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)     

Synthesis of ZnO nanorods by the thermal reduction process of a mixture of ZnO and Al powder

Single‐crystalline Zinc oxide (ZnO) nanorods were firstly synthesized on gold‐coated Si substrate via a simple thermal reduction method from the mixture of ZnO and Al powder. The growth process was carried out in a quartz tube at different temperature (550‐700 °C) and at different oxygen partial pressure. Their structure properties were investigated by X‐ray diffraction (XRD), scanning electron microscope (SEM), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The length of the as‐prepared ZnO nanorods was up to several micrometers and their diameters were about 130 nm. The X‐ray diffraction patterns, transmission electron microscopic images, and selective area electron diffraction patterns indicate that the one‐dimensional ZnO nanorods are a pure Single‐crystal and preferentially oriented in the [0001] direction. The reaction mechanism of ZnO nanorods was proposed on the basis of experimental data. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile synthesis and characterization of hierarchical CuO nanoarchitectures by a simple solution route

The controlled synthesis of hierarchical CuO nanomaterials in a solution phase has been realized with high yield at low temperature using copper acetate hydrate and NaOH as starting materials with the assistance of surfactant under hydrothermal conditions. X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet‐visible spectroscopy (UV‐Vis) were used to characterize the products. It was shown that the hierarchical CuO nanoarchitectures were formed through aggregation of tiny single‐crystal CuO nanorods. Experiments demonstrated that the morphology of CuO products was significantly influenced by hydrothermal temperature and reaction time. A rational growth mechanism based on oriented attachment was proposed for the selective formation of the hierarchical CuO nanoarchitectures. Our work demonstrated the growth of hierarchical CuO nanoarchitectures built from one‐dimentional nanorods through a one‐step solution‐phase chemical route under controlled conditions. In addition, The UV‐Vis spectrum of the hierarchical CuO nanoarchitectures showed large blue shift because of the quantum size effect. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of passivation and postannealing on the photoluminescence properties of MgO/SiO2 core‐shell nanorods

MgO nanorods were grown by the thermal evaporation of Mg₃N₂ powders on the Si (100) substrate coated with a gold thin film. The MgO nanorods grown on the Si (100) substrate were a few tens of nanometers in diameter and up to a few hundreds of micrometers in length. MgO/SiO₂ core‐shell nanorods were also fabricated by the sputter‐deposition of SiO₂onto the MgO nanorods. Transmission electron microscopy (TEM) and X–ray diffraction (XRD) analysis results indicated that the cores and shells of the annealed core‐shell nanorods were a face‐centered cubic‐type single crystal MgO and amorphous SiO₂, respectively. The photoluminescence (PL) spectroscopy analysis results showed that SiO₂ coating slightly decreased the PL emission intensity of the MgO nanorods. The PL emission of the MgO/SiO₂ core‐shell nanorods was, however, found to be considerably enhanced by thermal annealing and strongly depends on the annealing atmosphere. The PL emission of the MgO/SiO₂ core‐shell nanorods was substantially enhanced in intensity by annealing in a reducing atmosphere, whereas it was slightly enhanced by annealing in an oxidative atmosphere. The origin of the PL enhancement by annealing in a reducing atmosphere is discussed with the aid of energy‐dispersive X‐ray spectroscopy analyses. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterization of ZnO nanorods grown on Si substrates coated with NiCl2

ZnO nanorods were synthesized on NiCl₂‐coated Si substrates via a chemical vapor deposition (CVD) process. The as‐fabricated nanorods with diameters ranging from 150 nm to 200 nm and lengths up to several tens of micrometers grew preferentially arranged along [0001] direction, perpendicular to the (0002) plane. The clear lattice fringes in HRTEM image demonstrated the growth of good quality hexagonal single‐crystalline ZnO. Room temperature photoluminescence (PL) spectra illustrated that the ZnO nanorods exhibit strong UV emission peak and green emission peak, peak centers located at 388 nm and 506 nm. A possible growth mechanism based on the study of our X‐ray diffraction (XRD), electron microscopy and PL spectroscopy was proposed, emphasizing the effect of NiCl₂ solution (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High-yield synthesis of single-crystal short Eu2O3 nanorods through a facile sol–gel template approach

