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Metallic Nanomaterials (Part B) || 3. Size and Shape Controlled Synthesis of Pd Nanocrystals
摘要： Palladium (Pd) has attracted substantial academic interest due to its remarkable properties and extensive applications in many industrial processes and commercial devices. The development of Pd nanocrystals (NCs) would contribute to reduce overall precious metal loadings, and allow the e?cient utilization of energy at lower economic costs. Furthermore, some of the important properties of Pd NCs can be substantially enhanced by rational designing and tight controlling of both size and shape. In this review, we have summarized the state-of-the-art research progress in the shape and size-controlled synthesis of noble-metal Pd NCs, which is based on the wet-chemical synthesis. Pd NCs have been categorized into ?ve types: (1) single-crystalline Pd nano-polyhedra with well-de?ned low-index facets (e.g. {100}, {111} and {110}); (2) single-crystalline Pd nano polyhedra with well-de?ned high-index facets, such as Pd tetrahexahedra with {hk0} facets; (3) Pd NCs with cyclic penta-twinned structure, including icosahedra and decahedra; (4) monodisperse spherical Pd nanoparticles; (5) typical anisotropic Pd NCs, such as nanoframes, nanoplate, nanorods/wires. The synthetic approach and growth mechanisms of these types of Pd NCs are highlighted. The key factors that control the structures, including shapes (surface structures), twin structures, single-crystal nanostructures, and sizes are carefully elucidated. We also introduce the detailed characterization tools for analysis of Pd NCs with a speci?c type. The challenges faced and perspectives on this promising ?eld are also brie?y discussed. We believe that the detailed studies on the growth mechanisms of NCs provide a powerful guideline to the rational design and synthesis of noble-metal NCs with enhanced properties.
关键词： size,shape,Pd,crystal growth,nanocrystal
更新于2025-09-11 14:15:04
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Structural, Optical, Mechanical and Laser Damage Threshold Studies on an active Nonlinear Optical Material: Potassium Thiourea Bromide (KTB) in a Novel Crystal System
摘要： The enhancement of optical transparency, crystalline perfection, laser damage threshold values and principally, mechanical strength of thiourea doped potassium bromide crystals grown under slow evaporation solution growth technique were assessed. The validation and morphology were done by X-ray diffraction analysis. The sample KTB crystallized in orthorhombic system is unique and novel. The vibrational range in the FT-IR affirmed the functional groups present in the title compound. The energy gap Eg found to be 4.12eV with broad transparency window between 300.600nm to 1100nm. Second harmonic studies manifest the suitability of the crystal for frequency conversion and doubling applications. The positive photo conducting nature of the material aspires that the sample would be more electrically conductive on the absorption of electromagnetic radiation. The laser damage threshold value indicates the aptness of the sample to confront against high power intensities. The elastic(C11), plastic, fracture traits(Kc) along with the yield strength(σv) and brittleness index(Bi) were calculated and reported for the first time under orthorhombic system. The result also evident appreciable mechanical strength of the crystal, as it holds cardinal importance in technological applications.
关键词： Crystal growth,Mechanical properties,Non linear optical material,Characterization,LDT,Photoconductivity
更新于2025-09-11 14:15:04
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Scintillation properties and increased vacancy formation in cerium and calcium co-doped yttrium aluminum garnet
摘要： Co-doping with divalent elements is known to improve the light yield and decay times of some cerium-activated scintillators, despite the stabilization of tetravalent Ce4+, previously believed to be non-luminescent, from the Ce3+ state. Ce4+ stabilization is a charge compensation mechanism which results from divalent ion substitution of a 3 + site. To elucidate the underlying mechanisms, which remain poorly understood, we have grown three Ce,Ca:YAG crystals with di?erent amounts of calcium co-dopants by the Czochralski method and characterized their scintillation and defect properties. Calcium co-doping reduces the decay times and stabilizes the formation of Ce4+ as expected. Interestingly, X-ray ?uorescence analysis reveals a decreased concentration of cerium within the YAG crystal for the sample doped with high levels of Ca, which could contribute to the observation that scintillator properties are improved only for low levels of Ca co-doping. Additionally, positron annihilation spectroscopy reveals an increase in the concentration of vacancies with increasing Ca concentration, while thermoluminescence is observed to show no detectable signal. Furthermore, room temperature photo-luminescence of the Ce 4f to 5d1 transition demonstrates decreased emission with increasing Ca co-doping. These data suggest that Ca co-doping decreases the decay time by creating defects with non-radiative decay pathways.
