Synthesis of cubic and monoclinic hafnia nanoparticles by pulsed plasma in liquid method

Hafnia (HfO₂, hafnium dioxide) is a wide band gap and high-κ material, and the metastable cubic hafnia has a much higher permittivity compared with the normal monoclinic hafnia. Here, we employ a one-step process, the pulsed plasma in liquid (PPL) method to synthesize two types of hafnia nanoparticles (NPs): one which is mainly in cubic phase (cubic: 81.7 at%, monoclinic: 18.3 at%) and the other which is in monoclinic phase. High-resolution transmission electron microscopy images showed that the particles were small (particle size ~3 nm). X-ray absorption fine structure analysis showed no chemical shifts, indicating that the synthetic hafnia NPs contained no oxygen vacancy. The synthetic hafnia NPs mainly in cubic phase showed a much higher relative permittivity than that of the commercial hafnia (monoclinic), and have a larger band gap than the synthetic monoclinic hafnia NPs.     

White luminescence of bismuth and samarium codoped Y2O3 phosphors

In this work Sm³⁺ (0–2.0 at%) and Bi³⁺ (0–2.0 at%) doped Y₂O₃ luminescent powders were prepared by a sol–gel method from yttrium acetylacetonate, samarium and bismuth nitrates as metal sources. The as prepared powders (chemical composition is close to stoichiometric Y₂O₃) present the cubic structure from 700 °C, and at 900 °C are characterized by the presence of rounded particles with heterogeneous size of 42.9 nm. Luminescent effect of ions of Sm³⁺ and Bi³⁺ into Y₂O₃ host as was studied on heat treated powders from 800 to 1100 °C. The combination of the red luminescence from the Sm³⁺ ions and the bluish from Bi³⁺, makes the synthesized phosphors candidates to be used in fabrication of phosphor-converted light-emitting diodes (LEDs).     

Synthesis,structural and optical properties of ZnS,CdS and HgS nanoparticles from dithiocarbamato single molecule precursors

Dithiocarbamate complexes of Zn(II), Cd(II) and Hg(II) were synthesize and characterized by elemental analysis, thermogravimetric analysis, UV–Vis, FTIR, ¹H- and ¹³C-NMR spectroscopy. The complexes were thermolyzed at 180°C to prepare HDA-capped ZnS, CdS and HgS nanoparticles. The optical properties of the nanoparticles showed absorptions that are blue shifted with respect to the bulk and narrow emissions. The ZnS nanoparticles are in the cubic phase with average crystallite sizes of 3–5 nm. The CdS nanoparticles consist of a mixture of cubic and hexagonal phases with particle sizes of 8–22 nm, while the HgS nanoparticles are in the cubic phase with average crystallite sizes of 7–14 nm.     

Fabrication,microstructure and spectroscopic properties of Yb:Lu2O3 transparent ceramics from co-precipitated nanopowders

Ytterbium doped lutetium oxide (Yb:Lu₂O₃) transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) of the powders synthesized by the co-precipitation method. The effects of calcination temperature on the composition and morphology of the powders were investigated. Fine and well dispersed 5?at% Yb:Lu₂O₃ powders with the mean particle size of 67?nm were obtained when calcined at 1100?°C for 4?h. Using the synthesized powders as starting material, we fabricated 5?at% Yb:Lu₂O₃ ceramics by pre-sintering at different temperatures combined with HIP post-treatment. The influence of pre-sintering temperature on the densities, microstructures and optical quality of the 5?at% Yb:Lu₂O₃ ceramics was studied. The ceramic sample pre-sintered at 1500?°C for 2?h with HIP post-treating at 1700?°C for 8?h has the highest in-line transmittance of 78.2% at 1100?nm and the average grain size of 2.6?µm. In addition, the absorption and emission cross sections of the 5?at% Yb:Lu₂O₃ ceramics were also calculated.     

Cathode plasma electrolytic deposition of Al2O3 coatings doped with SiC particles

Semiconductor particles doped Al₂O₃ coatings were prepared by cathode plasma electrolytic deposition in Al(NO₃)₃ electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings.     

