Fabrication of silica nanotube arrays from vertical silicon nanowire templates

A simple thermal oxidation-etching process was developed to translate vertical silicon nanowire arrays into silica nanotube arrays. The obtained nanotubes perfectly retain the orientation of original silicon nanowire arrays. The inner tube diameter ranges from 10 to 200 nm. High-temperature oxidation produces relative thick, rigid, and pinhole-free walls that are made of condensed silica. This method could be useful for fabrication of single nanotube sensors and nanofluidic systems.     

钯纳米线电极的制备及其应用于乙醇的电化学氧化研究

纳米线作为纳米科学领域中的重要一员,因其优异的光学、电学及磁学等特性引起了凝聚态物理学界、化学界以及材料科学界科学家们的极大关注,并己成为当今纳米科技研究的热点领域[1].纳米线的制备方法有多种,本文提及的模板法制备纳米线结构技术是20世纪90年代初发展起来的一种既经济又简便实用的新工艺[2].     

An investigation of the surface-enhanced Raman scattering effect from new substrates of several kinds of nanowire arrays

Silver, titanium, nickel, and aluminum nanowire arrays with diameters from 90 to 110 nm were prepared on AAO templates by laser molecular beam epitaxy. On the several kinds of nanowire arrays, high-quality surface-enhanced Raman scattering (SERS) spectra of probe molecules of the red dye Sudan II (C(18)H(16)N(2)O) were obtained. In particular, the SERS spectrum of Sudan II on an aluminum nanowire array is reported for the first time.     

Solution‐Liquid‐Solid Synthesis of Hexagonal Nickel Selenide Nanowire Arrays with a Nonmetal Catalyst

Inorganic nanowire arrays hold great promise for next‐generation energy storage and conversion devices. Understanding the growth mechanism of nanowire arrays is of considerable interest for expanding the range of applications. Herein, we report the solution‐liquid‐solid (SLS) synthesis of hexagonal nickel selenide nanowires by using a nonmetal molecular crystal (selenium) as catalyst, which successfully brings SLS into the realm of conventional low‐temperature solution synthesis. As a proof‐of‐concept application, the NiSe nanowire array was used as a catalyst for electrochemical water oxidation. This approach offers a new possibility to design arrays of inorganic nanowires.     

微含水量电解液中高管径比TiO_2纳米管阵列的制备

通过阳极氧化法在微含水量为0.5wt%的NH4F/乙二醇/H2O酸性电解质体系中制备了管径大、高管径比的二氧化钛(TiO2)纳米管阵列。采用SEM、XRD等测试手段对TiO2纳米管阵列形貌及晶相进行表征,探讨了不同氧化时间、电压对纳米管阵列形貌的影响,微含水量下氧化电压可以适当增加,更容易得到规整的长纳米管阵列;通过测定样品的光电流和紫外-可见光漫反射吸收光谱,研究分析了含水量以及超声工艺对纳米管光吸收及光电流特性,微含水量下得到的纳米管阵列可见光吸收边红移至420nm,对480~700nm可见光有明显的光吸收,光电流显著增大;丙酮作为超声介质可有效去除纳米管阵列表面的集束,能进一步提高纳米管阵列的光电性能。     

碳化硼纳米线的制备和结构

以碳纳米管为模板，通过加热碳纳米管与硼粉的混合物，获得了笔直的硼碳纳米线.对纳米线的结构和成分进行研究，结果表明纳米线主要为B4C纳米线.在部分B4C纳米线的端部存在Ni颗粒，这些端部具有Ni颗粒的纳米线构成了纳米磁针.讨论了B4C纳米线的生长机制，B4C纳米线的生长主要为硼原子在碳纳米管中扩散并发生化学反应，使得碳纳米管晶格结构发生重组，形成B4C纳米线.反应后，硼原子部分取代了碳纳米管中碳原子，修补了碳纳米管中的晶格缺陷，获得了形态笔直的B4C纳米线.     

微含水量电解液中高管径比TiO2纳米管阵列的制备

通过阳极氧化法在微含水量为0.5wt%的NH₄F/乙二醇/H₂O酸性电解质体系中制备了管径大、高管径比的二氧化钛（TiO₂）纳米管阵列。采用SEM、XRD等测试手段对TiO₂纳米管阵列形貌及晶相进行表征,探讨了不同氧化时间、电压对纳米管阵列形貌的影响,微含水量下氧化电压可以适当增加,更容易得到规整的长纳米管阵列;通过测定样品的光电流和紫外-可见光漫反射吸收光谱,研究分析了含水量以及超声工艺对纳米管光吸收及光电流特性,微含水量下得到的纳米管阵列可见光吸收边红移至420nm,对480~700nm可见光有明显的光吸收,光电流显著增大;丙酮作为超声介质可有效去除纳米管阵列表面的集束,能进一步提高纳米管阵列的光电性能。     

Fabrication and catalytic properties of Pt and Ru decorated TiO2⧹CNTs catalyst for methanol electrooxidation

Highly ordered anodic titania nanotube arrays provide a large surface area for electrodepositing nickel nanoparticles which are used as the catalyst for carbon nanotube growth. Pt and Ru nanoparticles, approximately 3 nm in diameter, are uniformly electrodeposited on the as synthesized titania-supported carbon nanotubes (CNTs), constructing a novel catalyst for electrocatalytic oxidation of methanol. An enhanced and stable catalytic activity is obtained due to the uniformly dispersed Pt and Ru nanoparticles, and the large CNT network facilitating the electron transfer between the adsorbed methanol molecules and the catalyst substrate. An oxidation peak current density of 55 mA/cm² is achieved at a low Pt load of 0.126 mg/cm² with a Pt/Ru mole ratio of 1:1.     

