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single crystals
摘要： 3at.%Tm3+:Ca1?xGdxF2+x (x = 0, 0.005, 0.01, 0.02) single crystals were grown by the vertical Bridgman method, where Gd3+ ions play the role of manipulating ions for local structure to form a disordered lattice site. Spectral properties of these crystals were investigated. Compared to 3at.%Tm3+:CaF2, the spectral parameters of 3at.%Tm3+:Ca1?xGdxF2+x were drastically enhanced in a large scale. LD pumped lasers have been demonstrated in the crystals for the first time. For CW operation, the slope efficiency up to 49.7% was achieved with output power of 1.927 W at 1970 nm. With a birefringent quartz plate, wavelength-tunable laser operation with a tuning range of more than 176 nm was realized.
关键词： Spectral properties,Single crystals,Gd3+ ions,LD pumped lasers
更新于2025-09-23 15:23:52
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A study on structural, spectral, and magnetic properties of Pr–Bi co-doped M-type barium–strontium hexaferrites via the solid-state reaction method
摘要： Pr–Bi co-doped M-type Ba–Sr hexaferrites with nominal compositions Ba0.35Sr0.65?xPrxFe12.0?xBixO19 (0.00 ≤ x ≤ 0.40) were synthesized for the first time by the solid-state reaction method. These hexaferrites were characterized by X-ray diffractometer (XRD), Fourier transformer infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM) and thermogravimetric analyzer (TGA). XRD patterns showed that the single M-type hexaferrite phase was obtained only if Pr–Bi content (x) ≤ 0.24. FT-IR frequency bands in the range (608–610) cm?1 and (445–447) cm?1 correspond to the formation of tetrahedral and octahedral clusters of metal oxides in the hexaferrites, respectively. FE-SEM micrographs indicated that the grains were of platelet-like shapes. The saturation magnetization (Ms), remanent magnetization (Mr), magnetic anisotropy field (Ha), first anisotropy constant (K1) and coercivity (Hc) first increased with Pr–Bi content (x) from 0.00 to 0.08, and then decreased when Pr–Bi content (x) ≥ 0.08. The Curie temperature (Tc) decreased with increasing Pr–Bi content (x) from 0.00 to 0.40.
关键词： Pr–Bi co-doped,structural properties,solid-state reaction method,spectral properties,magnetic properties,M-type barium–strontium hexaferrites
更新于2025-09-23 15:21:01
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Synthesis and Spectral Characteristics of BODIPY Dyes with Two or Three Dipyrrin Domains
摘要： Several boron-dipyrrin (BODIPY) based fluorophores with two and three dipyrrin cores were synthesized and investigated in solvents under the concentration variation. Comparative analysis of spectral and photophysical changes under increasing the number of the cores in the dye molecule was made. Mutual influence of dipyrrin cores was detected leading to the increasing of the compounds rigidity and, thus, the absence of fluorescent molecular rotor effects under the viscosity variation. Aggregation induced quenching, which was observed for many mono-domain BODIPY dyes is reduced in case of investigated poly-domain compounds.
关键词： Aggregation induced spectral changes,Intramolecular rotation,Spectral properties,Synthesis,BODIPY
更新于2025-09-23 15:21:01
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The morphology regulation and plasmonic spectral properties of Au@AuAg yolk-shell nanorods with controlled interior gap
摘要： Au@AuAg yolk-shell nanorods with tunable and uniform interior gap were synthesized through galvanic replacement reaction, where Au@Ag core-shell nanorods served as sacrificial templates and HAuCl4 solution served as reductant. The effects of HAuCl4, Ag shell thickness and aspect ratio (AR) of Au nanorods on the morphology of Au@AuAg yolk-shell nanorods had been investigated systemically. The results clearly indicated that AuAg alloy shell thickness of Au@AuAg yolk-shell nanorods could be increased from 3.6 to 10.0 nm by varying the amount of HAuCl4. Meanwhile, the shape of AuAg alloy shell could be tuned by changing the shape of Ag coating. With the increasing of Ag coating thickness, the interior gap could be finely tuned in the range from 2.6 to 8.1 nm. The uniformity of interior gap could be improved by increasing the AR of Au nanorods. All these tunable geometries can further affect the plasmonic spectral properties of Au@AuAg yolk-shell nanorods. Because of the appearance of interior gap, the longitudinal localized surface plasmon resonance (LSPR) peak of Au@AuAg yolk-shell nanorods was located between that of bare Au nanorods and Au@Ag core-shell nanorods without interior gap. The increase of outer AuAg shell thickness can weaken the coupling between the inner and outer surface of the AuAg shell and lead to the decrease of AR, so the transverse and longitudinal LSPR bands gather together. The decrease of Ag coating thickness can enhance the coupling between inner Au nanorod and outer AuAg shell, which results in the red shift of the longitudinal LSPR band. This paper provides a method for studying the plasmonic coupling between two metal surfaces with a metal layer or a dielectric layer, which is also a new approach for regulating the plasmonic spectral properties of bimetallic nanoparticles. The controllability of Au@AuAg yolk-shell nanorods in both the interior gap and outer alloy shells makes them have potential applications in biomedicine, catalysis, nanoreactors, and energy storage.
