A simple solution route to single-crystalline Sb2O3 nanowires with rectangular cross sections

We report a simple solution route to large-scale synthesis of uniform, single-crystalline, and well-faceted orthorhombic antimony trioxide (Sb(2)O(3)) nanowires with rectangular cross sections by direct air oxidation of bulk metal antimony (Sb) in a mixed solution made of ethylenediamine (EDA) and deionized water (DIW). The as-synthesized products were analyzed by range of methods, such as XRD, SEM, EDX, TEM, SAED, HRTEM, FTIR, Raman, UV-vis absorption, and photoluminescence (PL) spectra. The as-synthesized Sb(2)O(3) nanowires with rectangular cross sections are usually hundreds of micrometers in length, typically 80-100 nm in width, and 60-80 nm in thickness. The novel room temperature photoluminescence properties of Sb(2)O(3) nanowires with rectangular cross sections displayed a significant UV luminescence with a strong emission band at 374 nm, which was reported for the first time, indicating the as-synthesized products with an optical band gap E(g) = 3.3 eV. It is expected that as-synthesized Sb(2)O(3) nanowires would be a new member of functional materials and used in the manufacture of advanced nanodevices.     

Single-crystalline LaB6 nanowires

Lanthanum hexaboride nanowires produced by chemical vapor deposition are single-crystalline and grown along the [111] direction. Streaks appearing in the electron diffraction spots indicate the lateral direction perpendicular to the nanowire growth axis.     

Single-crystalline CeB(6) nanowires

Considered to be one of the best electron emission materials, CeB6 nanowires are of great scientific and industrial interest. CeB6 nanowires of square cross section with about 50 nm in lateral dimension and more than several micrometers in length have been successfully produced using a chemical vapor deposition method. The nanowires are grown in the 100 lattice direction, and both the tip top and the side surfaces are terminated with the {100} lattice planes.     

Single-crystalline Sb-doped SnO2 nanowires: synthesis and gas sensor application

The synthesis of semiconducting Sb-doped SnO2 nanowires in mass production by an in situ doping approach are reported, and the ethanol sensing results demonstrated that Sb-doped SnO2 nanowires have a promising application for the fabrication of gas sensors with low resistance, and quick response and recovery times.     

New defect vanadium dioxide phases

Two new monoclinic V₂O₄ phases were prepared at high pressure from the regular monoclinic (M₁) form of V₂O₄. The unit cell dimensions for the unmodified monoclinic (M₂) phase are: a = 9.083, b = 5.763, c = 4.532 Å, and β = 91.30°. The space group $\text{C 2}\text{m}$ is consistent with the crystallographic data. The new vanadium dioxide exhibited a structural transition and an abrupt, reversible change in resistivity (approx. 4 orders of magnitude) at 66°C similar to that observed in M₁-type V₂O₄. This new form of V₂O₄ is believed to be stabilized by chemical and structural defects. Controlled substitution of V⁵⁺ for V⁴⁺ in the structure led to yet another monoclinic (M₃) phase. This phase is closely related to the M₂ phase. The M₃ unit cell dimensions are: a = 4.506, b = 2.899, c = 4.617 Å, and β = 91.79°, having the space group $\text{P 2}\text{m}$. The substitution of V³⁺ yielded only monoclinic (M₁) derivatives. The modified products have varied semiconductor to metal transition temperatures which depend on the type and amount of substitution and defect structure.     

Theory of half-collision cross sections

Standard Lippmann–Schwinger theory does not apply to decay of metastable or unstable states due to failure of the adiabatic hypothesis. In the Fock–Tani representation, discrete unstable states can be described by state vectors orthogonal to the asymptotic states representing their decay fragments, and a decay/formation interaction is exhibited explicitly as a portion of the total interaction Hamiltonian. This allows a straightforward derivation of a generalized Lippmann–Schwinger “half-collision” differential decay cross section without the need of projection operators. It reduces in first order to the product of a resonance line shape by a Golden Rule matrix element squared. In the general case the line shape is non-Lorentzian and the matrix element factor contains final-state interaction contributions. The exact expression is expected to be applicable to a variety of processes such as predissociation, autoionization, and Auger effect. The derivation employs the van Hove resolvent formalism to exhibit the dependence of the cross section on the complex self energy of the decaying state.     

Attachment-driven morphology evolvement of rectangular ZnO nanowires

The rectangular cross-sectional ZnO nanowires were synthesized in a solution method. An attachment-driven growth mechanism was proposed for the morphology evolvement of ZnO nanocrystals from nanoparticles to nanoplates and eventually to nanowires. Due to the pileup attachment of the nanoplates to recrystallize into nanowires, unique one-dimensional (1D) ZnO nanowires with the rectangular cross section were obtained, which is different from those nanowires in the previous reports. It is the first time the evidence that "oriented attachment" can occur not only for nanoparticles but also for nanoplates was obtained, suggesting that "oriented attachment" is an intrinsic behavior for nanosized materials. According to the growth model proposed based on the direct TEM observations, ZnO nanocrystals can be easily controlled as nanoparticles, nanoplates, or nanowires by tuning the synthetic parameters.     

