石英基底上定向单壁碳纳米管阵列可控生长

以铜为催化剂,甲烷为碳源,采用化学气相沉积法在石英单晶基底上生长定向单壁碳纳米管阵列,分别用扫描电子显微镜、原子力显微镜对其结构进行表征,研究了使用聚合物聚乙烯丙烯酸甲脂（PMMA）分散催化剂对碳纳米管密度和定向性的影响,利用PMMA分散催化剂能提高催化剂的活性,增加定向碳纳米管的密度,使催化剂形成规则的条状,能进一步提高其密度和定向性。采用微加工工艺做成器件,并利用半导体参数测试仪对器件进行了电学测试。

生长环阵列超宽频带天线设计

本文针对多网合一无线通信终端设备对微波多频段兼容天线的性能要求,将方形角缺陷分形天线结构和生长环阵列结合,设计了一款超宽频带天线。这款天线尺寸较小、辐射强度较高、性能冗余充足,能够同时工作于移动通信、射频识别(RFID)、超宽带(UWB)、移动数字电视(DTV)等多个无线通信系统,具有优异的兼容性,可以作为多网合一无线通信系统终端天线得到大规模应用。

Altered expression of mitochondrial related genes in the native Tibetan placents by mitochondrial cDNA array analysis

Objective： To explore the mechanism of native Tibetan fetuses adaptation to hypoxia, we tried to find the different expression genes about mitochondrial function in the native Tibetan placents. Methods： In this study, the placents of native Tibetan and the high-altitude Hart （ha-Hart） were collected. After the total RNA extraction, the finally synthesized cDNAs were hybridized to mitochondrial array to find the altered expression genes between them. Then, the cytochrome c oxidase 17 （Coxl7）, dynactin 2 （DCTN2, also known as p50）, and vascular endothelial growth factor receptor （VEGFR, also known as KDR） were chosen from the altered expression genes to further verify the array results using the SYBR Green real-time PCR. Because the altered expression genes （such as Cybb and Cox 17） in the array results related to the activities of COXI and COXIV, the placental mitochondria activities of COXI and COXIV were measured to find their changes in the hypoxia. Results： By a standard of≥1.5 or ≤0.67, there were 24 different expressed genes between the native Tibetan and the ha-Han placents, including 3 up-regulated genes and 21 down-regulated genes. These genes were related to energy metabolism, signal transduction, cell proliferation, electron transport, cell adhesion, nucleotide-excision repair. The array results of Cox17, DCTN2 and KDR were further verified by the real-time RT-PCR. Through the mitochondria respiration measurements, the activity of COXI in the native Tibetan placents were higher than that of ha-Han, there was no difference in COXIV activity between them. Conclusion： The altered mitochondrial related genes in the native Tibetan placents may have a role in the high altitude adaptation for fetuses through changing the activity of mitochondrial COX.

垂直生长碳纳米管阵列可见光高吸收比标准研制及其特性表征分析

研究采用原子层沉积(ALD)工艺,利用垂直碳纳米管阵列(VACNTs)的稀疏结构和碳纳米管本身具有的中空结构,探索制备具有超黑性质的垂直生长碳纳米管阵列薄膜,研究测试材料在(500~1000)nm绝对吸收比,调节阵列结构,实现高吸收比标准片的研制。

Controlled growth of Cu_3Se_2 nanosheets array counter electrode for quantum dots sensitized solar cell through ion exchange

Copper selenide （CurSe） has great potential as counter electrode for quantum dots sensitized solar cell （QDSSC） due to its excellent electrocatalytic activity and lower charge transfer resistance. A novel ion exchange method has been utilized to fabricate Cu3Se2 nanosheets array counter electrode. CdS layer was first deposited by sputtering and used as a template to grow compact and uni- form Cu3Se2 film in a typical chemical bath. The morphology and thickness of the Cu3Se2 nanosheets were controlled by the deposition time. The final products （2h-Cu3Se2） showed significantly improved electrochemical catalytic activity and carrier transport property, leading to a much increased power conversion efficiency （4.01%） when compared with the CuS counter electrode CdS/CdSe QDSSC （3.21%）.

Stability range of tilted dendritic arrays during directional solidification

The stability range of primary spacing of the tilted dendritic arrays in directional solidification has been studied by quantitative phase-field simulations. Results show that both the real growth direction and morphological shapes of dendritic arrays change with the primary spacing for different misorientation angles(θ0). It has been found that the lower limit of primary spacing is independent of θ0, but the upper limit of primary spacing is strongly influenced by that. The two kinds of tertiary branching instabilities result in different behaviors of the variation of the upper limit with misorientation angle for different pulling velocities.

Epitaxial growth of horizontally aligned single-crystal arrays of perovskite

Well-aligned single-crystal nanowire arrays of CH3NH3PbIs have shown potentials in laser sources and photovoltaic applications.Here we developed a solution based epitaxial method to grow CH3NH3PbI3nanowire arrays.By confining the precursor solution between a silicon wafer and ST-cut quartz,the evaporation rate of the solvent was slowed down which brings a more stable and controllable solution environment.Relying on the lattice match between CH3NH3PbI3 and ST-cut quartz,arrays of single-crystal nanowires of CH3NH3PbI3have been grown epitaxially.The densities and lengths of CH3NH3PbI3 nanowires can be tuned. The lengths of the resultant crystals range from several microns to over one millimeter.Such CH3NH3PbI3arrays with good alignment and crystallinity were then applied to fabricate photovoltaic devices with good performances.