High-yield Eu₂O₃ short nanorods have been prepared by a facile sol-gel method with polystyrene/polyelectrolyte (PS/PE) microreactor as template in an aqueous solution of europium nitrate in the presence of ammonia and urea. The properties of Eu₂O₃ nanorods were characterized by powder X-ray diffraction, thermogravimetric analysis, transmission electron microscopy (TEM), high-resolution transmission electron microscopy, field emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy. The particle sizes measured from TEM and FESEM are about 200 nm×500 nm (W×L). A possible mechanism for the formation of such high-yield oxide nanorods is discussed.     

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.     

Facile morphology‐controlled hydrothermal synthesis of flower‐like self‐organized ZnO architectures

Flower‐like self‐organized crystalline ZnO architectures were obtained through a facile and controlled hydrothermal process. As‐synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), electron diffraction and UV‐Vis spectroscopy. XRD and electron diffraction results confirmed the obtained materials are pure wurtzite ZnO. The effects of different ratios of starting materials and solvent on the morphologies of ZnO hydrothermal products were also evaluated by SEM observations. It is suggested that the use of water, rather than ethanol as the solvent, as well as employing a precursor of Zn(Ac)₂ and 2NaOH (v/v) in hydrothermal reactions are responsible for the generation of specific flower‐like self‐assembled ZnO structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low temperature synthesis of thiol‐functionalized CdTe nanoclusters with different tellurium contents

In recent years thiol‐functionalized cadmium telluride nanoparticles act as a core layers for obtaining high photovoltaic efficiency in conjugated polymer/inorganic nanocrystal solar cells and also provide easy tuning of quantum size effect by varying thiol groups and processing temperature. In this work, thiol functionalized CdTe nanoclusters were prepared for different tellurium concentrations at low temperature and its impact has been discussed. Structural parameters estimated by X‐ray diffraction revealed hexagonal phases at lower tellurium concentration and cubic phase at higher tellurium concentrations. Surface morphology of the samples analyzed by transmission electron microscopy, exhibited cluster type of morphology. Optical band gap energy estimated by diffused electron microscopy showed an increase with Te content and band edge emission has been observed in the photoluminescence spectra of CdTe nanoclusters around 620 nm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Enhancement of the emission from TeO2 nanorods by encapsulation with ZnO

TeO₂‐core/ZnO‐shell nanorods were synthesized by a two–step process comprising thermal evaporation of Te powders and atomic layer deposition of ZnO. Scanning electron microscopy images exhibit that the core‐shell nanorods are 50 ‐ 150 nm in diameter and up to a few tens of micrometers in length, respectively. Transmission electron microscopy and X‐ray diffraction analysis revealed that the cores and shells of the core‐shell nanorods were polycrystalline simple tetragonal TeO₂ and amorphous ZnO with ZnO nanocrystallites locally, respectively. Photoluminescence measurement revealed that the TeO₂ nanorods had a weak broad violet band at approximately 430 nm. The emission band was shifted to a yellowish green region (∼540 nm) by encapsulation of the nanorods with a ZnO thin film and the yellowish green emission from the TeO₂‐core/ZnO‐shell nanorods was enhanced significantly in intensity by increasing the shell layer thickness. The highest emission was obtained for 125 ALD cycles (ZnO coating layer thickness: ∼15 nm) and its intensity was much higher than that of the emission from the uncapsulated TeO₂ nanorods. The origin of the enhancement of the emission by the encapsulation is discussed in detail. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis by organic molten salt method and characterization of chalcopyrite AgInS2 nanorods

