Dynamics of formation of CN(B2Σ+) fragment from HCN and DCN in an argon afterglow

The dissociative excitation of HCN and DCN producing CN(B²Σ⁺) in collision with Ar(³P_0,2) was investigated in a flowing afterglow. The Δν = 0, ?1, and ?2 sequences of the CN(BX) violet emission were analyzed by computer simulation, and the vibrational and rotational distributions of the CN(B²Σ⁺) fragment were obtained. Possible reaction pathways were studied on the basis of a linear surprisal analysis of the observed distributions and their isotope effects.     

Determination of molybdenum in natural waters after selective adsorption on sephadex gel

Molybdenum(VI) ions are adsorbed on Sephadex G-25 gel at pH 3.5. and are desorbed reversibly with a complexing agent, EDTA. The adsorbability is much greater than that for boron(III) and vanadium(V). Large amounts of sodium chloride have little effect on the adsorption. Molybdenum concentrations in natural waters, especially in seawater, can be determined with good precision and accuracy after selective preconcentration of molybdenum by a Sephadex G-25 gel column. The detection limit for 250-ml water samples is about 1 μg l^-1 by atomic absorption spectrometry or by spectrophotometry with bromopyrogallol red as reagent.     

Analysis of the effect of interfacial slippage on the elastic moduli of a particle-filled polymer

An attempt was made to study the effect of interfacial slippage on the filler reinforcement based on the boundary condition that the constituents of a particle-filled composite can slip relative to each other, but no cavities are formed at the interfaces. The elastic field satisfying these conditions is derived using the linear theory of elasticity and the effective elastic moduli of the composite are calculated. The following assumptions are made: (1) Filler particles are spherical, (2) fillers are completely dispersed, and (3) the volume fraction of fillers is sufficiently small that the interaction among fillers may be neglected. The expression for the shear modulus of the composite μ^**, which is derived here, is consistent with the viscosity of a suspension which has been derived by Oldroyd. Experiments who that the increase of Young's modulus by glass beads (GB) is lower in polystyrene (PS) than in epoxy resin (Ep). The reinforcement in Ep-GB systems can be estimated by the well known formula derived assuming perfect adhesion. However, the reinforcement in PS-GB systems is in rather good agreement with the formula derived here assuming interfacial slippage.     

Photoreflectance spectroscopy of the chalcopyrite semiconductor <Emphasis Type="Bold">AgInS</Emphasis><Subscript>2</Subscript> for ordinary and extraordinary rays

Photoreflectance spectra have been measured on the chalcopyrite semiconductor silver indium disulfide (\(\hbox {AgInS}_{2}\)) for light polarization \({\varvec{E}}\) perpendicular (\({\varvec{E}} \bot {c}\)) and parallel to the c-axis (\({\varvec{E}} \vert \vert {c}\)) at temperature between 10 and 300 K. The measured photoreflectance spectra revealed distinct structures at 1.8–2.1 eV. The lowest bandgap energies \(E_{0A}\), \(E_{0B}\), and \(E_{0C}\) of \(\hbox {AgInS}_{2}\) show unusual temperature dependence at low temperatures (\(\le\)140 K). The \(E_{0\alpha }\) (\(\alpha =A, B, C\)) is found to increase with increasing temperature from 10 to \(\sim\)140 K and decreases with a further increase in temperature. This result has been successfully explained by taking into account the effects of thermal expansion and electron–phonon interaction. The spin–orbit and crystal-field splitting parameters of \(\hbox {AgInS}_{2}\) are determined to be \(\Delta _{{\mathrm{so}}}=38\) meV and \(\Delta _{{\mathrm{cr}}}=-168\) meV at T = 10 K, respectively, and are discussed from an aspect of the electronic energy band structure consequences. The temperature dependence of spin–orbit and crystal-field splitting parameters of \(\hbox {AgInS}_{2}\) was also presented.     

Optical response of mesoporous synthetic opals to the adsorption of chemical species

We have demonstrated the fabrication of a colloidal crystalline array (synthetic opal) from monodispersed mesoporous silica spheres (MMSS) and the control of its optical response simply by changing the amount of benzene vapor adsorbed into the pores of MMSS. It was revealed that the refractive index of the colloidal crystal of MMSS showed an 11.7% increase by taking advantage of benzene adsorption, and thereby, the structural color changed reversibly. We also conducted the same measurement on silica spheres without mesopores and observed no change in the refractive index or the structural color. This optical response gives rise to the possibility of using MMSS colloidal crystals not only for controlling light reflection but also as sensing devices based on color change due to vapor adsorption. We have also incorporated an organic dye, the porphyrin derivative alpha,beta,chi,delta,-tetrakis(1-methylpyridinium-4-yl)porphyrin rho-toluenesulfonate (TMPyP), into the pores of MMSS. By adopting an electrophoretic deposition process in ethanol, periodic arrays fabricated from TMPyP-MMSS conjugates with absolute zeta-potentials near zero were obtained. The Bragg diffraction peak of the colloidal crystalline array shifted to longer wavelengths due to an increase in the refractive index with increasing amounts of TMPyP adsorbed in the pores. The current work demonstrates the new possibility of creating colloidal crystals from MMSS with mesopores filled with various kinds of adsorbates to control the optical response effectively.     

Environmentally friendly synthesis of highly monodisperse biocompatible gold nanoparticles with urchin-like shape

We report a facile and environmentally friendly strategy for high-yield synthesis of highly monodisperse gold nanoparticles with urchin-like shape. A simple protein, gelatin, was first used for the control over shape and orientation of the gold nanoparticles. These nanoparticles, ready to use for biological systems, are promising in the optical imaging-based disease diagnostics and therapy because of their tunable surface plasmon resonance (SPR) and excellent surface-enhanced Raman scattering (SERS) activity.