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- 2018
- tumor imaging
- conductivity
- MRI
- EPT
- Electrical properties tomography
- Optoelectronic Information Science and Engineering
- Ghent University
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Optical, magnetic and ferroelectric properties of Ba0.2Cu0.8-xLaxFe2O4 (x?=?0.2–0.6) nanoparticles
摘要： The Ba0.2Cu0.8-xLaxFe2O4 (x = 0.2, 0.4 & 0.6) (BCLF) nanoparticles were prepared by hydrothermal method and further characterized for structural, morphological, optical, magnetic, and ferroelectric properties. The structural analysis was carried out using X-ray diffraction spectra. These results revealed that all the samples showed the presence of cubic spinel phases. The Fourier transform infrared (FTIR) studies expressed the formation of broad (ν1) and narrow (ν2) absorption bands which can reflect the arrangement of cations between tetrahedral (ν1) and octahedral (ν2) sites. The surface morphology was studied using the field emission scanning and transmission electron microscopes (FESEM & TEM). The FESEM pictures expressed the gradual formation of nanofibers with increase of La-content. The variation of optical bandgap (Eg~1.96–2.15 eV) as a function of substituent concentration was elucidated. The magnetization versus applied magnetic field (M–H) loops of BCLF nanoparticles showed the superparamagnetic nature which can be useful for the biomedical applications. The cation distribution was made between the octahedral (B) and tetrahedral (A) sites using the Neel's two-sublattice model.
关键词： Nanoparticles,Structure,Optical properties,Rare Earth,Magnetic properties
更新于2025-09-23 15:23:52
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The first synthesis of CdFe12O19 nanostructures and nanocomposites and considering of magnetic, optical, electrochemical and photocatalytic properties
摘要： CdFe12O19 nanostructures and nanocomposites were synthesized via sol-gel auto-combustion method. The CdFe12O19/CdTiO3 nanocomposites were prepared at 850 ?C after 1 h calcination, when molar ratio of Cd:Ti is 1:1. Effects of the molar ratio of Cd:Ti, type of precursor and calcination temperature were investigated. Both nanostructures and nanocomposites were ferromagnetic at room temperature, with saturation magnetizations (Ms) 2.561 and 11.269 emu g–1, and coercivities (Hc) 696.517 and 969.068 Oe, respectively. SEM, TEM, FTIR, EDS and XRD showed morphology, composition and particle size of the products. VSM, UV-Vis and CV were used to investigate the magnetic, optical and electrochemical properties. The band gap values of the nanocomposites were larger than that in the nanostructures. Also photocatalytic properties of the nanocomposites were investigated. This is the first attempt on the study of photocatalytic performance of the cadmium hexaferrite nanostructures and nanocomposites. The effects of various factors including composition and particle size of the nanocomposites, the Ti:Cd molar ratio and also kind of organic dye on the photocatalytic behavior of the products were evaluated. The photocatalytic activity achieved a maximum when ratio of Ti:Cd was 1:1. Methyl orange, methylene blue and methylene violet decompositions were about 71.35, 55.08 and 62.27% by nanocomposites, respectively.
关键词： Nanostructures,Photocatalytic,Optical properties,Ferrites.,Magnetic properties
更新于2025-09-23 15:23:52
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Prediction of Structural, Vibrational and Nonlinear Optical Properties of Small Organic Conjugated Molecules Derived From Pyridine
摘要： Nonlinear optical (NLO) effects of organic materials are caused by delocalized electrons and large polarization in molecules. In the present work, theoretical study by using the Density Functional Theory (DFT) at B3LYP/6-311G(d,p) level of theory on three types of pyridine derivates 2,6-dimethoxy-3,5-dinitropyridine (M1), 2-methoxy-3-nitropyridine (M2) and 2-methoxy-5-nitropyridine (M3) is reported. The nuclear magnetic resonance (1H- and 13C-NMR) chemical shifts of the title compounds were calculated using the Gauge Independent Atomic Orbital (GIAO) method and compared to the observed results. Both infrared absorption and Raman are complementary to provide characteristic fundamental vibrations that are necessary for the identification of the molecular structures. Electronic properties such as frontier molecular orbital (HOMO, LUMO), ionization potential (IPad) and electronic affinity (EAad) were determined to get better insight into the molecular properties. Using the Time-Dependent Density Functional Theory (TD-DFT), electronic absorption spectra have been predicted and closely matching the experimental findings. The natural bonding orbital (NBO) calculations were performed in order to elucidate various second order interactions in between the filled and vacant orbitals which are a measure of the intermolecular as well as the delocalization within the molecule. In addition, we have demonstrated that these molecular systems have large first static hyperpolarizabilities and may have potential applications in the development of NLO materials.
