Search

Currently, hunting for anti-temperature-degradation high-efficiency phosphors has become crucially significant for fabricating high-brightness phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, we show that photoluminescence in a kind of full-solution-processed K2SiF6:Mn4+ red phosphor exhibits an extraordinarily large negative thermal quenching property. For instance, under the excitation of 477 nm laser light, the sample photoluminescence intensity amazingly increases by 347-fold when the temperature is increased from 4 to 477 K. The temperature-driven transition probability enhancement of the phonon-induced luminescence around Mn4+ ions in the phosphor is argued to be responsible for the large negative-thermal-quenching phenomenon. We also demonstrate a pc-WLED with R a of 82 and correlated color temperature of 2701 K by using the K2SiF6:Mn4+ red phosphor + commercial yellow phosphor of YAG:Ce3+.

With increasing environmental pollution, the utilization of green techniques, such as photocatalysis, is required to degrade harmful sources without secondary pollution. In this study, we synthesized an efficient photocatalyst, i.e., a h-BN/BiPO4 heterostructure modified by Ag nanoparticles at the interface (Ag/BN/BPO) by photodeposition and a hydrothermal method, and investigated photocatalytic degradation performance for rhodamine B dye (RhB). It was found that 95% of RhB was removed by Ag/BN/BPO (optimal ratio) after 60 min of light exposure. Compared to BiPO4 and BN/BiPO4, the removal efficiency was improved by 50 and 30%, respectively. The high photocatalytic degradation activity of Ag/BN/BPO could be possibly attributed to the synergistic effect of the improved separation efficiency of electron–hole pairs by the special heterostructure design and the increased adsorption capacity due to the large specific surface area of the layered h-BN. This study provided a possible route for the development of highly efficient photocatalysts for the degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

In this study, we investigated the fundamental properties of the MgCl2 monolayer via first-principles calculations. Its stability was confirmed by the formation energy, phonon dispersion, ab initio molecular dynamics simulations and elastic constant calculations. The MgCl2 monolayer exhibits insulating characteristics with a wide direct band gap of 5.90 eV. Its band gap can be modulated flexibly in a large range by applied strain and layer control and a direct–indirect band gap transition can be obtained. The band gaps of MgCl2 nanoribbons along the y direction increase slightly with increasing ribbon width and are no more than 5.50 eV. But Eg oscillates along the x direction in a large range from 5.02 eV to 5.98 eV. The MgCl2 nanoribbons have direct or indirect band gaps, relying on the cutting direction and the resulting edge configuration. Its absorption coefficient is extremely high in the ultraviolet region. The wide band gap, large dielectric constant and weak interfacial interaction with graphene endow the MgCl2 monolayer as a promising substrate or dielectric material for nanodevices in sensing and catalytic applications. [ABSTRACT FROM AUTHOR]

Native point defects in ZnO are so complicated that most of them are still debating issues, although they have been studied for decades. In this paper, we experimentally reveal two sub-components usually hidden in the low energy tail of the main broad green luminescence band peaking at 547 nm (~2.267 eV) in intentionally undoped ZnO single crystal by selecting the below-band-gap (BBG) optical excitations (e.g. light wavelengths of 385 nm and 450 nm). Moreover, both sub-components are manifested as long persistent phosphorescence once the BBG excitations are removed. With the aid of a newly developed model, the energy depths of two electron traps involved within the long lived orange luminescence are determined to be 44 meV and 300 meV, respectively. The candidates of these two electron traps are argued to be most likely hydrogen and zinc interstitials in ZnO.

By using the particle swarm optimization algorithm combined with first-principles methods, we report the prediction of a stable structure of two-dimensional (2D) boron monolayer (δ5 sheet) with P6/M space group and 6 atoms in the unit cell that can be grown on a Ni (111) surface. The metallic nature of the δ5 sheet is proved by the calculated band structure and density of states. Its dynamical and thermal stabilities are confirmed by the phonon spectrum and ab initio molecular dynamics simulation. We find that the Ni substrate stabilizes the δ5 sheet by the electron transfer between them and chemical hybridization at the B-Ni interface. The properties of both δ5 sheet and MoS2 monolayer are preserved in the combined heterostructure, indicating that the δ5 sheet can be used as an electrode material for future nanodevices. [ABSTRACT FROM AUTHOR]

Adipose tissue is a primary site for lipid storage containing trace amounts of glycogen. However, refeeding after a prolonged partial fast produces a marked transient spike in adipose glycogen, which dissipates in coordination with the initiation of lipid resynthesis. To further study the potential interplay between glycogen and lipid metabolism in adipose tissue, the aP2-PTG transgenic mouse line was utilized since it contains a 100- to 400-fold elevation of adipocyte glycogen levels that are mobilized upon fasting. To determine the fate of the released glucose 1-phosphate, a series of metabolic measurements were made. Basal and isoproterenol-stimulated lactate production in vitro was significantly increased in adipose tissue from transgenic animals. In parallel, basal and isoproterenol-induced release of nonesterified fatty acids (NEFAs) was significantly reduced in transgenic adipose tissue vs. control. Interestingly, glycerol release was unchanged between the genotypes, suggesting that enhanced triglyceride resynthesis was occurring in the transgenic tissue. Qualitatively similar results for NEFA and glycerol levels between wild-type and transgenic animals were obtained in vivo during fasting. Additionally, the physiological upregulation of the phosphoenolpyruvate carboxykinase cytosolic isoform (PEPCK-C) expression in adipose upon fasting was significantly blunted in transgenic mice. No changes in whole body metabolism were detected through indirect calorimetry. Yet weight loss following a weight gain/loss protocol was significantly impeded in the transgenic animals, indicating a further impairment in triglyceride mobilization. Cumulatively, these results support the notion that the adipocyte possesses a set point for glycogen, which is altered in response to nutritional cues, enabling the coordination of adipose glycogen turnover with lipid metabolism. glycogenolysis; fasting; lipolysis; protein phosphatase-1 doi: 10.1152/ajpendo.00741.2009.

Recent studies have established that vitamin D plays multiple biological roles beyond calcium metabolism; however, whether vitamin D is involved in energy metabolism is unknown. To address this question, we characterized the metabolic phenotypes of vitamin D receptor (VDR)-null mutant mice. Under a normocalcemic condition, VDR-null mice displayed less body fat mass and lower plasma triglyceride and cholesterol levels compared with wild-type (WT) mice; when placed on a high-fat diet, VDR-null mice showed a slower growth rate and accumulated less fat mass globally than WT mice, even though their food intake and intestinal lipid transport capacity were the same as WT mice. Consistent with the lower adipose mass, plasma leptin levels were lower and white adipocytes were histologically smaller in VDR-null mice than WT mice. The rate of fatty acid [beta]-oxidation in the white adipose tissue was higher, and the expression of uncoupling protein (UCP) 1, UCP2 and UCP3 was markedly upregulated in VDR-null mice, suggesting a higher energy expenditure in the mutant mice. Experiments using primary brown fat culture confirmed that 1,25-dihydroxyvitamin [D.sub.3] directly suppressed the expression of the UCPs. Consistently, the energy expenditure, oxygen consumption, and C[O.sub.2] production in VDR-null mice were markedly higher than in WT mice. These data indicate that vitamin D is involved in energy metabolism and adipocyte biology in vivo in part through regulation of [beta]-oxidation and UCP expression. adipocytes; uncoupling proteins; energy metabolism