Continuous production of fine zinc oxide nanorods by hydrothermal synthesis in supercritical water

Continuous production of highly crystalline ZnO nanorods by supercritical hydrothermal synthesis was reported in this article. Zinc nitrate aqueous solution was pressurized to 30 MPa at room temperature and rapidly heated to 673 K by mixing with supercritical water and then fed into a tubular reactor. Residence time is about 10 s. Production of ZnO nanorod particles with uniform particle size distribution showed a strong ultraviolet light emission at room temperature. This article also reported in-situ surface modification of ZnO nanorods with organic reagents by the supercritical hydrothermal synthesis.     

Hydrothermal synthesis of surface-modified iron oxide nanoparticles

We synthesized surface-modified iron oxide nanoparticles in aqueous phase by heating an aqueous solution of iron sulfate (FeSO₄) at 473 K with a small amount of either n-decanoic acid (C₉H₁₉COOH) or n-decylamine (C₁₀H₂₁NH₂), which is not miscible with water at room temperature. Transmission electron microscopy showed that the addition of n-decanoic acid or decylamine changed the shape of the obtained nanoparticles. X-ray diffraction spectra revealed that the synthesized nanoparticles were in α-Fe₂O₃ or Fe₃O₄ phase while Fourier transform infrared spectroscopy and thermogravimetry indicated the existence of an organic layer on the surface of the nanoparticles. In the synthetic condition, decreased dielectric constant of water at higher temperature increased the solubility of n-decanoic acid or n-decylamine in water to promote the reaction between the surface of iron oxide nanoparticles and the organic reagents. After the synthesis, the used organic modifiers separated from the aqueous phase at room temperature, which may help the environmentally benign synthesis of surface-modified metal oxide nanoparticles.     

Supercritical hydrothermal synthesis and in situ organic modification of indium tin oxide nanoparticles using continuous-flow reaction system

ITO nanoparticles were synthesized hydrothermally and surface modified in supercritical water using a continuous flow reaction system. The organic modification of the nanoparticles converted the surface from hydrophilic to hydrophobic, making the modified nanoparticles easily dispersible in organic solvent. The addition of a surface modifier into the reaction system impacted the crystal growth and particle size as well as dispersion. The particle size was 18 nm. Highly crystalline cubic ITO with a narrow particle size distribution was obtained. The advantages of short reaction time and the use of a continuous reaction system make this method suitable for industrial scale synthesis.     

Fabrication of TiO2 nanoparticles loaded on coal fly ash composite with enhanced photocatalytic activity

By immobilized on the coal fly ashes, the TiO2 nanoparticles photocatalysts were obviously improved in removing organic compounds of the contaminated water. These composite catalysts were fabricated by three different methods involving hydrothermal method, physical blending and sol-gel method. The resulting materials have been characterized by XRD, SEM and FTIR. The photocatalytic activity of these as-prepared samples was assessed by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature under UV-light irradiation. The experimental results indicated that TiO2 nanoparticles were tightly dispersed on the surface of spherical coal fly ash particles, where the adsorption ability of the catalysts is effectively promoted. It was found that the catalysts prepared by hydrothermal method exhibited the highest photocatalytic activity than that prepared by physical blending or sol-gel method which mainly resulted from the synergistic effect of TiO2 nanopartcles and coal fly ashes.     

Composite-hydroxide-mediated approach for the synthesis of nanostructures of complex functional-oxides

We demonstrate a generic approach for the synthesis of single-crystal complex oxide nanostructures of various structure types, such as perovskites, spinels, monoclinic, corundum, CaF(2) structured, tetragonal, and even metal hydroxides. The method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide eutectic at approximately 200 degrees C and normal atmosphere without using an organic dispersant or capping agent. The synthesis technique is cost-effective, one-step, easy to control, and is performed at low temperature and normal atomospheric pressure. The technique can be expanded to many material systems, and it provides a general, simple, convenient, and innovative strategy for the synthesis of nanostructures of complex oxides with important scientific and technological applications in ferroelectricity, ferromagnetism, colossal magnetoresistance, fuel cell, optics, and more.     

