EDTA-directed synthesis of highly active porous titania with bicrystalline framework

Porous titania with bicrystalline (anatase and rutile) framework was successfully synthesized by a facile hydrothermal process using inexpensive and nontoxic organic molecules, EDTA (ethylenediamine-tetra-acetic acid) or its sodium salts as a template, which could be removed from porous titania by the extraction with sodium hydroxide aqueous solution and then easily recovered by acidification. XRD investigation suggested that the ratio of anatase to rutile could be readily tuned by employing different sodium salts of EDTA. All of as-prepared porous titania showed higher activities than the commercial photocatalyst P25 for the degradation of methyl orange (MO), because of the high surface area, bicrystalline phase composition and bimodal porous structures.     

Synthesis and characterization of novel flower-like CeF3 nanostructures via a rapid microwave method

Novel flower-like CeF₃ nanostructures with a mean diameter of 190 nm were successfully synthesized via a rapid and facile microwave irradiation route using ethylenediaminetetraacetic acid disodium as the complexing reagent. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence (PL). XRD patterns showed that the CeF₃ nanoflowers were hexagonal phase and had good crystallinity and purity. TEM and SEM images showed that the as-prepared CeF₃ samples displayed 3D flower-like nanostructures and had uniform sizes and morphologies. The experimental results revealed that the as-prepared CeF₃ nanoflowers might be assembled by nanodisks. The formation process of the CeF₃ nanoflowers was preliminarily investigated.     

Bicrystalline zinc oxide nanocombs

Bicrystalline ZnO nanocombs have been prepared by zinc powder evaporation at 650 degrees C. Structural analysis showed that as-synthesized samples are composed of two crystals that form a twin structure parallel to the (113) plane with the growth direction of the branching nanowires and the main stem closely parallel to (0001) and (0110), respectively. Due to the unique twin structures, both sides of the main stems could be Zn-terminated ZnO(0001) polar surfaces. The chemically active surfaces make the aligned branching nanowires grow from both sides of the main stems, which is consistent with the structure of the obtained bicrystalline nanomaterials. The growth of bicrystalline ZnO nanocombs can be explained by polar-surface dominated growth and twins induced growth mechanisms.     

Synthesis of nano-particles of anatase-TiO2 and preparation of its optically transparent film in PVA

Anatase-TiO₂ nano-particles have been synthesized by using long-carbon chain carboxylic acid and titanium tetrachloride (TiCl₄). As-prepared powder has been calcined at 500 °C to obtain highly crystalline TiO₂. Broad X-ray diffraction (XRD) pattern of as-prepared as well as calcined powder showed all prominent peaks for tetragonal crystal structure representing anatase-TiO₂. The particle diameter by applying Scherrer formula was found to be about 20 nm. It was possible to load as-prepared particles in poly vinyl alcohol (PVA) for optical studies. Optically transparent film showed sharp absorption band for TiO₂ nano-particles at ∼ 300 nm. Photoluminescence (PL) studies of the solution showed emission wavelength at about 330 nm. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed that the particles in the film have uniform distribution and even for the powder no agglomeration was observed. Thermal analysis (TGA) showed that the stability of host polymer is enhanced. FTIR spectra showed presence of carboxylate functional group in the powder.     

Synthesis of hexagonal close-packed nanocrystalline nickel by a thermal reduction process

Hexagonal close-packed nickel has been synthesized through reduction of nickel chloride by KBH₄ in ethylenediamine at 300 °C. X-ray powder diffraction and selected-area electron diffraction showed that the as-prepared samples were nickel with a hexagonal close-packed structure. Transmission electron microscopy indicated that the products were nanoclusters, which consist of nickel nanoparticles. The magnetic coercivity of the hcp nanocrystalline nickel is as high as 94.3 Oe.     

A complexant-assisted hydrothermal route for the synthesis of nickel phosphide

Dendritic Ni₂P microstructures were successfully synthesized by a facile hydrothermal route. X-ray powder diffraction, energy dispersive X-ray spectrometer analysis, and Field-emission scanning electron microscopy were used to characterize the as-obtained products. The results showed that the as-prepared product had a hexagonal phase and was composed of a large quantity of well-defined dendrites which have the secondary branch-like structure. Further study shows that the morphology of the as-obtained Ni₂P microstructures was highly dependent on the amount of ethylenediamine tetraacetic acid, the reaction temperature, and the reaction time. Then based on some captured intermediates, a possible growth mechanism of the as-obtained Ni₂P dendrites was proposed.     

