Controllable fabrication of Au micro/nanostructures on self-doped polyaniline nanofibers via electrochemical deposition and its application for DNA immobilization

Four electrochemical methods, cyclic voltammetric deposition, potentiostatic electrodeposition, multi-potential step electrodeposition and three-step electrodeposition, were used to fabricate Au micro/nanostructures on self-doped polyaniline nanofibers-coated glassy carbon electrodes (Au/nanoSPAN/GCEs). The Au micro/nanostructures deposited on the nanoSPAN-modified electrodes were shown by scanning electron microscopy to exhibit different morphologies, such as Au nanoparticle clusters, monodisperse nanoparticles and homogeneously dispersed flower-like microparticles, depending on the deposition method. This phenomenon demonstrates that control over the morphology of Au metal can be easily achieved by adjusting the electrodeposition method. The electrochemical behaviors of the Au/nanoSPAN/GCEs also varied with above four methods, which were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In comparison with Au nanoparticle clusters and monodisperse Au nanoparticles, homogeneously dispersed flower-like Au microparticles had the largest surface area and obviously enhanced electrochemical response towards the redox reactions of [Fe(CN)₆]^3?/4? on the modified electrode. DNA immobilization on the Au/nanoSPAN/GCEs was investigated by differential pulse voltammetry using [Fe(CN)₆]^3?/4? as an indicator. The efficiency of DNA immobilization was inherently related to their different Au micro/nanostructure morphologies. The Au/nano-SPAN/GCE fabricated by three-step electrodeposition showed the largest capacity for immobilization of single stranded DNA, which makes it a promising DNA biosensor.     

Fabrication of carbon nanotube/graphene core/shell nanostructures on SiO2 substrates using organic solvents: A molecular dynamics study

Using molecular mechanics and molecular dynamics simulations,we demonstrate that it is difficult to fabricate single-walled carbon nanotube (SWNT)/carbon nanoscroll (CNS) core/shell nanostructures on solid substrates because of the strong interaction between the graphene (GN) and the substrate.We propose an effective way to reduce the interaction between the GN and the substrate;SWNT/CNS core/shell nanostructures can be fabricated easily on SiO2 substrates by exploiting the volatilization of organic solvents,and inducement with SWNTs.These SWNT/CNS core/shell nanostructures on SiO2 substrates have the potential to be applied in telecom network transmission,or as electronic components in apparatuses such as microcircuit interconnects,nanoelectronics devices,heterojunctions,or sensors.     

γ′-Fe4N薄膜的制备及其磁性

采用直流磁控溅射方法, 以Ar/N₂为放电气体（N₂/(Ar+N₂)=10％）, 在玻璃和NaCl(100)单晶片上分别沉积获得Fe-N薄膜样品. 利用X射线衍射(XRD)、 原子力显微镜(AFM)和超导量子干涉仪(SQUID)对样品的结构、 形貌和磁性能进行分析, 研究基片和基片温度等条件对薄膜的影响. 结果表明, 以NaCl单晶为基片获得单相γ′-Fe₄N薄膜, 与玻璃基片相比可降低其生成的基片温度并可扩大形成温度的范围, 且比饱和磁化强度略有增大.      

Effects of substrate temperature and ambient oxygen pressure on growth of Ba(Fe1/2Nb1/2)O3 thin films by pulsed laser deposition

Ba(Fe1/2Nb1/2)O3 thin films were grown on Pt/TiO2/SiO2/Si substrates with pulsed laser deposition (PLD) at temperatures ranging from 823 to 923 K with the varied ambient oxygen pressure. X-ray diffraction (XRD) data confirmed the single phase of polycrystalline Ba(Fe1/2Nb1/2)O3 thin films. The effects of substrate temperature and ambient oxygen pressure on the surface morphologies of the thin films were investigated by atomic force microscopy (AFM) and the growth dynamics of thin films was discussed. Larger grains and denser surface morphologies were observed with increasing substrate temperature. While finer grains were produced with increasing ambient oxygen pressure due to more frequent collisions between the ejected species and ambient oxygen molecules. The influence of the substrate temperature and ambient oxygen pressure on the dielectric properties was also discussed. Improved dielectric constant and decreased dielectric loss was observed for the thin film deposited at evaluated temperature.     

Simple method to rapidly fabricate chain-like carbon nanotube films and its field emission properties

A simple process to fabricate chain-like carbon nanotube (CNT) films by microwave plasma-enhanced chemical vapor deposition (MPCVD) was developed successfully. Prior to deposition, the Ti/Al₂O₃ substrates were ground with Fe-doped SiO₂ powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.     

