Solvothermal synthesis of ceria nanoparticles with large surface areas

Ceria nanoparticles were obtained by the calcination of precursors synthesised via the solvothermal reaction of cerium acetate. The CeO₂ samples obtained by the thermal decomposition of Ce(C₇H₁₅COO)₃·xH₂O synthesised by solvothermal reaction in 1,4-butanediol in the presence of octanoic acid had an extremely large surface area of 180 m²/g. The Ru catalyst supported on this CeO₂ sample showed a high catalytic activity for benzyl alcohol oxidation.     

Self-assembly of diverse alumina architectures and their morphology-dependent wettability

This work reports the fabrication of diverse nanostructured alumina films under high-field anodization in oxalic-acid electrolytes. Different surface morphologies of these alumina films can be obtained by adjusting reaction parameters, which was ascribed to the anisotropic chemical etching induced by the reaction heat and the concentration gradient of the oxalic-acid solution along the nanopore channels during the high-field anodization process. These alumina surfaces without coating low energy materials show remarkable morphology-dependent wettability. Specially, the alumina surface consisting of porous underlayer and nanowire pyramids with no chemical modification reveals excellent super water-repellent behavior for the first time. This study could provide a new approach for designing functional surfaces with tunable wettability.     

Phospholipid-assisted synthesis of size-controlled gold nanoparticles

Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV-vis spectra.     

CeF3 nanoparticles: synthesis and characterization

CeF₃ nanoparticles 5-10 nm in size were prepared using the polyol method. CeCl₃ and HF were heated up in ethylene glycol. At a temperature of 180 °C crystalline CeF₃ nanoparticles were formed. The material was washed with ethanol, centrifugated and dried. The particles were characterized by EDX, XRD and TEM.     

Dendrigraft polymer-based synthesis of silver nanoparticles showing bright blue fluorescence

A novel method is reported here for the synthesis of optically clear and stable colloidal solutions of silver nanoparticles. According to size they show different colours depending upon their plasmonic absorption frequencies. The materials have been synthesized at room temperature by chemical reduction of silver ions (silver nitrate) coordinated with dendrigraft polymer, polyethyleneimine (PEI) using formaldehyde in aqueous medium. UV-vis absorption and transmission electron microscopy (TEM) studies show single-band absorption with peak maximum at 354 nm for ∼3 nm sized particles, whereas a side band at ∼400 nm was observed when the particle size increased to ∼20 nm. Highly narrow particle size distribution was observed in case of samples having ∼3 nm size silver particles and also the process of reduction could be completed within minutes. More interestingly, the 3-nm sized particles showed strong blue (474 nm) fluorescence under UV excitation. Thin films of all synthesized samples were prepared on silica substrate by fine spray coating technique.     

Reliable synthesis of bismuth nanoparticles for heavy metal detection

A reliable and facile pathway is described here for preparing high-quality bismuth nanoparticles. Combined with hydrothermal method and confined growing effect of polymer, bismuth nanoparticles with uniform size and shape were obtained with remarkable productivity. The nanoparticles is proved to be pure Rhombohedral structure Bi crystals with R-3m space group and the diameter of the nanoparticles is about 80 nm with a quite narrow particle size distribution. Those bismuth nanoparticles were predicted to grow from a rolling process by sheet-like Bi nanocrystal intermediates. The obtained bismuth nanoparticles were used to prepare modified electrode for the detection of Cd²⁺ and Pb²⁺ in water solution by stripping analysis. Compared with naked glassy carbon electrodes, the modified electrode showed two obvious responses at −0.85 V and −0.62 V, corresponding to the reduction process of Pb²⁺ and Cd²⁺ and this well-resolved stripping response can be observed when the concentration is as low as 10 μg/L, indicating potential application in electroanalysis for environmental inspection.     

A novel synthesis of micrometer silica hollow sphere

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented.     

VO2(B) nanospheres: Hydrothermal synthesis and electrochemical properties

Monodisperse VO₂(B) nanospheres with an average size of 100 nm were synthesized by hydrothermal method. Experiments showed that the surfactant octadecyl-amine played an important role during the formation of the nanospheres, and possible mechanism was suggested. Moreover, the potential uses of VO₂ nanospheres were primarily probed as electrodes for lithium-ion batteries.     

