Vertically forced surface wave in weakly viscous fluids bounded in a circular cylindrical vessel

Two-time scale perturbation expansions were developed in weakly viscous fluids to investigate surface wave motions by linearizing the Navier-Stokes equation in a circular cylindrical vessel which is subject to a vertical oscillation. The fluid field was divided into an outer potential flow region and an inner boundary layer region. A linear amplitude equation of slowly varying complex amplitude, which incorporates a damping term and external excitation, was derived for the weakly viscid fluids. The condition for the appearance of stable surface waves was obtained and the critical curve was determined. In addition, an analytical expression for the damping coefficient was determined and the relationship between damping and other related parameters (such as viscosity, forced amplitude, forced frequency and the depth of fluid, etc.) was presented. Finally, the influence both of the surface tension and the weak viscosity on the mode formation was described by comparing theoretical and experimental results. The results show that when the forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when the forcing frequency is high, the surface tension of the fluid is prominent.

Fabrication of ZnO and its enhancement of charge injection and transport in hybrid organic/inorganic light emitting devices

ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly [2- methoxy-5 - (3',7'-dimethyloctyloxy)- 1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electrolummescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection. (c) 2007 Elsevier B.V. All rights reserved.

Surface Disorder of GaN Irradiated by Highly Charged Arq+-Ions

Surface damage of gallium nitride films irradiated by Arq+ (6 ≤ q ≤ 16) ions at room temperature is studied by the atomic force microscopy. It is found that when charge state exceeds a threshold value, significant swelling was turned into obvious erosion in the irradiated region. The surface change of the irradiated region strongly depends on the charge state and ion fluence. On the other hand, surface change is less dependent on the kinetic energy nearly in the present experimental range (120 keV≤ Ek ≤ 220 keV). For q ≤ 14, surface of the irradiated region iscovered with an amorphous layer, rough and bulgy. A step-up appears between the irradiated and un-irradiated region. Moreover, the step height and the surface roughness are functions of the ion dose and charge state...

Study of the interaction of highly charged ions with SiO2 surface

Highly charged ions (HCIs) AO(q+)/Pbq+ are extracted from ECR source and impacted on solid surface Of SiO2 Sputtering yield as a function of incident angle is measured by multi-channel plate (MCP). The results have been fitted by a new formula. We proposed the cooperation model to explain the formula. The results demonstrate that the potential assisted kinetic sputtering yield increases with the charge state and potential sputtering (PS) could be induced by impact of HCIs. At larger incident angles, the sputtering yield is dominated by elastic collision between HCIs and material atoms. It is found that, smaller the incident angle, larger the contribution from the potential sputtering. (C) 2009 Elsevier B.V. All rights reserved.

Surface erosion of GaN bombarded by highly charged Pb-208(q+)-Ions

Surface change of gallium nitride specimens after bombardment by highly charged Pbq+-ions (q = 25, 35) at room temperature is studied by means of atomic force microscopy. The experimental results reveal that the surface of GaN specimens is significantly etched and erased. An unambiguous step-up is observed. The erosion depth not only strongly depends on the charge state of ions, but also is related to the incident angle of Pbq+-ions and the ion dose. The erosion depth of the specimens in 60 incidence (tilted incidence) is significantly deeper than that of the normal incidence. The erosion behaviour of specimens has little dependence on the kinetic energy of ion (E-k = 360, 700 keV). On the other hand, surface roughness of the irradiated area is obviously decreased due to erosion compared with the un-irradiated area. A fiat terrace is formed.

X-ray spectra induced by Xe-129(q+) impacting the metal surface

Using the slow highly charged ions Xe-129(q+) (q = 25, 26, 27; initial kinetic T-0 <= 4.65 keV/a.u.) to impact Au surface, the Au atomic M alpha characteristic X-ray spectrum is induced. The result shows that as long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10(-8) and increases with the kinetic energy and potential energy of projectile. By measuring the Au M alpha-X-ray spectra, Au atomic N-level lifetime is estimated at about 1.33x10(-18) s based on Heisenberg uncertainty relation.

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.

Electron emission induced by the interaction of highly charged ions Pb-207(q+) (24 <= q <= 36) with solid surface of Si(110)

The electron emission induced by highly charged ions Pb-207(q+) (24 <= q <= 36) interacting with Si(110) surface is reported. The result shows that the electron emission yield Y has a strong dependence on the projectile charge state q, incidence angle psi and impact energy E. In fitting the experimental data we found a nearly 1/tan psi dependence of Y. Theoretical analysis shows that these processes are closely related to the process of potential electron emission based on the classical over-the-barrier model.

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.

