Selected-control synthesis of ZnO nanowires and nanorods via a PEG-assisted route

Long-chain polymer-assisted growth of one-dimensional (1D) nanostructures has been investigated in previous research. This kind mild method has lots of merits such as not requiring complex procedures, without template supporting etc. Can the short-chain polymer also be used to grow long nanowires? In the present work, a short-chain polymer (PEG400) was found to promote the formation of 1D ZnO nanostructures, which cannot be obtained by long-chain polymers (such as PEG10000). Moreover, nanowires and nanorods can be selectively synthesized by using short-chain polymers. The influence factors for the formation of 1D ZnO nanostructures were also investigated in detail. The XRD, Raman spectrum, XPS, SEM, TEM, ED, HRTEM, EDXA, and PL spectra have been provided for the characterization of the as-obtained nanowires and nanorods.     

Simple, one-step synthesis of gold nanowires in aqueous solution

A simple procedure to synthesize gold nanowires based on the reduction of hydrogen tetrachloroaurate by 2-mercaptosuccinic acid in aqueous solution is presented. This procedure requires no additional capping or reduction agent and produces wires with an apparent curly morphology several micrometers in length with diameters as thin as 15 nm. Some of the wires produced end in a ribbonlike structure, finally terminated by a flat triangular prism. Investigations by scanning electron microscopy, transmission electron microscopy (bright and dark field), scanning transmission electron microscopy, and atomic force microscopy as well as conductivity measurements indicate fully connected, polycrystalline gold objects.     

Controlled synthesis of CuO nanostructures by a simple solution route

A simple solution route has been developed to prepare nanostructured CuO with Cu(NO₃)₂·3H₂O and NaOH as starting materials. CuO nanoribbons or nanorods and their assemblies into hierarchical structures have been synthesized, respectively, by controlling the molar ratio of NaOH to Cu(NO₃)₂, reaction temperature and the concentration of the starting NaOH solution. Experiments demonstrate that the molar ratio of NaOH to Cu(NO₃)₂ is an important parameter which may decide whether CuO exists in nanoribbons (nanorods) or assemblies into hierarchical structures. Whether Cu(NO₃)₂ is dissolved in ethanol or water also influences the formation of monodispersed CuO nanoribbons (nanorods). The growth mechanism of these nanostructures is discussed. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy (HRTEM) and their optical absorption spectra were also studied.     

Synthesis and study of plasmon-induced carrier behavior at Ag/TiO2 nanowires

Nanocomposites of Ag/TiO(2) nanowires with enhanced photoelectrochemical performance have been prepared by a facile solvothermal synthesis of TiO(2) nanowires and subsequent photoreduction of Ag(+) ions to Ag nanoparticles (AgNPs) on the TiO(2) nanowires. The as-prepared nanocomposites exhibited significantly improved cathodic photocurrent responses under visible-light illumination, which is attributed to the local electric field enhancement of plasmon resonance effect near the TiO(2) surface rather than by the direct transfer of charge between the two materials. The visible-light-driven photocatalytic performance of these nanocomposites in the degradation of methylene blue dye was also studied, and the observed improvement in photocatalytic activity is associated with the extended light absorption range and efficient charge separation due to surface plasmon resonance effect of AgNPs.     

Controlled one-step synthesis of a diblock copolymer

Well-defined block copolymers were obtained from 4-hydroxy-butyl-2-bromoisobutyrate dual initiator, combining tert-butylmethacrylate ATRP and ε-caprolactone ROP in a one-step process. Using AlEt₃ as coinitiator in a ROP catalytic process, the variation of the AlEt₃/initiator ratio permits to modulate the ROP rate and so to control the final block copolymer composition. Nevertheless, slight interferences between the two polymerizations were observed.     

双模板体系中多级结构碳酸钡晶体的控制合成

在用细乳液聚合法制备聚合物微球的基础上,以此聚合物形成的不溶性自组装膜与可溶性的修饰剂聚丙烯酰胺组成的双模板为三维聚合物模板体系,成功完成了多孔、刺球等具有复杂多级结构碳酸钡晶体的制备.实验过程中发现,调节双模板的组成可精确调控碳酸钡晶体的成核与生长.同时,多孔碳酸钡晶体为典型的大孔材料,孔径为103.4 rm,BET...     

