Rapid synthesis of dendrite‐ and platelet‐like α‐Fe2O3 via a hydrothermal oxidation route

Dendrite and platelet‐like α‐Fe₂O₃ microcrystals were synthesized by the oxidation reaction of K₄Fe(CN)₆and NaClO₃ through a simple hydrothermal method. The structures and morphologies of the as‐prepared samples were characterized in detail by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The experiment results show that NaOH played an important role in controlling the morphology of the final products. The possible mechanism was discussed to elucidate the formation of different morphologies of the α‐Fe₂O₃ microstructures. Besides, the magnetic property of the dendrite α‐Fe₂O₃ microstructure was characterized by a vibrating sample magnetometer (VSM). (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ionic liquid‐assisted hydrothermal synthesis of γ‐Al2O3hierarchical nanostructures

The boehmite (Al₂O₃·H₂O) hierarchical nanostructure with spindle‐like morphology has been successfully synthesized via ionic liquid‐assisted hydrothermal synthetic method under mild condition using an ionic liquid 1‐butyl‐3‐dimethylimidazolium bromide ([Bmim][Br]) as a template. The proposed formation mechanism has been investigated and the hydrogen bond‐co‐π–π stack mechanism is used to be responsible for the present formation of the precursor hierarchical nanostructure. The γ‐Al₂O₃ hierarchical nanostructure was obtained by calcining the as‐synthesized precursor at 500 °C for 2 h, preserving the same morphology. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Capsule‐like α‐Fe2O3 nanoparticles: Synthesis,characterization, and growth mechanism

Uniform capsule‐like α‐Fe₂O₃ particles were synthesized via a simple hydrothermal method, employing FeCl₃ and CH₃COONa as the precursors and sodium dodecyl sulfate (SDS) as soft template. X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy were used to characterize the structure of synthesized products. Some factors influencing the formation of capsule‐like α‐Fe₂O₃ particles were systematically investigated, including different kinds of surfactants, the concentration of SDS, and reaction times. The investigation on the evolution formation reveals that SDS was critical to control the morphology of final products, and a possible five‐step growth mechanism was presented by tracking the structures of the products at different reaction stages.     

Synthesis and properties of α‐Fe2O3 nanorods

We report synthesis of α‐Fe₂O₃ (hematite) nanorods by reverse micelles method using cetyltrimethyl ammonium bromide (CTAB) as surfactant and calcined at 300 °C. The calcined α‐Fe₂O₃ nanorods were characterized by X‐ray diffraction (XRD), high‐resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The result showed that the α‐Fe₂O₃ nanorods were hexagonal structure. The nanorods have diameter of 30‐50 nm and length of 120‐150 nm. The weak ferromagnetic behavior was observed with saturation magnetization = 0.6 emu/g, coercive force = 25 Oe and remanant magnetization = 0.03 emu/g. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal synthesis of ultralong single‐crystalline α‐Ni(OH)2 nanobelts and corresponding porous NiO nanobelts

Ultralong α‐Ni(OH)₂ nanobelts with uniform size have been prepared on large scale via a facile template‐free hydrothermal method. The as‐prepared nanobelts were single crystals, with several tens of microns in length and about 100 nm in width. For the whole process, a novel nucleation–aggregation–dissolution–seed‐directed growth mechanism was proposed based on the experimental results. The roles of aqueous ammonia and hydrothermal temperature were also discussed. Furthermore, porous NiO nanobelts were obtained by annealing the as‐prepared Ni(OH)₂ nanobelts. This facile, template‐free, and low cost method might feasibly be scaled up for industrial production. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rapid synthesis and catalytic performance of α‐Mn2O3 single‐crystal nanowires

Single‐crystal α‐Mn₂O₃ nanowires were prepared via a “self‐sacrificing template” route, simply by calcining the prepared α‐MnO₂ nanowire precursors at 550 °C for 1.5 h. XRD, TEM, SEM and HRTEM characterizations show that the as‐prepared α‐Mn₂O₃ samples are all phase pure and the nanowires have uniform diameters of approximately 15‐30 nm and lengths up to several micrometers. The catalytic performances of the prepared α‐Mn₂O₃ nanowires were studied in the degradation of coking wastewater with H₂O₂ as the oxidant, and the technological conditions were optimized by single‐factor and orthogonal experiments. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Well‐defined Sb2S3 nanostructures: citric acid‐assisted synthesis,electrochemical hydrogen storage properties

