Fabrication of Novel Superhydrophobic Surfaces and Water Droplet Bouncing Behavior - Part 1: Stable ZnO-PDMS Superhydrophobic Surface with Low Hysteresis Constructed Using ZnO Nanoparticles

A superhydrophobic surface has many advantages in micro/nanomechanical applications, such as low adhesion, low friction and high restitution coefficient, etc. In this paper, we introduce a novel and simple route to fabricate superhydrophobic surfaces using ZnO nanocrystals. First, tetrapod-like ZnO nanocrystals were prepared via a one-step, direct chemical vapor deposition (CVD) approach. The nanostructured ZnO material was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) and the surface functionalized by aminopropyltriethoxysilane (APS) was found to be hydrophobic. Then the superhydrophobic surface was constructed by depositing uniformly ZnO hydrophobic nanoparticles (HNPs) on the Poly(dimethylsiloxane) (PDMS) film substrate. Water wettability study revealed a contact angle of 155.4 +/- 2 degrees for the superhydrophobic surface while about 110 degrees for pure smooth PDMS films. The hysteresis was quite low, only 3.1 +/- 0.3 degrees. Microscopic observations showed that the surface was covered by micro- and nano-scale ZnO particles. Compared to other approaches, this method is rather convenient and can be used to obtain a large area superhydrophobic surface. The high contact angle and low hysteresis could be attributed to the micro/nano structures of ZnO material; besides, the superhydrophobic property of the as-constructed ZnO-PDMS surface could be maintained for at least 6 months. (C) Koninklijke Brill NV, Leiden, 2010

Synthesis and field emission of diamond-like carbon nanorods on TiO2/Ti nanotube arrays

Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 degrees C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3-10 mu m. Raman spectra show two strong peaks about 1332 cm (1) and 1598 cm (1), indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/mu m, no evident decay at 3.4 mA/cm(2) in 480 min. (C) 2009 Elsevier B. V. All rights reserved.

Effect of substrate and annealing on the structural and optical properties of ZnO:Al films

ZnO:Al thin films with c-axis preferred orientation were deposited on glass and Si substrates using RF magnetron sputtering technique. The effect of substrate on the structural and optical properties of ZnO:Al films were investigated. The results showed a strong blue peak from glass-substrate ZnO:Al film whose intensity became weak when deposited on Si substrate. However, the full width at half maxima (FWHM) of the Si-substrate ZnO:Al (0 0 2) peaks decreased evidently and the grain size increased. Finally, we discussed the influence of annealing temperature on the structural and optical properties of Si-substrate ZnO:Al films. After annealing, the crystal quality of Si-substrate ZnO:Al thin films was markedly improved and the intensity of blue peak (similar to 445 nm) increased noticeably. This observation may indicate that the visible emission properties of the ZnO:Al films are dependent more on the film crystallinity than on the film stoichiometry. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

Synthesis, Reactivity, and Characterization of Sodium and Rare-Earth Metal Complexes Bearing a Dianionic N-Aryloxo-Functionalized -Ketoiminate Ligand

The synthesis and reactivity of a series of sodium and rare-earth metal complexes stabilized by a dianionic N-aryloxo-functionalized beta-ketoiminate ligand were presented. The reaction of acetylacetone with 1 equiv of 2-amino-4-methylphenol in absolute ethanol gave the compound 4-(2-hydroxy-5-methylphenyl)imino-2-pentanone (LH2, 1) in high yield.

Effects of ammonia and cetyltrimethylammonium bromide (CTAB) on morphologies of ZnO nano- and micromaterials under solvothermal process

Submicrometer zinc oxide (ZnO) with different morphologies including spindle-like, pencil-like, branch rod-like and frizzy flower-like shapes, have been hydrothermally synthesized in mixed solvents of ethanol and water at 140 degrees C. It was found that the volumes of added ammonia, surfactant (cetyltrimethylammonium bromide, CTAB), and mixed solvent play crucial roles in morphological control of ZnO nanostructures. Increasing the volume of ammonia added to the reaction system, the shape of ZnO evolves from spindle into branch rod-like. Synergetic influence between CTAB and ammonia can only be observed at high concentration of ammonia.

