Fabrication and chemical etching of Ag/C nanocables

In this paper, Ag/C nanocables were synthesized via a one-step simple hydrothermal route by using glucose as reducing agent and carbon source, AgNO3 as silver source. The products are characterized in detail by multiform techniques: X-ray diffraction, energy-dispersive X-ray analysis, scanning electron microscopy, transmission electron microscopy. The results show that the obtained products are coaxial nanocables with lengths of several micrometers, about 200-500 nm in diameter, and a surrounding sheath about 80-100 nm in thickness. Different products including carbonaceous nanotubes and nanocables with fragmentary Ag core were obtained by adjusting time of chemical etching.     

Synthesis and chemical etching of Te/C nanocables

In this paper, Te/C nanocables were fabricated by a hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). The products were characterized in detail by multiform techniques: transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis and Fourier transform infrared (FTIR) spectroscopy. The results showed that the products were nanocables with lengths of several microns, core about 20 nm in diameter, and a surrounding sheath of about 60–80 nm in thickness. Te/C nanocables were tailored freely by chemical etching. Carbonaceous nanotubes and Te/C nanocables with fragmentary Te core were obtained by adjusting time of chemical etching.     

Large-scale growth of Cu2ZnSnSe4 and Cu2ZnSnSe4/Cu2ZnSnS4 core/shell nanowires

We present a fast and simple protocol for large-scale preparation of quaternary Cu(2)ZnSnSe(4) (CZTSe), as well as CZTSe/Cu(2)ZnSnS(4) (CZTS) core/shell nanowires using CuSe nanowire bundles as self-sacrificial templates. CuSe nanowire bundles were synthesized by reacting Cu(2 - x)Se nanowire bundles with sodium citrate solution. CZTSe nanowires were prepared by reacting CuSe nanowire bundles with Zn(CH(3)COO)(2) and SnCl(2) in triethylene glycol. X-ray diffraction (XRD) and selected area electron diffraction studies show that stannite CZTSe is formed. The formed CZTSe nanowire bundles have diameters of 200-400 nm and lengths of up to hundreds of micrometers. CZTSe/CZTS nanocable bundles with similar morphologies were grown by the addition of some elemental sulfur to the reaction system for growth of CZTSe bundles. The stannite CZTSe/kesterite CZTS core/shell structure of the grown nanocables was confirmed by XRD and high-resolution transmission electron microscope investigation. The influence of S/Se molar ratio in the reaction system on the crystallographic structures and optical properties of CZTSe/CZTS nanocables was studied. The obtained CZTSe/CZTS core/shell nanocable bundles show broad and enhanced optical absorption over the visible and near-infrared region, which is promising for use in photovoltaic applications.     

Synthesis of chainlike In2Ge2O7/amorphous GeO2 core/shell nanocables and their luminescence

Novel chainlike In2Ge2O7/amorphous GeO2 core/shell nanocables were successfully synthesized by the simple thermal evaporation method without the presence of catalyst. The growth process of the nanocables is based on vapor-solid (VS) growth mechanism. Its morphology and microstructures were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Studies indicate that typical chainlike nanocables consist of single crystalline In2Ge2O7 nanowires (core) with diameter of about 30 nm and amorphous GeO2 chainlike nanostructures (shell). Four emission peaks, namely 401 nm, 448.5 nm, 466.5 nm, and 491 nm, were observed in the room-temperature photoluminescence measurements.     

酞菁铁固态热裂解制备新型炭纳米材料

研究了酞菁铁在密封体系中固态热裂解制备新型炭纳米材料的方法。通过这种方法，可以大量制备排列整齐又很直的碳纳米管。实验发现，升高热裂解温度，尤其温度高于800℃时，有利于碳管的生长。同时，这种方法还是一种非常有效的制备特殊结构纳米炭材料的方法。如用这种方法可以得到很长的具有电缆型结构的纳米炭，在其中具有单晶结构的炭化铁形成了电缆的金属芯。其他一些特殊炭结构，如项链型炭结构、管中管炭结构等也可以用这种方法制备出来。     

Spectroscopic study of nitrogen doping of multi-walled carbon nanotubes

Combined spatially resolved electron-energy loss spectroscopy (EELS) and high resolution near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have been used to investigate the nitrogen doping of multi-walled carbon nanotubes (N-MWNT). EELS indicates that most of the tubes are nitrogen-doped. NEXAFS spectroscopy reveals pyridine-like and nitrile N structures. High resolution NEXAFS experiments show that the main nitrogen concentration originates from a high amount of molecular N2 encapsulated into only a small quantity of tubes.     