Well‐defined (three‐dimensional) 3‐D dandelion‐like Sb₂S₃ nanostructures consisted of numerous nanorods have been achieved via a facile citric acid‐assisted solvothermal process. The as‐prepared products were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM), respectively. The influence factors of the formation of the hierarchical Sb₂S₃ nanostructures are discussed in details based on FESEM characterizations. By simply controlling the quantity of citric acid, the nucleation and growth process can be readily tuned, which brings the different morphologies and nanostructures of the final products. On the basis of a series of contrastive experiments, the aggregation‐based process and anisotropic growth mechanism are reasonably proposed to understand the formation mechanism of Sb₂S₃ hierarchical architectures with distinctive morphologies including nanorods, and dandelion‐like nanostructures. Charge‐discharge curves of the obtained Sb₂S₃ nanostructures were measured to investigate their electrochemical hydrogen storage behaviors. It revealed that the morphology played a key role on the hydrogen storage capacity of Sb₂S₃ nanostructure. The dandelion‐like Sb₂S₃ nanostructures exhibited higher hydrogen storage capacity (108 mAh g⁻¹) than that of Sb₂S₃ nanorods (95 mAh g⁻¹) at room temperature.     

α‐Fe2O3 nanospindles loaded with ZnO nanocrystals: Synthesis and improved gas sensing performance

ZnO/α‐Fe₂O₃ nanocomposites were fabricated through a two‐step hydrothermal method. The morphology and composition of the as‐synthesized products were characterized by X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The gas sensing properties of the fabricated products were investigated towards ethanol, acetone, propanol, isopropanol, formaldehyde, chloroform and so on. The results demonstrated that the ZnO/α‐Fe₂O₃ nanocomposites exhibited excellent sensing properties and showed remarkably higher sensing responses and much lower optimum operating temperature compared to individual ZnO and α‐Fe₂O₃. In addition, the ZnO/α‐Fe₂O₃ nanocomposites have some selectivity for ethanol, propanol and isopropanol. The possible gas sensing mechanism was also proposed. Our studies demonstrate that our fabricated materials could be widely used in the future.     

Low‐temperature urea‐assisted hydrothermal synthesis of Bi2S3 nanostructures with different morphologies

Different morphologies of single‐crystalline orthorhombic phase bismuth sulfide (Bi₂S₃) nanostructures, including sub‐microtubes, nanoflowers and nanorods were synthesized by a urea‐assisted hydrothermal method at a low temperature below 120 °C for 12 h. The as‐synthesized powders were characterized by X‐ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and UV‐vis spectrophotometry. The experimental results showed that the sulfur sources had a great effect on the morphology and size of the resulting powders. The formation mechanism of the Bi₂S₃ nanostructures with different morphologies was discussed. All Bi₂S₃ nanostructures showed an appearance of blue shift relative to the bulk orthorhombic Bi₂S₃, which might be ascribed to the quantum size effect of the final products. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal synthesis of anatase flower‐like nanostructures for photocatalytic degradation of dye

Flower‐like hierarchical nanostructures of titanium dioxide (TiO₂) have been synthesized in large scale by a facile and controlled hydrothermal and after annealing process. The morphologies of flower‐like hierarchical nanostructures are formed by self‐organization of several tens of radially distributed thin flakes with a thickness of several nanometers holding a larger surface area. The materials are characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The ultraviolet photocatalytic degradation of R6G dyes has been studied over this flower‐like hierarchical nanostructures and the activity is compared with that of commercial P25 TiO₂ under same conditions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase‐manipulable synthesis of Cu‐based nanomaterials using ionic liquid 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate

