Morphology of polythiophene and polyphenyl films produced via surface polymerization by ion-assisted deposition

Conducting polymer films are grown by either mass-selected or non-mass-selected, hyperthermal thiophene ions coincident on a surface with a thermal beam of organic monomers of either alpha-terthiophene (3T) or p-terphenyl (3P) neutrals. Previous experiments verified polymerization of both 3T and 3P by 200 eV C(4)H(4)S(+) during surface polymerization by ion-assisted deposition (SPIAD). A wide variety of structures are observed by scanning electron microscopy to form in the SPIAD polythiophene and polyphenyl films. These structures include microscale islands, lamellar structures, fractal-like growth patterns, and nanoscale crystallites. Some of the deposited films diffract X-rays while others show electron micrographs of crystallites. The variation of these patterns with deposition conditions clearly indicate that ion-induced polymerization mediates film morphology through control of ion energy and ion/neutral ratio. Furthermore, these ion-assisted events mediate important thermal processes such as sublimation.     

Identification of a novel series of alkylitaconic acids in wood cultures of Ceriporiopsis subvermispora by gas chromatography/mass spectrometry.

A novel series of long-chain unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid has been identified by gas chromatography/mass spectrometry during in vitro decay of eucalypt wood by the white-rot basidiomycete Ceriporiopsis subvermispora. The major compounds were identified as tetradecyl-, 7-hexadecenyl- and hexadecylitaconic acids by their mass fragmentation patterns. Other members of the same compound series, identified as dodecanyl-, tridecanyl-, tetradecenyl-, pentadecanyl-, octadecenyl- and octadecanylitaconic acids, were present in very minor amounts or traces. Whereas hexadecenylitaconic acid has already been reported in cultures of C. subvermispora, to our knowledge this is the first report of the presence of the other alkylitaconic acids in fungal cultures. These new alkylitaconic-type metabolites may constitute a source for peroxidizable lipids involved in lignin degradation during wood decay by C. subvermispora and other white-rot basidiomycetes.     

Quenching of giant hysteresis effects in La(1-z)Y(z)Hx switchable mirrors

Hydrogen atoms adsorbed on TiO2(110)-(1x1) surfaces have been characterized by scanning tunneling microscopy (STM) combined with electron stimulated desorption (ESD) technique. Certain amounts of H atoms are unexpectedly found on the TiO2 surfaces annealed at 900 K. Two forms of adsorption were discriminated in STM images from the different sensitivity to ESD and tentatively assigned to hydroxyl-type (O-H) and hydride-type (Ti-H) species.     

Lead Sulfide Nanocrystal-Polymer Composites for Optoelectronic Applications

Summary: Nanocomposite films were prepared by two methods in which lead sulfide (PbS) nanocrystals were contained in an organic matrix. One method used a wet chemical synthesis of the nanocrystals in the direct presence of a polymer, where the polymer controlled nanocrystal growth. The second method was gaseous deposition of nanocrystals into the organic phase. The two methods were similar in that the nanocrystals in the composites were free from surfactant capping layers that otherwise would add an interfacial region between the nanocrystal and the organic matrix. The gaseous deposition technique had several advantages over the wet chemical synthesis in that it allowed direct control over nanocrystal size and density, improved flexibility in the choice of organic phase, and was compatible with lithographic methods.     

L-asparaginase fromErwinia carotovora

A large-scale process was developed to purify L-asparaginase from submerged cultures of Erwinia carotovora. Cells from 880 L of fermentation broth were harvested and washed using a plate and frame type filter press. A cellular acetone powder was prepared from the washed cells by suspending the cells twice in acetone and the residual acetone was removed by washing the acetone powder in the filter press with 10 mM phosphate buffer (pH 7.0). The cellular acetone powder was extracted with 10 mM borate buffer at pH 9.5. The enzyme-rich borate extract was recovered by filtration and clarified by an in-line bag filter. The filtrate was adjusted to pH 7.5 and filtered through a 1-micron bag filter precoated with Celite and then through a 0.22-micron cartridge filter. The cell-free extract, containing 21 x 10(6) IU of enzyme and 448 g of total protein, was applied to an L-asparagine Sepharose 6 Fast Flow affinity column (9 L) using a bag filter loaded with Cell Debris Remover as an in-line prefilter. The affinity gel was prepared by coupling L-Asn at pH 9.0 to epoxy-activated Sepharose 6 Fast Flow beads. A total of 14 x 10(6) IU of enzyme (35 g protein) was eluted at pH 9.0 in 10.5 L. The eluted enzyme was determined to be greater than 90% pure using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The total process time from whole broth to affinity column elution was 68 h and the enzyme yield was 38%. This improved process for the 880 L fermentation broth produced a cell-free extract of high specific activity, shortened the process time, increased the column capacity, and yielded a product with high purity.     

Photoemission studies of polythiophene and polyphenyl films produced via surface polymerization by ion-assisted deposition

Conducting polymer films are grown by mass-selected, hyperthermal thiophene ions coincident on a surface with a thermal beam of organic monomers of either alpha-terthiophene (3T) or p-terphenyl (3P) neutrals. Mass spectrometry and X-ray photoelectron spectroscopy previously verified polymerization of both 3T and 3P by 200 eV C(4)H(4)S(+) during surface polymerization by ion-assisted deposition (SPIAD). The electronic structure of these films are probed here by ultraviolet photoelectron spectroscopy (UPS) and polarized near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and compared with similar spectra of evaporated films. The conducting polymer films formed by SPIAD display new valence band features resulting from a reduction in both their band gap and barrier to hole injection, which are calculated from the occupied and unoccupied valence band states measured by UPS and NEXAFS. These changes in film electronic structure result from an increase in the electron conjugation length and other changes in film structure induced by SPIAD.