Effect of europium concentration on the photoluminescent and thermoluminescent properties of HfO2:Eu3+ nanocrystals

This work is aimed to determine the influence of the europium concentration on the photoluminescent and thermoluminescent properties of the HfO₂:Eu³⁺ synthesized by hydrothermal method. Samples were prepared at Eu³⁺ contents of 0, 1, 3, 5 and 7?at%. The structural, morphological, photoluminescent and thermoluminescent characteristics of the material, as well as the kinetic parameters of the glow curve when it was exposed to UV radiation at 254?nm are presented. The maximum response for the photoluminescence and thermoluminescence properties, with an integrated signal more than six times greater than the signal obtained for the intrinsic sample, was found for the sample with 5?at% Eu³⁺. Nanocrystal sizes of 28?nm were obtained for the pure sample and 46?nm for the sample doped with the highest concentration of Eu³⁺.The microcrystals showed a preferential growth in the (022) direction.     

Natural fuel assisted synthesis of Mg–Cu ferrite nanoparticles: Evaluation of structural,dielectric, magnetic and humidity sensing properties

The effects of lemon juice and annealing treatment on phase composition, vibrational modes, microstructural and dielectric behavior of Mg doped copper ferrite nanoparticles have been synthesized and analyzed in detail in this present work. The various characterization techniques are used to examine the phase, microstructural, vibrational and dielectric nature of the samples at different annealing temperatures (600 °C and 900 °C). The phase and microstructure of Mg substituted CuFe₂O₄ nanoparticles have been analyzed by XRD, SEM and TEM. The secondary phase peaks free XRD spectra revealed that the as burst and the annealed Mg–CuFe₂O₄ nanoparticles have single phase cubic spinel structure. The average crystallite size of the as burnt, annealed 600 °C and annealed 900 °C of as prepared nanoparticles are calculated as 8.9 nm, 12.8 nm and 31.6 nm respectively. Another verification of the spherical shaped particle's size was confirmed by TEM analysis and it found as average size of 28.7 nm, this result is well matched with XRD analysis. The effect of size with impact of annealing treatment on magnetic and dielectric properties also analyzed. The size-dependent Mg–CuFe₂O₄ nanostructures exhibit promising sensing properties which ensure them as a potential candidate for humidity sensor applications. The as-burnt and annealed samples both show a humidity response over the humid range of 10–95 %RH. The sample annealed at 900 °C has the highest average sensor response (6.02 MΩ/%RH) among the as-burnt sample (6.38 MΩ/%RH) and annealed sample at 600 °C (7.11 MΩ/%RH).     

Sol-gel synthesis and luminescent properties of YVO4 : Eu nanoparticles

Experimental results on the synthesis of luminescent YVO₄: Eu nanoparticles with the method of metalopolymer gel decomposition are presented. The sizes of the coherent scattering regions according to the X-ray diffraction data range from 25 to 40 nm and increase with the increase of the annealing temperature from 800 to 1000°C. It was shown that the obtained nanoparticles demonstrate good luminescent properties. The luminescence intensity and lifetime of the excited state increase with the increase of the annealing temperature. Nanoparticles are good candidates to use as luminescent labels.     

The photoluminescence characteristics of Tb2S3 nanoparticles embedded in sol–gel silica xerogel

The silica xerogel doped with Tb₂S₃ nanocrystallites has been prepared by sol–gel process. UV–Vis spectra, transmission electron micrograph (TEM), excitation spectra and photoluminescence (PL) spectra of doped xerogel samples have all been investigated at room temperature. A novel luminescent phenomenon has been observed from Tb₂S₃ nanoparticles doped silica xerogel. The emission spectrum of the doped sample shows high fluorescence intensity. The photoluminescence spectrum of the doped samples consists of two emission bands, one at 440 nm and the other at 600 nm. The sharp emission band of Tb₂S₃ from the doped samples has been assigned to the luminescence centers of Tb₂S₃ quantum dots in the porous phosphorescence silica xerogel.     