Microwave-assisted synthesis of hydroxyapatite hollow microspheres in aqueous solution

We report a template-free microwave-assisted hydrothermal method for the preparation of hydroxyapatite hollow microspheres constructed by the self-assembly of nanosheets using Ca(CH₃COO)₂, Na₂HPO₄, NaH₂PO₄ and sodium citrate in aqueous solution. X-ray powder diffraction (XRD) patterns indicated that the as-prepared samples consisted of hydroxyapatite. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) micrographs showed that the as-prepared products were composed of hollow microspheres assembled with nanosheets and had three-dimensional nanoporous nanostructured networks. The experimental parameters were varied to investigate their effects on the product, and a possible formation mechanism was proposed. The as-prepared hydroxyapatite hollow microspheres have a potential application in drug delivery.     

Improvement of morphology and luminescence of CaS:Eu<Superscript>2+</Superscript> red-emitting phosphor particles via carbon-containing additive strategy

CaS:Eu²⁺ red-emitting phosphors particles, were prepared by the precipitation method, followed by sintering in the atmosphere over the mixture of sulfur powder, Na₂CO₃, and carbon-containing compounds such as tartaric acid, citric avid, glucose, and cane sugar. The structure, morphology and photoluminescence performance of the as-prepared samples were investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence spectrum (PL), respectively. The influences of carbon-containing additives on its crystallization behavior, morphology, and enhancement in luminescence of CaS:Eu²⁺ particles were studied. CaS:Eu²⁺ particles without additive show inhomogeneous, rough and aggregation with the size of 75–125 nm, but the spherical particles with mean size of about 110 nm were obtained by adding carbon-containing compounds. Compared with phosphor without additive, the addition of carbon-containing materials induced a remarkable increase of PL, in the order of cane sugar, glucose, citric acid, and tartaric acid. This enhancement is duo to the improvement of crystallinity, particle morphology and size distribution of the samples by adding carbon-containing additive.     

Synthesis, and study of magnetic properties, of Bi1?xCdxFeO3

Ceramic Bi_1−x Cd _x FeO₃ (x = 0.0, 0.05, and 0.1) samples were prepared by a citrate-gel method. The as-prepared compounds were calcined at 600 °C for 3 h to obtain nearly single-phase materials. The crystal structure, examined by X-ray powder diffraction (XRD) and Rietveld analysis, confirmed that the samples crystallize in a rhombohedral (space group, R-3c no. 161) structure. Magnetic measurements were carried out on the resultant powders from 300 to ~2.5 K. Magnetic hysteresis loops showed a significant increase in magnetization as a result of Cd doping in BiFeO₃.     

Synthesis of nanocrystalline TiO2 with high photoactivity and large specific surface area by sol-gel method

Nano-TiO₂ powder was prepared by sol-gel method with modified precursor, tetrabutyl titanate (TBT), and photocatalytic oxidation was applied in removal of organics in the powder. The microstructure of as-prepared nano-TiO₂ was determined using UV-vis, TEM, XRD and BET. The results indicated that the nano-TiO₂, with grain size of 3.8 nm and specific surface area of 359.1 m²/g, was composed of anatase alone, and that it exhibited significant blue-shift in its UV-vis spectrum. The decomposition of organics in the sample was systematically investigated using FT-IR and TG-DTA. According to the testing results, we could conclude that organics in the samples were completely eliminated by means of photocatalytic oxidation. With photocatalytic decoloration of active brilliant red X-3B in aqueous solution as model reaction, the photocatalytic activity of as-prepared nano-TiO₂ was investigated and was compared with that of the samples experiencing heat treatment and Degussa P-25 as well. The experimental results indicated that the photoactivity of as-prepared nano-TiO₂ is much higher than that of the samples experiencing heat treatment.     