Facile synthesis of α-MnO2 nanostructures for supercapacitors

Various α-MnO₂ nanostructures have been successfully synthesized by a simple hydrothermal method based on the redox reactions between the MnO₄⁻ and H₂O in mixture containing KMnO₄ and HNO₃. The effect of varying the hydrothermal time to synthesize MnO₂ nanostructures and the forming mechanism of α-MnO₂ nanorods were investigated by using XRD, SEM and TEM. The results revealed an evolvement of morphologies ranging from brushy spherical morphology to nanorods depending upon the hydrothermal time. The surface area of the synthesized nanomaterials varied from 89 to 119 m²/g. Electrochemical properties of the products were evaluated using cyclic voltammetry and galvanostatic charge–discharge studies, and the sample obtained by hydrothermal reaction for 6 h at 120 °C showed maximum capacitance with a value of 152 F/g. In addition, long cycle life and excellent stability of the material were also demonstrated.     

Sonochemical preparation of bimetallic Co/Cu nanoparticles in aqueous solution

Co/Cu bimetallic nanocrystallites, with average diameter of 50 nm, were prepared by a sonochemical method in the hydrazine solution of copper chloride and cobalt chloride. Cobalt was face-centered cubic phase when synthesized and remained fcc phase throughout the annealing process. X-ray diffractometer (XRD), transmission electron microscope (TEM), differential scanning calorimetry (DSC), vibrating sample magnetometry (VSM), inductively coupled plasma-atomic emission spectrometer (ICP-AES) measurements were carried out to investigate their structural and magnetic properties. It was found that the magnetic properties of bimetallic nanocrystallites were close to that of the sputtered alloys.     

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.     

Formation mechanism of monodispersed spherical core-shell ceria/polymer hybrid nanoparticles

Very unique core-shell ceria (cerium oxide)/polymer hybrid nanoparticles that have monodispersed spherical structures and are easily dispersed in water or alcohol without the need for a dispersant were reported recently. The formation mechanism of the unique nanoparticles, however, was not clear. In order to clarify the formation mechanism, these nanoparticles were prepared using a polyol method (reflux heating) under varied conditions of temperature, time, and concentration and molecular weight of added polymer (poly(vinylpyrrolidone)). The size of the resultant nanoparticles was strongly and complicatedly dependent on the set temperature used during reflux heating and the poly(vinylpyrrolidone) molecular weight. Furthermore, the size of the nanoparticles increased by a 2-step process as the reflux heating time increased. The IR spectral changes with increasing reflux time indicated the increase in the number of cross-linked polymers in the shell. From these results, the formation mechanism was discussed and proposed.     

Microwave irradiation assisted rapid synthesis of Fe-Ru bimetallic nanoparticles and their catalytic properties in water-gas shift reaction

Fe-Ru bimetallic nanoparticles were prepared by a microwave irradiation assisted glycol reduction method using poly-N-vinyl-2-pyrrolidone (PVP) as protective agent. The structure and morphology of the nanoparticles were characterized by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA) and high-resolution transmission electron microscopy (HRTEM). EDXA and XRD analysis confirmed the presence of Fe and Ru. The bimetallic nanoparticles were subsequently loaded onto an MgAl₂O₄ supporter with K₂O as promoters and used as catalyst for water-gas shift reaction. The results indicated that the FeRu bimetallic nanoparticles exhibit high catalytic activity for water-gas shift reaction due to the synergistic effect between iron and ruthenium. Potassium oxide can enhance the CO selectivity of the catalyst significantly besides increasing the catalyst activity.     

Large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles with a simple route and their application to photocatalytic degradation

We report the large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles by the esterification between zinc acetate and alcohol. The morphology of the ZnO nanoparticles was investigated by transmission electron microscopy, selected area electron diffraction and scanning electron microscopy measurements. The synthesized ZnO nanoparticles are single-crystalline with hexagonal phase and show a strong UV emission at −378 nm due to the excellent crystallinity of particles. A possible formation mechanism of the hexagonal cone-shape structure is proposed. Furthermore, the as-prepared ZnO particles exhibit high photocatalytic activity for the photocatalytic degradation of Rhodamine B, indicating that the ZnO nanostructure is promising as a semiconductor photocatalyst.     

Microwave-hydrothermal synthesis of γ-Fe2O3 nanoparticles and their magnetic properties

Nanosized γ-Fe₂O₃ is synthesized by the microwave-hydrothermal method. Powder X-ray diffraction and transmission electron microscopic studies showed that the average particle size is 10 nm. Magnetic studies reveal that the γ-Fe₂O₃ nanoparticles are superparamagnetic at room temperature, with a superparamagnetic blocking temperature of 200 K. The magnetic characteristics of the nanoparticles indicate their strongly interacting nature.     

