Proposal for studying N* resonances with the (p)over-barp -> (p)over-barn pi(+) reaction

A theoretical study of the (p) over barp -> (p) over barn pi(+) reaction for antiproton beam energy from 1 to 4 GeV is made by including contributions from various known N* and Delta* resonances. It is found that for the beam energy around 1.5 GeV, the contribution of the Roper resonance N-(1440)* produced by the t-channel sigma exchange dominates over all other contributions. Since such a reaction can be studied in the forthcoming PANDA experiment at the GSI Facility of Antiproton and Ion Research (FAIR), the reaction will be realistically the cleanest place for studying the properties of the Roper resonance and the best place for looking for other "missing" N* resonances with large coupling to N sigma.

Damage accumulation in gallium nitride irradiated with various energetic heavy ions

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe+ and Mo+ ions of 110 keV), swift heavy ions (Pb-208(27+) ions of 1.1 MeV/u) and slow highly-charged heavy ions (Xen+ ions of 180 keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413 K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3 keV/nm(3)),. which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions.

Molecular vibration spectroscopy study of irradiation effect in C-60 films induced by low energy ion

Irradiation effect in C-60 films induced by 170 keV B ion was investigated by means of Fourier transform infrared (FTIR) and Raman spectroscopies. The damage cross section sigma and the effective damage radius R are deduced from the experimental data of all four IR active modes and evident four Raman active modes of C-60 molecule. The differences on irradiation sensitivity and structural stability of the different active modes of C-60 molecule are compared. The results indicate that T-1u (4) of infrared active mode and A(g) (1) of Raman active mode are most sensitive for B ion irradiation. On the other hand T-1u (2) of infrared active mode and H-g (3) of Raman active mode are comparatively stable under B ion irradiation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3512968]

Structural stability of C-60 films under the bombardment of 1.95 GeV Kr ions

The structural stability of C-60 films under the bombardment of 1.95 GeV Kr ions is investigated. The irradiated C-60 films were analyzed by Fourier Transform Infrared (FTIR) spectroscopy and Raman scattering technique. The analytical results indicate that the irradiation induced a decrease of icosahedral symmetry of C-60 molecule and damage of C-60 films; different vibration modes of C-60 molecule have different irradiation sensitivities; the mean efficient damage radius obtained from experimental data is about 1.47 nm, which is in good agreement with thermal spike model prediction.

Metal nanomaterials and carbon nanotubes - synthesis, functionalization and potential applications towards electrochemistry

This review focuses on the synthesis, assembly, surface functionalization, as well as application of inorganic nanostructures. Electrochemical and wet- chemical methods are demonstrated to be effective approaches to make metal nanostructures under control without addition of a reducing agent or protecting agent. Owing to the unique physical and chemical properties of the nano-sized materials, novel applications are introduced using inorganic nanomaterials, such as electrocatalysis, photoelectricity, spectrochemistry, and analytical chemistry.

Facile electrochemical approach to fabricate hierarchical flowerlike gold micro structures: Electrodeposited superhydrophobic surface

A templateless, surfactantless, electrochemical approach is proposed to directly fabricate hierarchical flowerlike gold microstructures (HFGMs) on an indium tin oxide (ITO) substrate. The as-prepared HFGMs have been characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and cyclic voltammetry.

Ultrathin platinum-group metal coated hierarchical flowerlike gold microstructure: Electrochemical design and characterization

The deliberate tailoring of hierarchical flowerlike gold microstructure (HFGMs) at the ultrathin level is an ongoing challenge and could introduce opportunities for new fabrication and application in many fields. In this paper. a templateless, surfactantless, electrochemical strategy for fabrication of ultrathin platinum-group metal coated HFGMs is proposed. HFGMs were prepared by simple electrodeposition on an indium tin oxide (ITO) substrate.

The electrochemical behavior of a system with a limited number of molecules

In this paper, based on Einstein relationship between diffusion and random walk, the electrochemical behavior of a system with a limited number of molecules was simulated and explored theoretically. The transition of the current vs time responses from discrete to continuous was clearly obtained as the number of redox molecules increased from 10 to 10(6).

Small-molecule-directed assembly: A gold nanoparticle-based strategy for screening of homo-adenine DNA duplex binders

By using AuNP-modified homo-adenine DNA conjugate as a model system, simple colorimetric and resonance Rayleigh scattering assays have been developed for screening small molecules that trigger the formation of the non-Watson-Crick homo-adenine duplexes. The assay presented here is more simplified in format as it involves only one type of ssDNA modified Au-NP, and can be easily adapted to high-throughput screening.

Morphology control of nanoscale PbS particles in a polyol process

Nanostructured PbS with different morphologies and particle sizes have been prepared through a polyol process. Narrow size distribution for star-shaped, octahedral, tetradecanehedral, and cubic products were achieved by slowly introducing the source materials using a peristaltic pump in the presence of poly(vinylpyrrolidone) (PVP) as additive. Systematic variation of the kinetic factors, including the additive, the reaction temperature, the duration time, the ratio of source materials, the Sulfur sources, and the Pb(Ac)(2)center dot 3H(2)O concentration, reveals that the morphology depends mainly on the supersaturation degree of the free sulfur ions released from thiourea under elevated temperature.

Self-assembly of lambda-DNA networks/Ag nanoparticles: Hybrid architecture and active-SERS substrate

In this article, highly rough and stable surface enhanced Raman scattering (SERS)-active substrates had been fabricated by a facile layer by-layer technique. Unique lambda-DNA networks and CTAB capped silver nanoparticles (AgNP) were alternatively self-assembled on the charged mica surface until a desirable number of bilayers were reached. The as-prepared hybrid architectures were characterized by UV-vis spectroscopy, tapping mode atomic force microscopy (AFM) and confocal Raman microscopy, respectively.

Novel Hybrid Electrocatalyst with Enhanced Performance in Alkaline Media: Hollow Au/Pd Core/Shell Nanostructures with a Raspberry Surface

In this paper, a hollow Au/Pd core/shell nanostructure with a raspberry surface was developed for methanol, ethanol, and formic acid oxidation in alkaline media. The results showed that it possessed better electrocatalyst performance than hollow Au nanospheres or Pd nanoparticles. The nanostructure was fabricated via a two-step method. Hollow Au nanospheres were first synthesized by a galvanic replacement reaction, and then they were coated with a layer of Pd grains. Several characterizations such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to investigate the prepared nanostructures.

Large-Scale and Template-Free Growth of Free-Standing Single-Crystalline Dendritic Ag/Pd Alloy Nanostructure Arrays

Large-scale arrays consist of dendritic single-crystalline Ag/Pd alloy nanostructures are synthesized for the first time. A simple galvanic replacement reaction is introduced to grow these arrays directly on Ag substrates. The morphology of the products strongly depended on the reaction temperature and the concentration of H2PdCl4 solution. The mechanism of the formation of alloy and the dendritic morphology has been discussed. These alloy arrays exhibit high surface-enhanced Raman scattering (SERS) activity and may have potential applications in investigation of "in situ" Pd catalytic reactions using SERS. Moreover, electrocatalytic measurements suggest that the obtained dendritic Ag/Pd alloy nanostructures exhibit electrocatytic activity toward the oxidation of formic acid.