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

The coulomb potential energy effect on the intensity of the characteristic lines at highly charged ion incendence on Al surface

The Al atomic characteristic spectral lines were induced by the impact of Ar-40(q+) ions (8 <= q <= 16; kinetic energy 150 keV) on Al surface. The result shows that by Penning impinging and resonant capture, the ion energy is deposited on the Al surface to excite the target atom, which is different from light excitation. Not only are the transitions betweem electronic configurations of the atomic complex excited, but the enhancing tendency of the characteristic spectral line intensity is consistent with the enhancing tendency of the coulomb potential energy of the incident ions with increasing charged states.

The electron emission yield induced by the interaction of highly charged argon ions with silicon surface

The electron emission yield of the interaction of highly charged argon ions with silicon surface is reported. The experiment was done at the Atomic Physics Research Platform on the Electron Cyclotron Resonance (ECR) Ion Source of the National Laboratory HIRFL (Heavy Ion Research Facility in Lanzhou). In the experiment, the potential energy and kinetic energy was selected by varying the projectile charge states and extracting voltage, thus the contributions of the projectile potential energy deposition and electronic energy loss in the solid are extensively investigated. The results show that, the two main factors leading to surface electron emission, namely the potential energy deposition and the electronic energy loss, are both approximately proportional to the electron emission yield per ion.

Potential sputtering by Highly Charged Ion bombardment on Au surface

The sputtered particle yields produced by Pbq+ (q=4-36) with constant kinetic energy bombardment on An surface were measured. The sputtering Could be separated to two parts: no potential sputtering is observed when q<24 (E-pot = 9.6 keV) and the sputtering yield increases with E-pot(1.2) for the higher charge states of q >= 24. The potential sputtering is mainly contributed by the relaxation of electronic excitations on target surface produced by the potential energy transfer from projectile to target atoms.

High-spin states in Au-188: Further evidence for nonaxial shape

The high-spin level structure of Au-188 has been investigated via the Yb-173(F-19,4n gamma) reaction at beam energies of 86 and 90 MeV. The previously reported level scheme has been modified and extended significantly. A new I-pi = 20(+) state associated with pi h(11/2)(-1) circle times nu i(13/2)(-2)h(9/2)(-1) configuration and two new rotational bands, one of which is built on the pi h(9/2) circle times nu i(13/2) configuration, have been identified. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around Au-188 for the pi h(9/2) circle times nu i(13/2) bands in odd-odd Au isotopes. Evidence for pi h(11/2)(-1) circle times nu i(13/2)(-1) structure of nonaxial shape with gamma < -70 degrees has been obtained by comparison with total Routhian surface and cranked-shell-model calculations.

Surface potential images of polycrystalline organic semiconductors obtained by Kelvin probe force microscopy

P-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyanina-tocopper (F16CuPc) polycrystalline films were investigated by Kelvin probe force microscopy (KPFM). Topographic and corresponding surface potential images are obtained simultaneously. Surface potential images are related with the local work function of crystalline facets and potential barriers at the grain boundaries (GBs) in organic semiconductors. Based on the spatial distribution of surface potential at GBs, donor- and acceptor-like trapping states in the grain boundaries (GBs) of p-CuPc and n-F16CuPc films are confirmed respectively.

Surface charge influence on the surface plasmon absorbance of electroactive thiol-protected gold nanoparticles

Gold nanoparticles (3.1-5.0 nm in size) surface-derivatized with both electroactive and nonelectroactive self-assembled monolayers were synthesized. The surface-derivatized electroactive particles can be easily oxidized/reduced at an electrode surface based on the diffusion-controlled current-voltage curve observed in cyclic voltammetry measurements. Spectroelectrochemical investigation demonstrated that the maximum absorbance of the nanoparticles in their oxidized state red-shifted compared with their reduced state to a different extent according to their size distribution. In the case of the particles surface-derivatized with nonelectroactive monolayers, much less shift was observed. This study showed that surface plasmon absorbance of gold nanoparticles was not only related to core charge states but was also influenced by surface charge states as well.

