Cetyltrimethyl ammonium bromide assisted hydrothermal growth of hematite hollow cubes

Hematite hollow cubes have been prepared by forced hydrolysis of ferric chloride solutions under hydrothermal conditions. The effects of reaction time, reaction temperature and cetyltrimethyl ammonium bromide on the transformation process from akageneite to hematite were investigated in detail. The products were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. It is found that cetyltrimethyl ammonium bromide was a critical factor influencing the phase transformation process of akageneite and the final morphology of the as-prepared products. With cetyltrimethyl ammonium bromide, hematite hollow cubes and porous spheres were obtained. Otherwise only dense cubes were observed even prolonging reaction time or increasing reaction temperature. The mechanism was proposed.     

Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide

Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 °C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).     

Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH)₂, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m²/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.     

Synthesis of two-dimensional micron-size single-crystalline Prussian blue nanosheets by hydrothermal methods assisted by glucose

Prussian blue Fe₄[Fe(CN)₆]₃ nanosheets have been successfully prepared by a simple hydrothermal process employing the reactions between K₃[Fe(CN)₆] and glucose (C₆H₁₂O₆). X-ray diffraction and transmission electron microscopy measurement results show that the Prussian blue nanosheets are highly crystalline with a face-centered-cubic structure of a = 10.26 Å. It was found the C₆H₁₂O₆ is not only a reductant, but also may be a template for synthesizing the nanosheets.     

Large-scale synthesis of ultralong Sb2S3 sub-microwires via a hydrothermal process

This paper describes an ethylene glycol (EG)-assisted approach to the large-scale ultralong Sb₂S₃ sub-microwires, formed by a simple hydrothermal reaction between SbCl₃ and Na₂S in the presence of distilled water. Transmission electron microscopy and scanning electron microscopy studies indicate that these Sb₂S₃ sub-microwires possess a diameter around 200 nm and length up to 100 μm. High-resolution transmission electron microscopy and selected area electron diffraction studies reveal that each Sb₂S₃ sub-microwire is a single-crystal along the [0 0 1] direction. The possible formation mechanism of the sub-microwires was discussed. The effects of volume ratio of EG/water, reaction temperature and the concentration of CO(NH₂)₂ on the morphology of Sb₂S₃ sub-microwires were also investigated.     

Synthesis of Cu2O nanoboxes, nanocubes and nanospheres by polyol process and their adsorption characteristic

Nanoboxes, nanocubes and nanospheres of cuprous oxides were readily synthesized by reducing Cu(CH₃COO)₂·H₂O with ethylene glycol at different concentrations of poly(vinyl pyrrolidone); the formation mechanism of as-synthesized Cu₂O nanostructures was investigated. Moreover, we report the highly selective adsorption characteristic of as-synthesized Cu₂O nanostructures to anionic dyes and suggest the mechanism is electrostatic adsorption.     

Carbon-assisted synthesis of nanowires and related nanostructures of MgO

MgO nanowires and related nanostructures have been prepared by carbon-assisted synthesis, starting from polycrystalline MgO or Mg without the use of metal catalysts. The study has been carried out with different sources of carbon, all of them yielding the nanostructures with some differences. It has been possible to obtain nanotrees and other interesting nanostructures by this method. It has also been possible to obtain aligned MgO nanowires by carbon-assisted synthesis over Au-coated Si substrates. A vapor-solid mechanism of one-dimensional growth seems to be operative in the reactions carried out in bulk, but a vapor-liquid-solid mechanism applies when Si substrates are used.     

Synthesis and optical properties of ZnS hollow spheres from single source precursor

A facile one-pot synthesis of ZnS hollow spheres has been carried out via a chemical transformation induced inside-out Ostwald ripening process from a single source precursor. The size and shell thickness of the ZnS hollow spheres can be controlled by adjusting the reaction temperature and reaction time, respectively. Photoluminescence spectra show a dominant emission peak at 470 nm accompanied by several weaker peaks. UV-vis measurement reveals that the obtained ZnS hollow spheres exhibit “hollow effect”. The formation process of ZnS hollow spheres has been discussed.     