Kinetics-controlled growth SnO2 nanorod arrays for superior rate performance of aligned mesocrystalline lithium-ion batteries with

A general method for facile kinetics-controlled growth of aligned arrays of mesocrystalline SnO2 nanorods on arbitrary substrates has been developed by adjusting supersaturation in a unique ternary solvent system comprising acetic acid, ethanol and water. The hydrolysis processes of Sn（IV） as well as the nucleation and growth of SnO2 crystals were carefully controlled in the mixed solvents, leading to an exclusively heterogeneous nucleation on a substrate and the subsequent growth into mesocrystalline nanorod arrays. In particular, aligned arrays of hierarchically structured, [001]-oriented mesocrystalline SnO2 nanorods with four {110} lateral facets can be readily grown on Ti foil as well as many other inert substrates such as fluoride-doped tin oxide （FTO）, Si, graphite, and polytetrafluoroethylene （Teflon）. Due to the unique combination of the mesocrystalline structure and the one-dimensional nanoarray structure, the obtained mesocrystalline SnO2 nanorod arrays grown on metallic Ti substrate exhibited an excellent rate performance with a high initial Coulombic efficiency of 65.6% and a reversible capacity of 720 mA.h/g at a charge/discharge rate of 10 C （namely, 7,820 mA/g） when used as an anode material for lithium-ion batteries.

Large-area growth of ultra-high-density single-walled carbon nanotube arrays on sapphire surface

A scalable approach to obtaining high-density, large-area single-walled carbon nanotube （SWNT） arrays is essential for realizing the full potential of SWNTs in practical electronic devices; this is still a great challenge. Here, we report an improved synthetic method for large-area growth of ultra-high-density SWNT arrays on sapphire surfaces by combining Trojan catalysts （released from the substrate, to assure ultra-high density） with Mo nanoparticles （loaded on the surface, to stabilize the released Trojan catalysts） as cooperating catalysts. Dense and perfectly aligned SWNTs covered the entire substrate and the local density was as high as 160 tubes/pro. Field-effect transistors （FETs） built on such arrays gave an output current density of -488 μA/μm at the drain-source voltage （Vds） = the gate-source voltage （Vgs） = -2 V, corresponding to an on-conductance per width of 244 μS/μm. These results confirm the wide range of potential applications of Trojan-Mo catalysts in the structure-controlled growth of SWNTs.

In Situ TEM Observation of the Gasification and Growth of Carbon Nanotubes Using Iron Catalysts

We report the in situ transmission electron microscope (TEM) observation of the catalytic gasification and growth of carbon nanotubes (CNTs). It was found that iron catalysts can consume the CNTs when pumping out the precursor gas, acetylene, at the growth temperature, and reinitiate the growth when acetylene is re-introduced. The switching between gasification and growth of CNTs can be repeated many times with the same catalyst. To understand the phenomenon, thermogravimetric analysis (TGA) coupled with mass spectroscopy was used to study the mechanism involved. It was shown that the residual water molecules in the growth chamber of the TEM react with and remove carbon atoms of CNTs as carbon monoxide vapor under the action of the catalyst, when the precursor gas is pumped out. This result contributes to a better understanding of the water-assisted and oxygen-assisted synthesis of CNT arrays, and provides useful clues on how to extend the lifetime and improve the activity of the catalysts.

Wafer-level site-controlled growth of silicon nanowires by Cu pattern dewetting

An approach for the wafer-level synthesis of size- and site-controlled amorphous silicon nanowires （α-SiNWs） is presented in this paper. Microscale Cu pattern arrays are precisely defined on SiO2 films with the help of photolithography and wet etching. Due to dewetting, Cu atoms shrink to the center of patterns during the annealing process, and react with the SiO2 film to open a diffusion channel for Si atoms to the substrate, α-SiNWs finally grow at the center of Cu patterns, and can be tuned by varying critical factors such as Cu pattern volume, SiO2 thickness, and annealing time. This offers a simple way to synthesize and accurately position a SiNW array on a large area.

Effect of growth time on morphology and photoelectrochemical performance of TiO_2 nanorod arrays grown on transparent conducting substrates

TiO_2 nanorod arrays(NRAs) were synthesized directly on the fluorine tin oxide(FTO) coated glass substrates by a facile hydrothermal route.The effects of growth time on the photoelectrochemical(PEC) properties of TiO_2 NRAs are investigated.The samples synthesized for 4 h exhibit a photocurrent intensity of 0.37 mA/cm^2 at the irradiation of Xe lamp and a bias of 0 V.As the growth time increases,the thickness and order degree of the NRAs are enhanced,but the photocurrent is reduced a lot.It might be associated with the hindering of a high background electron density in NRs due to the long-time hydrothermal reaction in acid environment.Moreover,the decline behavior is observed,which is attributed to the poor charge separation capacity of TiO_2 array electrodes and could be suppressed efficiently by applying a suitable positive bias.

ZnO nanorod arrays:Field-assisted growth in aqueous solution and field emission properties

ZnO nanorod arrays were fabricated in aqueous solutions under external voltages.The morphology and length of the nanorods could be readily controlled by varying such parameters as the voltage magnitude,growth time,solution concentration and substrate type.The external voltage,which made the adsorption of the Zn 2+ cation-containing complexes more possible,modified the growth behavior of the ZnO crystals and played a key role in guaranteeing the orderliness of the arrays.The increase in the nanorod length with the prolonged growth time gradually saturated due to the balance between the growth and the erosion.The ZnO nanorods respectively grown on the Zn and Si substrates differed considerably in both morphology and defect concentration.Field emission was extracted from arrays of nanorods with tapered ends.This field-assisted solution route for fabricating ZnO nanorods featured simplicity in manipulation,inexpensiveness in instrumentation,and effectiveness in controlling the morphology and length.