In this paper, chalcopyrite AgInS₂ nanorods were synthesized for the first time by a one‐step, ambient pressure, environment friendly organic molten salt (OMS) method at 200 °C. The as‐synthesized products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The XRD results reveal that the as‐synthesized products at 120–160 °C under ambient pressure contain AgIn₅S₈ which will decrease with the increase of growth temperature. A sample containing only the chalcopyrite AgInS₂ phase is successfully obtained at 200 °C. Furthermore, the elemental compositions are found to become increasingly stoichiometric with increasing temperature. UV‐Vis and photoluminescence (PL) spectra are utilized to investigate the optical properties of AgInS₂ nanorods. By testing on UV‐Vis spectra, it is concluded that the limiting wavelength of the AgInS₂ nanorods is 661 nm and the band gap is 1.88 eV. A broad red emission band peak centered at about 1.874 eV (662 nm) is clearly observed at room temperature, and the intensity of the emission increases with excitation wavelength. In addition, the photoluminescence quantum yield (PLQY) of the nanocrystals at the excitation wavelength of 250 nm was determined to be 13.2%. A possible growth mechanism of AgInS₂ nanorods was discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fabrication of CdS nanorods in inverse microemulsion using HEC as a template by a convenient γ-irradiation technique

Cadmium sulfide (CdS) nanocrystals were successfully prepared in inverse microemulsion under γ-irradiation at room temperature. Their shape can be controlled by changing the surfactant concentrations and the addition of hydroxyethyl cellulose (HEC) as the template. CdS nanorods were successfully obtained under γ-irradiation using HEC as the template, which was confirmed by the observation of transmission electron microscopy (TEM). Without the addition of HEC, spherical CdS crystals were formed. X-ray powder diffraction (XRD) pattern and electron diffraction (ED) analysis showed the hexagonal lattice of CdS in the nanorods. Additionally, the optical properties of CdS nanorods were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy.     

Micelle-assisted hydrothermal synthesis of the uniform Co3O4 nanorods and its chemoluminescence properties of CO oxidation

Uniform Co₃O₄ nanorods were prepared by a micelle-assisted hydrothermal method. The samples were characterized by scanning electron microscopy (SEM), energy disperse spectra (EDS), transmission electron microscopy (TEM), selected area electron diffraction (ED), X-ray diffraction (XRD), and N₂ adsorption. The chemoluminescence and catalytic oxidation properties of CO and CH₄ over Co₃O₄ nanorods were investigated. The results showed that the micelles played a key role in the formation of uniform nanorods, that the nanorods with a high crystallinity were obtained after being treated hydrothermally, and that the nanorods showed a higher chemoluminescence (CL) intensity of CO oxidation and a higher activity for CH₄ combustion than the bulk one. The adopted ‘one-pot’ synthesis is a facile method, since no further annealing at high temperatures is needed.     

Sonochemical synthesis and characterization of ZnO nanorod/Ag nanoparticle composites

A simple sonochemical route for the synthesis of Ag nanoparticles on ZnO nanorods is reported. Ultrasonic irradiation of a mixture of ZnO nanorods, Ag(NH₃)₂⁺, and formaldehyde in an aqueous medium yields ZnO nanorod/Ag nanoparticle composites. The powder X‐ray diffraction of the ZnO/Ag composites shows additional diffraction peaks corresponding to the face‐center‐cubic structured Ag crystalline, apart from the signals from the ZnO nanorods. Scanning electron microscopy and transmission electron microscopy images of the ZnO/Ag composites reveal that the ZnO nanorods are coated with Ag nanoparticles with a mean size of several tens nanometer. The absorption band of ZnO/Ag composites is distinctly broadened and red‐shifted, indicating the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. This sonochemical method is simple, mild and readily scaled up, affording a simple way for synthesis of other composites. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystalline bismuth oxide nanorods fabricated on Pt‐coated substrates using a trimethylbismuth and oxygen mixture

The current work reports the fabrication of crystalline Bi₂O₃ nanorods on Pt‐coated Si substrates using trimethylbismuth and O₂ as the bismuth and the oxygen sources, respectively, in the metalorganic chemical vapor deposition process. Their microstructures were characterized by scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy. The obtained nanorods were crystalline, with their diameters in the range of 20–200 nm. The absence of tip‐nanoparticle and the presence of predeposited Bi₂O₃ layer indicated that the growth was dominated by a vapor‐solid process. The photoluminescence measurements of the Bi₂O₃ nanorods at room temperature exhibited an emission band peaked at around 422 nm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The effect of ZnO buffer layer on structural and optical properties of ZnO nanorods

