Template-free solvothermal synthesis of hierarchical boehmite hollow microspheres with strong affinity toward organic pollutants in water

Three-dimensional hierarchical boehmite hollow microspheres with a very high yield at low cost were successfully synthesized via a one-pot template-free solvothermal route using aluminum chloride hexahydrate as precursor in a mixed ethanol–water solution with assistance of trisodium citrate. The as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption/desorption techniques. The results show that Cl⁻ and addition amount of trisodium citrate have significant effect on the morphologies of the resultant products, and 6–8 mmol of trisodium citrate is optimal for the synthesis of boehmite hollow microspheres assembled from randomly interconnecting and aligned nanorods with solvothermal time no less than 15 h. A synergistic mediation mechanism of citrate ions and Cl⁻ to form boehmite hollow spheres via self-assembly morphology evolution was proposed based on the experimental results. Interestingly, the typical boehmite hollow microspheres with a surface area of 102 m² g⁻¹, pore volume of 0.37 cm3 g⁻¹, and the average pore size of 14.6 nm show superb adsorption properties for Congo red with maximum capacity of 114.7 mg g⁻¹ which is higher than that of a commercial boehmite. This simple synthetic route is a very promising way for the design and synthesis of new functional hierarchical nanostructured materials with desired adsorptive properties.     

Development of macroporous calcium phosphate scaffold processed via microwave rapid drying

Porous hydroxyapatite (HA) scaffold has great potential in bone tissue engineering applications. A new method to fabricate macroporous calcium phosphate (CP) scaffold via microwave irradiation, followed by conventional sintering to form HA scaffold was developed. Incorporation of trisodium citrate dihydrate and citric acid in the CP mixture gave macroporous scaffolds upon microwave rapid drying. In this work, a mixture of β-tricalcium phosphate (β-TCP), calcium carbonate (CaCO₃), trisodium citrate dihydrate, citric acid and double distilled de-ionised water (DDI) was exposed to microwave radiation to form a macroporous structure. Based on gross eye examinations, addition of trisodium citrate at 30 and 40 wt.% in the CP mixture (β-TCP and CaCO₃) without citric acid indicates increasing order of pore volume where the highest porosity yield was observed at 40 wt.% of trisodium citrate addition and the pore size was detected at several millimeters. Therefore, optimization of pore size was performed by adding 3–7 wt.% of citric acid in the CP mixture which was separately mixed with 30 and 40 wt.% of trisodium citrate for comparison purposes. Fabricated scaffolds were calcined at 600 °C and washed with DDI water to remove the sodium hydroxycarbonate and sintered at 1250 °C to form HA phase as confirmed in the X-ray diffraction (XRD) results. Based on Archimedes method, HA scaffolds prepared from 40 wt.% of trisodium citrate with 3–7 wt.% of citric acid added CP mixture have an open and interconnected porous structure ranging from 51 to 53 vol.% and observation using Scanning electron microscope (SEM) showed the pore size distribution between 100 and 500 μm. The cytotoxicity tests revealed that the porous HA scaffolds have no cytotoxic potential on MG63 osteoblast-like cells which might allow for their use as biomaterials.     

Solution combustion synthesis of hierarchical porous LiFePO4 powders as cathode materials for lithium-ion batteries

Hierarchical porous LiFePO₄ powders were prepared by solution combustion method using a mixture of cetyltrimethylammonium bromide (CTAB) and glycine as fuel. The effects of fuel contents on structural, microstructural, and electrochemical properties were studied by various characterization methods such as X-ray diffraction, infrared spectroscopy, scanning electron microscopy, N₂ adsorption–desorption isotherms, and galvanostatic charge/discharge. Single phase LiFePO₄ powders were crystallized by calcination at 700 °C. Phase evolution was depended on the nature and amount of intermediate phases. The hierarchical porous microstructure was obtained at an appropriate amount of mixed fuels. LiFePO₄ powders showed the high specific discharge capacity of 110 mAh g^?1 and high capacity retention of 98% at 1C which were attributed to their high crystallinity and high specific surface areas. The porous microstructure and small particle size were benefitted for the electrode kinetics, as indicated by electrochemical impedance spectroscopy.     

One-pot synthesis of magnetic γ-Fe2O3 nanoparticles in ethanol-water mixed solvent

Maghemite (γ-Fe₂O₃) nanoparticles were synthesized via a low-temperature solution-based method using ferric chloride hexahydrate and ferrous chloride tetrahydrate as precursors in the mixed solvent of ethanol and water. X-ray diffraction, energydispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy revealed that the obtained product was pure γ-Fe₂O₃. Transmission electron microscopy showed the morphology of the nanoparticles to be approximately spherical in shape with an average diameter of 11 nm. Magnetization measurements indicated the dry powders exhibit ferromagnetic behavior with a maximum saturation magnetization of 41.1 emu/g at room temperature.     

