Hydrothermal synthesis and characterization of hexagonal and monoclinic neodymium orthophosphate single-crystal nanowires

Hexagonal and monoclinic NdPO₄ nanowires about 5-50 nm in diameter and up to several micrometers long were prepared through hydrothermal reaction in 100°C and 220°C, respectively. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, both the temperature and the pH value influence on the products were investigated.     

One-step template-free solution route for Cu(OH)<Subscript>2</Subscript> nanowires

Cu(OH)₂ nanowires with a diameter of 8–10 nm and lengths of tens of micrometers were fabricated in the basic solution by dropping simply NaOH solution into CuCl₂ solution at ambient temperature. The formation mechanism of nanowires was discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the samples. This article was submitted by the authors in English.     

Solvothermal synthesis and characterization of uniform CdS nanowires in high yield

Large-scale CdS nanowires with uniform diameter and high aspect ratios were synthesized using a simple solvothermal route that employed CdCl₂ and S powder as starting materials, ethylenediamine (en) as the solvent. X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) images show that the products are hexagonal structure CdS nanowires with diameter of 40 nm and length up to 10 μm. Selected area electron diffraction (SAED) and high resolution TEM (HRTEM) studies indicate the single-crystalline nature of CdS nanowires with an oriented growth along the c-axis direction. The optical properties of the products were characterized by optical absorption spectra and photoluminescence spectra. Based on the results of contrastive experiments, it is found that the sulfur source and the solvent play significant roles in the formation of uniform nanowires. A possible formation mechanism of nanowires is discussed.     

Hierarchical Titanate Nanostructures through Hydrothermal Treatment of Commercial Titania Powders

Hierarchical titanate nanostructures were hydrothermally synthesized in concentrated base solutions using commercial titania powders as starting materials. By varying the base concentration, nanowire arrays, flowers of nanosheets and nanotubes, and urchin‐like nanostructures of nanowires and nanotubes were sequentially fabricated. If the NaOH concentration was higher than 6 M , hydrated Na₂Ti₆O₁₃ nanowire arrays, with nanowire diameters of 20–90 nm and an aspect ratio of 1100–5000, were produced at suitable reaction temperatures over a large area. In 10 M KOH solutions, aligned nanowires with a diameter of 30 nm and a lenght of 80 μm formed. In 4 M NaOH solutions, micrometer‐sized flowers of nanotubes and nanosheets formed. Reactions in 2 M NaOH solutions produced urchin‐like materials with a size of ca. 10 μm that were composed of nanotubes and nanowires. The adsorption behavior of the urchin‐like materials resembled macroporous materials with micropores. Since both base concentration and reaction temperature affected the reaction rate, the formation of various titanate nanostructures was proposed as a growth speed controlled process.     

A simple wet chemical route for large-scale synthesis of Cu(OH)2 nanowires

Polycrystalline Cu(OH)₂ nanowires with an average diameter of ca. 8 nm and lengths of up to hundreds of micrometers were synthesized by using a simple chemical route at ambient temperature. The crystallity, purity, morphology, and structure features of the as-prepared Cu(OH)₂ nanowires were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The growth mechanism of the Cu(OH)₂ nanowires were studied in detail.     

Controlled synthesis of single-crystalline Mg(OH)2 nanotubes and nanorods via a solvothermal process

The synthesis of Mg(OH)₂ one-dimensional (1D) nanostructures was systematically investigated in different solvents at various temperatures with Mg₁₀OH₁₈Cl₂·5H₂O nanowires as source materials. The results showed that the characters of the products, such as crystal size, shape, and structure, were strongly influenced by the solvent and temperature during the solvothermal process. 1D nanotubes of Mg(OH)₂, with 80-300 nm outer diameter, 30-80 nm wall thickness, and several tens of micrometers in length were obtained by choosing bidentate ligand solvents such as ethylenediamine and 1,6-diaminohexane as the reaction solvent. But when using monodentate ligand pyridine as the reaction solvent, the obtained samples showed nanorods morphology. The Mg(OH)₂ thus produced was analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM), and selected-area electron diffraction (SAED). The possible growth mechanism of the 1D nanostructure Mg(OH)₂ was discussed.     

Synthesis and characterization of silver nanowires with zigzag morphology in N,N-dimethylformamide

Zigzag silver nanowires with a uniform diameter of 20±5 nm were prepared by reducing silver nitrate (AgNO₃) with N,N-dimethylformamide (DMF) in the presence of tetrabutyl titanate (TBT) and acetylacetone (AcAc) at 373 K for 18 h. X-ray and selected area electron diffraction (XRD and SAED) patterns reveal that the prepared product is made of pure silver with face centered cubic structure. Transmission electron microscopy (TEM) investigations suggest that the amount of silver nanowires is enhanced with increase in reaction time, and the end-to-end assemblies of silver nanorods are observed during the reaction process. After 18 h reaction, silver nanowires with zigzag morphology are obtained. In this paper, a possible growth process of silver nanowires with this interesting shape is described. Silver nanoparticles with small sizes were obtained by reducing Ag⁺ ions with DMF, providing seeds for homogeneous growth of silver nanorods. With the extending reaction time, the synthesized silver nanorods were connected in an end-to-end manner, and the interface between the connections of two nanorods gradually disappeared. The final product shows zigzag morphology with various angles. The angles between two connecting straight parts of zigzag nanowires exhibit an alterable range of 74-151°. These silver nanowires show tremendous potential applications in future nanoscale electronic circuits.     