Synthesis and characterization of TiO2@C core-shell nanowires and nanowalls via chemical vapor deposition for potential large-scale production

TiO(2) nanowires and nanowalls core structures covered with carbon shell were selectively synthesized by a simple chemical vapor deposition (CVD) method using commercial titanium powder as the starting material. Morphology and structure of the products were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The core shell structure is composed of single crystalline rutile titanium dioxide wrapped by amorphous carbon shell. By adjusting the growth temperature, morphology of the products can be controlled from one-dimensional nanowires to two-dimensional nanowalls. While TiO(2)@C nanowires were a preferred structure at higher temperature, TiO(2)@C nanowalls dominated the final product at lower temperature. A growth mechanism was proposed based on the initial growth state of these nanostructures, in which solid-state diffusion of the elements involved in the reaction was assumed to play an essential role. The obtained TiO(2)@C core shell structures may find potential applications in various nanoscale realms such as optoelectronic, electronic and electrochemical nanodevices and the simple synthesis procedure promises large scale production and commercialization of the titanium oxide@carbon nanostructures.     

Controlled synthesis of mesoporous SiO2/Ni3Si2O5(OH)4 core-shell microspheres with tunable chamber structures via a self-template method

Mesoporous SiO2/Ni3Si2O5(OH)4 core-shell microspheres with tunable chamber structures have been synthesized by the reaction between Ni(Ac)2.4H2O and SiO2 microspheres via a simple self-template approach.     

Fabrication of aligned TiO2 one-dimensional nanostructured arrays using a one-step templating solution approach

In this letter, we report a one-step templating synthetic strategy to prepare aligned TiO2 nanotube and nanowire arrays on Si substrate from a solution at ambient temperature. The deposition of TiO2 and the selective-etching of the ZnO template proceeded at the same time through the careful control of process parameters. The different thickness of TiO2 sheaths, leading to the formation of nanotubes or nanorods, can be precisely controlled by the deposition time. The idea of selective etching and deposition is applicable to other oxide materials, and such a facile method is expected to find widespread applications.     

Synthesis of TiO2 photocatalysts in supercritical CO2 via a non-hydrolytic route

Nanoscaled TiO2 powders with narrow size dispersion were prepared in supercritical carbon dioxide via non-hydrolytic acylation/deacylation of titanium alkoxide precursors with or without tris-fluorination. The microstructures of these powders were characterized by spectroscopic (FTIR, TGA, and XRD), microscopic (SEM or TEM), and surface area (BET) measurements. Photocatalytic oxidation of 1-octanol on these calcined TiO2 powders and on commercial T805 TiO2 suspended in aerated supercritical carbon dioxide revealed relative reactivity controlled by the powder microstructures. Calcined TiO2 prepared from titanium(IV) isopropoxide and trifluoroacetic anhydride was effectively dispersed in aerated supercritical carbon dioxide under stirring and exhibited high photocatalytic oxidation activity.     

Controlled synthesis of magnetic Pd/Fe3O4 spheres via an ethylenediamine-assisted route

A simple route based on time-dependent growth was employed to synthesize solid and hollow spheres of Pd/Fe(3)O(4) nanocomposite. Transmission electron microscopic (TEM) imaging shows that the spheres are composed of nanocrystals with the solid spheres having a diameter of 533 nm whereas the hollow ones having a diameter of 520 nm and a shell thickness of 100 nm. An assembly-then-growth mechanism for the formation of the magnetic Pd/Fe(3)O(4) nanocomposite has also been elucidated on the basis of the experimental observations. It is demonstrated that the Pd/Fe(3)O(4) nanocomposite functions as a heterogeneous catalyst for the hydrogenation reaction of p-nitrophenol at room temperature under atmospheric pressure. Both the solid and hollow spheres possess unique magnetic properties so that they may be conveniently separated and recovered by a magnet after the catalytic reaction.     

Rutile TiO2 nanowires on anatase TiO2 nanofibers: a branched heterostructured photocatalysts via interface-assisted fabrication approach

A water-dichloromethane interface-assisted hydrothermal method was employed to grow rutile TiO(2) nanowires (NWs) on electrospun anatase TiO(2) nanofibers (NFs), using highly reactive TiCl(4) as precursor. The water-dichloromethane interface inhibited the formation of rutile NWs in water phase, but promoted the selective radial growth of densely packed rutile NWs on anatase NFs to form a branched heterojunction. The density and length of rutile NWs could be readily controlled by varying reaction parameters. A formation mechanism for the branched heterojunction was proposed which involved (1) the entrapment of rutile precursor nanoparticles at water-dichloromethane interface, (2) the growth of rutile NWs on anatase NFs via Ostwald ripening through the scavengering of interface-entrapped rutile nanoparticles. The heterojunction formed at anatase NF and rutile NW enhanced the charge separation of both under ultraviolet excitation, as evidenced by photoluminescence and surface photovoltage spectra. The branched TiO(2) heterostructures showed higher photocatalytic activity in degradation of rodamine B dye solution than anatase NFs, and the mixture of anatase NFs, and P25 powders, which was discussed in terms of the synergistic effect of enhanced charge separation by anatase-rutile heterojunction, high activity of rutile NWs, and increased specific area of branched heterostructures.     

