- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Fabrication of alkali metal sulfate–doped zinc tungstate and their photoluminescence
摘要： The enhancement of photoluminescence of alkali metal sulfate-doped zinc tungstate was investigated. All samples were prepared by solid-state reaction at 800 °C using ZnO, WO3, and alkali metal sulfates as starting powders. The zinc tungstate phase was confirmed from the samples by X-ray diffraction. The emission peak of the samples excited at 275 nm was observed at 465 nm. Rb2SO4 > K2SO4 > Cs2SO4 > undoped > Na2SO4 > Li2SO4 was the order of peak emission intensity of alkali metal sulfate-doped samples. Alkali metals with a large ionic radius (K, Rb, Cs) enhanced the emission of intrinsic luminescence in the blue wavelength region. Moreover, sulfates had the potential to change the luminescence activities of the samples.
关键词： Solid-state reaction,Alkali metal,Zinc tungstate,Sulfate,Photoluminescence
更新于2025-09-23 15:23:52
-
Electronic structure and hydrogen evolution reaction in layered ReS<sub>2</sub> regulated by alkali-metal atom intercalation
摘要： Recently, the atom intercalation method has been developed and applied into two-dimensional (2D) materials to regulate their pristine physical property. However, as an important application in hydrogen evolution reaction (HER), the influence of alkali-metal-intercalated technology upon 2D material's electronic structure and catalytic activity should be investigated systematically. In this work, layered ReS2 crystals with a charge decoupling are chosen as a model to explore changes in electronic structure and Gibbs free energies induced by alkali-metal intercalated compounds and external strain. The calculated results disclose that the structural transformation induced by intercalated alkali atom and external strain not only leads to decrease in band gap of ReS2 but also make Gibbs free energy of adsorbed hydrogen close to zero. Our calculations provide an insight to improve HER performance by a simple alkali-metal-intercalated technology.
关键词： hydrogen evolution reaction,electronic structure,alkali-metal-intercalated technology
更新于2025-09-23 15:22:29
-
Alkali Metal Ions: A Secret Ingredient for Metal Nanocluster-Sensitized Solar Cells
摘要： The presence of alkali metal ions (AMIs) during the adsorption of thiolated Au nanoclusters (NCs) onto TiO2 plays a critical role in achieving high power conversion efficiency and suppressing anomalous current?voltage hysteresis in metal nanocluster-sensitized solar cells. This hidden role of the AMIs is intimately related to the adsorption strength between the NCs and TiO2, indicating the importance of seeking a comprehensive understanding of NC?TiO2 interfaces and devising interfacial engineering techniques to support the next advance in light energy conversion applications of NCs.
关键词： alkali metal ions,metal nanoclusters,current?voltage hysteresis,power conversion efficiency,solar cells
更新于2025-09-23 15:21:01
-
Synergic effect of pore size engineering and an applied electric field on the controlled permeation of alkali metal atoms and ions across pristine and defect-containing h-BN sheets
摘要： The permeation and selectivity of alkali metal atoms and ions through normal and defected hexagonal boron nitride was studied in the presence and absence of water and an electric field. The defects include one (VB & VN), two (VBN) and three atom (VN2B) vacancies. The morphology and size of the pore (defect) in the h-BN sheet significantly affect the energy barriers. These results indicate that an h-BN sheet with appropriate pore size possesses good Li/Li+ selectivity. The permeation of lithium atoms through VN2B-h-BN is almost a barrierless process (1.75 kcal mol?1). Moreover, the VBN h-BN nanosheet selectively allows the passage of Li atoms at room temperature with the highest selectivity ratio of 1.58 × 1013. The presence of water molecules increases the barrier of alkali metal atom permeation. The effect of water molecules is more pronounced for alkali metal atom permeation through a defected h-BN nanosheet as compared to alkali metal ions. An applied electric field perpendicular to the h-BN sheet further decreases the permeation barriers. For example, the energy barrier is reduced to 31 kcal mol?1 (from 34 kcal mol?1) in the presence of an electric field for the permeation of lithium through H2O–VB h-BN–H2O. These studies can be extended to investigate the separation capability of porous hexagonal boron nitride nanosheets for other metal atoms and ions.
关键词： electric field,permeation,water molecules,alkali metal atoms,hexagonal boron nitride,defects,ions,selectivity
更新于2025-09-23 15:21:01
-
Lithium-Doping Effects in Cu(In,Ga)Se2 Thin-Film and Photovoltaic Properties
摘要： The beneficial effects of heavy alkali-metals such as K, Rb, and Cs in enhancing Cu(In,Ga)Se2 (CIGS) photovoltaic efficiencies are widely known, though the detailed mechanism is still open for discussion. In the present work, the effects of the lightest alkali-metal, Li, on CIGS thin-film and device properties are focused upon and compared to the effects of heavy alkali-metals. To date, the beneficial effects of elemental Li on Cu2ZnSnS4 (CZTS) photovoltaic devices in enhancing efficiencies have been reported in the literature. On the other hand, it is shown in the present work that the beneficial effects of Li on CIGS are not so significant. In contrast to the effects of Na or Rb in enhancing CIGS (112) growth orientation, Li was revealed not to affect CIGS growth orientation. The most distinctive feature observed between Li and other alkali-metals was the elemental depth profile in CIGS films. Namely, Na and heavier alkali-metals show a concentration peak near the surface region (relatively Cu-poor region) of CIGS films, whereas elemental Li showed no such trend, suggesting that Li has no significant effect on CIGS surface modification. Nonetheless, Li was found to have some effect in enhancing the PL peak intensity and photovoltaic performance of CIGS, though the effect is relatively small in comparison to that obtained with other alkali-metals.