Complexing reagent-assisted microwave synthesis of uniform and monodisperse disk-like CeF3 particles

Highly uniform and monodisperse disk-like CeF₃ particles with diameter about 230 nm and thickness about 76 nm were successfully synthesized via a mild and facile microwave irradiation assisted by a complexing reagent, ethylenediamine tetraacetic acid disodium salt (Na₂H₂EDTA). The morphologies and crystal structure of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). XRD patterns showed that the as-prepared CeF₃ products have hexagonal structure and high crystallinity. SEM images showed that these disk-like CeF₃ nanocrystals had rough surfaces which were covered with many sheet-like structures. It was found that the reaction time and the complexing reagent played crucial roles on formation of uniform disk-like CeF₃ particles. A possible formation mechanism of the disk-like CeF₃ particles was preliminarily presented.     

Synthesis and characterization of nanosized micro-mesoporous Zr–SiO2 via Ionic liquid templating

A series of micro-mesoporous Zr–SiO₂ composites with nanoscale domains were prepared by using ionic liquid (IL) as a template at 373 K in only 3 h with one-step. The synthesized Zr–SiO₂ materials were characterized by N₂ adsorption–desorption, scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, diffuse reflectance UV–Vis spectroscopy, thermogravimetric analysis and temperature program desorption technologies. The results show that the synthesized composite materials possess nanoparticle with a mean diameter of about 100 nm and a large surface area more than 1000 m²/g, and the hierarchically porous structure is preserved after removing template by calcination at high temperature and treating in boiling water for 72 h. The heteroatom of zirconium has been successfully incorporated into the structure framework and/or has been highly dispersed on the surface of materials. The prepared materials contain moderate to strong acid sites and the surface acid site concentration is 0.18–0.42 sites/nm². The amount of strong acid sites increases with a decrease of Si/Zr ratio, which leads to increased temperature for removing IL templates.     

The synthesis and photocatalytic properties of epitaxial SnO2-ZnS nanocomb heterostructure

A growth of SnO₂-ZnS heterostructure was realized by a rational two-step thermal evaporation method. Starting with Sn powder, the SnO₂ bicrystalline nanoribbons were grown on the silicon wafers. The secondary growth of ZnS on the former SnO₂ nanostructures correspondingly resulted in the SnO₂-ZnS nanocomb structures. We investigated the morphology, detailed structure by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). It revealed that the ZnS nanobranches with [001] growth direction are epitaxial grown from the (− 101) crystal plane of the SnO₂ trunks with a good lattice match. The nanocomb exhibited an effective photocatalytic activity.     

Synthesis and characterization of copper sulfide nanocrystal with three-dimensional flower-shape

New copper sulfide nanocrystals with three-dimensional (3D) flower-shape were synthesized by using copper acetate (Cu(ac)₂) and citric acid (cit) and thiourea (Tu) as precursors at 160 °C in an anhydrous ethanol by a solvothermal route. The structure and properties of as-prepared products were characterized by X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscope and scanning electron microscope. The optical properties of copper sulfide nanocrystals were examined by UV–vis and FTIR. The crystal growth mechanism was also proposed.     

Surfactant/co-polymer template hydrothermal synthesis of thermally stable, mesoporous TiO2 from TiOSO4

Industrial TiOSO₄ solution was used as inorganic precursor to prepare mesoporous titania via composite template route, using cetyl-trimethylammonium bromide (CTAB) and tri-block copolymer EO₂₀PO₇₀EO₂₀ (P-123) as structure-directing agents (SDA) under high acidic conditions. Mesoporous TiO₂ with high thermal stability was obtained via controlling the hydrolysis and condensation rate of industrial TiOSO₄ solution by adjusting the pH value and post hydrothermal treating. The as-prepared materials were characterized by XRD, nitrogen adsorption-desorption, SEM and HRTEM. The powder calcined at 723 K for 2 h showed higher thermal stability, with BET specific surface area of 218.7 m²/g and an average pore diameter of 3.63 nm.     

