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Near-infrared laser driven white light continuum generation: materials, photophysical behaviours and applications
摘要： The pursuit of efficient light sources has stimulated continued effort in the search of materials and methods for generating white light emission. In addition to the white light produced by light-emitting diodes (LEDs) and fluorescent lamps that involves spectral conversion of high energy to low energy emission, recent studies showed that it was also possible to produce white visible light by irradiating different active materials with near-infrared (NIR) constant-wave (CW) lasers. In this review, we begin by introducing and categorizing different materials that exhibit NIR laser driven white light emission, including normal inorganic phosphors, organometallic compounds, graphene, etc. We then discuss the photophysical behavior of this process in terms of optical spectra, temperature evolution and photoelectric response. Different mechanisms of while light generation are analyzed afterwards, and the possibility of a more general physical picture of this process is discussed. This review is concluded with a summary of the current understanding and discussion on potential applications and future perspectives.
关键词： graphene,near-infrared laser,optical spectra,photoelectric response,organometallic compounds,temperature evolution,inorganic phosphors,photophysical behavior,white light emission
更新于2025-09-23 15:19:57
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Remarkable Oxygen-Evolution Activity of Ca2-xSrxFe2O6-δ
摘要： The unprecedented catalytic activity of an iron-based oxygen-deficient perovskite for oxygen-evolution reaction (OER) is reported, given the need for catalysts based on earth-abundant elements. In addition, systematic trends in oxygen-evolution activity as a function of composition, defect-order and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca2Fe2O6-δ < CaSrFe2O6-δ < Sr2Fe2O6-δ. The latter material, which has the highest electrical conductivity and a unique type of defect-order, exhibits the best OER activity. In conventional experiments using glassy carbon electrode, this compound shows superior OER activity compared to the current state of the art catalysts, Ba0.5Sr0.5Co0.8Fe0.2O3?δ and RuO2. It also offers an additional advantage, namely high intrinsic electrical conductivity, which allows Sr2Fe2O6-δ to act as a catalyst without the need for glassy carbon electrode or carbon powder, that are frequently used for enhancing the charge transport in OER catalysts. Indeed, pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.
关键词： oxygen-evolution reaction,perovskite phases,iron,defect-order,electrical conductivity
更新于2025-09-23 15:19:57
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - All Dielectric Mode Order Transformation Photonic Structure Design by Evolutionary Optimization Approach
摘要： In this manuscript, an evolutionary algorithm is applied to design a mode order converter photonic crystal structure for achieving transformation of the propagating fundamental mode to the higher order mode. In order to transform incident light mode from an even mode to an odd mode, predefined mask object functions are employed. The cross-sectional field profiles at the output face of the optimized structure are utilized to evaluate the optimization cost function to achieve mode order transformation task. In the study, the optimized structure composed of dielectric alumina (Al2O3) rods and time domain analyses of the optimization process are done by using finite-difference time domain method. Furthermore, numerical results are confirmed by experiments for designed structure at the microwave frequencies. It is shown that the numerical calculations and experimental measurements agree well with each other.
关键词： mode order converter,differential evolution algorithm,phase shift,photonic crystals,integrated optics
更新于2025-09-23 15:19:57
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Calibrating the <i>James Webb Space Telescope</i> Filters as Star Formation Rate Indicators
摘要： We have calibrated the 6.5 m James Webb Space Telescope (JWST) mid-infrared (MIR) ?lters as star formation rate (SFR) indicators, using JWST photometry synthesized from Spitzer spectra of 49 low-redshift galaxies, which cover a wider luminosity range than most previous studies. We use Balmer-decrement-corrected Hα luminosity and synthesized MIR photometry to empirically calibrate the Spitzer, WISE, and JWST ?lters as SFR indicators. Our Spitzer and WISE calibrations are in good agreement with recent calibrations from the literature. While MIR luminosity may be directly proportional to SFR for high-luminosity galaxies, we ?nd a power-law relationship between MIR luminosity and SFR for low-luminosity galaxies (L ~ 1- ). We ?nd that for galaxies with an Hα luminosity of 10 erg s ), the corresponding JWST MIR ν Lν luminosity is between 1040.50 and 10. Power-law ?ts of JWST luminosity as a function of Hα luminosity have indices between 1.17 and 1.32. We ?nd that the scatter in the JWST ?lter calibrations decreases with increasing wavelength from 0.39 to 0.20 dex, although F1000W is an exception where the scatter is just 0.24 dex.