关键词： NLO properties,Electronic properties,DFT,Optical spectra,NBO
更新于2025-09-23 15:23:52
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Structural and Optical Properties of CeO2 Nanoparticles Synthesized by Modified Polymer Complex Method
摘要： Ceria nanoparticles (Ceria-NPs) were synthesized using a modified polymer complex method and their structural and optical properties were evaluated. The solids were heated at 550 °C and characterized using Raman, UV–Vis absorption, diffuse reflectance, X-ray photoelectron and photoluminescence spectroscopies, X-ray diffraction (XRD) and scanning and transmission electron microscopy. The primary particles obtained presented a size of ~ 10 nm. The XRD indicated that CeO2 was the only crystalline phase. From the UV–Vis and diffuse reflectance spectra, energy values of 3.8 eV and 3.4 eV were obtained, values that can be associated with band—band electronic transitions and/or with those that involve ionized states located within the gap caused by defects and isolated atoms of Ce3+. Photoluminescence spectra reiterated the existence of localized states in the gap. Raman spectra revealed the existence of peroxide (O2^2-) and superoxide (O2^-) over the surface of the ceria-NPs. The XPS results indicated that the concentrations of Ce3+ and Ce4+ were ～ 20.5% and ～79.5% respectively, and that the stoichiometry of oxygen was 1.9 per atom of Ce. The results obtained from the characterization of CeO2-NPs synthesized make it as promising material for environmental remediation, biomedicine, gas sensing and optoelectronic applications.
关键词： Modified polymer complex,Structural properties,Ceria-NPs,Optical properties,Synthesis
更新于2025-09-23 15:23:52
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A comparative ab initio study of the structural, mechanical, electronic and optical behaviors of ZnO:Ni thin films with nanometer scale
摘要： The electronic and optical properties of undoped and Ni–doped ZnO thin films with nanometer scale have been studied in the wurtzite phase, by first–principle approach. Density functional theory has been employed to calculate the fundamental properties of the films using full–potential linearized augmented plane–wave method. Ni doping was found to reduce the bandgap value of the material. Additionally, DOS effective mass of the electrons was evaluated. It was revealed that the effective mass of the electrons at the bottom of conduction band increased with Ni doping. Decrease of reflectance for thin films with nanometer scale in the UV–vis region was observed. The substitution by Ni decreased the intensity of the peaks, and a red shift was observed in the absorption peak. Moreover, the static dielectric constant, and static refractive index decreased with Ni content. Energy loss function of the modeled compounds was also evaluated. All calculated parameters were compared with the available experimental and other theoretical results.
关键词： DFT,band structure,structural properties,electronic behaviors,optical properties,ZnO:Ni thin film
更新于2025-09-23 15:23:52
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Tuning photoresponsive and dielectric properties of PVA/CdSe films by capping agent change
摘要： In the present work, hybrid organic-inorganic nanocomposite films based on poly(vinyl alcohol) (PVA) and CdSe quantum dots synthesized in aqueous medium were prepared without the use of organic solvents, by casting aqueous solutions of both PVA and nanoparticles. The effect of different capping agents employed during quantum dot synthesis on thermal, optical, and dielectric properties of nanocomposites was analyzed, finding that capping agents not only affect the interactions between nanoparticles and polymeric matrix, but also the size and photoluminescence of quantum dots, among other properties. Optical, thermal, dielectric and morphological characterization of nanocomposites has been carried out in terms of UV-vis spectroscopy, spectrofluorometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS) and atomic force microscopy, respectively, finding that by the use of different capping agents, final properties of nanocomposites can be tuned, as interactions between PVA and CdSe quantum dots determine their final properties.