Novel solution phase metathetic pathway for the synthesis of MnV2O6·H2O

A novel solution-based approach for the metathetic synthesis of hydrated MnV₂O₆ driven by microwave energy has been successfully demonstrated. The metathetic pathway of synthesizing this technologically important material is confirmed by the presence of high lattice energy by-product NaCl as per the reaction.

     

Sonochemical synthesis of ZnO nanoparticles: The effect of temperature and sonication power

ZnO nanoparticles were synthesized by drop-wise addition of ZnCl₂ solution to KOH, in different temperatures and sonication output powers. The morphologies and structure of resulting materials were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The morphology of the products was determined to be a mixture of nano rods as well as nanoparticles depending to sonication output power and temperature. A reduction in nanoparticles and aggregates sizes as well as amount of byproducts was observed by increasing the sonication output power. A combination of sonication output power and temperature was also studied on the properties of the product. At 70 °C and 45 W sonication output power, the smallest nanoparticles as well as narrower range of sizes in addition to minimum amount of byproducts was obtained in this work.     

CuO urchin-nanostructures synthesized from a domestic hydrothermal microwave method

This letter reports the synthesis of CuO urchin-nanostructures by a simple and novel hydrothermal microwave method. The formation and growth of urchin-nanostructures is mainly affected by the addition of polyethylene glycol (PEG). The hierarchical malachite particles are uniform spheres with a diameter of 0.7-1.9 μm. CuO urchin-nanostructures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FEG-SEM) and nitrogen adsorption (BET). The specific surface area of the CuO nanostructured microspheres was about 170.5 m²/g. A possible mechanism for the formation of such CuO urchin-nanostructures is proposed.     

Role of glycine-to-nitrate ratio in influencing the powder characteristics of La(Ca)CrO3

Ultrafine La(Ca)CrO₃ (LCC) powders were prepared through glycine-nitrate gel combustion process. The effect of glycine-to-nitrate ratio on batch size, particle size, nature of agglomeration and densification was studied. As-prepared powders when calcined at 700 °C resulted in LCC along with a small amount of CaCrO₄. The primary particle size obtained in case of stoichiometric and fuel-rich precursor was found to be 25–60 and 60–180 nm, respectively. It was found that the final powder had softer agglomerates with increasing glycine-to-nitrate ratio, which in turn improved the sintered density. The powder obtained through fuel-rich precursor could be sintered to ≈98% of its theoretical density at 1300 °C without applying any ball milling operation.     

Comparative studies between synthetic routes of SiO2@Au composite nanoparticles

We studied two different methods for the deposition of Au nanoparticles (Au NPs) onto the functionalized silica microspheres. One method was to mix the two kinds of particles together and react at room temperature overnight. The other one was to reduce hydrochloroauric acid to Au NPs with sodium citrate in the presence of the functionalized silica microspheres (one for the naked silica microspheres, the other for the Au-attached silica microspheres). We investigated the morphologies of SiO₂@Au composite nanoparticles synthesized by these two methods, and found that the latter achieved a denser Au coverage on silica microspheres. Furthermore, we studied the effect of the pH values in a wide range, respectively, for the two methods. A possible mechanism was put forward to interpret the formation of SiO₂@Au composite nanoparticles and the effects of the synthetic routes and pH values on the morphologies and optical properties.     

Synthesis of hierarchical Ni11(HPO3)8(OH)6 superstructures based on nanorods through a soft hydrothermal route

In this paper, we reported the successful synthesis of hierarchical Ni₁₁(HPO₃)₈(OH)₆ superstructures based on nanorods via a facile hydrothermal route, employing NiCl₂·6H₂O and NaH₂PO₂·H₂O as the reactants in the presences of polyvinylpyrrolidone (PVP) and CH₃COONa·3H₂O. The reaction was carried out at 170 °C for 10 h. HPO₃²⁻ ions were provided via the dismutation reaction of H₂PO₂⁻ ions in a weak basic solution. The as-obtained products were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). Some factors influencing the morphology of the hierarchical Ni₁₁(HPO₃)₈(OH)₆ nanorods, such as the reaction temperature, time, the amounts of PVP and CH₃COONa, and the initial concentration of Ni²⁺ ions, were systematically investigated. A possible growth mechanism was proposed based on experimental results.     

