Tuning lithium-peroxide formation and decomposition routes with single-atom catalysts for lithium-oxygen batteries.

Lithium-oxygen batteries with ultrahigh energy density have received considerable attention as of the future energy storage technologies. The development of effective electrocatalysts and a corresponding working mechanism during cycling are critically important for lithium-oxygen batteries. Here, a single cobalt atom electrocatalyst is synthesized for lithium-oxygen batteries by a polymer encapsulation strategy. The isolated moieties of single atom catalysts can effectively regulate the distribution of active sites to form micrometre-sized flower-like lithium peroxide and promote the decomposition of lithium peroxide by a one-electron pathway. The battery with single cobalt atoms can operate with high round-trip efficiency (86.2%) and long-term stability (218 days), which is superior to a commercial 5 wt% platinum/carbon catalyst. We reveal that the synergy between a single atom and the support endows the catalyst with excellent stability and durability. The promising results provide insights into the design of highly efficient catalysts for lithium-oxygen batteries and greatly expand the scope of future investigation.

Realizing Formation and Decomposition of Li2O2 on Its Own Surface with a Highly Dispersed Catalyst for High Round-Trip Efficiency Li-O2 Batteries.

The rapid and effective formation and decomposition of Li2O2 during cycling is crucial to solve the problems associated with the practical limitation of lithium-oxygen (Li-O2) batteries. In this work, a highly dispersed electrocatalyst with Ru nanoclusters inside the special organic molecular cage (RuNCs@RCC3) through a reverse double-solvent method for Li-O2 batteries has been proposed for the first time. This RuNCs@RCC3 shows an effective catalyst enabling reversible formation and decomposition of the Li2O2 at the interface between the Li2O2 and the liquid electrolyte, rather than the sluggish solid-solid interface reactions on commonly used solid catalysts. As a result, the Li-O2 cells with RuNCs@RCC3 show enhanced electrochemical performance, including low overpotential (310 mV at a current density of 100 mA g-1), high specific capacity (15,068 mAh g-1), good rate capability (1,800 mAh g-1 at a current density of 2.8 A g-1), and especially superior cycle stability up to 470 cycles.

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.

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.

Geniposide inhibits airway inflammation and hyperresponsiveness in a mouse model of asthma.

Our group recently reported the strong anti-inflammatory effects of geniposide (Gen), a bioactive iridoid glucoside derived from gardenia jasminoides, in a mouse acute lung injury model. Herein, we hypothesized that Gen might also have potential therapeutic benefits in treatment of asthma, which was tested in a mouse model of ovalbumin (Ova)-induced allergic airway inflammation. Ova-sensitized and -challenged BALB/c mice, as compared with control animals, displayed airway hyperresponsiveness (AHR), bronchoalveolar lavage eosinophilia, mucus hypersecretion, and increased T help 2 (Th2)-associated cytokine and chemokine amounts, as well as serum Ova-specific immunoglobulin E (IgE) level. Being compared with the Ova-induced hallmarks of asthma, intraperitoneal Gen treatment prevented eosinophilic pulmonary infiltration, attenuated the increases in interleukin (IL)-4, IL-5, and IL-13, and reduced eotaxin and vascular cell adhesion molecule 1 (VCAM-1) expression. Also, Gen significantly ameliorated the Ova-driven airway hyperresponsiveness, mucus hypersecretion, and allergen-specific IgE level, which are the cardinal pathophysiological symptoms in allergic airway diseases. In addition, the efficacy of Gen was comparable to that of dexamethasone (Dex), a currently available anti-asthmatic drug. Collectively, our findings reveal that the development of immunoregulatory strategies based on Gen may be considered as an effective adjuvant therapy for allergic asthma.

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.