Investigation on preparing boron nitride by nitriding pure boron at 1200–1550 1C

Boron nitride (BN) was prepared by nitriding pure boron (B) deposited on carbon substrates by chemical vapor deposition (CVD). Thermodynamic analysis of preparing BN by nitriding CVD B at 1200–1550 1C was firstly performed. And then, the effects of nitridation conditions, including temperature, nitridation atmosphere and CVD B microstructure, on the conversion of B to BN were analyzed by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Results show that the conversion degree of B to BN firstly increased and then slightly decreased with rising temperature. The nitridation degree was controlled by mutual actions between the nitridation of B and consumption of the effective nitrogen source (NH3). The morphology of products and the reaction mechanism between B and N were influenced by nitridation temperature. At high temperatures (1400–1500 1C), BN with highly ordered microstructure was produced. On using N2–H2 as nitridation atmosphere instead of NH3–H2– N2, no BN was obtained in the studied temperature range. The microstructure and component of BN obtained in nitridation process were little affected by the microstructure of CVD B.     

MnO2/碳纳米球电化学超级电容器电极材料的制备与性能研究

利用水热法合成了纳米棒状的MnO_2/碳纳米球(CNPs)作为电化学超级电容器的电极材料.利用场发射扫描电镜(FESEM)、X射线衍射光谱分析(XRD)对样品的微观形貌、物相进行分析;利用循环伏安法和恒电流充放电测试材料的电化学性能.结果表明:纳米棒状MnO_2/CNPs复合材料具有良好的电化学性能.在0.1 A/g的电流密度,1 mol/L Na_2SO_4电解液中,电极材料的比电容高达305.6 F/g,远高于纯碳球的比电容(49.3 F/g),当电流密度增至5 A/g时,材料的比电容为235 F/g,比电容仍能保持76.9%.     

Synthesis of single-walled carbon nanotubes by the vertical floating catalyst method

The vertical floating catalyst method is first used to produce single-walled carbon nanotubes (SWNTs) continuously on a large scale by a newly developed technique and pyrolysis of n-hexane. Diameter distributions, microstructure and purity of the SWNTs film, rope and web are measured by Raman spectroscopy and electron microscope. The results show that SWNTs product has a high degree of orientation, a wide distribution of diameters (0.7–2.0 nm) and high purity of >80%.     

反应等离子体制备碳锥及其表征

利用等离子体增强热丝化学气相沉积系统,用CH4、H2和NH3为反应气体,分别在沉积有钛膜和碳膜的Si片衬底上制备了锥形碳结构,采用场发射扫描电子显微镜(FESEM)、X射线能谱仪(EDX)和显微Raman光谱仪对其形貌和结构进行了表征.SEM结果表明在沉积有碳膜的Si片衬底上易形成碳锥,EDX谱和Raman谱进一步表明形成的碳锥为碳氮结构,由sp3 C-N、sp2 C和sp2 C=N键形成.根据溅射机制和扩散机制,分析了碳锥的形成.同时,还对碳锥Raman谱的荧光背景进行了分析,结果表明由于氮的掺杂,使得碳锥由非极性的碳材料变成为极性碳材料.     

Deposition behavior and tribological properties of diamond-like carbon coatings on stainless steels via chemical vapor deposition

A systematic investigation was carried out to observe the deposition rate of a diamond-like carbon (DLC) coating on two stainless steel substrates by chemical vapor deposition (CVD). The objective of this research is to study the deposition behavior of the DLC coating and its tribological properties in different combinations of methane (CH₄) and nitrogen, which were used as precursor gases. The results reveal that the deposition rate increases with increasing CH₄ content up to 50vol%. The hardness of the DLC-deposited layer also increases while the friction coefficient decreases with increasing CH₄ gas content up to 50% in the precursor gas mixture.     

Direct growth of single-walled carbon nanotubes on substrates

As one of the most promising candidate material for next generation electronic devices, the reliable and controllable synthesis of high quality single-walled carbon nanotubes (SWNTs) has long been an essential and important issue in the field. Direct growth of SWNTs on flat substrates by chemical vapor deposition (CVD) process is the best way to obtain SWNTs because it is immediately ready for building nano-devices. The orientation of the SWNTs has been well controlled by gas flow or substrate lattice during the CVD growth process. The chirality and structure control of SWNTs is still a big challenge. However, the conductivity selective growth has already partially succeeded. New catalysts have been explored to obtain SWNTs of higher quality. Along with the further progress in the study of the SWNT growth, the precise control over the orientation, position and conductivity of SWNTs is expected to meet the requirements of carbon-based nanoelectronics.     