Synthesis and characterization of porous ZnO nanoparticles by hydrothermal treatment of as pure aqueous precursor

The presence of the complexing agents in the growth solution poses risk of the unintentional doping in the synthesized product and hence is likely to adversely affect the intrinsic properties. Herein we report the synthesis of ZnO nanoparticles with porous microstructure using pure aqueous precursor. Crystalline ZnO nanoparticles were synthesized by thermal treatment of aqueous solution of zinc acetate in an open bath. The size of the nanocrystals was controlled by changing the initial precursor concentration. The structural and optical properties of the synthesized nanocrystals were analyzed by X-ray diffraction, high resolution transmission electron microscopy, UV-vis absorption and room temperature photoluminescence measurement techniques. The TEM and UV-vis spectral signature analyses confirmed the formation of dispersed single crystalline ZnO nanoparticles. The nanopowders were found to have disordered mesoporous structure. The synthesized nanocrystals exhibited characteristic band edge emission as well as to surface defect related deep level visible luminescence.     

A novel solution-phase route for the synthesis of crystalline silver nanowires

A unique solution-phase route was devised to synthesize crystal Ag nanowires with high aspect-ratio (8-10 nm in diameter and length up to 10 μm) by the reduction of AgNO₃ with Vitamin C in SDS/ethanol solution. The resultant nanoproducts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and electron diffraction (ED). A soft template mechanism was put forward to interpret the formation of metal Ag nanowires.     

Surfactant controlled synthesis of crystalline phosphovanadate nanorods

Phosphovanadate nanorods were obtained in a reaction of vanadium (V) oxide as a precursor and a cationic surfactant, dodecylpyridinium chloride, as structure directing template at pH ∼3 at room temperature. The composition and morphology of the nanorods was established by powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The obtained nanorods have diameters of 40-60 nm with lengths up to 1 μm. The effect of reaction parameters such as concentration of surfactant and pH of the solution on the growth of nanorods has been investigated. A plausible mechanism involving the coalescence of nanoparticle ‘seeds’ leading to one-dimensional nanorods is also discussed. The same reaction when performed under hydrothermal condition, keeping other reaction parameters unchanged, resulted in the formation of phosphovanadate nanospheres of diameter 10-15 nm.     

Controlled synthesis of cadmium carbonate nanowires, nanoribbons, nanorings and sphere like architectures via hydrothermal method

Crystalline nanowires, nanoribbons, nanorings and sphere like architectures of cadmium carbonate have been synthesized with the spontaneous self-assembly of nanocrystals in aqueous solution under hydrothermal condition. The powder X-ray diffraction (PXRD) patterns of these materials exhibit phase pure hexagonal structure. The perfect circular nanorings with radius 375-437 nm, as a new member of nanostructured cadmium carbonate family are being reported for the first time. The width of the cadmium carbonate nanowires/nanoribbons and nanorings, respectively are found to be in the range 11-30 and 26-50 nm as observed by transmission electron microscope (TEM). The effect of temperature and concentration of urea on the cadmium carbonate morphology is discussed. The plausible growth mechanism for the formation of nanorings is also proposed.     

Hydrothermal synthesis of spindle-like ZnS hollow nanostructures

Spindle-like hollow nanostructures of zinc sulfide (ZnS) have been successfully synthesized by hydrothermal process using a simple surfactant emulsion template. The morphologies of ZnS nanostructures were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FE-SEM). It is found that most of the products including twin ellipsoids with connected hollow cores are reminiscent of spindle-like structures. The lengths, widths and the thickness of the shell are in the range of 1-2 μm, 300-450 nm and 20-40 nm, respectively. Selected area electron diffraction (SAED) and X-ray powder diffraction (XRD) patterns show that the shell is composed of sphalerite ZnS polycrystals.     

Large-scale preparation of hollow graphitic carbon nanospheres

Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 °C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g⁻¹ after 60 cycles when used as anode materials for Li-ion batteries.