Direct Hydrothermal Synthesis of Carbonaceous Silver Nanocables for Electrocatalytic Applications

This study demonstrates a facile but efficient hydrothermal method for the direct synthesis of both carbonaceous silver (Ag@C core–shell) nanocables and carbonaceous nanotubes under mild conditions (<180 °C). The carbonaceous tubes can be formed by removal of the silver cores via an etching process under temperature control (60–140 °C). The structure and composition are characterized using various advanced microscopic and spectroscopic techniques. The pertinent variables such as temperature, reaction time, and surfactants that can affect the formation and growth of the nanocables and nanotubes are investigated and optimized. It is found that cetyltrimethylammonium bromide plays multiple roles in the formation of Ag@C nanocables and carbonaceous nanotubes including: a shape controller for metallic Ag wires and Ag@C cables, a source of Br^? ions to form insoluble AgBr and then Ag crystals, an etching agent of silver cores to form carbonaceous tubes, and an inducer to refill silver particles into the carbonaceous tubes to form core–shell structures. The formation mechanism of carbonaceous silver nanostructures depending upon temperature is also discussed. Finally, the electrocatalytic performance of the as‐prepared Ag@C nanocables is assessed for the oxidation reduction reaction and found to be very active but much less costly than the commonly used platinum catalysts. The findings should be useful for designing and constructing carbonaceous‐metal nanostructures with potential applications in conductive materials, catalysts, and biosensors.     

Structure and optical properties of ZnS/SiO2 nanocables

The nanocables with a single crystal ZnS core and a thin amorphous SiO₂ shell were successfully synthesized by a simple thermal evaporation method with the mechanism of Vapor-Solid growth. Its morphology and microstructure were determined by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and photoluminescence spectroscopy (PL). The ZnS/SiO₂ nanocables have diameters in the range of 20 nm-250 nm, lengths of several tens of micrometers. The core of the nanocable has a cubic sphalerite structure with the coexistence of periodically alternating twins along the [111] growth direction and stacking fault. The nanocables show strong room-temperature photoluminescence with four emission bands centering at 548 nm, 614 nm, 649 nm and 670 nm that may originate to the impurity of ZnS, existence of Si and oxide-related defects.     

Se-SiO2三维光子晶体的制备

报道了一种新的调节二氧化硅光子晶体带隙的方法;通过化学镀向SiO2胶体晶体中填充半导体材料Se,获得了Se-SiO2两种介质复合的三维光子晶体;采用扫描电子显微镜(SEM)、X射线衍射和紫外-可见光谱仪(UV-VIS)等对Se-SiO2三维光子晶体的形貌、结构和光学性能进行了观察测试.研究结果表明,Se以纳米晶粒的形式均匀地包覆在SiO2微球表面,形成了Se壳层,与相同晶格周期的SiO2光子晶体相比,Se-SiO2光子晶体的带隙发生了明显的红移.     

Self-assembled vapor-liquid-solid growth of aligned Cu-SiO2 core-shell nanocable arrays on Cu substrates

The Cu-SiO2 core-shell nanocable arrays on the Cu wafers have been synthesized via a simple thermal evaporation of the SiO powder. The morphology and structure of the as-synthesized Cu-SiO2 core-shell nanocables are characterized by using scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray energy dispersive spectrometer. The growth of amorphous SiO2 shell follows a vapor-liquid-solid mechanism, and then molten metal Cu will be diffused into the SiO2 nanotubes, forming the Cu-SiO2 core-shell nanocable arrays. It is found that the aligned Cu-SiO2 core-shell nanocables prefer to grow along the grooves of the Cu substrate, and the density of the Cu-SiO2 core-shell nanocable arrays can be controlled by adjusting the growth temperature.     

Near infrared nonlinearity in silver telluride-core/carbon-sheath and tellurium-core/carbon-sheath nanostructures synthesized by reduction carbonization approach

A reduction-carbonization approach for the formation of one-dimensional (1D) silver telluride nanocables and tellurium nanorods with a sheath of amorphous carbon are proposed. Here the carbon shell is obtained with the assistance of glucose which behaves as carbonizing agent; silver nitrate and sodium tellurite are utilized as precursors and ethylene glycol acts as reducing agent. The results demonstrate the Ag₂Te/C and Te/C nanostructures with average diameters of 150 and 100 nm, respectively. The crystal structures, morphology, and composition are studied using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and Energy-dispersive X-ray spectroscopy characterizations. The formation mechanism of amorphous carbon sheath and finally core–shell nanostructures is elaborated on the basis of the experimental results. In addition, nonlinear absorption and refraction coefficients along with 3rd order nonlinear optical properties are investigated by open/closed-aperture Z-scan measurements using femtosecond pulse laser at 800 nm in a systematic way. This study provides a guide to the nonlinear properties, which may hold promise as advanced materials for various applications.     