Synthesis and Properties of Boron Doped NaxCo2O4 Nanocrystalline Ceramics

Sodium cobalt oxide (NaCo₂O₄) nanofibers with diameters ranging between 20 and 200?nm were prepared by electrospinning a precursor mixture of PVA/(Na–Co) acetate. This was the first time any such attempt was made. Afterwards, the electrospun nanofibers were subjected to calcination treatment. The characteristics of the fibers were investigated using a Fourier transform infrared spectroscopy, a X-ray diffractometer, and a scanning electron microscopy. The boron doped and undoped NaCo₂O₄ nanofibers calcined at 850?°C were polycrystalline of the γ Na_xCo₂O₄ phase having diameters ranging between 20 and 60?nm with grain sizes of 5–10?nm, and the nanofibers calcined at 800?°C were single crystals having linked particles or crystallites with particle sizes ranging between 60 and 200?nm. The results indicated a significant effect of calcination temperature on the crystalline phase and morphology of the nanofibers. It could be seen in the SEM micrograph of the fibers that when boron was added, this resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123?nm, respectively. The grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118?nm, respectively.     

Structural,optical, morphological properties of silver doped cobalt oxide nanoparticles by microwave irradiation method

The synthesis of silver doped cobalt oxide nanoparticles by microwave-assisted method and their structural, optical, antibacterial activities are presented in this study. The doping concentrations were chosen as 5, 10, 15, and 20 wt percentages. The sample was undergone powder X-ray diffraction studies and the result shows the good crystalline nature of the sample. Also, the average crystallite size increases from 13.95 nm, 21.26 nm, 26.13 nm, and 28.35 nm with different doping concentrations. The transmission electron microscopy image shows cubic and spherical morphology. The optical properties were tested by UV–vis–NIR absorption spectrum. It indicates the decrease of band gap value. From the antibacterial activity studies, the 20 wt % Ag doped nanoparticles exhibit better activity.     

Role of doped nitrogen and sulphur in cobalt/cobalt-zirconium nanoferrites synthesized by facile methods

Nitrogen/sulphur doped cobalt and cobalt zirconium mixed nanoparticles were synthesised by coprecipitation/wet impregnation methods. X-ray diffraction and X-ray fluorescence spectroscopic studies reveal the formation of monophasic cubic spinel structure with expected stoichiometries. Average crystallite sizes vary in the range of 17–26 nm. X-ray photoelectron and energy dispersive X-ray spectroscopic studies indicate the successful incorporation of non-metal elements into the ferrite lattice. Fourier-Transform infrared and Raman spectroscopic studies confirm the presence of stable cubic spinel ferrite structure of cobalt ferrite after doping. Evidences point towards the insertion of sulphur and nitrogen as cations, contrary to other metal oxides like titania. Thermal stability studies prove that ferrite formation is a continuous process producing stable crystalline spinel nanoparticles around 700 °C. Magnetic measurements at room temperature indicate decrease in saturation magnetisation with doping whereas coercivity increases with reduction in the particle size. DC resistivity measurements in the range of 30–400 °C show decrease in resistivity with increase in temperature, indicating semiconducting behaviour. The results of microstructural, magnetic and dielectric properties suggest that the prepared nanoparticles are suitable for catalysis, adsorption recycle, high frequency devices, inductors and biomedical applications.     

Chemical synthesis and structural characterization of nanocrystalline powders of pure zirconia and yttria stabilized zirconia (YSZ)

Nanocrystals of pure zirconia and yttria stabilized zirconia (YSZ) are obtained by a simple chemical synthesis route using sucrose, polyvinyl alcohol (PVA) and metal nitrates. The reaction mixture on pyrolysis and calcination gives nanocrystals. These are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size of the nanocrystallites for pure zirconia is in the range of about 7.0–45.0 nm and for yttria stabilized zirconia, is in the range of about 5.0–24.0 nm at 200°C and above, according to the preparative condition. At 200°C, pure zirconia forms cubic phase and this cubic phase is stable up to 600°C and then slowly transformed into monoclinic form. For yttria stabilized zirconia, the crystals are tetragonal in the temperature range from 200 to 1200°C.     