模板组装Fe纳米线阵列及其微结构

铝在硫酸溶液中经直流阳极氧化,得到多孔铝阳极氧化膜(AAO). 以AAO膜为模板,通过交流电沉积的方法,在AAO模板孔内成功组装了Fe纳米线.TEM分析表明,Fe纳米线的长度约为2.5 μm,其长度分布十分均匀；粗细均匀,直径约为25 nm. XRD实验分析证实,所制备的Fe纳米线为α-Fe.选区电子衍射（SAED）实验分析表明,α-Fe纳米线具有单晶结构.     

质子交换膜燃料电池Pd修饰Pt/C催化剂的电催化性能

通过对Pt催化剂表面进行Pd修饰提高质子交换膜燃料电池阴极催化剂的氧还原反应(ORR)活性. 采用乙二醇还原法制备了不同比例的Pd修饰Pt/C催化剂. 透射电镜(TEM)和X射线衍射(XRD)测试结果表明, 制备的催化剂贵金属颗粒粒径主要分布在1.75～2.50 nm之间, 并均匀地分散在碳载体表面. 循环伏安方法(CV)研究表明Pd修饰Pt/C催化剂的电化学活性面积低于传统的Pt/C催化剂. 但通过旋转圆盘电极(RDE)测试研究发现, 制备的催化剂具有比传统Pt/C催化剂高的ORR活性.     

阳极氧化铝模板法可控制备金属纳米线和纳米管阵列的生长机制

利用阳极氧化铝模板(AAO)进行Ni的电化学沉积, 通过在溶液中引入螯合剂控制电解质的有效浓度和电沉积的过电位, 实现了Ni纳米线和纳米管阵列的可控制备. 通过分析电沉积过程中纳米线和纳米管在不同位置生长速率(侧壁(Vw)和底端(Vb))的控制因素, 我们提出了纳米线和纳米管生长的可能机制. 当电解质浓度高而还原电位更负(如-1.5 V)时, 或者当电解质浓度低而还原电位较负(如-0.5 V)时, Vw>Vb, 可以获得Ni纳米管阵列; 当电解质浓度高而还原电位较负(如-0.5 V)时, 或者当电解质浓度低而还原电位更负(如-1.5 V)时, Vw≈Vb, 可以获得Ni纳米线阵列. 这种生长机制适用于多种金属纳米管或者纳米线阵列的可控制备.     

Synthesis and electrochemical properties of vanadium pentoxide nanotube arrays

Nanotube arrays of amorphous vanadium pentoxide (V(2)O(5)) were synthesized via template-based electrodeposition, and its electrochemical properties were investigated for Li-ion intercalation applications. The nanotubes have a length of 10 microm, outer diameter of 200 nm and inner diameter of 100 nm. Electrochemical analyses demonstrate that the V(2)O(5) nanotube array delivers a high initial capacity of 300 mAh/g, about twice that of the electrochemically prepared V(2)O(5) film. Although the V(2)O(5) nanotube array shows a more drastic degradation than the film under electrochemical redox cycles, the nanotube array reaches a stabilized capacity of 160 mAh/g, which remains about 1.3 times the stabilized capacity of the film.     

Template-free directional growth of single-walled carbon nanotubes on a- and r-plane sapphire

We report high-throughput growth of highly aligned single-walled carbon nanotube arrays on a-plane and r-plane sapphire substrates. This is achieved using chemical vapor deposition with ferritin as the catalyst. The nanotubes are aligned normal to the [0001] direction for growth on the a-plane sapphire. They are typically tens of micrometers long, with a narrow diameter distribution of 1.34 +/- 0.30 nm. In contrast, no orientation was achieved for growth on the c-plane and m-plane sapphire, or when Fe films, instead of ferritin, were used as the catalyst. Such orientation control is likely related to the interaction between carbon nanotubes and the sapphire substrate, which is supported by the observation that when a second layer of nanotubes was grown, they followed the gas flow direction. These aligned nanotube arrays may enable the construction of integrable and scalable nanotube devices and systems.     

