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Effects of precursors and caustic bases on structural and vibrational properties of ZnO nanostructures elaborated by hydrothermal method
摘要： The effects of zinc ions source (zinc acetate and zinc sulfate) and caustic bases (sodium and potassium hydroxides) on structural, morphological and vibrational properties of ZnO nanostructures elaborated by simple low temperature wet chemical process are studied. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (FTIR) and Raman spectroscopies. XRD results show that ZnO structures are polycristalline hexagonal wurtzite with high crystal quality. SEM images reveal that the morphologies of the nanostructures are nanopencils except in those synthesized with zinc sulfate precursor and sodium hydroxide caustic base, where pencils agglomerate to form sand rose-like morphologies. EDAX measurements confirm the purity of the elaborated specimens by the presence of only Zn and O atoms in the samples. Raman spectroscopy studies show that the peaks, related to E2 high mode, are more intense in ZnO structures elaborated with zinc acetate when NaOH is used, and in ZnO structures elaborated with zinc sulfate when KOH is employed.
关键词： alkali hydroxides,hydrothermal synthesis,ZnO,structure,morphology,source precursor
更新于2025-09-23 15:23:52
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Synthesis of cyclo-PLAI using a combination of solid- and solution-phase methods
摘要： Cyclo-PLAI was successfully synthesized using a combination of solid- and solution-phase methods. This current synthesis was found to be faster than the previously reported synthesis for the cyclic peptide. The linear precursor was synthesized on 2-chlorotrityl resin with Fmoc/t-Bu strategy. HATU/HOAt was employed as the coupling reagent in the amide bond formation on the resin. Cyclization of the linear precursor was experimented with HATU/HOAt reagents with different conditions. However, the linear precursor was best cyclized using HATU reagent in DIPEA by stirring the reaction mixture at 0 °C for 1 h and followed by stirring the reaction mixture at room temperature for 30 min, giving the cyclic product in 70% yield (calculated from the linear peptide). Both linear and cyclic products were characterized using HR-TOF-ESMS, 1H-NMR, 13C-NMR, and compared with previously reported spectral data for the cyclic product.
关键词： 2-chlorotrityl resin,Cyclo-PLAI,cyclotetrapeptide,HATU cyclization,solid-phase peptide synthesis
更新于2025-09-23 15:23:52
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Photoluminescence of partially reduced Eu2+/Eu3+ active centers in a NaF–Al2O3–P2O5 glassy matrix with tunable smooth spectra
摘要： In this work, a series of photoluminescent materials have been synthesized based on optically transparent and chemically stable glasses of the nominal composition Na3Al2(PO4)2F3 (NaF–Al2O3–P2O5 system) doped with 1 wt % of europium. It has been shown that the synthesis conditions (mainly the temperature and duration of the melting stage under reducing conditions) strongly affected the photoluminescence spectra of the material. This effect has been ascribed to varying proportions between Eu3+ and Eu2+ ions concentrations, imposed by the synthesis conditions, which was confirmed by XPS, absorption and decay times measurements. As both Eu3+ and Eu2+ centers exhibit photoluminescence in different ranges of the visible spectra (Eu3+ – red, and Eu2+ – mainly blue) the possibility, shown by us, to control relative proportions of the oxidation states of europium and consequently to control the photoluminescence spectra, may be advantageous from the viewpoint of potential applications of such materials as novel phosphors for white LEDs with the emission spectra resembling natural light.
关键词： glassy matrix,europium facile reduction,scalable synthesis,tunable luminescence
更新于2025-09-23 15:23:52
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[IEEE 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Novosibirsk, Russia (2018.10.2-2018.10.6)] 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Synthesis of Group Delay Time Correctors on the Basis of Two Types Directional Couplers
摘要： A group delay time correctors on the basis of contra-directional and trans-directional couplers are considered. The formulas for calculating the frequency characteristics of the load resistors forming a given frequency dependence of the phase and group delay time are obtained.
关键词： Synthesis,directional couplers based on coupled strip lines,group delay time correctors
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Iasi, Romania (2018.10.18-2018.10.19)] 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Limits and Particularities of the Synthesis of Ba<inf>1-x</inf>Ca<inf>x</inf>TiO<inf>3</inf> for Piezoelectric Applications, by Topochemical Conversion from Molten Salt Solutions
摘要： Because of the unique properties of the ferroelectric perovskite particles with a well-defined anisotropic form like shape- and size dependent at low dimensions they have all the attention of the scientific world. Extensive morpho-structural techniques will be used to characterize the piezoelectric material.
关键词： synthesis,solid solutions,morpho-structural characteristics
更新于2025-09-23 15:22:29
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[IEEE 2018 9th International Conference on Mechanical and Aerospace Engineering (ICMAE) - Budapest (2018.7.10-2018.7.13)] 2018 9th International Conference on Mechanical and Aerospace Engineering (ICMAE) - Resident Space Objects Streak Extraction and Angular Measurement Error Analysis Base on Space Image Synthesis System
摘要： To maintain awareness, space development of space-based visible system has gained much attention in recent years. Because the angular measurement accuracy of space-based sensor is very sensitive to orbit determination, it’s necessary to analyze the factors of angular measurement error, which can provide references for optimal design of space-based sensor. In this paper, a space image synthesis system is developed to provide the image source for resident space object detection and extraction. Then image extraction error and pose error of observation platform are analyzed, with which that the angle measurement error decreases as the focal length and size of pixel increase under same image extraction error can be concluded. Compared with position and velocity error of satellite, attitude angle error has greater impact on angle measurement error of RSOs. By using Otsu method and mathematical morphology method, the angle measurement error of RSOs can be controlled within 7 arcseconds.