Synthesis of Se nanoparticles by using TSA ion and its photocatalytic application for decolorization of cango red under UV irradiation

In this study, we describe a size-controlled synthesis of selenium nanoparticles based on the reduction of selenious acid (H₂SeO₃) by UV-irradiated tungstosilicate acid (H₄SiW₁₂O₄₀, TSA) solution which serves both as reducing reagent and stabilizer. The nanoparticles are characterized by ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), the Raman spectra, transmission electron microscopy (TEM) and Zetasizer, respectively. The characteristic catalytic behavior of the Se nanoparticles is established by studying the decolorization of cango red in the presence of UV light. It is obvious that selenium catalyzes the reaction efficiently. The results show that the rate of dye decolorization varies linearly with the nanoparticle concentration and the rate of dye decolorization decreases with the size of the Se nanoparticles increasing.     

Synthesis and purification of bimetallic catalysed carbon nanotubes in a horizontal CVD reactor

Carbon nanotubes (CNTs) were synthesised by a conventional chemical vapour deposition (CVD) method using acetylene as carbon source and a bimetallic catalyst of Fe–Co supported on a CaCO₃ support. The CNTs were characterised by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), energy dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA). The TEM images show clustered CNTs and reveal the outer and inner diameters of these nanomaterials. The XRD analysis shows the characteristic broad peak of graphitised carbon; the RS indicates that these materials have a high degree of crystallinity while the TGA shows the high thermal stability of the materials. EDS analysis also indicates that the purification method employed was able to remove the impurities in the CNT samples.     

A novel fabrication method of magnetic Co/Ni0.4Zn0.6Fe2O4 coaxial nanocables

A highly ordered Co/Ni0.4Zn0.6Fe2O4 coaxial nanocable array has been synthesized based on porous anodized aluminum oxide template via a new approach, which combines an improved sol-gel template method and alternating current electrochemical deposition. Scanning electron microscopy and transmission electron microscopy images show the nanocables are uniform with outer diameter of about 50 nm and inner diameter of about 17 nm. X-ray diffraction patterns and energy dispersive spectrometer confirm that Co nanowires are successfully deposited into the pores of the Ni0.4Zn0.6Fe2O4 nanotubes. Normalized magnetic hysteresis loops demonstrate the coercive force and the squareness with the applied field parallel to the axis of the nanocables increase dramatically compared with that of the nanotubes.     

Facile synthesis of 1-(N-butyl-1,8-naphthalimide-4′-yl)-3-(4-methoxyl-phenyl)-5-phenyl-pyrazoline/polyaniline core-shell nanofibers and polyaniline nanotubes

1-(N-butyl-1,8-naphthalimide-4′-yl)-3-(4-methoxyl-phenyl)-5-phenyl-pyrazoline (BMPP)/polyaniline core-shell nanofibers were synthesized by in situ chemical oxidative polymerization of aniline using BMPP nanofibers as template. BMPP/polyaniline core-shell nanofibers exhibited uniform fibrilliar morphology and possessed BMPP nanofiber core and polyaniline shell, which existed in the form of nanoparticles. BMPP nanofibers were fabricated by the modified reprecipitation method with water as poor solvent. After BMPP/polyaniline core-shell nanofibers were washed with ethanol as good solvent to remove BMPP cores, polyaniline nanotubes with netlike structures were obtained. The molecular structures of BMPP/polyaniline nanocables were characterized by Fourier transform infrared spectroscopy and UV-vis spectroscopy, respectively. The core/shell structures of BMPP and polyaniline endowed BMPP/polyaniline core-shell nanofibers good electrochemical properties in comparison with BMPP nanofibers.     

Visible light photocatalytic degradation of paraoxon and parathion pesticides on carbon-doped TiO<Subscript>2</Subscript> nanorod thin films

In the present work the nanostructured carbon-doped TiO₂ thin films with nanorod morphology were deposited on glass substrate by a combination of ultrasonic and chemical vapor deposition methods, and for the first time were applied for the photocatalytic degradation of paraoxon and parathion organophosphorus pesticides under visible light irradiation. X-ray Diffraction, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, and scanning electron microscopy techniques were used for characterization of the prepared thin films. Obtained results show that presence of carbon element and also special nanorod morphology of the thin films remarkably improve the optical properties of TiO₂ in visible light region and results in the good visible light photocatalytic activity of the thin films for degradation of the pesticides. The photonic efficiencies of the prepared thin films were also examined based on the international ISO-10678:2010 standard protocol for photocatalytic degradation of methylene blue under UV light irradiation. The results show a maximum photonic efficiency of 0.0312% for the carbon-doped TiO₂ thin film with 570 nm thickness, which compared to a reference standard TiO₂ films indicates a 30% improvement in photonic efficiency.     