Influence of target-substrate distance and sputtering power on chromium oxide films prepared by medium-frequency magnetron sputtering

Chromium oxide films were deposited on Si (100) substrates by medium-frequency (MF) unbalanced magnetron sputtering at different target-substrate distances D _TS (60, 100, 120 mm) and sputtering power (2.8, 5.6, 11.2 kW), respectively. The structure, surface morphologies, and microhardness of the chromium oxide films were examined by X-ray diffraction (XRD), atomic force microscopy (AFM), and microhardness tester. The results indicate that elevated MF sputtering power can improve the crystallization of the films; The D _TS value affects the structure of the films by changing the preferential orientation from CrO₃ (221) to Cr₂O₃ (116); The microhardness of the chromium oxide films is found to increase with the sputtering power. For preparing the Cr₂O₃-dominated films with comparatively high-performance, the optimized condition is the target-substrate distance of 100 mm and MF sputtering power of 11.2 kW.     

Recent progresses on the new condensed forms of single-walled carbon nanotubes and energy-harvesting devices

We demonstrate an effective method to prepare a new condensed form of single-walled carbon nanotubes (crystal of SWNTs) using a series of diamond wire drawing dies. X-ray diffraction indicates that the SWNTs form a two-dimensional triangular lattice with a lattice constant of 19.62 ?. An intertube spacing of 3.39 ? of between adjacent SWNTs results in a sharp (002) reflection in the X-ray diffraction pattern. Meanwhile, we developed an approach based on the Coulomb explosion to separate SWNTs from their bundle. The separated SWNTs have a typical length of several microns and form a nanotree at one end of the original bundle. The separation is convenient and involves no surfactant. In studying devices comprising SWNTs, we find that a four-probe technique can be employed to study the filling of and flow within the inner channel of an individual SWNT. Current/voltage can drive water molecules to have directional flow along an SWNT, and the flowing of water inside an SWNT can induce a voltage gradient force (an induced electromotive force) along the SWNT. This energy conversion is realized by the mutual coupling of water dipoles and charge carriers present in SWNTs. The results suggest that SWNTs can be exploited as molecular channels for water and may find potential application in nanoscale energy conversion. Moreover, a surface-energy generator comprising SWNTs was demonstrated to harvest the surface energy of ethanol. The performance (the induction rate for V _oc, the value of V _oc and the output power) can be significantly enhanced by the Marangoni effect.     

DC磁控溅射沉积FexN薄膜成分及生长机制

使用直流磁控溅射方法,Ar/N2作为放电气体,在玻璃衬底上沉积FexN薄膜.利用X射线光电子能谱(XPS)、掠入射小角X射线散射(GISAXS)、X射线衍射(XRD)、掠入射非对称X射线衍射(GIAXD)和原子力显微镜(AFM)研究薄膜的成分和生长机制.实验结果表明,在5%N2流量下获得FeN0.056单相化合物,薄膜中氮原子含量为14%,该值与α"-Fe16N2相中的氮原子的化学计量(11%)接近;GISAXS和AFM对薄膜表面分析表明,随溅射时间增加,薄膜变得愈加不光滑,用动力学标度的方法定量分析结果为:薄膜表面呈现自仿射性质,静态标度指数α≈0.65,生长指数β≈0.53±0.02,动力学标度指数z≈1.2,薄膜生长符合Kolmogorov提出的能量波动概念的KPZ模型指数规律.     

Effect of oxygen partial pressure and transparent substrates on the structural and optical properties of ZnO thin films and their performance in energy harvesters

Zinc oxide (ZnO) thin films were deposited onto different substrates-tin-doped indium oxide (ITO)/glass, ITO/polyethylene naphthalate (PEN), ITO/polyethylene terephthalate (PET)-by the radio-frequency (RF) magnetron sputtering method. The effect of various O₂/(Ar+O₂) gas flow ratios (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) was studied in detail. ZnO layers deposited onto ITO/PEN and ITO/PET substrates exhibited a stronger c-axis preferred orientation along the (0002) direction compared to ZnO deposited onto ITO/glass. The transmittance spectra of ZnO films showed that the maximum transmittances of ZnO films deposited onto ITO/glass, ITO/PEN, and ITO/PET substrates were 89.2%, 65.0%, and 77.8%, respectively. Scanning electron microscopy (SEM) images of the film surfaces indicated that the grain was uniform. The cross-sectional SEM images showed that the ZnO films were columnar structures whose c-axis was perpendicular to the film surface. The test results for a fabricated ZnO thin film based energy harvester showed that its output voltage increased with increasing acceleration of external vibration.     