X-ray spectrum emitted by the impact of Xe-129(q+) on Mo surface

We studied the characteristic X-ray spectra produced by the interaction of highly charged ions of X-129(q+) (q =25, 26, 27) with surface of metallic Mo. The experimental result shows that highly charged ions can excite the characteristic X-ray spectra of L-shell of Mo when the beam' s intensity is not more than 120 nA. The X-ray yield of single ion reaches a quantitative level of 10(-8) and increases with the increment of the ion' s kinetic energy and ionic charge (potential energy). By measuring the X-ray spectra of Mo-L alpha(1) the M-level lifetime of Mo atom is estimated by using Heisenberg uncertainty relation.

Adsorption of 4,4 '-thiobisbenzenethiol on silver surfaces: surface-enhanced Raman scattering study

Adsorption of 4,4'-thiobisbenzenethiol (4,4'-TBBT) on a colloidal silver surface and a roughened silver electrode surface was investigated by means of surface-enhanced Raman scattering (SERS) for the first time, which indicates that 4,4'-TBBT is chemisorbed on the colloidal silver surface as dithiolates by losing two H-atoms of the S-H bond, while as monothiolates on the roughened silver electrode. The different orientations of the molecules on both silver surfaces indicate the different adsorption behaviors of 4,4'-TBBT in the two systems.

Bump-Surface Multicompartment Micelles from a Linear ABC Triblock Copolymer: A Combination Study by Experiment and Computer Simulation

Novel bump-surface multicompartment micelles formed by a linear amphiphilic ABC triblock copolymer via self-assembly in selective solvent were successfully observed both in simulation and experiment. The results revealed that the block A forms the most inner core, and the blocks B and C form the inner and outer layers, respectively, and the bumps were formed by block A and more likely to be born on curving surfaces. Moreover, the micelle shape could be controlled by changing the solvent selectivity of the blocks A and B. Spherical, cylindrical, and discoidal micelles with bumpy surfaces were obtained both in experiment and simulation.

Pt Nanoparticles Supported on TiO2 Colloidal Spheres with Nanoporous Surface: Preparation and Use as an Enhancing Material for Biosensing Applications

An easy surface-modified method has been developed to link -NH2 groups to the TiO2 colloidal spheres with nanoporous surface (f-TiO2). It was found that the as-prepared f-TiO2 is positively charged in neutral conditions and could act as an electrostatic anchor for nanosructures with opposite charge, Furthermore, platinum nanoparticles (Pt NPs) are successfully assembled on the f-TiO2 mainly via electrostatic interaction to fabricate a new kind of Pt NPs/TiO2 hybrid nanomaterial (f-TiO2-Pt NPs). The morphology, structure, and composition of the hybrids were characterized by the means of diverse techniques such as transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, and Raman spectra. Electrochemical experiments indicate the electrode modified with f-TiO2-Pt NPs shows prominent electrocatalytic activity toward the oxidation of hydrogen peroxide.

Counterion exchange at the surface of polyelectrolyte multilayer film for wettability modulation

Counterions present at the surface of polyelectrolyte multilayers (PEMs) were utilized for modulation of surface wettability via ion exchange. The PEM film was dipped in aqueous solutions of different anions, respectively, and the water contact angle of the surface varied from about 10 degrees to 120 degrees, depending on the hydration characteristics of the anion. The ion exchange mechanism was verified by X-ray photoelectron spectroscopy. The process was rapid and reversible. Ionic strength of the polyelectrolyte solution used for preparing the PEMs was found to be crucial to the surface wetting properties and the reversibility and kinetics of the process, and the effects were correlated to the surface density of the excess charge and counterion. This work provides a general, facile and rapid approach of surface property modulation.

The adsorption of dopamine on gold and its interactions with iron(III) ions studied by microcantilevers

The adsorption of dopamine (DA) molecules on gold and their interactions with Fe3+ were studied by a microcantilever in a flow cell. The microcantilever bent toward the Au side with the adsorption of DA due to the change Of Surface stress induced by the intermolecular hydrogen bonds of DA or the charge transfer effect between adsorbates and the Substrate. The interaction process between DA adsorbates and Fe3+ was revealed by the deflection curves of microcantilever. As indicated by the appearance of a variation during the decline of curves, two steps were observed in the curve at relative high concentrations of Fe3+. In this case, Fe3+ reacted with DA molecules only in the outer layers and the complexes removed with solution. Then Fe3+ reacted further with DA molecules forming the surface complex in the first layer next to the gold. At this stage, the stability Of Surface complexes was time dependent, i.e., unstable initially and stable finally. This may be due to the surface complexes change from mono-dentate to bi-dentate complexes. In another case, i.e., at relative low concentration of Fe3+, only the first step was observed as indicated by the absence of a variation.