关键词： stars: formation,galaxies: general,galaxies: photometry,galaxies: evolution
更新于2025-09-23 15:19:57
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Growth-Rule-Guided Structural Exploration of Thiolate-Protected Gold Nanoclusters
摘要： Understanding the structure and structure?property relationship of atomic and ligated clusters is one of the central research tasks in the field of cluster research. In chemistry, empirical rules such as the polyhedral skeleton electron pair theory (PSEPT) approach had been outlined to account for skeleton structures of many main-group atomic and ligand-protected transition metal clusters. Nonetheless, because of the diversity of cluster structures and compositions, no uniform structural and electronic rule is available for various cluster compounds. Exploring new cluster structures and their evolution is a hot topic in the field of cluster research for both experiment and theory. In this Account, we introduce our recent progress in the theoretical exploration of structures and evolution patterns of a class of atomically precise thiolate-protected gold nanoclusters using density functional theory computations. Unlike the conventional ligand-protected transition metal compounds, the thiolate-protected gold clusters demonstrate novel metal core/ligand shell interfacial structures in which the Aum(SR)n clusters can be divided into an ordered Au(0) core and a group of oligomeric SR[Au(SR)]x (x = 0, 1, 2, 3, ...) protection motifs. Guided by this “inherent structure rule”, we have devised theoretical methods to rapidly explore cluster structures that do not necessarily require laborious global potential energy surface searches. The structural predictions of Au38(SR)24, Au24(SR)20, and Au44(SR)28 nanoclusters were completely or partially verified by the later X-ray crystallography studies. On the basis of the analysis of cluster structures determined by X-ray crystallography and theoretical prediction, a structural evolution diagram for the face-centered-cubic (fcc)-type Aum(SR)n clusters with m up to 92 has been preliminarily established. The structural evolution diagram indicates some basic structural and electronic evolution patterns of thiolate-protected gold nanoclusters. The fcc Aum(SR)n clusters show a genetic structural evolution pattern in which each step of cluster size increase results in the formation of another Au4 tetrahedron or Au3 triangle unit in the Au core, and every increase of a structural unit in the Au core leads to an increase of two electrons in the whole cluster. The unique one- or two-dimensional cluster size evolution, the isomerism of the Au?S framework, and the formation of a double-helical and cyclic tetrahedron network in the fcc Aum(SR)n clusters all can be addressed from this evolution pattern. The summarized cluster structural evolution diagrams enable us to further explore more stable cluster structures and understand their structure?electronic structure?property relationships.
关键词： face-centered-cubic,thiolate-protected gold nanoclusters,density functional theory,electronic structure,structural evolution
更新于2025-09-23 15:19:57
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Latitude dependence of the solar granulation during the minimum of activity in 2009
摘要： Context. Knowledge of the latitude variation of the solar granulation properties (contrast and scale) is useful to better understand interactions between magnetic field, convection, differential rotation, and meridional circulation in the solar atmosphere. Aims. We investigated the latitude dependence of the contrast and scale of the solar granulation, with the help of HINODE/SOT blue continuum images taken in the frame of the HOP 79 program, along the central meridian and along the equator on a monthly basis in 2009 during the last solar minimum of activity. Methods. We selected the sharpest images in latitude and longitude intervals. The selected images in all the N-S and E-W scans taken in 2009 were combined to get statistically reliable results. Results. The contrast of the solar granulation decreases towards the poles and the scale increases, but not regularly since a perturbation occurs at around 60? where both quantities return close to their values at the disk center. Conclusions. Such a latitude variation in a period of minimum of activity (2009), is probably not due to magnetic field, neither the quiet magnetic field at the surface, nor the strong magnetic flux tubes associated with active regions, which could be embedded more or less deeply in the convection zone before they reach the surface. The decrease in contrast and increase in scale towards the pole seem to be related to the differential rotation and the perturbation around 60? to the meridional circulation.
关键词： Sun: evolution,Sun: granulation,Sun: rotation,Sun: interior,Sun: magnetic fields
更新于2025-09-23 15:19:57
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Enhancing Electrocatalytic Water Splitting Activities via Photothermal Effect over Bifunctional Nickel/Reduced Graphene Oxide Nanosheets
摘要： Electrocatalytic water splitting has huge potential for generating hydrogen fuel. Its wide application suffers from high energy loss and sluggish reaction kinetics. The adoption of appropriate electrocatalysts is capable of reducing the overpotential and accelerating the reaction. Present research mainly focuses on adjusting electrocatalysts, but the performances are also dependent on other parameters. Therefore, the development of an efficient strategy to enhance electrocatalytic performance through integrating with other driving force, especially a renewable driving force, is of great interest. Herein, we present a photothermal-effect-driven strategy to promote the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities of nickel/reduced graphene oxide (denoted as Ni/RGO) bifunctional electrocatalysts. The Ni/RGO composite exhibited significant enhancement of activities after exposure to light irradiation (49 mV and 50 mV decrease of overpotential at 10 mA/cm2 for HER and OER, respectively). It was found that the improved electrocatalytic activities arose from the photothermal effect of Ni/RGO, which can efficiently facilitate the thermodynamics and kinetics of electrocatalytic reactions. Furthermore, the photothermal-effect-induced enhancement for electrocatalysis showed good stability, indicating its promising potential in practical application.
