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Transformation of the Anion Sublattice in the Cation-Exchange Synthesis of Au <sub/>2</sub> S from Cu <sub/>2-x</sub> S Nanocrystals
摘要： Cation exchange is a versatile post-synthetic technique that has been exploited in the synthesis of metastable nanocrystals through preservation of the anion sublattice. Here we report on the mechanistic details of the synthesis of metastable Au2S via cation exchange with Cu2-xS nanocrystals. This conversion requires a transformation of the anion sublattice, from hcp in Cu2-xS to bcc Au2S accompanied by an expansion of the unit cell. The ligand environment plays a key role in the driving force of the reaction as the presence of oleylamine allows the conversion to proceed at room temperature while the addition of trioctylphosphine hinders the reaction. By employing transmission electron microscopy (TEM) on faceted nanocrystals and partial cation exchange of nanocrystals, it was demonstrated that the reaction proceeds in a highly directional manner through the pyramidal facets. Since cation exchange produces high quality nanocrystals as seen through XRD and TEM, UV-Vis and Raman spectroscopy were used to characterize the optoelectronic properties of the metastable Au2S nanocrsytals. A Tauc plot analysis revealed a band gap of 2.6 eV, while two intrinsic Raman modes were identified at 265 cm-1 and 329 cm-1. Density functional theory (DFT) calculations of structures, energy bands, optical spectra, and phonon spectra were performed and combined with the experimental data to provide additional insights into the characterization of Au2S nanocrystals.
关键词： XRD,Raman spectroscopy,UV-Vis,trioctylphosphine,nanocrystals,TEM,Cation exchange,DFT,Cu2-xS,anion sublattice transformation,Au2S,oleylamine
更新于2025-09-09 09:28:46
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Incorporation of ZnO Nanostructures in MIS Architecture through Chemical Routes
摘要： Because it’s physical properties, ZnO is considered a potential semiconductor compound for fabricating electronic and optoelectronic functional devices. In this regard, several growth techniques have been developed in order to meet the requirements of commercial devices based in this material. On the pathway for improving the performance of the current devices, low-dimensional ZnO structures seem a promising alternative. Here, we report the process to obtain a metal-insulator-semiconductor (MIS) structure based on ZnO nanostructures grown on the surface of an anodized aluminum substrate (Al2O3/Al) by chemical routes.
关键词： SEM,morphology,MIS,ZnO,XRD
更新于2025-09-09 09:28:46
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Hydrothermal synthesis and characterization of visible light-driven I-doped Bi2MoO6 photocatalyst
摘要： 0–3% I-doped Bi2MoO6 samples as visible light-driven-photocatalysts were successfully synthesized by a hydrothermal method. Structure, morphology, composition and optical properties of as-synthesized samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, BET surface area analysis, X-ray photoelectron spectroscopy, UV–visible absorption and photoluminescence spectroscopy. The photocatalytic activities of Bi2MoO6 and I-doped Bi2MoO6 samples were investigated through degradation of rhodamine B as a pollutant model induced by visible radiation. The experimental results show that Bi2MoO6 exhibits enhanced photocatalytic activity by doping with iodine. In addition, the mechanism for photocatalytic degradation of organic molecules by I-doped Bi2MoO6 was discussed.
关键词： XRD,I-doped Bi2MoO6,XPS,Photocatalysis
更新于2025-09-09 09:28:46
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Magneto-structural properties and photocatalytic performance of sol-gel synthesized cobalt substituted Ni Cu ferrites for degradation of methylene blue under sunlight
摘要： In this study, Ni0.5-xCoxCu0.5Fe2O4 (with x varying from 0.0 to 0.5) ferrites have been synthesized by a sol-gel auto-combustion method using urea as fuel. The influence of Cobalt (Co2+) content on the structural, optical and magnetic Ni-Cu ferrites was studied by X-ray diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis Spectroscopy (UV-DRS) and vibrating sample magnetometer (VSM). Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) analysis have been used to determine morphology and compositions respectively. The X-ray diffraction studies have been carried out by considering the distance between adjacent crystal planes, lattice constant and average crystallite size which decrease from 44-35 nm with substitution of Co2+. FT-IR spectra show two major stretching bands around 400-600 cm-1. The magnetic parameters were measured at room temperature where increase in saturation magnetization was observed with increase in concentration of Co2+ in Ni-Cu ferrites. The photocatalytic performance study of Co2+ substituted Ni-Cu ferrites was carried out under visible and direct sunlight on methylene blue (MB) dye. The increase in degradation percentage was observed with Co2+ substitution in both visible and sunlight. The catalyst was found to be more efficient in sunlight with 91% degradation of MB within 120 minutes.