A low‐temperature synthetic route was used to prepare oriented arrays of ZnO nanorods on ITO conducting glass substrate coated with buffer layer of ZnO seeds in an aqueous solution. The corresponding growth behavior and optical properties of ZnO nanorod arrays were studied. It was found that the nature of the buffer layer had effect on the microstructures and optical properties of the resultant ZnO nanorod arrays. X‐ray diffraction (XRD) results showed the nanorods were preferentially grown along (002) direction, but the diameter of the nanorods prepared with the buffer layer was much smaller than the without one, which can be clearly seen from the scanning electron microscopy (SEM) results. And it also found that the buffer layer was not only enhanced the density of overall coverage but also beneficial to grown the oriented arrays. Photoluminescence spectroscopy (PL) results indicated that the all the samples had the better optical behaviors. By computation, the relative PL intensity ratio of ultraviolet emission (I_UV) to deep level emission (I_DLE) of ZnO nanorods grown with the pure substrate was much higher than that of the sample with the buffer layer. The defects on the surface increased with the size reduction of nanorods caused by the buffer layer may be the main reason for it. And the small shift in the UV emission was caused by the rapid reduction in crystal size and compressive stress from Raman spectra results. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bulk-quantity SnO2 nanorods synthesized from simple calcining process based on annealing precursor powders

Tin dioxide (SnO₂) nanorods have been successfully synthesized in bulk quantity by a calcining process based on annealing precursor powders in which sodium chloride, sodium carbonate, and stannic chloride were homogeneously mixed. Transmission electron microscopy shows that the as-prepared nanorods are structurally perfect and uniform, with widths of 10–25 nm, and lengths of several hundreds nanometers to a few micrometers. X-ray diffraction and energy-dispersive X-ray spectroscopy analysis indicate that the as-prepared nanorods have the same crystal structure and chemical composition found in the tetragonal rutile form of SnO₂. Selected area electron diffraction and high-resolution transmission electron microscopy reveal that the as-prepared nanorods grow along the [1 1 0] crystal direction. We found that the calcined temperature has a strong influence on the size and morphology of SnO₂ nanorods. The growth process of SnO₂ nanorods is suggested to follow an Ostwald ripening mechanism. Our findings indicate that other nanorods or nanowires may be manipulated by using this technique, and might provide insight into the new opportunities to control materials fabrication.     

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)     

Self-assembly of LiFePO4 nanodendrites in a novel system of ethylene glycol–water

In this work, a novel system of ethylene glycol/water (EG/W) was employed to synthesize LiFePO₄, in which dodecyl benzene sulphonic acid sodium (SDBS) was used as soft template to control particle morphology. The samples were characterized by X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX). The LiFePO₄ sample obtained by the reported method displays interesting hierarchical nanostructure (i.e. nanodendrites), which was constructed by nanorods of 3–5 μm in length and ∼50 nm in diameter. The EG/W ratio, amount of SDBS added, hydrothermal temperature and duration played important roles in the assembly of the hierarchical nanostructures. A formation mechanism was proposed and experimentally verified. It is concluded that the nanodendrites were formed due to the end-to-end self-assembly of nanorods. Compared to previously reported methods, the reported approach shows obvious advantages of one-step synthesis, environmental friendliness and low cost, to name a few. The nanodendrites as a cathode material have a higher capacity, compared with the other samples.     

反应条件对PbWO4纳米棒形貌和光致发光性能的影响

采用反相微乳液辅助的溶剂热法合成了不同形貌的PbWO4纳米棒,用X射线衍射(XRD)、透射电镜(TEM)和光致发光(PL)谱等技术对产物进行了结构表征和发光性能的测试.结果表明:通过改变反应条件如反应温度、时间和表面活性剂的浓度可以得到不同结构与形貌的PbWO4纳米棒,其发光性能也随其形貌不同而不同.