Fabrication of three-dimensional snowflake-like bismuth sulfide nanostructures by simple refluxing

Three-dimensional snowflake-like bismuth sulfide nanostructures were successfully synthesized by simple refluxing at 160 °C in ethylene glycol, using bismuth citrate and thiourea as reactants. The crystal structures and morphologies of the products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX). The Bi₂S₃ nanostructure was built up by highly ordered one-dimensional Bi₂S₃ nanorods, which was aligned in an orderly fashion. Ethylene glycol plays a critical role in the creation of bismuth sulfide three-dimensional nanostructures, which serves as an excellent solvent and structure director. Bismuth citrate, a linear polymer, also makes for the formation of the three-dimensional nanostructures.     

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.     

Synthesis of cobalt-doped barium cerate-zirconate and its evaluation for hydrogen production and electrochemical characterization

Cobalt-doped barium cerate-zirconate was synthesized using an oxalate co-precipitation route. The material was characterized using X-ray diffraction, transmission and scanning transmission electron microscopy coupled with X-ray energy dispersive spectroscopy. Results indicated that homogeneous cubic phase material was obtained at very high heat-treatment temperatures. Catalytic activity of the material toward CH₃OH partial-oxidation was tested at different temperatures and O₂:CH₃OH ratios. High hydrogen yields were obtained indicating that the material was a suitable catalyst for hydrogen generation. Impedance spectroscopy tests were conducted at different conditions to understand conduction processes occurring in the material. Results suggested mixed protonic–electronic conductivity in the presence of hydrogen. Thus, material is a potential candidate for the bi-functional role of electro-ceramic catalyst for simultaneous hydrogen generation and purification.     

Facile fabrication of hierarchical BiVO<Subscript>4</Subscript>/TiO<Subscript>2</Subscript> heterostructures for enhanced photocatalytic activities under visible-light irradiation

BiVO₄/TiO₂ nanocomposites were fabricated by a facile wet-chemical process, followed by the synthesis of TiO₂ hierarchical spheres via hydrothermal method. The BiVO₄/TiO₂ nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The results showed that prepared TiO₂ presented hierarchical spherical morphology self-assembled by nanoparticles and an anatase–brookite mixed crystal phase. The introduction of monoclinic BiVO₄ components retained the hierarchical structures and expanded the light response to around 510 nm. Type II BiVO₄/TiO₂ heterostructured nanocomposites exhibited improved photocatalytic degradation towards methylene blue under visible-light irradiation, especially for the composite photocatalysts with atomic Ti/Bi?=?10, which showed double degradation rate than that of pure BiVO₄. The enhanced photocatalytic mechanism of the heterostructured BiVO₄/TiO₂ nanocomposites was discussed as well.     

Controlled synthesis of three-dimensional hierarchical Bi2WO6 microspheres with optimum photocatalytic activity

Three-dimensional (3D) hierarchical Bi₂WO₆ microsphere and octahedral Bi₂WO₆ have been synthesized by a facile hydrothermal method using KNO₃ solution and distilled water as solvent, respectively. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, N₂ adsorption/desorption, and UV–vis diffuse reflectance spectroscopy in detail. The concentration of KNO₃ played a key role in the formation of 3D hierarchical Bi₂WO₆ microspheres. A possible formation mechanism of Bi₂WO₆ microsphere was proposed. The photocatalytic activity of the as-synthesized products was evaluated by monitoring the degradation of MB solution under sunlight irradiation. It was found that the photocatalytic activity of the 3D hierarchical Bi₂WO₆ microsphere was superior to the octahedral Bi₂WO₆, which was attributed to the larger surface area and special hierarchical structure of Bi₂WO₆ microsphere.     

Preparation of MnCo2O4 whiskers and spheroids through thermal decomposition of Mn1/3Co2/3C2O4 · 2H2O

The mixed oxalate Mn_1/3Co_2/3C₂O₄ · 2H₂O has been prepared in the form of whiskers 2–5 μm in diameter and up to 50 μm in length and spheroidal nanofiber arrays 20 μm in diameter using two different coprecipitation procedures. Thermal decomposition of this oxalate in air has led to the formation of MnCo₂O₄ particles very similar in morphology to their oxalate precursor. The materials have been characterized by chemical analysis, thermogravimetry, x-ray diffraction. IR spectroscopy, and scanning electron microscopy.     