Cytotoxic effect of functionalized superparamagnetic samarium doped iron oxide nanoparticles for hyperthermia application

Magnetic Fluid Hyperthermia (MFH) is an emerging and safe technique for cancer treatment. Radiotherapy and Chemotherapy are widely adopted techniques for treating cancer but cause damage to the nearby healthy tissue. This paves the way for hyperthermia treatment for cancer. Since healthy cells are more heat-tolerant than malignant cells, magnetic nanoparticles with superparamagnetic properties were used in hyperthermia treatment. Surface modified magnetite (Fe₃O₄) iron oxide nanoparticles with enhanced stability, solubility, bio-compatibility and magnetic property were employed in hyperthermia treatment. In the present study, Superparamagnetic Samarium doped magnetite (Fe₃O₄:Sm) nanoparticles were functionalized with Oleylamine (OAm) and polyvinyl alcohol (PVA) by the sol-gel process. The obtained nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and UV–Visible diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA) and Vibrating Sample Magnetometer (VSM). From XRD data, the crystallite size of oleylamine coated samarium doped magnetite (OAm–Fe₃O₄:Sm) and PVA-coated samarium doped Fe₃O₄ (PVA- Fe₃O₄:Sm) were found to be 9.5 nm and 10.9 nm, respectively. TEM images of the functionalized nanoparticles were visualized as a spherical structure with reduced agglomeration. UV-DRS gives the bandgap value of OAm–Fe₃O₄:Sm and PVA- Fe₃O₄:Sm coated samarium doped magnetite to be 2.3 eV and 2 eV respectively. VSM measurement of OAm-Fe₃O₄:Sm and PVA- Fe₃O₄:Sm coated, showed superparamagnetic behaviour. The cytotoxicity study on the L929 cell line shows that both oleylamine and PVA-coated samarium doped magnetite were less toxic and biocompatible compared to the uncoated Fe₃O₄:Sm. The hyperthermia study reveals a rise in temperature within a few seconds with a high Specific Absorption Rate (SAR) value, confirming that the functionalized Samarium doped Fe₃O₄ was an effective nanomaterial for hyperthermia application.     

Key processing of porous and fibrous LaCoO3 nanostructures for successful CO and propane sensing

Currently, perovskite structures have had an important impact in the development of gas sensors. In this work, perovskite LaCoO₃ nanoparticles were synthesized by a simple, economic and reproducible processing by the solution method. The reactive precursors were nitrates of lanthanum and cobalt, using ethylenediamine as a chelating agent and distilled water as solvent. The gel formed by the solvent evaporation (through microwave radiation) was dried at 200?°C and later calcined at 300, 400, 500, 600, and 700?°C for 5?h. The samples were analyzed by X-ray diffraction, infrared spectroscopy, thermogravimetry, scanning, transmission, and atomic force microscopies, and nitrogen physisorption. These analyses confirmed the formation of LaCoO₃ nanoparticles (size ~ 47?nm) at relatively low temperatures. The particles showed a continuous connectivity, generating a porous surface with a fibrous appearance. Starting with the synthesized powders, pellets were made and tested as gas sensors in carbon monoxide and propane atmospheres (at concentrations of 0–300?ppm) at different temperatures (25, 150, 250, and 350?°C). The nanoparticles presented high sensitivity, with a greater response in the propane atmosphere.     

Effect of sintering temperature on the microstructure and transparency of Nd,Y:CaF2 ceramics

1 at% Nd, 3 at% Y doped CaF₂ transparent ceramics were obtained by hot pressing at the sintering temperature varing from 500 to 800 °C under vacuum environment with co-precipitated CaF₂ nanopowders. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed that the obtained nanoparticles were single fluorite phase with grain size around 26 nm. Scanning electron microscopy (SEM) observations of the Nd, Y: CaF₂ ceramics indicated that the mean grain size of the ceramic sintered at 800 °C was about 748 nm. The influence of the temperature on the grain size, microstructure and optical transmittance was investigated. For the ceramic sintered at 800 °C, the transmittance was 85.49% at the wavelength of 1200 nm. The room temperature emission spectra of Nd: CaF₂ and Nd, Y: CaF₂ ceramics were measured and discussed.     

Aliovalent Ho3+ ion doped BaZrO3 thin films; Structural,optical and photoluminescence properties

Ho doped BaZrO3 thin film phosphors with varying Ho content (1, 2, 3 and 4?at%) were prepared via pulsed laser deposition technique. To understand the effect of doping on structural, morphological, optical and emission properties of thin films, X-ray Diffractrometer (XRD), Scanning Electron Microscopy (SEM), Spectroscopic Ellipsometry (SE) and Photoluminescence (PL) Spectroscopy have been used, respectively. Polycrystalline nature with single phase cubic crystalline structure of the films has been obtained. The optical band gap energy, as estimated by SE, has been found to increase with increase in the Ho content. The PL spectra of the synthesized phosphor exhibit green and yellow-orange as prominent emission bands in response to 328?nm as excitation wavelength.     