关键词： CIGS,lithium,thin-film solar cell,rubidium,chalcogenide,chalcopyrite,alkali-metal
更新于2025-09-23 15:21:01
-
Structure, electrical and nonlinear optical properties of $$\hbox {M@C}_{20}$$M@C20 (M?=?Li, Na, K, Be, Mg and Ca) nanoclusters
摘要： The decoration of Li, Na, K, Be, Mg and Ca metal atoms on C20 fullerene was studied using the density functional theory (DFT) method. It was shown that the structure of the fullerene was intensely affected by the metal atom present. All metal atoms have exothermic adsorption on C20 fullerene, while Be has the highest value of adsorption energy, enthalpy and free energy. The presence of the metal atom also has a slight effect on Eg while the lowest value of Eg was obtained for Ca@C20. The calculations of polarizability and the ?rst hyperpolarizability show that the metal atoms highly in?uence fullerenes. Among metal atoms, Ca atom had the highest effect and the other metal atoms led to an increase of the ?rst hyperpolarizability to a value of approximately 42000 a.u. The time-dependent (TD)-DFT studies showed that Ca@C20 has the lowest excitation energies which is in agreement with the calculated ?rst hyperpolarizability.
关键词： alkali metal atom,C20 fullerene,?rst hyperpolarizability,NLO,Ca atom
更新于2025-09-23 15:21:01
-
Alkali-metal-controlled changes of stability and NLO properties in ideal unscrewing process of double helix
摘要： Molecular machines were attractive for scientists due to their excellent dynamical properties and potential applications. Inspired by the feature of molecular machine, we designed an ideal unscrewing process of double-chain sexipyridine complex with four conformations and explored the variation of stability and optical properties. As a result, we found the double helices where the fragments bound by only weak π-π interaction had poor stability. Thus the conformation with stronger π-π interaction was more stable than others. But this could be changed by adding alkali metals, and different alkali metal atoms such as Li and Na could control the stability order because of their different atomic radii. For Li-doped molecules, Li-1 with tightly coiled strands was the most stable conformation. While for Na-doped molecules, Na-4 with unscrewed fragments was the most stable one. This mainly resulted from the intra-molecular interaction potential energy especially the interaction between metal and ligand. At the same time, the charge distribution showed corresponding variation. In the aspect of optical properties, the unscrewing process was followed by the variation of absorption intensity at about 500 nm in the UV–Vis absorption spectra because of the conformation change. Meanwhile, the first-order static hyperpolarizability (βtot) showed zigzag variation due to the change of frontier molecular orbital energy gap in the unscrewing process.
关键词： (un)screwing,NLO,Alkali metal doping,UV–Vis absorption,Double helix
更新于2025-09-16 10:30:52
-
Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application
摘要： M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.
关键词： Red phosphor,Eu3+ ions,W-LEDs,Alkali metal ions
更新于2025-09-16 10:30:52
-
Preparation and Photocatalytic Properties of Sr2-xAxFeMoO6 (X = 0, 0.1; A = Li, Na, K)
摘要： In this paper, the sol-gel method is used to synthesize a series of double perovskite oxides Sr2FeMoO6 and Sr1.9A0.1FeMoO6 (A = Li, Na, K). The crystal structure was investigated by X-ray powder diffraction. The results show that all the as-synthesized samples have tetragonal crystal structure, small amount of substitution has little effect to the structure of Sr2FeMoO6 and they can keep double perovskite structure. Their photocatalytic activities were evaluated by degradation of dye acid black 10 B. The effects of the dosage of photocatalyst, irradiation time, irradiation source, initial concentration of dye solutions and alkali metal ions doping on the photocatalytic activity of samples were investigated. The results show that all the samples present high photocatalytic activities. In the dye concentration range of 20-150 mg/L, the decolorizing rate of acid black 10 B can reach above 95 % when the dosage of photocatalyst Sr2FeMoO6 is 100 mg under UV irradiation for 40 min. Moreover, the photocatalytic activity of Li-doped sample is lower than that of the un-doped sample, but the photocatalytic activity of the Na- or K-doped samples are much better than the un-doped sample and the decolorizing rate is nearly 100 %.
关键词： Photocatalytic performance,Sr2FeMoO6,Alkali metal doping,Sol-gel method,Decolorizing rate
更新于2025-09-11 14:15:04
-
Theoretical explanation of strong enhancement of alkali metal ion neutralization on Au nanoclusters
摘要： We present a theoretical study of alkali metal ion neutralization on gold nanoclusters. The experimental time-of-flight measurements show that neutral fraction of alkali metal ions scattered from flat Au surface is low (3%-15%), but it increases up to 50% for small Au clusters. Several possible explanations of alkali metal ions neutralization enhancement on nanoclusters have been proposed earlier, but they do not fully explain existing experimental data. We introduce alternative explanation of neutralization probability enhancement for small clusters. It is based on ion energy level shift due to interaction with image/induced charges, which significantly differs in the case of metallic nanocluster and in the case of flat continuous metallic surface. Another known mechanism is greater neutralization rate on positively charged edge atoms of Au nanocluster. The combination of two mechanisms and difference in atomic radii possibly explains greater neutralization probability enhancement for Na+ in comparison to Li+.
关键词： Resonant Charge Transfer,Low Energy Ion Scattering (LEIS),Alkali Metal Ions,Neutralization Effect
更新于2025-09-09 09:28:46