关键词： E. Casting,B. Electrical properties,B. Optical properties,A. Nanocomposites
更新于2025-09-23 15:23:52
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Electronic structure, mechanical and optical properties of ternary semiconductors Si <sub/>1-x</sub> Ge <sub/>x</sub> C (X?=?0, 0.25, 0.50, 0.75, 1)
摘要： The electronic structure of silicon carbide with increasing germanium content have been examined using first principles calculations based on density functional theory. The structural stability is analysed between two different phases, namely, cubic zinc blende and hexagonal phases. The zinc blende structure is found to be the stable one for all the Si1-xGexC semiconducting carbides at normal pressure. Effect of substitution of Ge for Si in SiC on electronic and mechanical properties is studied. It is observed that cubic SiC is a semiconductor with the band gap value 1.243 eV. The band gap value of SiC is increased due to the substitution of Ge and the band gap values of Si 0.75 Ge 0.25 C, Si 0.50 Ge 0.50 C, Si 0.25 Ge 0.75 C and GeC are 1.322 eV, 1.413 eV, 1.574 eV and 1.657 eV respectively. As the pressure is increased, it is found that the energy gap gets decreased for Si1-x GexC (X = 0, 0.25, 0.50, 0.75, 1). The elastic constants satisfy the Born – Huang elastic stability criteria. The bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio are also calculated and compared with the other available results.
关键词： mechanical properties,electronic structure,optical properties,First principles study
更新于2025-09-23 15:23:52
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ZnO Micro- and Nanostructures Obtained by Thermal Oxidation: Microstructure, Morphogenesis, Optical, and Photoluminescence Properties
摘要： ZnO micro- and nanostructures were obtained through thermal oxidation of Zn powders at high temperature under air atmosphere. A detailed study of the microstructure, morphology, optical, and photoluminescence properties of the generated products at different stages of thermal oxidation is presented. It was found that the exposure time has a strong influence on the resulting morphology. The morphogenesis of the different ZnO structures is discussed, and experimental parameters for fabricating ZnO tetrapods, hollow, core-shell, elongated, or rounded structures by thermal oxidation method are proposed on the basis on the obtained results. Notoriously, the crystal lattice of the ZnO structures has negligible residual strain, although, the density of point defects increases when the thermal treatment is extended; as consequence, their visible luminescence upon UV excitation enhances.
关键词： growth mechanism,ZnO structures,thermal oxidation,physical properties
更新于2025-09-23 15:23:52
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Structures and electronic properties of Cu <i> <sub/>m</sub></i> Co <i> <sub/>n</sub></i> O <sub/>2</sub> ( <i>m</i> ? <i>+</i> ? <i>n</i> ?=?2–7) clusters
摘要： A theoretical study was carried out of CumConO2(2 ≤ m + n ≤ 7) clusters using density functional method. O2 molecules are adsorbed at top sites. After adsorption, O2 molecules are activated. The Δ2E value of CuCo3O2 cluster is obviously the smallest, indicating that its thermodynamic stability is the worst. While Cu6CoO2 displays stronger chemical stability. Charge transfer from Cu–Co to anti-bonding orbital of O2, which leads to O–O getting longer. The Mulliken charge population and PDOS analysis are also discussed.
关键词： electronic properties,O2 adsorption,density functional theory,structures and stability
更新于2025-09-23 15:23:52
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X-Shaped Polycyclic Aromatic Hydrocarbons: Optical Properties and Tunable Assembly Ability
摘要： Although a number of synthetic methodologies have been developed to prepare stable polycyclic aromatic hydrocarbons (PAHs), much less research has been devoted to functionalize the peripheral of molecules to tune the self-assembly ability or introduce functional groups without altering their photophysical properties. Herein, we report twisted “X” shaped molecules prepared through annulation of hexacene with benzoanthracene on the zigzag edge, and an investigation of their photophysical properties and self-assembly properties. The shape-complementary “X” shaped molecules prefer to dimerize, while the π-extension would lead to one dimensional π-stacking. Our findings gave some insights into the design of stable PAHs without disturbing the electronic structures.
关键词： Photophysical properties,Self-assembly,Polycyclic aromatic hydrocarbons,Dimerize
更新于2025-09-23 15:23:52