Yttrium doping of Ba0.5Sr0.5Co0.8Fe0.2O3-δ part I: Influence on oxygen permeation,electrical properties,reductive stability,and lattice parameters

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) exhibits a very high oxygen permeability in its cubic perovskite phase, making it a promising candidate for high-temperature energy-related applications such as oxygen-transport membranes. It suffers, however, from a pronounced phase instability at application-relevant temperatures below 840?°C which is presumed to result from a valence change of B-site cobalt. In an attempt to stabilize the cubic BSCF phase, monovalent Y³⁺ was doped in small concentrations (1–10?mol-% yttrium) onto its B-site. The influence of this doping on the physico-chemical properties (electrical conductivity, reductive stability, lattice constant), on the sintering behavior, and on the oxygen permeation of BSCF has been systematically investigated. Despite a slightly adverse effect to permeability (decrease in oxygen permeation by about 20–30%), a doping concentration of 10?mol-% Y is found to completely suppress secondary-phase formation and, hence, stabilize the cubic BSCF system at 800?°C. These findings are extremely promising with regard to a long-term operation of BSCF in atmospheres free of acidic impurity gases.     

Comparison of Effects of Calcium and Magnesium Doping on the Structure and Biological Properties of NaTaO3 Film on Tantalum

Tantalum is widely used in hip joint replacement and knee joint repair, but its clinical application is limited due to its poor biological activity and weak ability to promote new bone formation. Ca and Mg ions are thought to be involved in bone metabolism and play an important physiological role in the angiogenesis, growth, and mineralization of bone tissue. In this work, NaTaO₃ films doped with Ca²⁺ and Mg²⁺ were prepared by hydrothermal synthesis and molten salt method. The doping amounts of Ca²⁺ doped at 450, 550, 650 and 750 °C were 0.59, 3.44, 32.75 and 29.88 at%, and that of Mg²⁺ doped at 300, 350, 400, 450, 500, 550 and 650 °C were 0.62, 1.03, 1.54, 20.12, 21.38, 14.37 and 0.74 at%, respectively. Ca²⁺ and Mg²⁺ are evenly incorporated into NaTaO₃ and cause the change of crystal plane spacing without any significant changes of morphologies below 550 and 400 °C respectively. XPS shows that the cations are the A-site substitution of perovskite structure (ABO₃). According to the morphology and composition analysis of Ca-incorporated samples and Mg-incorporated samples, the optimal preparation temperature of them is 550?°C and 400?°C, respectively. The results show that for “550?°C-Ca” and “400?°C-Mg” the hydrophilicity is 13.9° and 96.1°, the roughness is 114.3 and 54.3?nm, the doping ion concentration of Ca and Mg is 3.44 and 1.54 at%, and the 7-day ICP results is 69.8 and 1.4?ppm, respectively. In addition, cell proliferation experiments and cell morphology related to biological activity and osteogenic properties are discussed, and it is found that the performance of “550?°C-Ca” is better than “400?°C-Mg”. Ca²⁺–NaTaO₃ is a promising implantable material that will be extensive used in bone implants, joint replacements and dental implants.

     

In3+离子在多孔SiO2干凝胶中的发光

采用常规的Sol-gel工艺合成了In^3 掺杂的多孔SiO2干凝胶，In^3 离子作为间隙离子存在于SiO2网络中，展示了一种新颖的发光现象，改变了多孔SiO2干凝胶的发射光谱。这种掺杂的多孔SiO2干凝胶的激发和发射光谱均由2个带组成，短波长的发光峰在440nm(λex=380nm），其相对荧光强度约是未掺杂的多孔SiO2干凝胶的4倍；长波长的发光峰（In^3 离子在多孔SiO2干凝胶的特征发射）在600nm(λex=476nm），其相对荧光强度约是In^3 掺杂ZnS纳米晶的10倍。由此可以看出：掺杂的多孔SiO2干凝胶是一种高效的发光材料。