Effects of annealing temperature on magnetic property and structure of amorphous Co49Pt51 alloy nanowire arrays prepared by direct-current electrodeposition

Co49Pt51 nanowire arrays with an average diameter of 35 nm and lengths up to several micrometers were grown in an ordered porous anodic aluminum oxide (AAO) template using direct-current electrodeposition. The as-deposited samples were annealed at 100, 200, 300, 400, 500, 600, and 700 degrees C, respectively. The temperature dependence of the magnetic property of the Co49Pt51 nanowire arrays associated with the microstructure was analyzed by X-ray diffraction and a vibrating sample magnetometer. Magnetic measurements show that the samples both as-prepared and annealed at low temperatures have excellent perpendicular anisotropy. The perpendicular coercivity (Hc(perpendicular)) of Co49Pt51 alloy nanowire arrays increases dramatically as the annealing temperature (T(A)) rises, reaches a maximum(Hc(perpendicular) = 2770 Oe) at 400 degrees C, and then decreases sharply as T(A) rises further. This phenomenon should be attributed to the special structure of the nanowire arrays/AAO, and the microstructure factors significantly change during the annealing process.     

单根TiO2纳米线一维电子输运性能

采用电化学诱导溶胶-凝胶法, 在多孔氧化铝模板(AAO)的纳米孔道内制备了直径分别为60 和20 nm的锐钛矿型TiO₂纳米线阵列. 利用原子力显微镜(AFM)技术, 在半接触模式下得到了TiO₂纳米线的形貌像, 在接触模式下测量了单根TiO₂纳米线的I-V曲线. TiO₂纳米线的电子输运性能表现为半导体的性质. TiO₂纳米线的导通电压值明显小于TiO₂块体,并且随着TiO₂纳米线直径的减小, 导通电压值增大.     

Fabrication of highly ordered TiO2 nanotube arrays using an organic electrolyte

Anodization of titanium in a fluorinated dimethyl sulfoxide (DMSO) and ethanol mixture electrolyte is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. Using a 20 V anodization potential (vs Pt) nanotube arrays having an inner diameter of 60 nm and 40 nm wall thickness are formed. The overall length of the nanotube arrays is controlled by the duration of the anodization, with nanotubes appearing only after approximately 48 h; a 72 h anodization results in a nanotube array approximately 2.3 mum in length. The photoelectrochemical response of the nanotube-array photoelectrodes is studied using a 1 M KOH solution under both UV and visible (AM 1.5) illumination. Enhanced photocurrent density is observed for samples obtained in the organic electrolyte, with an UV photoconversion efficiency of 10.7%.     

Preparation and magnetic properties of Fe0.3Co0.7 nanowire array

Fe_0.3Co_0.7 nanowire arrays were prepared by electrodeposition into the porous anodic aluminum oxide templates. The change of magnetic characteristic of the array with the diameter and heat treatment was investigated. It was found that the vertical magnetic anisotropy would drop lineally with the increase of the array diameter. Annealing can improve the coercively of the nanowire arrays. Coercivity as high as 3000 Oe was obtained in the sample annealing at 500°C. Magnetic properties of nanowire arrays may be developed to ultra-high-density recording on the quantum disk. __________ Translated from Journal of Lanzhou University, 2005, 41(4) (in Chinese)     

退火对TiO2纳米管/线复合阵列表面光电性质的影响

采用阳极氧化法制备了TiO2纳米管/线复合阵列. 利用表面光电压谱(SPS)和场诱导表面光电压谱(FISPS)研究了退火对TiO2纳米管/线复合阵列表面光电性质的影响. 结果表明, TiO2纳米管/线复合阵列在晶化前后的导带边缘均出现了束缚激子态, 晶化前由于自建场较弱, 束缚激子态能在正负电场作用下发生不对称偏转; 晶化后, 晶体结构从非晶态变为晶态, 自建场增强, 束缚激子态对正电场敏感并表现出明显的光伏响应, 而在负电场作用下束缚激子态没有任何光伏响应.     

氧化钛纳米管阵列制备及形成机理

采用电化学阳极氧化法在HF水溶液体系使纯钛表面形成一层结构规整有序的高密度TiO2纳米管阵列,考察了几种主要的实验参数（阳极氧化电压、温度、时间、电解液浓度）对TiO2纳米管阵列形貌和尺寸的影响.结果表明,阳极氧化电压是影响氧化钛形貌和纳米管尺寸的最主要因素,而温度和电解液浓度只影响TiO2纳米管阵列形成的时间.对TiO2纳米管阵列进行X射线衍射（XRD）和扫描电子显微镜（SEM）的分析,初步表征了TiO2纳米管阵列的电学性质.并讨论了TiO2纳米管的形成机理.     

不同催化剂对热解法制备CNx纳米管的影响

CNx nanotubes was synthesized by thermal decomposition ethylenediamine catalyzed by pure iron, cobalt, nickel, and ferrocene. The effect of the catalyst on the CNx nanotubes’ morphology and yield was studied. The catalysis growth mechanism was also discussed. The CNx nanotubes with the “bamboo-like” structure and lower yield are produced when iron or ferrocene is used as the catalyst, whereas the curved CNx nanotubes with many pleats through the nanotube walls and higher yield are generated when cobalt is used. The CNx nanotubes catalyzed by nickel are only helix tubes with the diameter of about 500 nm. Raman spectroscopy studies show that the CNx nanotubes catalyzed by ferrocene have a worse crystallinity due to a higher nitrogen incorporation.