Degradation of sulfated polysaccharide extracted from algal Laminaria japonica and its modulation on calcium oxalate crystallization

Sulfated polysaccharide (LPS) extracted from alga Laminaria japonica was degraded by hydrogen peroxide (H₂O₂). The average molecular weight of LPS was apparently decreased from 172,000 to 9550 after degradation, while the proportion of sulfate groups (–OSO₃^?) and carboxylic groups (–COO^?) in the molecular chains of LPS were slightly decreased from 4.5% and 5.20% to 3.9% and 4.64%, respectively. The effects of degraded and natural LPS on formation of calcium oxalate (CaOxa) crystals were investigated in vitro using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), zeta-potential, and atomic absorption spectroscopy. LPS could increase the concentration of soluble Ca²⁺ ions in the solution, decrease the weight of precipitated CaOxa, and increase the negative value of zeta-potential of CaOxa crystals. LPS also inhibits the formation of thermodynamically stable calcium oxalate monohydrate (COM) crystals, while inducing and stabilizing metastable calcium oxalate dihydrate (COD) crystals. These results suggested that both degraded and natural LPS could decrease CaOxa crystallization, but the inhibition efficiency of the degraded LPS was clearly superior to that of the natural LPS. We expected this investigation would provide encouragement for further exploration into new drugs for the prevention and treatment of urolithiasis.     

A simple chemical route to Bi2S3 hierarchical columniform structures assembled by nanorod-based lamellae

Bi₂S₃ hierarchical columniform structures assembled by nanorod-built lamellae have been first synthesized by a simple wet chemical method through the reaction between Bi(NO₃)₃?5H₂O and CS₂ at 80 °C for 14 h using DMSO as solvent without any surfactants. These new Bi₂S₃ structures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Compared to ethylene glycol and DMF, DMSO supplied an excellent chemical environment favorable to the generation of Bi₂S₃ quickly in heterogeneous condition. The influences of the synthetic parameters were discussed and a possible growth mechanism for the formation of these complex structures was proposed.     

Organic additive assisted hydrothermal synthesis and photoluminescence properties of CeF<Subscript>3</Subscript>:Tb<Superscript>3+</Superscript> and NaCeF<Subscript>4</Subscript>:Tb<Superscript>3+</Superscript> nanoparticles

A series of Tb³⁺ doped CeF₃ and NaCeF₄ nanoparticles with different morphology and dimension were synthesized via hydrothermal method. Different organic additives, including sodium dodecyl sulfonate (SDS), polyvinylpyrrolidone (PVP), cetyltrimethyl ammonium bromide (CTAB), oleic acid (OA), polyethylene glycol (PEG), trisodium citrate (Cit) were introduced to control the crystallite size and morphology. Powder X-ray diffraction (PXRD), fourier transform infra-red spectra (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and down-conversion (DC) photoluminescence spectra were used to characterize the samples. The emission peaks of all the prepared samples centered at 490, 545, 585 and 621 nm which can be ascribed to the ⁵D₄→⁷F_J (J?=?6, 5, 4, 3) transitions respectively of Tb³⁺ ion. However, emission intensities are strongly controlled by morphology and particle sizes which are influenced by different organic additives used in synthesis. Moreover, the crystal growth process was monitored through a series of time-dependent experiments and a possible formation mechanism has been proposed.     

Electrodeposition of poly(o-anisidine) coatings onto copper

Abstract

Uniform and strongly adherent poly(o-anisidine) (POA) coatings have been successfully electrodeposited onto copper (Cu) substrates from the aqueous bath containing sodium oxalate and o-anisidine by using cyclic voltammetry (CV). CV, UV visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements were used to characterise these coatings, which indicates that the aqueous sodium oxalate solution is a suitable medium for the formation and deposition of POA onto Cu substrates. It is observed that the electrodeposition of POA coatings takes place after the passivation of the Cu substrate via formation of copper oxalate (CuC₂O₄.H₂O) layer, which is confirmed by XRD measurement. The optical absorption spectroscopy study reveals the formation of the mixed phase of pernigraniline base (PB) and emeraldine salt (ES) forms of POA. The surface morphology of the coating is uniform, compact and featureless as revealed by SEM imaging.     

Optionally ultra-fast synthesis of CoO/Co3O4 particles using CoCl2 solution via a versatile spray roasting method

Crystalline CoO/Co₃O₄ particles with polyhedral morphologies have been successfully synthesized via a versatile spray roasting method. The feed solution was prepared using distilled water or ethanol–water mixture as solvent while CoCl₂·6H₂O as solute, and then sprayed by an inner mixed air-nozzle and roasted in an erective tubular resistance furnace with compressed air as carrier gas. The as-prepared specimens were characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and FT-IR spectroscopy. The results showed that pure crystalline Co₃O₄ particles have been obtained under the condition of H₂O was used as the sole menstruum while CoCl₂·6H₂O was used as the core materials. Meanwhile, the pure well-crystallized CoO particles with octahedron morphology were obtained successfully by dissolving CoCl₂ in ethanol–water mixture solution concentrated CH₃CH₂OH–H₂O (1:1, v/v) as reactants. The possible reaction mechanism of different solvent in the synthesis process was elucidated as well.     