Preparation, structure and photoluminescence properties of SiO2/ZnO nanocables via electrospinning and vapor transport deposition

SiO₂/ZnO nanocables were prepared by the combination of electrospinning technology and vapor transport deposition procedure. X-ray diffraction patterns indicated that ZnO with wurtzite structure was deposited on SiO₂ nanofibers templates successfully. Field emission scanning electron microscopy and transmission electron microscopy showed that the products were core/shell nanocables with a narrow distribution of the core/shell diameters. The nanocables showed a strong near band edge emission in ultraviolet region and a weak deep level emission at room temperature in their photoluminescence (PL) spectra. The anomalous temperature characteristic of integrated PL intensity in temperature-dependent PL spectra was discussed by considering carrier injection across the interface of SiO₂/ZnO nanocables.     

Modulating Ion Diffusivity and Electrode Conductivity of Carbon Nanotube@Mesoporous Carbon Fibers for High Performance Aluminum–Selenium Batteries

Selenium (Se)‐based rechargeable aluminum batteries (RABs), known as aluminum–selenium (Al–Se) batteries, are an appealing new battery design that holds great promise for addressing the low‐capacity problem of current RAB technology. However, their applications are hindered by mediocre high‐rate capacity (≈100 mAh g^?1 at 0.5 A g^?1) and insufficient cycling life (50 cycles). Herein, the synthesis of mesoporous carbon fibers (MCFs) by coating mesoporous carbon with short‐length mesopores and tunable mesopore sizes (2.7 to 8.9 nm) coaxially on carbon nanotubes (CNT) is reported. When compositing MCFs with Se for Al–Se batteries, a positive correlation between mesopore size and electrolyte ion diffusivity is observed, however when pore size is increased to 8.9 nm, large voids are created at the interface of CNT core and mesoporous carbon shell, leading to decreased electrode conductivity. The trade‐off between ion diffusivity and interfacial connectivity/conductivity determines MCF with pore size of 7.1 nm as the best host material for Al–Se batteries. The composite cathode delivers high specific capacities (366 and 230 mAh g^?1 at 0.5 and 1 A g^?1), good rate performance, and excellent cycling stability (152 mAh g^?1 after 500 cycles at 2 A g^?1), superior over previously reported Se cathodes and other cathodes for RABs.     

Photoinactivation of bacteria by using Fe-doped TiO<Subscript>2</Subscript>-MWCNTs nanocomposites

In this study, nanocomposites of Fe-doped TiO₂ with multi-walled carbon nanotubes (0.1– 0.5?wt. %) were prepared by using sol–gel method. The structural and morphological analysis were carried out with using X-ray diffraction pattern and transmission electron microscopy, which confirm the presence of pure anatase phase and particle sizes in the range 15–20?nm. X-ray photoelectron spectroscopy was used to determine the surface compositions of the nanocomposites. UV–vis diffuse reflectance spectra confirm redshift in the optical absorption edge of nanocomposites with increasing amount of multi-walled carbon nanotubes. Nanocomposites show photoinactivation against gram-positive Bacillus subtilis as well as gram-negative Pseudomonas aeruginosa. Fe-TiO₂-multi-walled carbon nanotubes (0.5?wt. %) nanocomposites show higher photoinactivation capability as compared with other nanocomposites. The photoluminescence study reveals that the Fe-TiO₂-multi-walled carbon nanotubes nanocomposites are capable to generate higher rate of reactive oxygen species species than that of other nanocomposites. Our experimental results demonstrated that the Fe-TiO₂-multi-walled carbon nanotubes nanocomposites act as efficient antibacterial agents against a wide range of microorganisms to prevent and control the persistence and spreading of bacterial infections.     

Nickel-cobalt nanoparticles supported on single-walled carbon nanotubes and their catalytic hydrogenation activity

Single-walled carbon nanotubes were synthesized from graphite using the arc discharge technique. A nickel/yttrium/graphite mixture was used as the catalyst. After purification by sonication in a Triton X-100 solution, nickel-cobalt metal nanoparticles were deposited on the surface of the single-walled carbon nanotubes. The resulting material and/or the nanotubes themselves were characterized by physisorption, Raman spectroscopy, high-resolution transition electron microscopy and X-ray diffraction. Raman spectroscopy indicates that the nanotubes, prepared by the arc discharge technique, are semi-conducting with a diameter centering at 1.4 nm. The average nickel-cobalt particle size is estimated to be in the region of 8 nm. The catalytic activity of the material was examined for the hydrogenation of unsaturated fatty acid methyl esters obtained from avocado oil. The carbon nanotube supported nickel-cobalt particles effectively hydrogenate polyunsaturated methyl linoleate to monounsaturated methyl oleate. In contrast to a conventional nickel on kieselghur catalyst, further hydrogenation of methyl oleate to undesired methyl stearate was not observed.