Designed synthesis and magnetic properties of Co hierarchical nanostructures

Size and shape controlled fabrication of magnetic Co microsphere, nanoribbon, nanochain and rose-like microarchitecture has been successfully realized via a simple hydrothermal route. X-ray diffraction analysis suggests that Co hierarchical nanostructures are identified as hexagonal phase. Magnetic hysteresis measurements demonstrate that the obtained different Co hierarchical structures show structure-dependent magnetic properties. Saturation magnetization (M_S) found for Co spherical flowers and spherical powders are larger than Co nanoribbons, smaller than sphere-rebuilt micro particles or chain-like structures. Chain-like and nanorribon structures have abnormally large coercivity (H_C). H_C values of Co nanoribbons and one dimensional chains become as large as 256 Oe and 316 Oe.     

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.     

CuS纳米空心管结构的水热合成

以氯化铜和硫代乙酰胺为原料,在碱性条件下,利用低温简单水热法合成了硫化铜纳米空心管结构。通过XRD、TEM、FT-IR等检测方法对产品进行了结构和形貌分析。结果表明,所得硫化铜产品为六方相铜蓝矿结构,纳米空心管结构,纳米管的直径为150～200nm,长度为1.5～2.5μm;在1110cm-1处出现Cu-S键的红外特征吸收峰;同时对可能的生长机理做了阐述。     

Hydrothermal microemulsion synthesis of stoichiometric single crystal hydroxyapatite nanorods with mono-dispersion and narrow-size distribution

The stoichiometric single crystal hydroxyapatite (HAp) nanorods with mono-dispersion and narrow-size distribution in diameter were successfully synthesized via a hydrothermal microemulsion method, and the as-synthesized powders were characterized by XRD, FETEM, FTIR and ICP-AES. In the present work, a novel technique of w/o microemulsions of CTAB/n-pentanol/n-hexane/water under hydrothermal condition to synthesize single crystal HAp nanorods with diameter 25–40 nm and length 55–350 nm, was described. The homogeneity in size distribution and shape of the HAp nanorods was probably attributed to the w/o nano-reactors and the soft template of the surfactants, and the high crystallization of the products was attributed to the hydrothermal treatment. The sintering ability of the nanorods and the mechanical properties of the fabricated HAp bioceramics were also preliminarily investigated. The results showed that the fabricated HAp bioceramics possessed high mechanical properties.     

Microwave-assisted synthesis of hydroxyapatite hollow microspheres in aqueous solution

We report a template-free microwave-assisted hydrothermal method for the preparation of hydroxyapatite hollow microspheres constructed by the self-assembly of nanosheets using Ca(CH₃COO)₂, Na₂HPO₄, NaH₂PO₄ and sodium citrate in aqueous solution. X-ray powder diffraction (XRD) patterns indicated that the as-prepared samples consisted of hydroxyapatite. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) micrographs showed that the as-prepared products were composed of hollow microspheres assembled with nanosheets and had three-dimensional nanoporous nanostructured networks. The experimental parameters were varied to investigate their effects on the product, and a possible formation mechanism was proposed. The as-prepared hydroxyapatite hollow microspheres have a potential application in drug delivery.     

羟基磷灰石纳米棒的水热制备及其晶体生长机理研究EI北大核心CSCD

以无水CaCl 2和(NH 4)2HPO 4为原料,尿素为均相沉淀剂,十六烷基三甲基溴化铵(CTAB)为模板剂,利用水热法制备了羟基磷灰石(HA)纳米棒。采用X射线衍射仪(XRD)、扫描电镜(SEM)和透射电镜(TEM)对产物的物相组成、微观形貌进行了表征。结果表明:通过改变反应温度和时间,可实现HA纳米形貌的可控微调。在120℃水热反应12 h可以制备出单晶密排六方结构HA纳米棒,其长约为0.5~1.0μm,直径约为15~30 nm。并从晶体结构的角度详细研究了CTAB在合成纳米棒结构中所起的作用,并通过实验进行了验证。     

Preparation of hollow hydroxyapatite microspheres

The preparation of hollow hydroxyapatite (HA) microspheres as potential drug-delivery vehicles was investigated. A lithium-calcium-borate (10Li₂O-15CaO-75B₂O₃) (mol%) glass, made by fusing the components at 1100°C for 1 h, was ground to a powder and passed through a flame at ∼1400°C to spheroidize the particles. The resulting glass microspheres (106–125 μm in diameter) were reacted in 0.25 M K₂HPO₄ solution for 5 days at 37°C and pH 10–12, resulting in the formation of porous, hollow microspheres of a calcium phosphate (Ca-P) material with external diameters similar to those of the original glass particles. Heat treatment at 600°C for 4 h partially converted the Ca-P material to HA, as confirmed by X-ray diffraction, and also increased the strength of the hollow microspheres.     