Zr(IV) basic carbonate complexes as precursors for new materials: synthesis of the zirconium-surfactant mesophase

Soluble anionic carbonate complexes of Zr(IV) are produced by addition of Zr(IV) salts to the excess of an alkali metal or ammonium carbonate. The solutions are metastable at pH 7-10 and can be used as the precursors for the synthesis of new materials, as illustrated by the example of the surfactant containing mesophase with a wormhole-like structure, prepared by means of reaction with cetyltrimethylammonium bromide.     

Preparation of Pt-Ru-Ni ternary nanoparticles by microemulsion and electrocatalytic activity for methanol oxidation

Ternary platinum-ruthenium-nickel nanoparticles are prepared by water-in-oil reverse microemulsions of water/Triton X-100/propanol-2/cyclohexane. Nanoparticles formed in the microemulsions are characterized by transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffractometry (XRD), energy dispersive X-ray analysis (EDX). These resulting materials showed a homogenous alloy structure, the mono-dispersion and an average diameter of 2.6 ± 0.3 nm with a narrow particle size distribution. The composition and particle size of ternary Pt-Ru-Ni nanoparticles can be controlled by adjusting the initial metal salt solution and preparation conditions. Pt-Ru-Ni ternary metallic nanoparticles showed an enhanced catalytic activity towards methanol oxidation compared to Pt-Ru bimetallic nanoparticles.     

Synthesis and surface plasmon resonance properties of carbon-coated Cu and Co nanoparticles

Carbon-coated Cu and Co nanoparticles were synthesized by the carbonization of PVA-metal hydroxide complexes. The possible reaction process and surface plasmon resonance (SPR) properties of the Cu and Co nanoparticles enwrapped in carbon layer were explored. The XRD results showed that no byproducts, such as oxides and carbides, were formed in the products, and the Cu and Co nanoparticles were effectively protected against oxidation by the carbon layer. The size ranges of the metal nanoparticles were 20-50 nm for Cu and 15-65 nm for Co, respectively. UV-vis absorption spectra showed that the SPR bands of the Cu and Co nanoparticles coated with carbon were red-shifted mainly due to the increase of the effective dielectric constant of the surrounding medium induced by the carbon layer.     

A novel nanostructured composite formed by interaction of copper octa(3-aminopropyl)octasilsesquioxane with azide ligands: Preparation, characterization and a voltammetric application

This study presents the preparation, characterization and application of copper octa(3-aminopropyl)octasilsesquioxane following its subsequent reaction with azide ions (ASCA). The precursor (AC) and the novel compound (ASCA) were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analyses and voltammetric technique. The cyclic voltammogram of the modified graphite paste electrode with ASCA (GPE-ASCA), showed one redox couple with formal potential () = 0.30 V and an irreversible process at 1.1 V (vs. Ag/AgCl; NaCl 1.0 M; v=20 mV s−1). The material is very sensitive to nitrite concentrations. The modified graphite paste electrode (GPE-ASCA) gives a linear range from 1.0 × 10⁻⁴ to 4.0 × 10⁻³ mol L⁻¹ for the determination of nitrite, with a detection limit of 2.1 × 10⁻⁴ mol L⁻¹ and the amperometric sensitivity of 8.04 mA/mol L⁻¹.     

Hybrid catalyst containing nano-sized LaMnO3 and carbon black for high yield and selective ketonization of n-butanol

An attempt has been made to synthesize a two-component hybrid material for highly selective catalytic ketonization of n-butanol. The perovskite-type oxide nano-crystallites were synthesized in the presence of carbon black particles by thermal transformation of equimolar mixture of lanthanum and manganese hydroxides into the perovskite-type oxide. The two-component material was tested as a catalyst for unconventional conversion of n-butanol to heptanone-4. The catalyst exhibited very high selectivity and yield towards the products, despite low content of LaMnO₃ in the two-component material (less than 10% by weight). The low oxide content led to the reduction of the cost of catalyst fabrication and is compensated by its high dispersion (grains ca. 20-30 nm in diameter) providing high conversion and yield comparable to pure-oxide catalysts. Catalyst fabrication is simple and environment friendly since it does not require organic solvents and excess amount of heavy metals (La and Mn).