Using the ionic liquid (IL), 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate, and the precursor Cu₇Cl₄(OH)₁₀·H₂O, series of phase‐manipulable Cu‐based nanomaterials were synthesized by hydrothermal and microwave assisted routes, respectively. The structural characters of the as‐prepared CuO, CuO/Cu₂O composites and pure Cu nanoparticles were investigated by XRD, SEM, TEM and HRTEM, and their surface photovoltaic properties were studied by surface photovoltage spectra. Via hydrothermal route Cu²⁺ ions were found to be reduced gradually into Cu⁺ and subsequently Cu⁰ with increasing the IL, and various phase ratio of CuO, Cu₂O and Cu composite nanosheets and pure Cu nanoparticles were obtained. This implies that the IL could function as both a reductant in the oxygen‐starved condition and a template for the nanosheet products. The ¹H‐NMR result of the IL supports it being a reductant. In microwave assisted route, however, only monoclinic single crystalline CuO nanosheets were obtained, which indicates the IL being a template only in oxygen‐rich condition. Therefore, the crystal phase, composition and morphology of the Cu‐based products could be controlled by simply adjusting the quantity of the IL and oxygen in solution routes. The molecular structure of the IL after oxidation reactions was investigated by ¹H‐NMR and a possible reaction mechanism was proposed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surfactant‐assisted synthesis of novel star‐like PbWO4 hierarchical architectures

Large‐scale star‐like PbWO₄ hierarchical architectures were controllably synthesized by a facile surfactant‐assisted technology under mild conditions in the presence of a mixed solvent of ethylene glycol and water. The morphology, structure, and phase composition of PbWO₄ architectures were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), field emission transmission electron microscopy (FE‐TEM), and nitrogen adsorption‐desorption isotherms. The possible formation mechanism of the star‐like PbWO₄ architectures (initial nucleating stage and a subsequent self‐assembly stage) was proposed based on the observations from a time‐dependent morphology evolution process, which may pave the way to shape‐controlled synthesis of inorganic nanocrystals with the complex structures. This route provides a facile strategy to fabricate complex hierarchical PbWO₄ structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

synthesis of high‐quality crystalline α‐MoO3 nanobelts

High‐quality crystalline MoO₃ nanobelts were successfully fabricated with a facile hydrothermal route by using common and inexpensive NaCl as a capping agent. The products are thoroughly characterized by the combination of different techniques. The results indicate that as‐prepared MoO₃ nanobelts have an orthorhombic crystal structure (α‐MoO₃) with growth preferential in the [001] direction, the size of the obtained MoO₃ nanobelts ranges from 200 nm to 300 nm in width and micrometers in length. The effects of the amount of NaCl on the morphology and size of the resultant MoO₃ were also investigated, it is clearly shown that the presence of appropriate amount of NaCl plays a crucial role in controlling the size and morphology of the obtained MoO₃. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal synthesis of nano‐crystalline BaMoO4 under mild conditions using simple additive

Large‐scale high‐quality BaMoO₄ nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have bone‐like, spindle‐like and wheatear‐like morphologies assembled from nanoparticles, nanofibers and have been characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results showed that experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room‐temperature photoluminescence indicated that the as‐prepared BaMoO₄ nanocrystals had a strong blue emission peak at 481.5 nm. This facile route could be employed to synthesize more promising nanomaterials with interesting self‐assembly structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low temperature synthesis of spindle‐like ZnO nanostructures under microwave irradiation

A simple and general microwave route is developed to synthesize nanostructured ZnO using Zn(acac)₂·H₂O (acac = acetylacetonate) as a single source precursor. The reaction time has a great influence on the morphology of the ZnO nanostructures and an interesting spindle‐like nanostructure is obtained. The microstructure and morphology of the synthesized materials are investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). It is found that all of them with hexagonal wurtzite phase are of single crystalline structure in nature. Ultraviolet–visible (UV‐vis) absorption spectra of these ZnO nanostructures are investigated and a possible formation mechanism for the spindle‐like ZnO nanostructures is also proposed.     

Synthesis of highly‐ordered hierarchical ZnO nanostructures and their application in dye‐sensitized solar cells

In order to improve the performance of ZnO‐based solar cells, highly‐ordered hierarchical ZnO nanostructures were design and fabricated. The hierarchical nanostructures were grown on FTO (fluorine doped tin oxide, SnO₂:F) glass substrates via a facile, low‐temperature, and low‐cost chemical route. The morphology and structure of the obtained products has been confirmed by field‐emission scanning electron microscopy and X‐ray diffraction measurements. The performance investigation of the prepared dye‐sensitized solar cells (DSSCs) demonstrates that the hierarchical ZnO nanostructure‐based solar cell shows a higher short‐circuit current density compared with the ZnO nanowire counterpart. The enhanced current density may be due to the fact that the surface area of the hierarchical nanostructures is increased. These results indicate that hierarchical ZnO nanostructures are more suitable for the application as photoelectrode of DSSCs. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The crystal structure of α‐SrGaBO4