关键词： resident space object,error analysis,angular measurement,space situational awareness,space image synthesis
更新于2025-09-23 15:22:29
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Facile green synthesis of organosilica nanoparticles by a generic “salt route”
摘要： Colloidal silica has wide applications and the global demand of specialty silica is continually increasing. Therefore, it is significant to develop a synthetic method that is simple, versatile, energy-saving, ecologically benign, and easily scalable. Biomimetic synthesis of colloidal silica represents a promising strategy; however, it often requires the synthesis or extraction of specialized macromolecules. In this paper, we present a novel aqueous, one-pot, and green route for synthesis of organosilica nanoparticles. The reaction systems contain only water, an organosilane precursor, a salt, and a commonly used surfactant or amphiphilic polymer. The reaction was performed at ambient conditions without adding any additional solvent, energy, and harsh chemicals. The key findings include the novel identification of 5 salts (i.e. nitrite, fluoride, dibasic phosphate, acetate, and sulfite) that can catalyze organosilica condensation and the resulting formation of nano-colloids. Moreover, the presence of amphiphilic molecules is essential for salt catalysis at low salt concentrations and at nearly neutral pH. Solid-state NMR and in-situ ATR-FTIR studies confirmed that organosilica condensation is highly efficient under the mild reaction condition. In conclusion, the present study demonstrates that "soft" interaction between salts and surfactants (or polymers) can be utilized to construct an effective platform for synthesis of "hard" organosilica particles. The proposed method is generic and applicable to a wide range of commonly used surfactants (viz. non-ionic, anionic, cationic) and amphiphilic polymers, as well as to organosilanes with various hydrophobic functional groups (e.g. mercaptopropyl, vinyl, and methyl).
关键词： Salts,Microreactors,Surfactants,Organosilica nanoparticles,Biomimetic synthesis,Colloids
更新于2025-09-23 15:22:29
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Two novel ESIPT benzothiazol derivatives and corresponding europium(Ⅲ) complexes: Synthesis and fluorescent properties
摘要： Two ESIPT benzothiazol derivatives and corresponding europium complexes were synthesized and characterized by the 1HNMR spectrum, Mass spectrum, Elemental analysis, UV–Vis analysis, Molar conductivity, Thermogravimetric analysis and FTIR analysis. The fluorescence intensity of the ligands and complexes are compared, and the fluorescence quantum yields are also calculated by the reference method. The results show that two ligands emit orange fluorescence due to the ESIPT process, but both complexes emit red fluorescence after coordinating with Eu3+. Compared with the ligands, the fluorescence intensity and fluorescence quantum yield of the complexes are enhanced, and the monochromaticity is also improved. Because of the stable tetradentate coordination, the fluorescence intensity of EuL7(NO3)3·2H2O is the strongest, and the order of fluorescence intensity is EuL7(NO3)3·2H2O > EuL6(NO3)3·2H2O > Ligand 6 > Ligand 7, so does the fluorescence quantum yields. The electrochemical properties of the complexes show that the HOMO energy level of EuL7(NO3)3·2H2O is higher than that of EuL6(NO3)3·2H2O, but LUMO energy level is lower than that of EuL6(NO3)3·2H2O. These ligands and complexes have potential applications in the field of life sciences and optical materials.
关键词： Electrochemical property,Benzothiazol derivative,Synthesis,ESIPT,Europium complex,Fluorescence property
更新于2025-09-23 15:22:29
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Magneto-Optical Effects in Colloidal Solutions of Barium Hexaferrite
摘要： Hydrothermal synthesis was used to obtain lamellar magnetic particles of barium hexaferrite, and colloidal solutions were prepared on their basis. Magneto-optical effects in colloid solutions of barium hexaferrite were examined. It was found that the aqueous colloidal solution of coarse planar particles of barium hexaferrite is a magneto-optical medium that is nearly two orders of magnitude more effective than the colloid formed from isometric cobalt ferrite particles. It was shown that measuring the frequency dependence of the magneto-optical effects and approximating the experimental data with the Debye function makes it possible to find the frequency f0 characteristic of the given colloid and to calculate the characteristic size of particles (or aggregates) creating the optical anisotropy in the colloid under the action of a magnetic field. A dichroism is observed in the aqueous colloid formed by coarse planar barium hexaferrite particles. This phenomenon is due to the change in the light scattering on coarse particles upon their orientation by a magnetic field.
关键词： lamellar magnetic particles,barium hexaferrite,colloidal solution,hydrothermal synthesis,magneto-optical effects
更新于2025-09-23 15:22:29
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Light Transmission of Glasses Synthesized on the Basis of Quartz Sand of Different Deposits
摘要： Container and sheet glass are synthesized from various batches with the equivalent addition of complexing decolorizers. The effect of ceria and potassium nitrate on the light transmission coefficient is investigated. Measurement of optical characteristics of the glasses shows that light transmittance increases up to 90–93% (λ = 500–750 nm). It is determined that an increase in the concentration of ceria and potassium nitrate up to particular values in the case of each composition results in the increase in hydrolytic stability, TLCE, and the light transmission coefficient.
关键词： discoloration,iron oxide,light transmission coefficient,chemical stability,quartz sand,synthesis of glass,raw materials
更新于2025-09-23 15:22:29