Waveguide-enhanced Raman spectroscopy of trace chemical warfare agent simulants.

We report the measurement of waveguide-enhanced Raman spectra from trace concentrations of four vapor-phase chemical warfare agent simulants: dimethyl methylphosphonate, diethyl methylphosphonate, trimethyl phosphate, and triethyl phosphate. The spectra are obtained using highly evanescent nanophotonic silicon nitride waveguides coated with a naturally reversible hyperbranched carbosilane sorbent polymer and exhibit extrapolated one-σ detection limits as low as 5 ppb. We use a finite-element model to explain the polarization and wavelength properties of the differential spectra. In addition, we assign spectral features to both the analyte and the sorbent, and show evidence of changes to both due to hydrogen bonding.

Preparation of a Proton-Exchange Me mbrane with -SO3H Group Based on Polyethylene and Poly(vinylidene fluoride) Film by Radiation-Induced Graft Polymerization for Proton-Exchange Fuel Cell.

This paper reports the preparation of a proton-exchange membrane (PEM) with sulfonic acid (-SO3H) groups based on polyethylene (PE) films and poly(vinylidene fluoride) (PVdF) films by the radiation-induced graft polymerization (RIGP) of sodium styrene sulfonate (NaSS) in the presence of the polymerizable access agents, such as acrylic acid and pyrollidone in a methanol solution. A PEM with -SO3H based on PE and PVdF films were confirmed by ATR, XPS and contact angle measurements. The water uptake (%), graft yield (%), ion-exchange content (mmol/g), and proton conductivity (S/cm), as well as the current density (mA/cm2), and power density (mW/cm) for PEM with -SO3H groups prepared by RIGP were evaluated. The PEM prepared with the -SO3H groups based on PE and PVdF films can be used as a proton-exchange fuel cell membrane.

Effect of reaction temperatures and media on crystal structure of colloidal nanocrystals synthesized from an aerosol flow system.

The CdSe and CdTe nanocrystals were successfully synthesized from the ultrasonic-assisted aerosol flow system using a surfactant/solvent system of oleic acid (OA)/trioctylphosphine (TOP)/trioctylphosphine oxide (TOPO)/octadecene (ODE). A comprehensive examination on the control of the CdSe and CdTe crystal structures and optical properties was performed as functions of reaction temperatures and amount of reaction media in the aerosol flow system. CdSe nanocrystals with spherical shape and having zinc blende structure were produced. It was found that the crystal structure and shape of CdSe are not affected by reaction temperature. However, it was found that reaction temperature significantly affects the crystal structure and morphology of CdTe. Zero-dimensional CdTe nanocrystals with spherical shape and having zinc blende structure were obtained at the temperature higher than 300 degrees C. Three-dimensional tetrapod-shaped CdTe nanocrystals having wurtzite structure were obtained at the temperature lower than 250 degrees C. Furthermore, the anisotropic growth was observed to be enhanced as increasing the amount of OA used at the temperature of 250 degrees C.

Formation of a protein monomolecular layer by a combined technique of LB and SA methods.

This paper describes a technique developed for the formation of the self-assembled protein monomolecular layer. The main idea is a direct transfer of protein molecules consisting of a Langmuir-Blodgett (LB) film onto the surface of another chemically modified metal substrate and induction of the spontaneous formation of a self-assembled monolayer (SAM) by chemisorption without protein aggregates. In the present experiments, a cytochrome c (cyt c) SAM on a gold substrate was prepared by incubating a EDC/MUA-modified gold substrate overlaid with a cyt c LB film in a phosphate buffer solution. Scanning tunneling microscopy (STM) image of a cyt c SAM shows that the size of cyt c clusters in the most part of the substrate is approximately 5 nm, indicating the cyt c monomolecular layer. The rectifying property of a cyt c monolayer was confirmed to remain by an asymmetric I-V curve in the applied bias from -1 V to 1 V.