A microfluidic platform for integrated synthesis and dynamic light scattering measurement of block copolymer micelles

Microfluidic devices were developed that integrate the synthesis of well defined block copolymers and dynamic light scattering (DLS) measurement of their micelle formation. These metal devices were designed to operate in contact with organic solvents and elevated temperatures for long periods, and thus were capable of continuous in-channel atom transfer radical polymerization (ATRP) of styrene and (meth)acrylate homopolymers and block copolymers. These devices were equipped with a miniaturized fiber optic DLS probe that included several technology improvements, including a measurement volume of only 4 microlitres, simple alignment, and reduced multiple scattering. To demonstrate the integrated measurement, poly(methyl methacrylate-b-lauryl methacrylate) and poly(methyl methacrylate-b-octadecyl methacrylate) block copolymers were processed on the device with a selective solvent, dodecane, to induce micelle formation. The in situ DLS measurements yielded the size and aggregation behavior of the micelles. For example, the block copolymer solutions formed discrete micelles (D(H) approximately = 25 nm) when the corona block was sufficiently long (f(MMA) < 0.51), but the micelles aggregated when this block was short. This study demonstrates the utility of these new devices for screening the solution behavior of custom synthesized polymeric surfactants and additives.     

Detection of OH stretching mode of CH3OH chemisorbed on Ni3+ and Ni4+ by infrared photodissociation spectroscopy

Structures of nickel cluster ions adsorbed with methanol, Ni3+ (CH3OH)m (m = 1-3) and Ni4+ (CH3OH)m (m = 1-4) were investigated by using infrared photodissociation (IR-PD) spectroscopy based on a tandem-type mass spectrometer, where they were produced by passing Ni3,4+ through methanol vapor under a multiple collision condition. The IR-PD spectra were measured in the wavenumber region between 3100 and 3900 cm-1. In each IR-PD spectrum, a single peak was observed at a wavenumber lower by approximately 40 cm-1 than that of the OH stretching vibration of a free methanol molecule and was assigned to the OH stretching vibrations of the methanol molecules in Ni3,4+ (CH3OH)m. The photodissociation was analyzed by assuming that Ni3,4+ (CH3OH)m dissociate unimolecularly after the photon energy absorbed by them is statistically distributed among the accessible modes of Ni3,4+ (CH3OH)m. In comparison with the calculations performed by the density functional theory, it is concluded that (1) the oxygen atom of each methanol molecule is bound to one of the nickel atoms in Ni3,4+ (defined as molecular chemisorption), (2) the methanol molecules in Ni3,4+ (CH3OH)m do not form any hydrogen bonds, and (3) the cross section for demethanation [CH4 detachment from Nin+ (CH3OH)] is related to the electron density distribution inside the methanol molecule.     

Rare direct imidation of aromatic metallacycle by reaction of CpCo(dithiolene) complex with N-halosuccinimide

The aromatic [CpCo(S₂C₂(R)(H))] (R = Ph, Me, 9-phenanthryl, H) complexes reacted with N-halosuccinimides (NXS; X = Cl, Br, I) in carbon tetrachloride at room temperature to undergo the N-succinimide substitution reaction on the dithiolene ring, but no halogenated dithiolene complex was obtained. The imidation products [CpCo(S₂C₂(R)(N-sccinimide))] were yielded up to 64% where X = I and R = 9-phenanthryl. The reaction of [CpCo(S₂C₂(Ph)(H))] with N-bromophthalimide (NBP) also gave the imidation product [CpCo(S₂C₂(Ph)(N-phthalimide))]. This is the rare direct imidation reaction to an aromatic metallacycle by NXS. The reaction of [CpCo(S₂C₂H₂)] (R = H) with NIS afforded the double imidation product. One by-product in this reaction was the dithiolene-dithiolene homo-coupling product [CpCo(S₂C₂(R))]₂ (R = Ph, Me, 9-phenanthryl). The microwave-enhanced (MW) reactions were attempted in the carbon tetrachloride solution. Although the solution temperature increased up to only 43 °C by MW irradiation, the imidation reaction worked with short reaction time.     

Micro-channel fabrication by femtosecond laser to arrange neuronal cells on multi-electrode arrays

The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO₃ chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in 〈101〉 direction. Local vibrational mode analysis confirms the presence of N–H and Ge–F vibrational modes in addition to Ge–O stretching modes. Energy dispersive studies reveal the presence of hexagonal α-phase GeO₂ crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow photoluminescence at room temperature.     

Formal synthesis of (−)-oleocanthal by means of a SmI2-promoted intramolecular coupling of bromoalkyne with α,β-unsaturated ester

A novel approach to the synthesis of (?)-oleocanthal starting from d-ribose, in which a SmI₂-promoted intramolecular coupling of bromoalkyne with α,β-unsaturated ester is a key step, has been developed.     

Highly sensitive chemiluminescence flow-injection detection of the red tide phytoplankton Heterosigma carterae

Two chemiluminescent flow-injection analysis systems for the detection of the red tide Phytoplankton Heterosigma carterae (formerly known as Heterosigma akashiwo) have been developed. In one system, the superoxide (O⁻₂) released by H. carterae reacts with 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]-pyrazin-3-one (MCLA), a superoxide specific probe. In the other system, the hydrogen peroxide released by H. carterae reacts with luminol catalyzed by Arthromyces ramosus peroxidase (ARP). The chemiluminescence is detected by a photomultiplier tube. This system is capable of the rapid determination of H. carterae; the time required for one measurement cycle is ca. 2 min using MCLA-dependant luminescence or 1 min in luminol/ARP luminescence. A linear response was observed from 10² to 10⁵ cells ml⁻¹ H. carterae. Several other species of phytoplankton gave no response using this system. The detection limit of this method is suitable for detecting H. carterae in the early stage of red tide formation.