Reversible, reagentless solubility changes in phosphatidylcholine-stabilized gold nanoparticles

Phosphatidylcholine (PC) is a versatile ligand for synthesizing gold nanoparticles that are soluble in either organic or aqueous media. Here we report a novel route to organic-soluble, PC-stabilized gold nanoparticles that can be re-suspended in water after removal of the organic solvent. Similarly, we show that PC-stabilized gold nanoparticles synthesized in water can be re-suspended in organic solvents after complete removal of water. Without complete removal of the solvent, the nanoparticles retain their original solubility and do not phase transfer. This change in solvent preference from organic to aqueous and vice versa without the use of an additional phase transfer reagent is novel, visually striking, and of utility for synthetic modification of nanoparticles. This approach allows chemical reactions to be performed on nanoparticles in organic solvents followed by conversion of the products to water-soluble materials. A narrow distribution of PC-stabilized gold nanoparticles was obtained after phase transfer to water as characterized by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM), demonstrating that the narrow distribution obtained from the organic synthesis is retained after transfer to water. This method produces water-soluble nanoparticles with a narrower dispersity than is possible with direct aqueous synthesis.     

Hybrid chemical vapour and nanoceramic aerosol assisted deposition for multifunctional nanocomposite thin films

Hybrid atmospheric pressure chemical vapour and aerosol assisted deposition via the reaction of vanadium acetylacetonate and a suspension of preformed titanium dioxide or cerium dioxide nanoparticles, led to the production of vanadium dioxide nanocomposite thin films on glass substrates. The preformed nanoparticle oxides used for the aerosol were synthesised using a continuous hydrothermal flow synthesis route involving the rapid reaction of a metal salt solution with a flow of supercritical water in a flow reactor. Multifunctional nanocomposite thin films from the hybrid deposition process were characterised using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The functional properties of the films were evaluated using variable temperature optical measurements to assess thermochromic behaviour and methylene blue photodecolourisation experiments to assess photocatalytic activity. The tests show that the films are multifunctional in that they are thermochromic (having a large change in infra-red reflectivity upon exceeding the thermochromic transition temperature) and have significant photocatalytic activity under irradiation with 254 nm light.     

多元酸修饰剂对水热法制备金红石型TiO2纳米棒的影响

采用偏钛酸和浓硫酸为原料制备TiOSO4溶液,采用碳酸钠水解,多元酸为表面修饰剂,进行了粒径可控的金红石型TiO2纳米棒的水热合成研究.并用X射线粉末衍射仪(XRD)和透射电子显微镜(TEM)对制得的样品进行表征.结果表明:多元酸修饰剂的加入对TiO2纳米棒的尺寸大小及尺寸分布影响很大,并对修饰剂的作用机理进行了讨论,修饰剂的位阻效应、羧基的络合作用及TiO2微晶表面的疏水性对TiO2纳米棒的大小和分布起着重要作用.     

Supercritical water synthesis of nano-particle catalyst on TiO2 and its application in supercritical water gasification of biomass

ABSTRACT

Hydrogen production by catalytic gasification in supercritical water (SCW) is a promising way to utilise biomass resource. Supercritical water not only provides homogeneous and rapid reaction environment for the biomass gasification but also causes catalyst agglomeration problems. In order to prepare activity and stable catalyst for biomass gasification in supercritical water, supercritical water synthesis method was utilised and the preparation method was investigated. Ni, Co, Zn and Cu metal elements were loaded on TiO₂ particles which was proved to be hythothermally steady in supercritical water. And nano-particles were successfully made. Based on gas chromatography/mass spectrometer (GC/MS), scanning electron microscopy, energy dispersive spectrometer (EDS) and X-ray diffraction analysis methods, it turned out that metal catalysts have a uniform spherical structure with diameter around 30 nm. Metal catalysts synthesised with supercritical hydrothermal method showed certain catalytic effects. Ni catalyst had the best performance in stability while Zn catalyst possessed highest hydrogen yield.     

A novel approach for transferring oleic acid capped iron oxide nanoparticles to water phase

A novel and simple method was described to transfer oleic acid stabilized iron oxide nanoparticles from organic solutions to water. The oxidation of OA by sodium periodate in mixed solvents formed a carboxyl group or vicinal diol to make the hydrophobic groups to hydrophilic groups on the surface of the nanoparticles. The characterization of nanoparticles indicated that the phase transfer based on the oxidation of OA was successful performed without change in the size and shape of the iron oxide nanoparticles. The hydrophilic groups on the iron oxide surface stabilized the nanoparticles in aqueous solution and the oxidized nanoparticles can be applied to bimolecular immobilization.     