关键词： A2. Czochralski method,B2. Scintillator materials,A2. Single crystal growth,A1. Defects,B3. Scintillators,A1. Doping
更新于2025-09-11 14:15:04
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Synthesis of plate-like B-site complex perovskite Ba(Zr0.1Ti0.9)O3 microcrystals
摘要： B-site complex perovskite Ba(Zr0.1Ti0.9)O3 microcrystals at micron size with a plate-like shape was successfully synthesized using topochemical microcrystal conversion and molten salt method. A plate-like Bi4(Zr0.1Ti0.9)3O12 precursor was first synthesized by Zr4+ substitution of Ti4+ using molten salt. Then plate-like 4–9 μm Ba(Zr0.1Ti0.9)O3 microcrystals with an average thickness <500 nm were synthesized by mixing BaCO3, Bi4(Zr0.1Ti0.9)3O12, and KCl molten salt at 800 °C. Finally, the topochemical microcrystal conversion reaction between BaCO3 and Bi4(Zr0.1Ti0.9)3O12 precursor was carried out. The results pave the way for fabricating plate-like B-site complex perovskite microcrystals.
关键词： Plate-like BaZr0.1Ti0.9O3,Topochemical microcrystal conversion,Texture,Crystal growth,Powder technology
更新于2025-09-11 14:15:04
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Improvement in Photocatalytic Properties of Synthesized Nano-structured ZnO in Magnetic Water and in Presence of Static Magnetic Field
摘要： This article presents the effects of magnetic water (MW), and static magnetic field (SMF) compared to non-magnetic water (NMW) on the synthesis and photocatalytic efficiency of ZnO nano-structures. ZnO nano-structures are synthesized in the three methods; in the MW (110 mT), in the presence of a SMF (75 mT) and NMW. The Different analysis is performed on the synthesized materials utilizing UV-visible spectrometer, XRD and FESEM. Then, the photocatalytic activities of the ZnO samples are comparatively studied. The results of the XRD analysis show that all the three nano-structures of ZnO are in hexagonal phase. The average size of the synthesized nano-structure ZnO crystals in the presence of SMF and MW are 10% and 19% bigger than the synthesized sample in the NMW. The FESEM images show the synthesized ZnO samples in the NMW, and the MW has a rod-like structure, but in the presence of SMF looks to be agglomerated. Photocatalytic activity of synthesized ZnO in the presence of the SMF and the MW are respectively 26% and 24% higher than the synthesized ZnO in NMW. Also, on comparing the performance of these ZnO nano-structures with the micron-sized sample, around 58% improvement in photocatalytic activity is observed.
关键词： ZnO,magnetic water,photocatalytic activity,crystal growth,hexagonal,nano-rod
更新于2025-09-11 14:15:04
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Pentacene Crystal Growth on Silica and Layer-Dependent Step-Edge Barrier From Atomistic Simulations
摘要： Understanding and controlling the growth of organic crystals deposited from the vapor phase is important for fundamental materials science and necessary for its application in pharmaceutical and organic electronics industries. Here this process is studied for the paradigmatic case of pentacene on silica by means of a specifically tailored computational approach inspired by the experimental vapor deposition process. This scheme is able to reproduce the early stages of the thin film formation, characterized by a quasi layer-by-layer growth, thus showcasing its potential as a tool complementary to experimental techniques for investigating organic crystals. Crystalline islands of standing molecules are formed at a critical coverage, as a result of a collective reorientation of disordered aggregates of flat-lying molecules. The growth then proceeds by sequential attachment of molecules at the cluster and then terrace edges. Free energy calculations allowed us to characterize the step edge barrier for descending the terraces, a fundamental parameter for growth models for which only indirect experimental measurements are available. The barrier is found to be layer dependent (approximately 1 kcal/mol for the first monolayer on silica, 2 kcal/mol for the second monolayer) and to extend over a distance comparable with the molecular length.