Ag/TiO2光催化氧化还原反应脱除水体中无机氮

采用光催化还原法制备了高活性的载银二氧化钛光催化剂,并用XRF、TEM、XRD及XPS、UV-Vis方法对催化剂进行了表征.考察了负载Ag的含量、催化剂制备时间、搅拌气体的种类以及Fe²⁺的添加等条件对该催化剂光催化水体脱氮活性的影响.结果表明:载银量1.0%时去除效果最佳;制备催化剂时光照时间不充分会使催化剂失去还原效力;氮气保护下催化剂反应活性更高;Fe²⁺的加入利于光催化反应;2 h光催化含氨氮和亚硝基氮的水样,总脱氮率达到了63.9%.     

A one-step solvothermal route for the synthesis of nanocrystalline anatase TiO2 doped with lanthanide ions

A one-step solvothermal synthesis is proposed for the preparation of nanocrystalline single-phase TiO₂ in the anatase form doped with lanthanide ions Eu³⁺, Er³⁺ and Sm³⁺. The structural properties of these products have been investigated by using X-ray powder diffraction, electron microscopy and Raman spectroscopy. Furthermore, the laser-excited luminescence spectra of the samples have been measured and analyzed. Following this route, the doping process turns out to be highly favorite and the resulting materials show an efficient luminescence in the visible region.     

Fabrication of superhydrophobic surfaces from microstructured ZnO-based surfaces via a wet-chemical route

The fabrication of a superhydrophobic surface is demonstrated via a wet chemical route, and this method offers advantages of being cleanroom free, cost efficiency, and wide applicability. The preferable growth of ZnO crystalline forms a microstructured surface, and a variety of alkanoic acids were adopted to tune the surface wettability. Although all surfaces show an advancing contact angle greater than 150 degrees , they substantially differ in the wetting mechanisms. It is found that only when the length of alkanoic acid is greater than 16, the microstructured surface shows a stable superhydrophobicity, in which the Cassie state dominates. While for those moderate-length alkanoic acids (C8-C14), their corresponding surfaces have a tendency to fall into the Wenzel state and display a great contact angle hysteresis.     

Controlled synthesis and self-assembly of highly monodisperse Ag and Ag(2)S nanocrystals

A facile method to control the synthesis and self‐assembly of monodisperse Ag and Ag₂S nanocrystals with a narrow‐size distribution is described. Uniform Ag nanoparticles of less than 4 nm were obtained by thermolysis of Ag–oleate complexes in the presence of oleic acid and dodecylamine, and monodisperse Ag nanoparticles of less than 10 nm were also prepared in one step by using dodecylamine and oleic acid as capping agents. Moreover, the surface‐enhanced Raman scattering (SERS) properties of the Ag substrates have also been investigated. It is worth mentioning that these Ag nanoparticles and assemblies show great differences in the SERS activities of Rhodamine B dye. In addition, the superlattices of Ag₂S nanocrystals were synthesized with Ag–oleate complexes, alkanethiol, and sulfur as the reactants. The resulting highly monodisperse nanocrystals can easily self‐assemble into interesting superstructures in the solution phase without any additional assembly steps. This method may be extended to the size‐controlled preparation and assembly of many other noble‐metal and transition‐metal chalcogenide nanoparticles. These results will aid the study of the physicochemical properties of the superlattice assemblies and construction of functional macroscopic architectures or devices.     

Direct synthesis of nanowires with anatase and TiO2-B structures at near ambient conditions

In this study, we present a new approach toward titanium oxide nanowires. In this approach, the growth formation of the wires sets in at a temperature as low as 40 degrees C under ambient pressure. Moreover, we provide evidence that nanowires with distinctive TiO2-anatase and TiO2-B structures can be directly produced without further thermal treatment using controlled reaction conditions.     

Controlled synthesis of multi-shelled transition metal oxide hollow structures through one-pot solution route

As one type of promising candidates for environmental and energy-related systems,multi-shelled transition metal oxide hollow structures(MS-TMOHSs) have drawn great scientific and technical interest in the past few years.This article highlights recent advances in one-pot solution synthesis of MSTMOHSs. We begin it with an overview of synthetic strategies that have been exploited to achieve these peculiar structures.We then focus on one-pot solution approaches in the following four sections:i) soft templates directed growth;ii) Ostwald ripening;iii) controlled etching;and iv) gas bubble assisted growth.After giving a brief discussion on the unique properties and applications of these multi-shelled hollow structures,we conclude this review with the general challenges and the potential future directions of this exciting area of research.