关键词： Bifunctional electrocatalysts,Oxygen evolution reaction,Ni/RGO nanosheets,Photothermal effect,Hydrogen evolution reaction
更新于2025-09-19 17:15:36
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A Highly Efficient and Durable Water Splitting System: Platinum Sub-Nanoclusters Functionalized Nickel Iron Layered Double Hydroxides as the Cathode and Hierarchical Nickel Iron Selenides as the Anode
摘要： Developing cost-efficient and effective catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a great challenge for the applications of high-efficiency water electrolyzers. In this work, we design a highly efficient and durable water splitting system in an alkaline solution, of which the platinum (Pt) sub-nanoclusters (average size: 0.59 nm) functionalized nickel iron layered double hydroxide nanosheets on carbon fiber cloth (Pt-NiFe LDH/CC) serve as the cathode and the hierarchical (Ni0.77Fe0.23)Se2 nanosheets on CC ((Ni0.77Fe0.23)Se2/CC) act as the anode. For the HER, the three-dimensional (3D) Pt-NiFe LDH/CC electrode with an ultralow Pt content (1.56 wt%) drives a current density of 10 mA cm-2 under an ultralow overpotential of 28 mV. For the OER, the edge-rich (Ni0.77Fe0.23)Se2/CC electrode displays a current density of 10 mA cm?2 under a small overpotential of 228 mV, and the Tafel slope is as low as 69 mV dec?1. More importantly, the assembled Pt-NiFe LDH/CC || (Ni0.77Fe0.23)Se2/CC water splitting electrolyzer exhibits a high current density of 30 mA cm?2 at a low cell voltage of 1.57 V, which is superior than that of electrolyzer assembled by the commercial 20 wt% Pt/C and RuO2 electrodes (30 mA cm?2 at 1.62 V). Additionally, the Pt-NiFe LDH/CC || (Ni0.77Fe0.23)Se2/CC electrolyzer displays excellent stability over 40 hours even at a high current density of 50 mA cm?2, which shows a great potential in the practical applications of full water splitting.
关键词： Hydrogen Evolution Reaction,Platinum Sub-Nanoclusters,Oxygen Evolution Reaction,NiFe Layered Double Hydroxide,Porous NiFe Selenide
更新于2025-09-19 17:15:36
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Morphological Evolution Induced through Heterojunction of W-decorated NiO Nanoigloos: Synergistic Effect on High-performance Gas Sensors
摘要： Morphological evolution accompanying a surface roughening and the preferred orientation is an effective way to realize a high-performance gas sensor because of its significant potential as a chemical catalyst by chemical potentials and atomic energy states. In this work, we investigated the heterojunction of both-sided W-decorated NiO nanoigloos fabricated through RF sputtering and a soft-template method. Interestingly, the morphological evolution characterized by a pyramidal rough surface and the preferred orientation of the (111) plane was observed upon decorating the bare NiO nanoigloos with W. The underlying mechanism of the morphological evolution was precisely demonstrated based on a van der Drift competitive growth model originating from the oxygen transport and chemical strain in a lattice. The gas sensing properties of W-decorated NiO show an excellent NO2 response and selectivity when compared to other gases. In addition, high response stability was evaluated under interference gas and humidity condition. The synergistic effects on the sensing performance were interpreted based on the morphological evolution of W-decorated NiO nanoigloos.
关键词： Gas sensor,Nanostructure,Morphological evolution,Heterojunction,NO2
更新于2025-09-19 17:15:36
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Smart yolk/Shell ZIF-67@POM Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction
摘要： The purpose of this research is to develop an effective and inexpensive oxygen evolution reaction (OER) electrocatalysts to achieve high-efficiency water decomposition. Herein, Keggin-type polyoxometalate (POM) nanoparticles coated with zeolitic imidazolate framework (ZIF-67) are successfully synthesized by facile methods. An efficient ZIF-67@POM catalyst with yolk/shell structure is reported. The POM nanomaterials are uniformly dispersed in the surface of ZIF-67. This unique yolk/shell structure with potential synergistic interaction between POM and ZIF-67 result in superior electrocatalytic activity in OER. When the current density is 10 mA cm-2, the overpotential is only 287 mV, and the Tafel slope is 58 mV per decade. Moreover, the as-prepared yolk/shell ZIF-67@POM catalysts exhibit excellent cycling stability, high surface area, abundant surface active sites and high diffusion efficiency comparable to the traditional noble-metal-free OER electrocatalyst.
关键词： polyoxometalate,metal-organic framework,electrocatalysis,oxygen evolution reaction
更新于2025-09-19 17:15:36