关键词： interior gap,localized surface plasmon resonance,spectral properties,morphology regulation,Au@AuAg yolk-shell nanorods
更新于2025-09-23 15:21:01
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Cryostat setup for measuring spectral and electrical properties of light-emitting diodes at junction temperatures from 81 K to 297 K
摘要： We introduce a cryostat setup for measuring fundamental optical and electrical properties of light-emitting diodes (LEDs). With the setup, the cryostat pressure and the LED properties of the forward voltage, junction temperature, and electroluminescence spectrum are monitored with temperature steps less than 1.5 K, over the junction temperature range of 81–297 K. We applied the setup to commercial yellow AlGaInP and blue InGaN LEDs. At cryogenic temperatures, the fine structure of the electroluminescence spectra became resolved. For the yellow LED, we observed the phonon replica at 2.094 eV that was located 87 meV below the peak energy at the junction temperature of 81 K. For the blue LED, we observed the cascade phonon replicas at 2.599 eV, 2.510 eV, and 2.422 eV with the energy interval of 89 meV. For both LED types, the forward voltage increased sharply toward the lower temperatures due to the increased resistivity of materials in the LED components. We found significant differences between the temperature dependent behaviors of the forward voltages, spectral peak energies, and bandgap energies of LEDs obtained from the Varshni formula. We also noted a sharp pressure peak at 180–185 K arising from the solid-vapor phase transition of water when the base level of the cryostat pressure was approximately 0.4 mPa.
关键词： spectral properties,light-emitting diodes,electrical properties,junction temperature,phonon replicas,cryostat setup
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Cr,Fe:ZnMnSe Laser Excited by Flash-Lamp Pumped Er:Glass Laser
摘要： Due to the wide use of coherent radiation in the mid-infrared (IR) region, the attention has been paid to both direct and indirect methods of generation of this radiation over the past two decades. While indirect methods are based on nonlinear conversion (OPOs or Raman scattering), the direct approach looks for a new active media that will allow generation of radiation in the mid-IR region in a single step [1]. It has been found that by replacing Zn2+ ions with Mn2+, Mg2+ or Cd2+ ions with comparable size in the ZnSe matrix, the position of the absorption and emission bands is shifted to the longer wavelengths by increasing concentration of these ions substitution [1, 2]. It allows a one laser oscillator to extend or to shift the emission spectrum further to the mid-IR part of the electromagnetic spectrum, which was previously exclusively based on the nonlinear processes or on the parametric generation.
关键词： Cr,mid-infrared,laser,spectral properties,Er:glass laser,Fe:ZnMnSe
更新于2025-09-12 10:27:22
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Transmissivity of solar radiation within a <i>Picea sitchensis</i> stand under various sky conditions
摘要： We tested the hypothesis that diffuse radiation from cloudy and overcast skies penetrates the canopy more effectively than direct radiation from clear skies. We compared the ?ux density and spectral properties of direct and diffuse radiation (around solar noon (±1 h)) above, within and below a forest stand under sunny, cloudy and overcast conditions in a thinned Sitka spruce (Picea sitchensis (Bong.) Carr.) forest (28 years old, with a leaf area index of approximately 5.2 m2 m?2). We recorded vertical pro?les of radiation penetration (from 350 to 1050 nm), and we also explored the horizontal pattern of radiation along a 115 m transect. We showed that in “clear sky” conditions, the photosynthetically active radiation in the lower parts of the canopy was substantially attenuated, more so than under cloudy and overcast skies. It was particularly depleted in the blue part of the spectrum, but only slightly blue-depleted when the sky was overcast or cloudy. Moreover, the red : far-red ratio under clear skies fell to values less than 0.3 but only to 0.6 under cloudy or overcast skies. Near the ground, the light climate was strongly in?uenced by the thinning pattern (carried out in accordance with standard forestry management practice).
