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Physicochemical study of multicolor BCNO phosphors using a urea combustion method
摘要： In this study, the physicochemical properties of BCNO phosphors were investigated based on the color of luminescence to study the luminescence mechanism. Multicolor BCNOs were synthesized by urea combustion methods using boron, carbon, and nitrogen sources consisting of boric acid, PEG 20k, and urea, respectively. The C/B ratio was varied from 0.3 to 2 with temperature variation between 700 and 800 °C, and synthesis time variation at 30 min, 45 min and 60 min. The synthesis process at 775 °C for 30 min with C/B 0.5 and at 750 °C for 45 min with C/B 1 produced samples with three different luminescent colors (violet-blue-yellow and blue-yellow-green respectively), where each color could be separated conventionally. The measurement of luminescence using a PL spectrometer showed photoluminescence at 413–485 nm for the 775 °C sample and 432–511 nm for the 750 °C sample. In the 775 °C sample, PL of sample red-shifted from violet to green, while the 750 °C sample red-shifted from blue to yellow. The result of the x-ray diffraction analysis (XRD) showed the h-BN phase shifting to a red wavelength from blue to yellow sample. The characterization of chemical functional groups using FTIR showed a wide B–N bond and increasingly sharp bonds of C=N, B–C, and B–N–B from yellow to blue sample. The morphology of the three different colors of the samples looked similar, with an irregular structure, but its EDX characterization showed an increasing B/N ratio for the green to blue sample. From these results, it can be concluded that the characteristics of BCNO are in?uenced by h-BN phase, where an increase of B/N leads to the photoluminescence shifting to blue.
关键词： BCNO,urea combustion method,multicolor luminescence
更新于2025-09-09 09:28:46
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Synthesis of nanocrystalline bismuth oxide and its visible photocatalytic activity in the degradation of an organic dye
摘要： Bismuth oxide powder was synthesized, characterized and employed as a visible light photocatalyst for the degradation of aqueous solutions of Orange G (OG), a mono azo dye that is a commonly used colouring agent in various industrial applications. A simple combustion method using urea as fuel was employed to synthesize the metal oxide nanopowders. The prepared material was found to be nanocrystalline in nature as confirmed by XRD analysis. The band gap energy of the material is calculated by plotting (Ah(cid:1))2 vs. h(cid:1) from the UV-DRS spectrum and it is found to be 2.7 eV. The surface morphology and roughness of the material was studied by FE-SEM and AFM techniques. XPS and EDAX studies confirmed the elemental purity and presence in the nanomaterial. Preliminary studies were carried out in order to optimize the solution pH, catalyst dosage and initial dye concentration. As the catalyst possessed good activity at all pH values, thereafter all the photocatalytic reactions were carried out at neutral pH to make the process less cumbersome and cost effective. An optimum catalyst dosage of 1.5 g/L was fixed for a dye solution of 5 mg/L concentration. Kinetic studies showed the photo-degradation to follow pseudo-first order kinetics. Studies on the effect of electrolytes in solution showed that there was a decrease in the efficiency of the catalyst in the presence of the electrolytes. Reusability studies were performed on the catalyst to estimate the economic viability of the system.
关键词： visible light,combustion method,Bismuth oxide,Orange G,photocatalysis
更新于2025-09-09 09:28:46
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Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method
摘要： ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm?1 represents E2H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.
关键词： Combustion method,Spintronics,Ferromagnetism,ZnO nanoparticles
更新于2025-09-09 09:28:46
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Influence of alkali substitution in La0.7Ca0.3Mn0.8Cr0.2O3 perovskite manganite on structural, magnetic, and transport properties
摘要： In order to study the effect of A-site cation mismatch on the structural, magnetic, and transport properties, a systematic investigation of La0.7Ca0.25A0.05Mn0.8Cr0.2O3 (A = Ca, Li, Na, K) has been undertaken. The XRD data of the materials, prepared by glycine-nitrate combustion method, have been analyzed by Rietveld refinement technique. The iodometric and EDX results show that except K doped sample, the desired stoichiometry of all the phases remains the same. The phases display a paramagnetic to ferromagnetic transition at low temperature with Tc found to decrease with decreasing ?rA?. It has been concluded that the conduction mechanism was dominated by small polaron hopping model in the high temperature paramagnetic semiconducting region.
关键词： Combustion method,Transport properties,Magnetic properties,Rietveld refinements
更新于2025-09-09 09:28:46