Low-temperature chemical synthesis of lanthanum copper oxide

Lanthanum copper oxide (La₂CuO₄) precursors for superconductors were synthesized by acetate/nitrate self-propagating combustion synthesis (SPCS) in the presence of urea at different ratio of O/F. Phase-pure La₂CuO₄ powder could be obtained by calcining the as-prepared precursors at temperature as low as 600 °C. It was demonstrated that the ratio of O/F strongly influenced the composition and morphology of the precursors as well as the samples calcined at various temperatures. We have studied the synthesis conditions, demonstrating the existence of a relationship between the calcination temperature and the calcination time needed to obtain the pure phase. An interesting stereoscopic network structure was observed on the samples synthesized at the ratio of O/F = 0.20, morphology evolution of the samples was also investigated. The emission of H₂O as well as CO₂ was responsible for the formation of the structure during the calcination process.     

Hydrothermal synthesis,characterisation and photocatalytic properties of BiOIO3 nanoplatelets

In this work, BiOIO₃ nanoplatelets were successfully prepared by a simple hydrothermal method. The as-prepared samples were characterised by energy-dispersive spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction and ultraviolet visible diffuse reflectance spectroscopy. The photocatalytic activities of the as-prepared BiOIO₃ nanoplatelets were evaluated by photodegradation of rhodamine B (RhB) under simulated solar light. The results showed that the change of temperature within a certain range has almost no influence on the morphology and size of BiOIO₃ nanoplatelets. However, it had an obvious effect on the photocatalytic performance of BiOIO₃ nanoplatelets. The results showed that the BiOIO₃ sample synthesised at 130 °C exhibited the highest photocatalytic activities compared to others, with RhB completely decomposed in 80 min. The products with proper crystallinity formed at 130 °C have the optimal rate of RhB photodegradation. It indicated that the most favourable crystallinity made it beneficial to improve the photocatalytic activity. The possible mechanism of the photocatalytic reaction based on deep analysis and the experimental results was discussed in detail.     

Combustion synthesis of La0.7Sr0.3Co0.5Fe0.5O3 (LSCF) porous materials for application as cathode in IT-SOFC

La_0.7Sr_0.3Co_0.5Fe_0.5O₃ (LSCF) porous materials have attracted a substantial interest for application as cathode in solid oxide fuel cells of intermediate temperature (IT-SOFC). This work investigates the effect of different propellants (urea, glycine, citric acid and sucrose) in the preparation of LSCF powders by the combustion method and also the influence of the sintering temperature on the porosity and electrical conductivity. TGA profiles of the as-prepared samples showed a lower weight loss for the sample prepared with glycine, associated with the higher combustion temperature. XRD patterns presented characteristic reflections of LSFC perovskite and a small formation of secondary phases, with nanometric crystallite sizes (9-20 nm). SEM analysis revealed the loose and porous structure of the powder materials. Densification studies were carried within 950-1100 °C, showing that porosity decreased with increasing sintering temperature. Electrical conductivity was measured in the temperature range 300-800 °C and correlated with the sintering temperature.     

Preparation of Crystalline Lisb(OH)6 Powders Prepared by Chemical Bath Deposition and Its Thermal Decomposition Process

Well-crystallized LiSb(OH)₆ powders with a hexagonal structure were prepared by chemical bath deposition. The thermal decomposition of as-prepared samples was examined. In order to obtain LiSb(OH)₆ powders, it was essential to use tartaric acid as a stabilizing agent for antimony ion and to add LiOH above pH 9 into the precursor solution. The crystal structure of the samples obtained was of hexagonal phase. The increase in pH value and keeping temperature indicated that the shape of samples changed from granule particles to plate-like particles. The granule particles heated at 800°C consisted of orthorhombic LiSbO₃. However, the plate-like particles resulted in the coexistence of both orthorhombic LiSbO₃ and tetragonal Li₃SbO₄     

Synthesis, characterization and magnetic properties of CoFe2O4 nanorods

In this work, we demonstrated a new precursor route to synthesize CoFe₂O₄ one-dimensional (1D) nanorods. CoFe₂O₄ nanorods were prepared via the thermal decomposition of CoFe₂(C₂O₄)₃ nanorod precursor, which was prepared by solvothermal method without the assistance of template or surfactant. The microstructure and magnetic property of the obtained products were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric (TG) and differential thermal analysis (DTA) and vibrating sample magnetometer (VSM). The results showed that the as-prepared CoFe₂O₄ nanorods were built by magnetic nanoparticles after calcining the precursor nanorods at different temperatures, and the size variation of magnetic nanoparticles with calcination temperatures leaded to variable magnetic properties.