关键词： SEM,VSM,Ni-Co-Cu Ferrites,XRD,Sol-Gel Auto-Combustion,Photocatalyst
更新于2025-09-09 09:28:46
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Annealing effects on the properties of tin thin films
摘要： The structure, absorption coefficient and electrical resistivity studies on TiN thin films are presented. The film of thickness 240 nm was grown on Si (100) substrate by DC reactive sputtering at an average deposition rate of ～8 nm/min. After deposition the samples were annealed for 1 h at 600 °C and 2 h at 700 °C in nitrogen ambient and vacuum furnace, respectively. Structural characterizations were performed by Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical properties were investigated by spectroscopic ellipsometry while a four point probe was used for electrical characterization. It was found that the post-deposition annealing of the films did not cause any variation in stoichiometry, but strongly affects the structural parameters such as lattice constant, micro-strain and grain size. The observed increase in the grain size after annealing leads to significantly lower value of the coefficient of absorption. These changes could be directly correlated with variation of electrical properties of TiN thin films.
关键词： RBS,annealing,sputtering,thin film,XRD,titanium nitride,TEM
更新于2025-09-09 09:28:46
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Thermal and Morphological Studies on Bismaleimide Modified ZnO Nanoparticles
摘要： The bismaleimide (N,N'-bismaleimide-4,4'-diphenylmethane) (BMI) modified siliconized zinc oxide nanoparticles were prepared in chloroform. The FT-IR spectroscopy analysis of BMI/ZnO reveals that -NH2 groups of siliconized ZnO reacts with the maleimide double bond of bismaleimide molecules through a nucleophilic (Michael) addition reaction. The thermal (TG) and morphological properties of bismaleimide modified zinc oxide nanoparticles (BMI/ZnO), were investigated. The particle size and morphology of zinc oxide nanoparticles and siliconized zinc oxide nanoparticles were determined by XRD. The SEM images indicate that the diameter of the zinc oxide nanoparticles is in the range of 25-40 nm with a strong aggregation process. It is observed that aggregates of bismaleimide modified siliconized zinc oxide nanocomposites of different size and shape are heterogeneously distributed in the elastomeric surface due to the low shear stress and processing time, which do not make an exfoliated material.
关键词： Bismaleimide modified zinc oxide nanoparticles,FT-IR,TG,SEM,XRD
更新于2025-09-09 09:28:46
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Influence of 120 MeV S9+ ion irradiation on structural, optical and morphological properties of zirconium oxide thin films deposited by RF sputtering
摘要： The calibrated and controlled swift heavy ions (SHI) beam irradiation generates defects which can cause modifications in various properties of the materials such as structural, optical, magnetic, morphological, and chemical etc. The passage of ion through the target material causes the nuclear energy losses (Sn) and electronic energy losses (Se). The Se dominates over Sn in SHI irradiation. In the present study, ZrO2 thin films were grown on silicon and glass substrate by using RF sputtering deposition technique. For the purpose of modifications induced by swift heavy ions, these films were irradiated by a 120 MeV S9+ ion beam of 1 pnA current, with varying ion fluences from 5E12 to 1E13 ions/cm2, using the tandem accelerator at the Inter University Accelerator Center (IUAC), New Delhi, India. The X-ray diffraction (XRD) patterns confirmed the formation of monoclinic and tetragonal phases and it was observed that XRD peak intensities increased up to the fluence of 5E12 ions/cm2 followed by opposite behavior at higher fluences. Atomic force microscope (AFM) study revealed the increased surface roughness after SHI irradiation. In addition to it, the formation of electronic transition states in optical band gap region and enhancement of absorption edge was observed from UV- visible spectroscopy (UV-Vis) results due to which direct band gap energy value decreased from those of un-irradiated samples. Photoluminescence (PL) broad emission spectra were determined using the excitation wavelength at 290 nm with the prominent peak at 415 nm which can be ascribed to Zr vacancies due to band edge emission as a result of free- exciton recombination. Rutherford backscattering spectrometry (RBS) technique was used for depth profiling and elemental composition in zirconia thin films. The expected role of electronic energy loss during ion irradiation to modify the properties of the material has been discussed.