One-pot synthesis of ultranarrow single crystal ZnSe nanowires

High-quality wurtzite-type ultranarrow single crystal ZnSe nanowires were synthesized via a one-pot, solution-based method for the first time. The as-prepared nanowires have diameters ranging from 1.0 nm to 3.5 nm and lengths up to 300 nm. The optical characterizations indicate that the as-synthesized ZnSe nanowires have a band gap of 3.31 eV, whose absorbance spectra are different from recent literatures. Both the quantum confinement and the vacancies of Zn in ZnSe or impurities were accounted for the phenomenon. The solvent employed in the synthesis is also playing a dominant role in the size and morphology control of the ZnSe nanowires. A reasonable mechanism was proposed to describe the function of solvent. The excellent properties of the ZnSe nanowires would render it a promising alternative functional material which might be widely used in short-wavelength lasers and other photoelectronic devices.     

Room-temperature synthesis of flowerlike Ag nanostructures consisting of single crystalline Ag nanoplates

We demonstrate a simple wet-chemical route for the high-yield synthesis of flowerlike silver nanostructures consisting of single crystalline Ag nanoplates by mixing AgNO₃ and p-phenylenediamine (PPD) in the presence of polyvinylpyrrolidone (PVP) at room temperature. PPD serves both as a reducing agent, and as an architecture soft template with PVP to the formation of such Ag nanostructures. It is found that the presence of PVP has a significant effect on the formation and growth of these novel nanostructures. The flowerlike silver nanostructures could serve as highly sensitive and reproductive surface-enhanced Raman scattering (SERS) substrates for chemical and biological detection.     

Templated photocatalytic synthesis of well-defined platinum hollow nanostructures with enhanced catalytic performance for methanol oxidation

Hollow metallic nanostructures exhibit important applications in catalysis, sensing, and phototherapy due to their increased surface areas, reduced densities, and unique optical and electronic features. Here we report a facile photocatalytic process to synthesize and tune hollow platinum (Pt) nanostructures. Through hierarchically structured templates, well-defined hollow Pt nanostructures are achieved. These nanostructures possess interconnected nanoporous framework as shell with high surface area for enhanced catalytic performance/mass transport for methanol oxidation.     

Zinc oxide nanostructures: synthesis and properties

This article provides a comprehensive review of the current research activities that focus on the ZnO nanostructure materials and their physical property characterizations. It begins with the synthetic methods that have been exploited to grow ZnO nanostructures. A range of remarkable characteristics are then presented, organized into sections describing the mechanical, electrical, optical, magnetic, and chemical sensing properties. These studies constitute the basis for developing versatile applications of ZnO nanostructures.     

Zinc stannate nanostructures: hydrothermal synthesis

Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature.     

Zinc stannate nanostructures: hydrothermal synthesis

Abstract

Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature.     

Hydrothermal synthesis of PbS hollow spheres with single crystal-like electron diffraction patterns

PbS hollow spheres were successfully prepared by a sodium citrate-assisted hydrothermal process at 120 degrees C for 12 h, employing lead acetate trihydrate, thiourea and sodium citrate as precursors. The diameter of PbS hollow spheres is 200-400 nm, which is composed of about 50-80 nm nanoparticles. The synthesized product was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), Fourier transform-infrared (FT-IR) spectroscopy, ultraviolet-visible spectrometer (UV-vis) and near-infrared absorption spectrometer (NIR). The effects of the reaction conditions on morphologies of PbS structures were investigated. Star-shaped and flat PbS crystals were obtained by changing some experiment conditions. The results show that temperature, sodium citrate concentration, sulfur sources and solvent play key roles on the final morphologies formation of PbS crystals. Especially, ED result indicates that PbS hollow spheres hold single crystal-like electron diffraction patterns. And the possible formation mechanism of hollow spheres was proposed.     

Defect-driven synthesis of self-assembled single crystal titanium nanowires via electrochemistry

One-dimensional single crystal nanostructures have garnered much attention, from their low-dimensional physics to their technological uses, due to their unique properties and potential applications, from sensors to interconnects. There is an increasing interest in metallic titanium nanowires, yet their single crystal form has not been actualized. Vapor-liquid-solid (VLS) and template-assisted top-down methods are common means for nanowire synthesis; however, each has limitations with respect to nanowire composition and crystallinity. Here we show a simple electrochemical method to generate single crystal titanium nanowires on monocrystalline NiTi substrates. This work is a significant advance in addressing the challenge of growing single crystal titanium nanowires, which had been precluded by titanium's reactivity. Nanowires grew non-parallel to the surface and in a periodic arrangement along specific substrate directions; this behavior is attributed to a defect-driven mechanism. This synthesis technique ushers in new and rapid routes for single crystal metallic nanostructures, which have considerable implications for nanoscale electronics.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.