巯基接枝氧化石墨烯/聚酰胺复合膜制备及反渗透脱盐性能

反渗透膜技术作为脱盐的核心技术,在海水和苦咸水淡化、超纯水制备、污水回水等领域具有广泛应用前景,但其渗透性-选择性之间的 “trade-off” 效应仍是限制反渗透技术发展的一大挑战。本研究将表面功能化(接枝巯基官能团)的氧化石墨烯(GO)掺入间苯二胺水相溶液中,通过水相间苯二胺和有机相均苯三甲酰氯界面聚合的方法制备出巯基接枝氧化石墨烯(GO-SH)/聚酰胺(PA)反渗透复合膜。利用TEM、SEM、EDS、FTIR和NMR对接枝后粉体进行表征,利用2 g·L?1 NaCl水溶液测试膜的脱盐性能,优化了界面聚合水相pH和反应时间的设定。研究结果表明,GO-SH能够更均匀地分散在PA中,优化后的pH为11,反应时间为4 min,当改性后粉体含量为0.09wt%时,复合膜水通量可达48 L·m?2·h?1,脱盐率达到99.6%,相较于本实验接枝前纳米材料复合的PA膜分别提高了30% 和2.54%。表面功能化的GO有效地解决了无机纳米粒子和有机聚合物的相容性,提高膜脱盐性能,有望进一步降低反渗透项目的运行成本。      

Hydrothermal Coating of Patterned Carbon Nanotube Forest for Structured Lithium‐Ion Battery Electrodes

Controlling the arrangement and interface of nanoparticles is essential to achieve good transfer of charge, heat, or mechanical load. This is particularly challenging in systems requiring hybrid nanoparticle mixtures such as combinations of organic and inorganic materials. This work presents a process to coat vertically aligned carbon nanotube (CNT) forests with metal oxide nanoparticles using microwave‐assisted hydrothermal synthesis. Hydrothermal processes normally damage delicate CNT forests, which is addressed here by a combination of lithographic patterning, transfer printing, and reduction of the synthesis time. This process is applied for the fabrication of structured Li‐ion battery (LIB) electrodes where the aligned CNTs provide a straight electron transport path through the electrode and the hydrothermal coating process is used to coat the CNTs with conversion anode materials for LIBs. These nanoparticles are anchored on the surface of the CNTs and batteries fabricated following this process show a fourfold longer cyclability. Finally, this process is used to create thick electrodes (350 µm) with a gravimetric capacity of over 900 mAh g^?1.     

Design and synthesis of polymetallic nanoparticles and their catalytic applications

High-temperature hydrogen reduction reactions enable the synthesis and processing of binary metal oxide composite nanoparticles starting from titanium, ruthenium, and silicon, while the use of a surface modifier and an organic surfactant enables the synthesis of catalytic thin films from binary semiconductor oxides. Surface characterization by XRD, SEM, TEM, AFM, Raman spectroscopy, and BET measurements indicate that the incorporation of binary oxide particles into the semiconductor materials altered the surface properties and morphology of the nanoparticles while the surface modifier and organic surfactant loading can be experimentally adjusted to obtain thin films of varying morphological characteristics.     

Surface-confined synthesis of silver nanoparticle composite coating on electrospun polyimide nanofibers

A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1) ). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO3 solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.     

One-Step Synthesis of Light Metal Nanoparticle from Metastable Complex

Metal nanoparticles have attracted considerable scientific and technological interest in recent years, most related explorations and reports are focused on transition and noble metals. However, the synthesis and application of light metal nanoparticles represented by Mg have not been fully exploited, limited by their ultrahigh reactivity in air and preparation in harsh conditions. In this work, a simple and effective one-step organic solvent-assisted ball-milling process is developed to synthesize Mg and Li nanoparticles, which permits the formation of MgH₂ in a hydrogen atmosphere in a one-step reaction process at ambient temperature. Further studies suggest that acetone chemisorbs on defects/surfaces of Mg during ball milling leading to the formation of a metastable magnesium complex, which significantly alters the physical and chemical characteristics of Mg grains. The formation of metastable complexes provides an attractive strategy to produce light metal nanoparticles and inspires the authors to study the interaction of organic solvents with light metals.     

Zn-assisted synthesis of high-performance adsorbent for methylene blue

The rapid removal of organic dyes from water under low temperature environment offers significant advantages when water purification is required in cold regions. In this work, porous lanthanum hexaboride (LaB₆) nanoparticles were fabricated via a facile low-temperature molten metal (LTMM) method in Zn media under argon atmosphere. As is evidenced by the characterization results, porous LaB₆ can be prepared at 400?°C. Elevated reaction temperature led to the growth of nanoparticles, serious aggregation and the residue of Zn element in the final product. Notably, LaB₆ nanoparticles prepared at 600?°C by such a LTMM method presented ultrafast adsorption, with a maximum MB sorption capacity of 606.2?mg·g^?1, which was competitive with most of reported sorbents. Owing to the photothermal conversion property, LaB₆ powder not only accelerated the melting of iced MB solution, but also achieved the efficient adsorption of MB in cold weather. LaB₆ nanoparticles could be used as an attractive sorbent for dye removal from contaminated water, because of its facile synthesis process, excellent sorption performance and photothermal conversion property.     