Growth of graphite film over the tops of vertical carbon nanotubes using Ni/Ti/Si substrate

A substrate with Ni/Ti/Si structure was used to grow vertical carbon nanotubes (CNTs) with a graphite fihn over CNT tops by thermal chemical vapor deposition with CH₄ gas as carbon source. The carbon nanotubes and the substrate were characterized by a field emission scanning electron microscope for the morphologies, a transmission electron microscope for the microstructures, a Raman spectrograph for the ctystallinity, and an Auger electron spectrometer for the depth distribution of elements. The result shows that when the thickness ratio of Ni layer to Ti layer in substrate is about 1, a graphite film with relatively good quality can be formed on the CNT tops.     

不同过渡层和电场方向对碳纳米管或纤维生长的影响

利用等离子体增强化学气相沉积系统沉积了碳纳米管或纤维，并用扫描电子显微镜研究了它们的生长和结构．为避免碳纳米管或纤维在生长过程中从衬底Si表面上脱落，先在Si表面上溅射沉积了金属过渡层Ti或Ta，然后再沉积催化剂NiFe．结果发现Ti和Ta过渡层对碳纳米管或纤维的结构有很大的影响．另外，还发现衬底Si放在支架的不同位置，碳纳米管或纤维的生长方向不同，这可能是由于辉光放电产生的非均匀电场所致．对不同过渡层和电场方向对碳纳米管或纤维生长的影响进行了分析和讨论．     

白光LED用橙色发射荧光粉Y_3Mg_2AlSi_2O_(12)∶Ce~(3+)的制备研究

采用X射线衍射(XRD)、扫描电子显微镜(SEM)、激发-发射光谱及反射光谱等手段,研究了以尿素为燃料的溶胶-凝胶燃烧法,制备白光LED用Y_3Mg_2AlSi_2O_(12)∶Ce~(3+)荧光粉过程中的还原温度、Ce~(3+)浓度等因素,对荧光粉结构、形貌和发光性能的影响.比较了溶胶-凝胶燃烧法和高温固相反应法制备的Y_3Mg_2AlSi_2O_(12)∶Ce~(3+)荧光粉的结晶度、形貌和发光性能,并从反应过程对造成两者差异的原因进行了讨论.     

Diameter-controlled growth of aligned single-walled carbon nanotubes on quartz using molecular nanoclusters as catalyst precursors

Molecular nanoclusters containing Fe and Mo atoms have been used as catalyst precursors for the growth of single-walled carbon nanotubes (SWNTs) on stable temperature (ST)-cut quartz substrates by chemical vapor deposition. Attribute to the uniform catalyst nanoparticles and the confinement effect of the crystalline substrates, well-aligned SWNTs with narrow diameter distribution have been synthesized. Atomic force microscopy measurements show that the mean diameter of the nanotubes obtained by thermal decomposition of ethanol at 900°C is 0.76 ± 0.16 nm, which is the smallest among all reported results for aligned SWNTs. The mean diameter of the nanotubes increases with growth temperature. In addition to using identical nanoclusters as the catalyst precursors, the avoidance of annealing treatment of catalyst precursors is also a key point for obtaining SWNTs with controlled diameters. Using these identical nanoclusters as catalyst precursors and carefully tuning the growth parameters make us closer to the ultimate goal of controlling the chirality of SWNTs.     

退火温度对N掺杂MgZnO薄膜光电性能的影响

采用射频磁控溅射技术, 用氮气作为掺杂源, 在石英基片上生长N掺杂Mg_xZn_1-xO薄膜, 并将薄膜分别在550,600,650,700 ℃真空中进行热退火处理. 结果表明: 晶体质量随退火温度的升高而提高; 薄膜中Mg和Zn的原子比发生了变化; Raman光谱中位于272,642 cm^-1处的振动峰逐渐消失; 室温光致发光光谱中薄膜的紫外激子发射峰变强, 且发生峰移; 随着退火温度的升高, 薄膜的导电类型发生转变, 当退火温度为600 ℃时, 薄膜呈最佳的p型导电性质.