关键词： diffuse radiation,direct radiation,canopy penetration,Sitka spruce,forestry management,spectral properties
更新于2025-09-10 09:29:36
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Optical Characteristics and Structural Properties of 3-(p-Nitrophenyl)-5-phenyl-1H-pyrazole
摘要： In this study, a conjugated 3-(p-nitrophenyl)-5-phenyl-1H-pyrazole (NPP) was synthesized using a microwave-assisted reaction. The photophysical characteristics of NPP, such as absorption, fluorescence, Stokes shift, and fluorescence quantum yield, under different solvent environments, concentrations, and pH values were studied. NPP in ethanol showed an absorption band at 316 nm. Moreover, the shape of the absorption spectrum was not affected by an increase in the concentration. Therefore, there was no aggregation formed in the ground state for all concentrations. On the other hand, the fluorescence spectrum of NPP in ethanol exhibited three distinctive bands around 411 nm, 436 nm, and 463 nm. The intensity of the fluorescence was directly proportional to the concentration even at higher concentrations. Most of the 1H-pyrazoles are affected by the alkalinity and acidity of media. Nevertheless, NPP was not significantly affected by the acidic or alkaline media in the ground or excited states.
关键词： spectral properties,pH effect,1H-pyrazole,proton transfer
更新于2025-09-10 09:29:36
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Synthesis and properties of merocyanine dyes derived from N-aryl-substituted pyridinium salts and cyanoacetic acids
摘要： A series of merocyanine dyes were synthesized by two-component condensation of N-aryl-4-picolinium salts and cyanoacetic acid derivatives. Physicochemical properties of the synthesized dyes were studied.
关键词： protonation,4-picolinium salts,merocyanine dyes,spectral properties,heterocycles
更新于2025-09-10 09:29:36
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Complex Formation of Cobalt(II) Octakis(3,5-di-tert-butylphenoxy)phthalocyanine with 2′-(Pyridin-4-yl)-5′-(Pyridin-2-yl)-1′-(Pyridin-2-ylmethyl)-2′,4′-Dihydro-1′H-Pyrrolo[ 3′,4′:1,2][C60-Ih][5,6]fullerene
摘要： The formation of the donor–acceptor complex of cobalt(II) octakis(3,5-di-tert-butylphenoxy)phthalocyanine with 2'-(pyridin-4-yl)-5'-(pyridin-2-yl)-1'-(pyridin-2-ylmethyl)-2',4'-dihydro-1'H-pyrrolo[3',4':1,2][C60-Ih][5,6]fullerene (Py3C60) in toluene was studied by chemical kinetics (thermodynamics) and spectroscopy methods in comparison with a similar system based on 4-picoline (Pic). In both cases, the reaction occurred in one step giving donor–acceptor complexes of 1 : 1 stoichiometry, which were characterized by key spectral (UV-vis, IR, 1H NMR) parameters and thermodynamic equilibrium parameters; in the case of reaction with pyridyl-substituted fullerene, full kinetic description was obtained. The stability constants for (Pic)CoPc(3,5-tBuPhO)8 and (Py3C60)CoPc(3,5-tBuPhO)8 are (1.01 ± 0.16) × 104 L/mol (logK = 4.00, Δ G = –22.84 kJ/mol) and (1.84 ± 0.16) × 105 L/mol (logK = 5.26, Δ G = –30.04 kJ/mol), respectively. The obtained results are relevant for the development of new efficient components for photovoltaic cells based on phthalocyanine–fullerene systems.
关键词： 4-picoline,thermodynamics,phthalocyanine–fullerene complex,kinetics,donor–acceptor complex formation,pyridyl-fullerene,spectral properties,cobalt(II) phthalocyanine
更新于2025-09-09 09:28:46