A nonmonotonic dependence of standard rate constant on reorganization energy for heterogeneous electron transfer processes on electrode surface

In the present work a nonmonotonic dependence of standard rate constant (k(0)) on reorganization energy (lambda) was discovered qualitatively from electron transfer (Marcus-Hush-Levich) theory for heterogeneous electron transfer processes on electrode surface. It was found that the nonmonotonic dependence of k(0) on lambda is another result, besides the disappearance of the famous Marcus inverted region, coming from the continuum of electronic states in electrode: with the increase of lambda, the states for both Process I and Process II ET processes all vary from nonadiabatic to adiabatic state continuously, and the lambda dependence of k(0) for Process I is monotonic thoroughly, while for Process II on electrode surface the lambda dependence of k(0) could show a nonmonotonicity.

In situ analysis of electropolymerization of aniline by combined electrochemistry and surface plasmon resonance

The combination of electrochemistry with surface plasmon resonance (SPR) has been used to characterize the growth of polyaniline (PAn) on a gold electrode surface during potential cycling. Potential-modulated SPR characteristics of the PAn film were also revealed. The potential switch between the oxidized and reduced states of PAn can lead to a large change of SPR response due to the variation in the imaginary part of the dielectric constant of PAn film resulting from the transition of the film in conductivity. The redox transition of the PAn film during potential cycling is very profitable to the SPR measurements. Two modes of SPR measurement, SPR angular scan (R-theta) and the time evolution of the reflectivity change at a fixed angle (R-t), were displayed to study the growth process of the PAn film. The angle shift of the resonance minimum recorded at each cathodic limit of cyclic potential scanning allows for the unambiguous measurement of the film growth. During cyclic potential scanning, the R-t curve was repeatedly modulated with the direction of the potential ramp as a result of the redox switch of the PAn film, and the amplitude of potential-modulated reflectivity change was well correlated with the cyclic number. The time differential of the R-t curve permits continuous monitoring of the film growth process. These results illustrate that the combined technique is suitable for studying the electropolymerization process of a conducting polymer.

SURFACE CHARACTERIZATION OF COBALT TETRAPHENYLPORPHYRIN MODIFIED GLASSY CARBON ELECTRODE BY XPS

Surface structure of the glassy carbon surface modified with cobalt tetraphenyl-porphyrin (CoTPP) by thermal-treatment has been studied by XPS, DTA and TG. During the thermal treatment a bond can be formed between the glassy carbon surface and TPP. Therefore the stability of electrode for the catalysis of dioxygen reduction is improved. Upon thermal treatment at 600 degrees C, FWHM of Co(2p(2/2)) is broadened, the reason is due to overlapping of peaks of multiple states, the spin orbit separation between Co (2p(1/2)) and Co (2p(3/2)) increases to 15.5-16.3eV, which indicated a change from low spin divalent states, the kinetic energy of Co L3VV Auger line and Auger parameter also increase. These changes of central cobalt ion provide a suitable redox potential for Co(III)/Co(II) which is related to the activity for catalysis of dioxygen reduction.

Dynamics of the cold-water event off the southeast coast of the United States in the summer of 2003

The cold-water event along the southeast coast of the United States in the summer of 2003 is studied using satellite data combined with in situ observations. The analysis suggests that the cooling is produced by wind-driven coastal upwelling, which breaks the thermocline barrier in the summer of 2003. The strong and persistent southwesterly winds in the summer of 2003 play an important role of lifting the bottom isotherms up to the surface and away from the coast, generating persistent surface cooling in July-August 2003. Once the thermocline barrier is broken, the stratification in the nearshore region is weakened substantially, allowing further coastal cooling of large magnitudes by episodic southerly wind bursts or passage of coastally trapped waves at periods of a few days. These short-period winds or waves would otherwise have no effects on the surface temperature because of the strong thermocline barrier in summer if not for the low-frequency cooling produced by the persistent southwesterly winds.