Synthesis and Characterization of SnO2 One-dimensional Nanostructures

Single-crystalline SnO2 nanowires have been successfully prepared in large scale on Au-coated silicon substrate by heating the mixture of self-made high-purity SnO2 powders and graphite powders at 900℃. Besides the line type nanowires some more features were observed. The products were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and Raman spectrum techniques. The results indicate that the tin dioxide nanowires have a rutile structure with diameters ranging from 30 to 120 nm and lengths up to several tens of micrometers. The possible mechanism of the growth and reaction for the nanowires was also discussed.     

A simple approach to the synthesis of silver nanowires by hydrothermal process in the presence of gemini surfactant

Silver nanowires were synthesized by the hydrothermal route in aqueous solution of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16) at a relatively low temperature. The as-prepared silver nanowires were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), transmission electron microscope (TEM), electron diffraction (ED), and UV-vis absorption spectrum. The obtained silver nanowires are of high aspect ratios with an average diameter of approximately 30 nm and length ranging from several to tens of micrometers.     

一步法水热合成 TiO2纳米线及其光催化性能

以钛酸丁酯和异丙醇为原料, 采用一步法在NaOH溶液中水解后直接进行水热反应, 经焙烧处理, 得到TiO2纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)和能谱分析(EDX)对产物进行了形貌、结构及成分的表征. 考察了不同水热温度、碱液浓度、水热反应时间及焙烧温度等因素对产物的影响. 结果表明, 获得较好形貌TiO2纳米线的最佳水热温度、碱液浓度和水热反应时间分别是180 ℃, 10 mol/L和24 h. 所得TiO2纳米线焙烧至950 ℃时仍为锐钛矿相, 说明本文制备方法迟滞了TiO2纳米线由锐钛矿相向金红石相的转变. 以甲基橙为目标降解物, 采用紫外-可见分光光度计研究了未掺杂和铕掺杂TiO2纳米线(Eu-TiO2)的光催化性能. 结果显示, 最佳掺铕量(摩尔分数)为1.6%. 在300 W紫外灯照射60 min时, 此掺铕量的TiO2纳米线对甲基橙溶液的降解率是未掺杂样品的1.5倍.     

Ultralong cadmium hydroxide nanowires: synthesis, characterization, and transformation into CdO nanostrands

Ultralong Cd(OH)2 nanowires were fabricated by a hydrothermal method from Cd(CH3COO)2 x H2O (0.01 mol/L) and C6H12N4 (0.015 mol/L) aqueous solution at 95 degrees C for 16 h without using any templates and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The length of the nanowires reached several micrometers, giving an aspect ratio of a few thousands. The formation mechanism of the nanowires is attributed to the oriented attachment of small particles. The growth method for the 1D nanostructure presented here offers an excellent tool for the design of other advanced materials with anisotropic properties. The Cd(OH)2 nanowires efficiently captured negatively charged dye, and the adsorbed dye molecules can be released after the addition of EDTA. The Cd(OH)2 nanowires as template compounds were further transformed into CdO semiconductor nanomaterials with similar morphology by calcination under 350 degrees C in air for 3 h.     

A simple method of fabricating large-area α-MnO2 nanowires and nanorods

α-MnO₂ nanowires or nanorods have been selectively synthesized via the hydrothermal method in nitric acid condition. The α-MnO₂ nanowires hold with average diameter of 50 nm and lengths ranging between 10 and 40 μm, using MnSO₄·H₂O as manganese source; meanwhile, α-MnO₂ bifurcate nanorods with average diameter of 100 nm were obtained by adopting MnCO₃ as starting material. The morphology of α-MnO₂ bifurcate nanorods is the first one to be reported in this paper. X-ray powder diffraction (XRD), field scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products. Experimental results indicate that the concentrated nitric acid plays a crucial role in the phase purity and morphologies of the products. The possible formation mechanism of α-MnO₂ nanowires and nanorods has been discussed.     

表面活性剂辅助合成CdWO4纳米棒和纳米线

以Na₂WO₄•2H₂O和CdCl₂ 为主要原料, 分别在十六烷基三甲基溴化铵(CTAB)和十二烷基苯磺酸钠(SDBS)表面活性剂中, 在180 ℃反应16 h, 水热制备了CdWO₄纳米棒和纳米线. 利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征, 并对其在室温下的发光特性进行了测定. 实验结果表明: 产物均为具有单斜结构的单相CdWO₄. 其中CdWO₄纳米棒具有单晶属性, 平均粒径约为63 nm, 长度近1 µm; 而CdWO₄纳米线具有多晶特性, 平均粒径约为12 nm, 长度达十几微米. 当激发波长为253 nm时均有460 nm强的发射峰, 其中CdWO₄单晶纳米棒的发光强度大于CdWO₄多晶纳米线. 分别对CdWO₄纳米棒和纳米线形成的可能机理进行了初步分析.     