Preparation of Hollow Carbon and Silicon Carbide Fibers with Different Cross-Sections by using Electrospun Fibers as Templates

Hollow carbon nanofibers with circular and rectangular opening were prepared by using electrospun silica fibers as templates. Silica fibers were synthesized by electrospinning, and they were coated with a carbon layer formed by thermal decomposition and carbonization of polystyrene under a nitrogen atmosphere. Hollow carbon nanofibers with circular and rectangular openings were then obtained after the silica core was etched by hydrofluoric acid. The carbon nanofibers with different morphologies also could be used as templates to fabricate silicon carbide fibers. The silicon carbide fibers with circular and rectangular openings could be obtained by using hollow carbon nanofibers and carbon belts as templates, respectively.

Multicolor Tuning of Manganese-Doped ZnS Colloidal Nanocrystals

In this paper, we report a facile route which is based Oil tuning doping concentration of Mn2+ ions in ZnS nanocrystals, to achieve deliberate color modulation from blue to orange-yellow under single-wavelength excitation. X-ray diffraction (XRD), transmission electron microscopy (TEM), as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. In this process, the relative emission intensities of both ZnS host (blue) and Mn2+ dopant (orange-yellow) are sensitive to the Mn2+ doping concentration, due to the energy transfer from ZnS host to Mn2+ dopant. As a result of fine-tuning of these two emission components, white emission can be realized for Mn2+-doped ZnS nanocrystals. Furthermore.

ZnO Nanorods as Scatterers for Random Lasing Emission from Dye Doped Polymer Films

A random lasing emission from 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped polystyrene (PS) thin films was realized by the scattering role of ZnO nanorods. The device was fabricated by spin-coating DCJTB doped PS on ZnO nanorods. The ZnO nanorods were grown on indium-tin-oxide (ITO) glass substrate by hydrothermal synthesis method. It can be seen that the device emits a resonance multimode peak at center wavelength of 630 nm with a mode line-width of less than 0.23 nm and exhibits threshold excitation intensity as low as 0.375 mJ pulse(-1) cm(-2). The agreement of the dependence of threshold pumped intensity on the excitation area with the random laser theory indicates that the lasing emission realized here is random laser. Our results demonstrate that the nanostructured ZnO nanorods are promising candidate as alternative sources of coherent light emission to realize organic lasers.

Facile transformation of hydrophilic cellulose into superhydrophobic cellulose

Superhydrophobic cellulose-based materials coupled with transparent, stable and nanoscale polymethylsiloxane coating have been successfully achieved by a simple process via chemical vapor deposition, followed by hydrolyzation and polymerization.

Low-temperature oxidation of methane to form formaldehyde: role of Fe and Mo on Fe-Mo/SiO2 catalysts, and their synergistic effects

The partial oxidation of methane with molecular oxygen was performed on Fe-Mo/SiO2 catalysts. Iron was loaded on the Mo/SiO2 catalyst by chemical vapor deposition of Fe-3(CO)(12). The catalyst showed good low-temperature activities at 723-823 K. Formaldehyde was a major condensable liquid product on the prepared catalyst. There were synergistic effects between iron and molybdenum in Fe-Mo/SiO2 catalysts for the production of formaldehyde from the methane partial oxidation. The activation energy of Mo/SiO2 decreased with the addition of iron and approached that of the Fe/SiO2. The concentration of isolated molybdenum species (the peak at 1148 K in TPR experiments) decreased as the ion concentration increased and had a linear relationship with the selectivity of methane to formaldehyde. The role of Fe and Mo in the Fe-Mo/SiO2 catalyst was proposed: Fe is the center for the C-H activation to generate reaction intermediates, and Mo is the one for the transformation of intermediates into formaldehyde. Those phenomena were predominant below 775 K.

