Estimation of dielectric function of biotin-capped gold nanoparticles via signal enhancement on surface plasmon resonance

Biotin-capped gold nanoparticles assembled on flat gold with volume fraction f are studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM) in order to estimate the dielectric function of the gold nanoparticles based on the Maxwell-Garnett (MG) theory. The complex dielectric function (epsilon',epsilon') of the spherical nanoparticles at three representative wavelengths in the vis-near-IR region, i.e., lambda = 543, 632.8, and 1152 nm, is estimated for a surface homogeneously covered with nanoparticles in order to discuss the wavelength dependence of the dielectric function. The SPR response of a surface covered with particles in 2D aggregates is also analyzed. The experimental SPR curve of the particle aggregates deviates from the theoretical predictions, suggesting dipole interactions between particles.     

Dynamic and collective electrochemical responses of tetrathiafulvalene derivative self-assembled monolayers

Electroactive tetrathiafulvalene (TTF)-containing alkanethiol self-assembled monolayers (SAMs) were designed and synthesized to elucidate the relationship between electrochemical responses and film structures. Two TTF derivative molecules having one alkanethiol chain (1) and two alkanethiol chains (2) were utilized to modulate the molecular packing arrangements in the SAMs, and the formation and structure of the SAMs were characterized by surface plasmon resonance spectroscopy (SPR). SPR measurements in various contacting media demonstrated loose packing of SAM 1 and close packing of SAM 2 due to the different space fillings of the molecules. Two successive one-electron redox waves were observed for both SAMs by cyclic voltammetry. The peak widths of the redox waves were strongly dependent on the oxidation states of the TTF moieties, the packing arrangement of the SAMs, and the contacting medium. We found that TTF-based SAMs exhibited collective electrochemical responses induced by dynamic structural changes, depending on the degree of freedom for the component molecules in the SAMs. These results imply that the molecular design, taking into account the electrochemical responses, extends the available range of molecular-based functionalities in TTF-based SAMs.     

Double-layered TiO2-SiO2 nanostructured films with self-cleaning and antireflective properties

Dual function of self-cleaning and antireflection can be created in double-layered TiO2-SiO2 nanostructured films. The film were prepared by (1) layer-by-layer deposition of multilayered SiO2 nanoparticles with polydiallyldimethylammonium (PDDA) cations, (2) layer-by-layer deposition of multilayered titanate nanosheets with polications on PDDA/SiO2 multilayer films, and (3) burning out the polymer and converting titanate nanosheets into TiO2 by hearing at 500 degrees C. The as-prepared films, consisting of a porous SiO2 bottom layer and a dense TiO2 top layer, improved the transmittance of glass or quartz substrates, as demonstrated by transmission spectra collected at normal incidence. The photocatalytic properties of the films were studied by the change of the water contact angle together with the decay of the IR absorption of the hydrocarbon chain of octadecylphosphonic-acid-modified films under 2.6 mW cm-2 UV illumination. Both the antireflective and the photocatalytic properties of the films were dependent on the number of PDDA/nanosheet bilayers deposited. however, excellent surface wettability of the films for water was obtained, independent of the preparation conditions. The experimental findings are discussed in terms of the special structure of the double-layered nanostructured film.     

Mechanical relaxation of single crystal mats of polyethylene in a crystalline dispersion region

Stress-relaxation measurements have been conducted over the temperature range 15°–105°C on mats of single crystals of two linear polyethylene fractions. The single crystals were grown isothermally at several different temperatures. The relaxation modulus was observed to be strain dependent, indicating that the single crystal mats exhibited nonlinearity.

In spite of this appearance of nonlinearity, it was found possible, when the relaxation modulus was extrapolated to zero strain by an appropriate method, to obtain correct relaxation spectra for the mats of single crystals prepared by isothermal crystallization. This spectrum was then used to calculate the dynamic viscoelastic functions and, for the unannealed sample crystallized at 80°C, good agreement was found between experimental results and calculated ones. Two annealed samples showed multiple absorptions and, under these circumstances, strict application of the method of reduced variables for time and temperature was impractical.

The effect of molecular weight on the intensity of the relaxation spectrum was investigated. It was found that the single crystal with the higher molecular weight showed an increased spectrum intensity.

Observations were also made of the effect of increased lamellar thickness on both the relaxation spectra and the dynamic complex moduli and the results obtained on the fractions studied were compared with prior studies in whole polymer.     

Non-upper-semicontinuity of algebraic dimension for families of compact complex manifolds

In this note we show that in a certain subfamily of the Kuranishi family of any half Inoue surface the algebraic dimensions of the fibers jump downwards at special points of the parameter space showing that the upper semicontinuity of algebraic dimensions in any sense does not hold in general for families of compact non-Kähler manifolds. In the Kähler case, the upper semicontinuity always holds true in a certain weak sense.     

Discrete Burgers’ Equation, Binomial Coefficients and Mandala

In discrete Burgers’ equation, time is discretized but space remains continuous. Reduction modulo 2 of discrete Burgers’ equation discretizes also space. This dynamical system generates an elegant pattern known since long time ago. We also propose to show that the Galois groups of particular solutions of Burgers’ equation are abelian. It would imply that the dynamical systems are integrable.