离子液体-水的混合溶剂中，合成条件对纳米TiO2结晶度的影响

0 Introduction Titania has been extensively used in a variety of applications such as gas sensors, dielectric ceram ics, catalysts for therm al or photoinduced processes, pho- tovoltaic solar cells, and pigm ents. One of the m ost im portant applications …     

Synthesis and characterization of layered double hydroxides with a high aspect ratio

A new route for synthesis of Mg/Al layered double hydroxide (Mg₆Al₂(OH)₁₆(CO₃)·4H₂O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1-6 μm and the thickness at ca. 35-60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO₃⁻ and CO₃²⁻ keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio.     

Facile solvent-free synthesis of pure-phased AlN nanowhiskers at a low temperature

Pure hexagonal aluminum nitride (AlN) nanowhiskers have been successfully synthesized by directly reacting AlCl₃ with NaN₃ in non-solvent system at the low temperature of 450 °C for 24 h. The obtained products are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and selected area electron diffraction, which show that the obtained products are hexagonal phase AlN nanowhiskers with width from 10 to 80 nm and length up to several micrometers. The influencing factors of the formation of AlN nanowhiskers were discussed and a possible growth mechanism for AlN nanowhiskers was proposed. Additionally, the study on the corresponding optical properties and catalytic properties is also carried out.     

Size- and shape-dependent transformation of nanosized titanate into analogous anatase titania nanostructures

A size- and shape-dependent morphological transformation was demonstrated during the hydrothermal soft chemical transformation, in neutral solution, of titanate nanostructures into their anatase titania counterparts. Specifically, lepidocrocite hydrogen titanate nanotubes with diameters of approximately 10 nm were transformed into anatase nanoparticles with an average size of 12 nm. Lepidocrocite hydrogen titanate nanowires with relatively small diameters (average diameter range of < or = 200 nm) were converted into single-crystalline anatase nanowires with relatively smooth surfaces. Larger diameter (>200 nm) titanate wires were transformed into analogous anatase submicron wire motifs, resembling clusters of adjoining anatase nanocrystals with perfectly parallel, oriented fringes. Our results indicate that as-synthesized TiO2 nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.     

溶胶-凝胶法制备Ca10(PO4)6(OH)2 /TiO2复合涂层及其在模拟生理体液中的行为

The composite films consisting of hydroxyapatite (HAP) submicron particles embedded in the gel composed of the titania nanoparticles were prepared on commercial Ti6A14V plates with titania buffer layer obtained by a spin-coating technique. The films were calcined in air at various temperatures, and the bioactivities of the films were investigated by immersing them in acellular simulated body fliud (SBF). X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), Field emission-scanning electron microscopy(FESEM) and Energy dispersive X-ray (EDS) analysis were employed to investigate the phase formation and structure of the films before and after immersion, and the variations of Ca and P contents in SBF were measured by Inductively Coupled Plasma Spectroscopy(ICP). The results show that the as-prepared films were dense, homogeneous, all well-crystallized, and there was a close interracial bond between the film and the substrate. The characterisatics of the grown layer on the surfaces of the HAP/TiO2 films after immersion in SBF for different periods of time are specially discussed.     

Removal of bisphenol A via a hybrid process combining oxidation on β-MnO2 nanowires with microfiltration

A novel hybrid process combining β-MnO₂ nanowires oxidation and microfiltration was adopted to remove bisphenol A (BPA), an endocrine disrupting chemical (EDC) in the aquatic environment. The β-MnO₂ nanowires synthesized via a facile hydrothermal method were characterized by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscope, and nitrogen sorption. It was demonstrated that β-MnO₂ nanowires can degrade BPA effectively. Investigation on operation parameters indicated that oxidation of BPA using β-MnO₂ nanowires was evidently dependent on pH, while humic acid and coexisting metal ions such as Ca²⁺, Mg²⁺, and Mn²⁺ induced suppressive effects. After oxidation, a crossflow microfiltration process was conducted to efficiently separate and recover the β-MnO₂ nanowires from treated water. Membrane fouling study showed that the as-synthesized β-MnO₂ nanowires possess excellent mechanical stability and was able to retain the 1D structure with high aspect ratios after reaction, thus significantly reducing membrane pore blocking in the microfiltration process.     

Gold nanocatalysts supported on protonic titanate nanotubes and titania nanocrystals

Gold nanoparticles were first supported on protonic titanate nanotubes with the formation of Au/titanate nanocomposites. They were further transformed to Au/titania nanocomposites via an acetic acid treatment at 70 °C for 60 h. The porosity, crystal structure and morphology of those composites have been studied by X-ray diffraction (XRD), High-resolution transmission electron microscope (HRTEM), and low-temperature nitrogen adsorption. Catalytic tests for CO oxidation show that the Au/titanate nanocomposites had a promising activity with complete conversion of CO at 70 °C and that of Au/titania was at room temperature (25 °C). Both catalysts exhibited good thermal and long-term stabilities. The influence of the crystal vacancies and surface properties of the titanate and titania supports on the catalytic activities were evaluated.