关键词： pentacene,atomistic simulations,silica,step-edge barrier,crystal growth
更新于2025-09-11 14:15:04
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MORPHOLOGY OF DIAMOND SINGLE CRYSTALS GROWN IN THE Fe-Co-Mg-C SYSTEM
摘要： Diamond single crystals in a Fe-Co alloy with addition of 5 and 10 wt. % Mg by temperature gradient method were grown and their morphology was studied. For crystals obtained in the Fe-Co alloy with 5 wt. % Mg, the faces of octahedron, cube, rhomb-dodecahedron and tetragon-trioctahedron {311} were observed. When the magnesium content in the solvent-alloy increase up to 10 wt. % under the same growth conditions the tetragon-trioctahedron {311} faces on diamond crystals were absent. The topography of diamond crystals faces grown in different systems indicates that octahedron and cube are active growth forms with their growth pyramids, and rhomb-dodecahedron and tetragon-trioctahedron {311} are forms of passive growth.
关键词： A1.Crystal morphology,B1. Diamond,A2. Single crystal growth,A2. Growth from high temperature solutions
更新于2025-09-10 09:29:36
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Study of indium and antimony incorporation into SnS2 single crystals
摘要： Pure SnS2, 5% In-doped SnS2, 15% In-doped SnS2, 5% Sb-doped SnS2 and 15% Sb-doped SnS2 single crystals are grown in closed sealed quartz ampoule by direct vapour transport technique. The energy dispersive analysis of X-rays analysis of all the five as-grown single crystals showed them to be stoichiometric. The X-ray diffraction analysis showed that all the crystals are single phase possessing a hexagonal structure with (001) preferential orientation. The surface morphology of as-grown single crystals studied by scanning electron microscopy and optical microscopy showed crystal growth is by layer growth mechanism supported by screw dislocation. Selected area electron diffraction showed hexagonal spot pattern confirming the single crystalline nature of the crystals. Optical bandgap of the as-grown crystals determined by UV-Vis-NIR spectroscopy showed that the single crystals possess direct optical bandgap and the value varied between 1.89 and 2.31 eV. The photoluminescence spectra study showed the presence of six peaks. The Raman spectra showed SnS2 type the A1g vibrational mode and shifting in A1g vibrational mode with In and Sb doping. The results are elaborated in details.
关键词： Single crystal growth,Doping,Characterization,Crystal morphology,X-ray diffraction,Crystal structure
更新于2025-09-10 09:29:36
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Crystal growth and optical characterization of an organic single crystal for frequency conversion applications
摘要： Organic nonlinear optical 2-methylquinolinium L-malate single crystals have been grown by slow evaporation solution growth technique from a mixture of 2-methylqiunoline and L-malic acid in ethanol solution at ambient temperature. Single crystal X-ray diffraction analysis reveals that grown crystal in monoclinic system with non-centrosymmetric space group P21 and the lattice parameters are a = 7.35 ?, b = 26.51 ?, c =10.83 ?, α = γ = 90o, β = 102.95o and V = 2057.4 ?3. UV-vis spectrum indicates that the crystal is transparent (75%) in the entire visible region with a cut-off wavelength of 437 nm and optical energy band gap Eg is found to be 2.71 eV. Microhardness measurement reveals the mechanical strength of the grown crystal. The photoluminescence spectrum shows the blue emission of the crystal. Laser damage threshold studies was carried out to ascertain the suitability of grown crystal for laser applications.The relative second harmonic generation efficiency of 2-methlquinolinium L-malate crystal was found to be two times greater than that of KDP.
关键词： Photoluminescence,Optical band gap,SHG studies,Laser damage threshold,Crystal growth
更新于2025-09-10 09:29:36
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Temperature Gradient Designing and Optical Properties of SrI2 and SrI2:Eu Crystals Grown by Edge-Defined Film-Fed Growth (EFG) Method
摘要： In this work, SrI2 and SrI2:Eu5% single crystals with size of ?10 9 60 mm3 and ?10 9 30 mm3 were successfully grown by edge-de?ned ?lm-fed growth (EFG) method. In the crystal growth process, the crack and turbidity of the crystal were solved by designing a temperature ?eld, thereby optimizing crystal quality and obtaining crack-free crystals. X-ray diffraction analysis was performed on the grown crystals, and the optical properties of these crystals have been investigated at room temperature. Under the excitation of ultraviolet (UV) light, the crystals exhibit a single luminescence peak centered at 435 nm (kex = 350 nm), and the photoluminescence (PL) decay time is 0.594 ls. In addition, the designed temperature ?eld also provides a reference value for other crystals grown by EFG method.
关键词： Crystal growth,temperature ?eld,scintillation materials,optical properties
更新于2025-09-10 09:29:36