Metal nanoparticles synthesis through natural phenolic acids

For being applied in medicine as therapeutic agents, nanostructures need to be biocompatible and eco‐friendly. Plant‐derived phenolic acids have been utilised for green synthesis of metallic or metallic oxide nanoparticles (NPs). The phenolic acids play role as both reducing agents and stabilisers in the process of NPs synthesis. Many experiments have been dedicated to develop efficient green synthesis techniques for producing metal NPs. Using phenolic acids represents a reproducible, simple, profitable, and cost‐effective strategy to synthesise metal NPs. As a phytochemical for metal NPs synthesis, phenolic acids are antioxidants that represent many health benefits. However, limited studies have been dedicated to the synthesis and characterisation of NPs produced by phenolic acids. Thus, this review focused on phenolic acids mediated nanomaterial synthesis and its biomedical applications. It should be noted the mechanism of metal ion bioreduction, phenolic acids surface adsorption, characterisation, and toxicity of metal NPs made with different phenolic acids have been discussed in this review.Inspec keywords: bio‐inspired materials, organic compounds, adsorption, nanofabrication, nanoparticles, biomedical materials, nanomedicineOther keywords: toxicity, biomedical applications, antioxidants, phytochemical synthesis, reducing agents, therapeutic agents, medicine, metallic oxide nanoparticles, plant‐derived phenolic acids, natural phenolic acids, metal nanoparticles synthesis, phenolic acids surface adsorption, metal ion bioreduction, nanomaterial synthesis, efficient green synthesis techniques     

超临界流体制备金属基纳米微粒的现状与展望

超临界流体技术是一门发展迅速、应用广泛的新技术。综述了超临界流体制备金属基纳米微粒的方法:超临界快速膨胀、超临界反溶剂、超临界水热合成、超临界干燥和超临界CO2微乳液,介绍了上述方法的原理、影响因素、特点、可行性及在制备金属基纳米微粒中的应用现状,分析了当前存在的问题,并展望了其今后的发展。     

Oleic-acid-coated CoFe2O4 nanoparticles synthesized by co-precipitation and hydrothermal synthesis

Oleic-acid-coated CoFe₂O₄ nanoparticles were synthesized by co-precipitation and hydrothermal synthesis. The coprecipitation of the nanoparticles was achieved by the rapid addition of a strong base to an aqueous solution of cations in the presence of the oleic acid surfactant, or without this additive. The nanoparticles were also synthesized by a hydrothermal treatment of suspensions of the precipitates, coprecipitated at room temperature in the presence of the oleic acid, or without it. The influence of the synthesis conditions, such as the valence state of the iron cation in the starting aqueous solution, the temperature of the treatment and the presence of oleic acid, on the particles size was systematically studied. X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed that, although spinel forms at room temperature, a substantial amount of Co was incorporated within the secondary, feroxyhyte-like phase when the iron cation was in the 2+ state. In contrast, when iron was in the 3+ state, the spinel forms at elevated temperatures of approximately 60 °C. The presence of the oleic acid further increased the formation temperature for the stoichiometric spinel. Moreover, the oleic acid impeded the particles’ growth and enabled the preparation of colloidal suspensions of the nanoparticles in non-polar organic solvents. The nanoparticles’ size was successfully controlled by the temperature of the synthesis in the region where superparamagnetism dominates to the region where mono-domain ferrimagnetism dominates the magnetic properties.     

EDTA辅助水热法制备不同形貌的氟化镁钠

以氟化钠、六水合氯化镁为主要原料, EDTA (乙二胺四乙酸二钠盐)为辅助剂, 通过水热法制备出不同形貌的氟化镁钠。考察了溶液pH、反应温度、时间和络合剂对产物形貌和物相的影响, 并对其形成机理进行了探讨。采用扫描电镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)等手段对产物形貌和物相进行了表征。结果表明: 在该反应体系中, EDTA既作为原料提供钠离子, 又作为络合剂与镁离子形成络合物; 反应温度、pH和络合剂对产物的形貌和物相有较大影响; 所得产物结晶度高, 有表面光滑的微米立方体晶体和纳米粒子聚集的微米空心球颗粒, 粒径均在1~3 μm之间。