A new compound α‐SrGaBO₄ has been synthesized by solid state reaction at high temperatures, and its structure has been solved by direct methods from powder X‐ray diffraction. α‐SrGaBO₄ has an orthorhombic system, Pccn space group, with lattice parameters a = 15.3154(7) Å, b = 8.9186(4) Å, c = 5.8130(3) Å, and Z = 8. The structure consists of infinite chains run parallel to the c axis and built up of GaO₄ tetrahedral and BO₃ triangles. The basic unit of these chains is a six ‐ membered Ga₂BO₈ ring formed by two GaO₄ tetrahedra and one BO₃ triangles. The Sr atom is bonded to eight oxygen atoms. The strontium atoms serve to hold the chains together through co‐ordination with oxygen atoms. DTA curve of noncrystalline glassy SrGaBO₄ was discussed. The XRD results show no phase transition occurs between ‐173 °C and 127 °C. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase‐selective crystallization of nickel phosphate VSB‐5 with (2‐hydroxyethyl) trimethylammonium hydroxide as template

Several nickel phosphate molecular sieves were synthesized by conventional heating (CH) and microwave assisted hydrothermal (MAH). Nickel phosphate VSB‐5 (Versailles Santa Barbara‐5) was synthesized with conventional oven for 72 h or with microwave for 1 h and followed by conventional oven for 48 h in the presence of (2‐hydroxyethyl) trimethylammonium hydroxide as template. The phase transformation is observed by variation of CH time for the synthesis of nickel phosphate molecular sieves. At CH time of 24 h, the VSB‐5 crystal together α‐Ni₂P₂O₇, Ni₂P₄O₁₂ and unknown phases were produced but the pure VSB‐5 crystal was obtained in the CH time of 48 h or more. At high content of nickel, a mixture of α‐Ni₂P₂O₇, Ni₂P₄O₁₂ phases and small amount of VSB‐5 crystal, was achieved but pure VSB‐5 crystal was obtained in the lower level of nickel and other phases are vanished. An efficient ultrasonic‐assisted aging was found for the synthesis of nickel phosphate molecular sieve, in which by ultrasonic mixing of 0.5 h followed microwave of 1 h, the CH time is significantly reduced from 48 to 24 h. The morphology of nickel phosphate crystals is highly influenced in the presence of ethylene glycol as co‐solvent. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microwave‐assistant route to hybrid semiconductor nanocrystals with quasi solution‐solid‐solid mechanism

A facile microwave‐assistant route was developed for the synthesis of hybrid nanocrystals. Colloidal hybrid nanocrystals, Ag₂S‐CdS, were prepared by using Ag₂S nanocrystals and cadmium diethyldithiocarbamate as raw materials under microwave irradiation. The fast ion conductor, Ag₂S nanocrystal, catalyzes the growth of CdS nano‐building blocks through a quasi solution‐solid‐solid mechanism. The ultraviolet‐visible absorption and photoluminescence spectra of the Ag₂S‐CdS hybrid nanocrystals were investigated. One of the main advantages for this synthesis is the efficiency of dramatically reducing overall processing time. This report provides a new route for the growth of semiconductor hybrid nanocrystals based on Ag₂S and may be extended to the preparation of other hybrid colloidal nanostructures.     

Surfactant directed synthesis of mesoporous alumina and α‐alumina single crystal

Mesoporous Al₂O₃ were positively synthesized via treatment of the freshly precipitated amorphous alumina gel using aluminium sulphate as aluminium source, and sodium dodecyl sulphate (SDS) as structure‐directing agent (SDAs). The microstructures, morphologies and textural properties of the as‐prepared materials were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and thermo gravimetric analysis (TG‐DTA). The calcined product at 600 °C was highly porous in nature having a BET surface area of 42 m²/g. These porous Al₂O₃ exhibits excellent adsorption performance for Congo red and the corresponding decolourisation efficiencies reached 99% in just 15 min at 27 °C. The subsequent calcined product at 1200 °C is the alpha alumina single crystal hexagonal platelets with rhombohedral crystallization.