关键词： PL,ZrO2 thin films,XRD,UV-Vis,AFM,RBS,SHI irradiation
更新于2025-09-09 09:28:46
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Tuning the optical properties of ZnO:Cd by doping La and Y
摘要： Zinc oxide doped with Cadmium and rare earth elements synthesized by solgel auto combustion route is reported in this work. The studies have been carried out to analyze the structural, morphological and optical properties of Cd doped ZnO and rare earth doped ZnCdO. The XRD analysis reveals that the addition of rare earth impurity decreases the particle size of ZnCdO. La doped ZnCdO has the least particle size among the samples of ZnCdO and rare earth doped ZnCdO. The morphological changes due to the addition of rare earth impurities have been found. Samples of La doped ZnCdO shows a pillar like morphology. The hexagonal structures are prominently seen in the SEM micrographs of the samples of ZnCdO. The UV-Visible spectral analyses show that the bandgap reduces when ZnCdO is doped with the rare earth impurities. The photoluminescence spectra show the broad spectrum in visible region exhibited by ZnO and a scanty UV emission. The UV emission of rare earth doped samples decreases due to the destruction in the crystal structure. The rare earth doped ZnCdO shows a small peak in green emission that decreases when rare earth impurities are doped. There is a uniform spectral response other than a small Gaussian like green peak. The overall analyses show that the samples can be used in optoelectronic applications to work in the visible region.
关键词： rare earth elements,structural properties,optical properties,UV-Visible spectral analyses,Cadmium,SEM micrographs,photoluminescence spectra,XRD analysis,Zinc oxide,solgel auto combustion,morphological properties
更新于2025-09-09 09:28:46
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Study of Polymorphism of Borovanadate Glass of Sodium by Raman Spectroscopy Low Frequencies
摘要： Sodium tetraborate (100 – x)(Na2B4O7.10H2O) – xV2O5, (x = 0 to 20 mole %) has been elaborated by splat cooling technique. Raman Measurements on the doped and non polish samples reveal the presence of the of α-NaVO3 crystal on the superficial layer. After polishing, Raman spectra characteristic of glasses are obtained with two main bands located at 555 and 1097 cm-1 in the undoped glass and four bands at 241, 381, 776 and 938 cm-1 for the vanadium oxyde doped glasses. The volume devitrification of these glasses occurs at 750° C and the β-NaVO3 crystalline phase is identified by Raman scattering.
关键词： Non-linear optics,Oxide glasses,XRD,Raman scattering,DSC
更新于2025-09-09 09:28:46
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Studies on zinc oxide thin films by chemical spray pyrolysis technique
摘要： Zinc oxide (ZnO) thin films were deposited by chemical spray pyrolysis (CSP) technique using zinc acetate dihydrate solutions on microscopic glass substrates by varying the precursor concentration. The prepared films were characterized structurally and optically, using the powder X-ray diffraction (XRD) and UV analysis and Photoluminescence analysis. Crystallographic properties were analyzed through powder XRD. The XRD patterns shows a hexagonal structure with c-axis orientation (0 0 2) on self texturing phenomenon. Optical transmittance properties of the optimized ZnO thin films were investigated by using UV-Vis spectroscopy. The optical studies predicated a maximum transmittance in the range of above 70% with direct band gap values in the range of 2.9 to 3.2eV for the zinc oxide thin films. Under excitation of 300 nm radiations, sharp deep level emission peak at 2.506 eV dominates the photoluminescence spectra with weak deep level and near band edge emission peak at 3.026 and 3.427 eV respectively.
关键词： Photoluminescence,Transparent conducting oxide (TCO),UV-Vis,Zinc Oxide thin film,CSP technique,X-ray diffraction (XRD)
更新于2025-09-09 09:28:46