Single-crystalline, size, and orientation controllable nanowires and ultralong microwires of organic semiconductor with strong photoswitching property

Single-crystalline, precise size-controlled nanowires and ultralong microwires with lengths reaching several millimeters of organic semiconductor 1 were prepared in large scale by cast assembly. The size and density of the nanowires and microwires could be controlled by simply adjusting the concentration of 1 in casting solutions. More importantly, the formation of these nanowires and microwires showed no substrate and solvent dependence and was orientation controllable. Highly reproducible and sensitive photo response characteristics were observed in these nanowires and microwires. Fast and reversible photoswitchers based on multiple or individual single-crystal microwires were fabricated via "multi times gold wire mask moving" technique with switch ratio over 100.     

Microstructures occurring in reduced vanadium dioxide

Slightly oxygen-deficient VO₂ contains small clusters of (121) CS planes which ultimately order into the V_nO_2n?1 series of oxides with increasing degrees of reduction. The fact that CS is limited to (121) planes within this system may be due to a specific degree of ionic relaxation within the CS plane. Nominal compositions near to M_xVO₂ in the AlVO, GaVO, and FeVO systems contain microstructures which are essentially similar to those of the binary system and no new CS plane types are found at temperatures of the order of 1400°K.     

Energy dependence of rotational cross sections

A modified exponential model for rotational state-to-state cross sections is proposed which accounts for most of the observed features for Ar-N₂ at large [Δj] and large total energy E. This empirical form gives rise to non-linear surprisals, and suggests that the prior transition probability, usually taken as a constant, is proportional to E^?1.     

Collision cross sections for protein ions

A method for the determination of cross sections for gas-phase protein ions, based on the energy loss of ions as they pass through a collision gas, is described. A simple model relates the energy loss to the number of collisions and hence the cross section. Results from a Monte Carlo model that support the validity of this approach are described. Experimental cross sections are reported for motilin, ubiquitin, cytochrome c, myoglobm, and bovine serum albumin. Cross sections range from approximately 800 Ų for motilin to approximately 14,000 Ų for bovine serum albumin and generally increase with the number of charges on the ion. Cytochrome c ions from aqueous solution show somewhat smaller cross sections than ions formed from solutions of higher organic content, suggesting that the gas-phase ions may retain some memory of their solution conformation.     

Parametrization of multiply differential cross sections

Multiply differential cross sections for two- and three-electron escape are parametrised in terms of generalised tensorial asymmetry parameters. The analysis is based exclusivly on rotational invariance as an exact symmetry for the experimental set up. No approximate assumptions are made on the correlated dynamics of many- electron systems. Results are valid for any atomic and molecular target. The new parameters may be used to describe experimental and theoretical data in a compact way, but also to link e.g. coincidence and non-coincidence measurements with each other.     

Random-phase approximation for transport cross sections

The random-phase approximation is tested for the first two transport cross sections with several potential functions. Fairly good results are obtained, and the approximation is recommended for exploratory calculations, since it requires very little computational effort.     

Partial photoionization cross sections of molecular oxygen

Measurements of partial photoionization cross sections of O₂ for excitation energies between 20 and 45 eV are reported and compared to a calculation using the Stieltjes-Tchebycheff moment theory. Positive evidence is obtained for a predicted σ-type shape resonance between 1 and 2 eV above threshold in certain ionic-state cross sections. Implications for angular distribution of photoelectrons from an oriented O₂ are discussed.     

State-to-state total cross sections for ion-pair formation

Relative total cross sections are reported for the production of electrons and anions in collisions between an alkali atom (Na, K, Cs) and the molecules O₂ and NO. The formation of electrons is due to autoionization of vibrationally excited O₂^? (gu′ ? 4) respectively NO^? (υ′ ? 1) molecules. The experiments have been performed with fast alkali atom beams in the laboratory energy range of 30–300 eV.     

Measurement of angular dependencies of M X-ray differential cross sections and production cross sections using 5.96 keV photons

The differential cross sections of the emission of M-shell fluorescence X-rays from Tl and Pb have been measured by 5.96 keV photons at seven angles ranging from 50° to 110°. The differential cross section is found to decrease with the increasing emission angle, showing an anisotropic spatial distribution of M-shell fluorescence X-rays. Furthermore, M-shell fluorescence cross sections and the average fluorescence yields were measured for Pt, Au, Hg, Tl, Pb, Bi, Th, and U at an excitation energy of 5.96 keV using a Si(Li) detector. The experimental results of the total M X-ray fluorescence cross sections and M-shell fluorescence yields were compared with the theoretical values.This revised version was published online in November 2005 with corrections to the Cover Date.     

Activation cross sections for the element rhenium

The¹⁸⁵Re(n,)¹⁸²Ta,¹⁸⁷Re(n,)¹⁸⁴Ta,¹⁸⁷Re(n,p)¹⁸⁷W and¹⁸⁷Re(n,2n)^186gRe reaction cross sections included by 13.5–14.7 MeV neutrons were measured by the activition method. The neutron fluences were determined by the cross section of the²⁷Al(n,)²⁴Na reaction. The neutron energies in these measurements were determined by the cross section ratios for⁹⁰Zr(n,2n)^89m+gZr and⁹³Nb(n,2n)^92mNb reactions.