The effect of tungsten additive on the surface characteristics of amorphous Ni-P alloy

The variation of surface compositions on amorphous Ni80.4W1.5P18.1 alloy by O-2 oxidation and H-2 reduction treatments have been studied by XPS, UPS and ISS. It shows that addition of tungsten in the amorphous Ni-P alloy leads to dramatic changes of the relating component distributions in the surface layers before and after these treatments. Oxidation of a Ni80.4W1.5P18.1 amorphous alloy in 1 bar of oxygen at 513 K caused a significant segregation of nickel in different oxide states at the surface. The subsequent reduction of the oxidized surface with I bar hydrogen at 553 K resulted in only a small portion of Ni and P being reduced into elemental states, while most of them was found to combine to form a kind of nickel phosphate compound. On the other hand, under the same conditions, the oxidation and reduction of a Ni80P20 alloy gave rise to metallic Ni and elemental P as the predominate species on the alloy surface. The addition of W in the amorphous alloy might act as nuclei for a favorable formation of the phosphate structure which was proposed to be an active species for hydrogen-relating catalytic reactions. (C) 1999 Elsevier Science B.V. All rights reserved.

Deposition of silver nanoparticles in geochemically heterogeneous porous media: predicting affinity from surface composition analysis.

The transport of uncoated silver nanoparticles (AgNPs) in a porous medium composed of silica glass beads modified with a partial coverage of iron oxide (hematite) was studied and compared to that in a porous medium composed of unmodified glass beads (GB). At a pH lower than the point of zero charge (PZC) of hematite, the affinity of AgNPs for a hematite-coated glass bead (FeO-GB) surface was significantly higher than that for an uncoated surface. There was a linear correlation between the average nanoparticle affinity for media composed of mixtures of FeO-GB and GB collectors and the relative composition of those media as quantified by the attachment efficiency over a range of mixing mass ratios of the two types of collectors, so that the average AgNPs affinity for these media is readily predicted from the mass (or surface) weighted average of affinities for each of the surface types. X-ray photoelectron spectroscopy (XPS) was used to quantify the composition of the collector surface as a basis for predicting the affinity between the nanoparticles for a heterogeneous collector surface. A correlation was also observed between the local abundances of AgNPs and FeO on the collector surface.

Ligation of cell surface GRP78 with antibody directed against the COOH-terminal domain of GRP78 suppresses Ras/MAPK and PI 3-kinase/AKT signaling while promoting caspase activation in human prostate cancer cells.

We have previously shown that treatment of prostate cancer and melanoma cells expressing GRP78 on their cell surface with antibody directed against the COOH-terminal domain of GRP78 upregulates and activates p53 causing decreased cell proliferation and upregulated apoptosis. In this report, we demonstrate that treatment of 1-LN prostate cancer cells with this antibody decreases cell surface expression of GRP78, Akt(Thr308) and Akt(Ser473) kinase activities and reduces phosphorylation of FOXO, and GSK3beta. This treatment also suppresses activation of ERK1/2, p38 MAPK and MKK3/6; however, it upregulates MKK4 activity. JNK, as determined by its phosphorylation state, is subsequently activated, triggering apoptosis. Incubation of cells with antibody reduced levels of anti-apoptotic Bcl-2, while elevating pro-apoptotic BAD, BAX and BAK expression as well as cleaved caspases-3, -7, -8 and -9. Silencing GRP78 or p53 gene expression by RNAi prior to antibody treatment abrogated these effects. We conclude that antibody directed against the COOH-terminal domain of GRP78 may prove useful as a pan suppressor of proliferative/survival signaling in cancer cells expressing GRP78 on their cell surface.

Intensification of summer rainfall variability in the southeastern United States during recent decades

The variability of summer precipitation in the southeastern United States is examined in this study using 60-yr (1948-2007) rainfall data. The Southeast summer rainfalls exhibited higher interannual variability with more intense summer droughts and anomalous wetness in the recent 30 years (1978-2007) than in the prior 30 years (1948-77). Such intensification of summer rainfall variability was consistent with a decrease of light (0.1-1 mm day-1) and medium (1-10 mm day-1) rainfall events during extremely dry summers and an increase of heavy (.10 mm day-1) rainfall events in extremely wet summers. Changes in rainfall variability were also accompanied by a southward shift of the region of maximum zonal wind variability at the jet stream level in the latter period. The covariability between the Southeast summer precipitation and sea surface temperatures (SSTs) is also analyzed using the singular value decomposition (SVD) method. It is shown that the increase of Southeast summer precipitation variability is primarily associated with a higher SST variability across the equatorial Atlantic and also SST warming in the Atlantic. © 2010 American Meteorological Society.