiza Scrophulariiflora, together with the two known compounds plantamajoside (4) and plantainoside D (5). Their structures were established by spectroscopic analyses and comparisons with data from related compounds. A pilot pharmacological study showed that picrogentiosides A (1) and B (2) have an immunomodulatory effect in vitro.