Effect of surface state properties of TiO2 nanoparticle film on its photocatalytic activity

TiO2 nanoparticle film catalysts with different thicknesses were prepared by plasma-enhanced chemical vapor deposition(PECVD) method and the surfaces were subsequently treated by TiCl4 or O-2 plasma. Two kinds of TiO2 films with different surface properties were obtained. Their surface microstructures and energy levels of surface states were tested by AFM, XRD, SPS, The photocatalytic activities of the catalysts were determined via photodegradation experiments of phenol. The results demonstrated that photocatalytic activities of samples whose surface was treated by O-2 plasma were greater than those treated by TiCl4 plasma. Moreover, photodegradation ratio of phenol during the first hour catalyzed by 0. 17 mu m thickness TiO2 nanoparticle film was greater than other samples. Especially, the difference of photocatalytic activities of TiO2 nanoparticle films treated by TiCl4 or O-2 plasma was respectively explained by energy band theory.

Study on the interface structure: Diamond thin film epitaxy on (001) silicon substrate

An interesting interface structure between diamond film and silicon substrate has been observed. That is, according to the deformation of the diamond film crystal sturcture, a strictly 3:2 matching of the two lattices across the interface is obtained. This result clearly indicates that misfit dislocations at the interface and "epitaxial tilting" are not the only two ways to overcome the 1.5% residual misfit.

碳纳米管探针的制作方法研究

碳纳米管的小直径、高纵横比、高强度和高弹性、优良的耐磨损性能以及独特的电学和化学特性,使其成为高分辨率原子力显微镜的理想探针针尖。本文根据制作工艺的特点,综述现有碳纳米管探针的代表性研究和制作方法:组装式和生长式。组装式是通过手工、电场或磁场的方式将制备好的碳纳米管粘附到常规硅探针的末端;而生长式是在常规硅探针末端或悬臂梁上定点催化生长出一定直径和长度的CNT。最后指出这些方法目前存在的主要问题。

Reductive elimination of hypersilyl halides from zinc (II) complexes. Implications for electropositive metal thin film growth

Treatment of Zn(Si(SiMe3)3)2 with ZnX2 (X = Cl, Br, I) in tetrahydrofuran (THF) at 23 °C afforded [Zn(Si(SiMe3)3)X(THF)]2 in 83–99% yield. X-ray crystal structures revealed dimeric structures with Zn2X2 cores. Thermogravimetric analyses of [Zn(Si(SiMe3)3)X(THF)]2 demonstrated a loss of coordinated THF between 50 and 155 °C and then single-step weight losses between 200 and 275 °C. The nonvolatile residue was zinc metal in all cases. Bulk thermolyses of [Zn(Si(SiMe3)3)X(THF)]2 between 210 and 250 °C afforded zinc metal in 97–99% yield, Si(SiMe3)3X in 91–94% yield, and THF in 81–98% yield. Density functional theory calculations confirmed that zinc formation becomes energetically favorable upon THF loss. Similar reactions are likely to be general for M(SiR3)n/MXn pairs and may lead to new metal-film-growth processes for chemical vapor deposition and atomic layer deposition.

Orthogonal orientation control of carbon nanotube growth.

Carbon nanotubes (CNTs) have attracted attention for their remarkable electrical properties and have being explored as one of the best building blocks in nano-electronics. A key challenge to realize such potential is the control of the nanotube growth directions. Even though both vertical growth and controlled horizontal growth of carbon nanotubes have been realized before, the growth of complex nanotube structures with both vertical and horizontal orientation control on the same substrate has never been achieved. Here, we report a method to grow three-dimensional (3D) complex nanotube structures made of vertical nanotube forests and horizontal nanotube arrays on a single substrate and from the same catalyst pattern by an orthogonally directed nanotube growth method using chemical vapor deposition (CVD). More importantly, such a capability represents a major advance in controlled growth of carbon nanotubes. It enables researchers to control the growth directions of nanotubes by simply changing the reaction conditions. The high degree of control represented in these experiments will surely make the fabrication of complex nanotube devices a possibility.