Property changes of urinary nanocrystallites and urine of uric acid stone formers after taking potassium citrate

The property changes of urinary nanocrystallites in 20 cases of uric acid (UA) stone formers after 1 week of potassium citrate (K₃cit) intake were comparatively studied by X-ray diffraction analysis, Fourier transform infrared spectroscopy, nanoparticle size analysis, and transmission electron microscopy. Before K₃cit intake, the urinary crystallites mainly contained UA and calcium oxalate. After K₃cit intake, the components changed to urate and UA; the qualities, species, and amounts of aggregated crystallites decreased; urine pH, citrate, and glycosaminoglycan excretions increased; and UA excretion, Zeta potential, and crystallite size decreased. The stability of crystallites followed the order: controls > patients after taking K₃cit > patients before taking K₃cit. Therefore, the components of urinary stones were closely related to the components of urinary crystallites.     

Preparation and characterization of NiO, Fe2O3, Ni0.04Zn0.96O and Fe0.03Zn0.97O nanoparticles

Nickel oxide (NiO), iron (III) oxide (Fe₂O₃), and mixed oxide (Ni_0.04Zn_0.96O and Fe_0.03Zn_0.97O) nanoparticles were synthesized by modified sol–gel method. The nanoparticle structural and morphological properties were investigated by infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), and Mössbauer spectroscopy. The mixed oxides were characterized by energy-dispersive X-ray spectroscopy (EDX). The oxide precursor powders were analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC). The average sizes of the obtained NiO and Ni_0.04Zn_0.96O nanocrystallites were evaluated by X-ray line broadening using Scherrer's equation and were found to be 36 and 23 nm, respectively. Fe₂O₃ and Fe_0.03Zn_0.97O nanoparticles presented similar sizes, around 19 nm. EDX spectroscopy indicated that the calculated compositions of the mixed oxides were nearly consistent with their estimated molar ratios.     

DC resistivity of Ni–Zn ferrites prepared by oxalate precipitation method

Polycrystalline ferrites with general formula Ni_1−xZn_xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by oxalate precipitation method. The samples were characterized by X-ray diffraction (XRD), IR and scanning electron microscope (SEM) techniques. All compositions show cubic Spinel structure. Lattice constant increases with increase in zinc content, obeying Vegard's law. The physical densities are about 98.14% of their X-ray density. Average crystallite size lies in the range 27.59–31.49 nm. Infrared studies show two absorption bands near about 400 cm⁻¹ and 600 cm⁻¹ for octahedral and tetrahedral sites, respectively. The resistivity of all the samples was studied. It is observed that the resistivity of nickel–zinc ferrites prepared by oxalate precipitation method is higher than that prepared by ceramic and citrate precursor method. It is attributed to greater homogeneity and smaller grain size. Activation energy in paramagnetic region is higher than that of ferrimagnetic region.     

Electrochemical co-deposition and characterization of MnO2/SWNT composite for supercapacitor application

Manganese oxide/single-wall carbon nanotubes (MnO₂/SWNT) composite was co-deposited by the potentiostatic method on a graphite slice. Morphological and structural performances for MnO₂/SWNT composite were characterized by means of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The wall surface of SWNT was wrapped by ramsdellite MnO₂ nanoparticles to fabricate MnO₂/SWNT coaxial nanotubes, which further interconnected other MnO₂ particles to form the porous MnO₂/SWNT composite. The electrochemical properties were examined by cyclic voltammograms, galvanostatic charge and discharge and electrochemical impedance spectrum. A high specific capacitance of 421 F g^?1 was obtained for overall MnO₂/SWNT composite electrode at the constant current density of 1 A g^?1 in 3 mol L^?1 KCl solution.     

Hydrothermal synthesis of PbWO4 uniform hierarchical microspheres

In this work, hierarchical PbWO₄ spheres assembled by nanorods were successfully synthesized through a tri-potassium citrate assisted hydrothermal process. The samples were studied by powder X-ray diffraction pattern (XRD), field scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that citrate played a key role on the morphology of PbWO₄ products. By adjusting concentration of citrate, PbWO₄ octahedrons, hierarchical spheres, hierarchical ellipses could be obtained. Based on time-dependent experiments, we found the growth of the hierarchical spheres followed a self-assembly process. The most interesting part was that the hierarchical spheres/ellipses showed a blue emission peak at 440 nm, which differs from the typical green one at 500 nm as reported.