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Abstract: High surface area and high dispersion Mo/MCM-41 catalysts were successfully prepared using high-purity silatrane and molybdenum glycolate precursors. The precursors were synthesized using the Oxide One Pot Synthesis (OOPS) process. Mo was loaded onto MCM-41 by impregnation before and after heat treatment. After heat treatment, the catalysts were characterized using DRUV, XRD, FTIR, Laser Raman and BET. The %Mo dispersion was as high as 10 mol% or 0.265 g MoO3/g SiO2 while the structure of MCM-41 was still retained. Bulk MoO3 was observed in the case of Mo-loaded onto the calcined support of MCM-41(c). The Mo-loaded uncalcined silicate MCM-41 support showed better catalytic activity during the peroxidative reaction. [Copyright &y& Elsevier]

Abstract: Pure phase of sillenite structure, Bi12TiO20, was directly synthesized using stoichiometric bismuth (III) nitrate pentahydrate and titanium glycolate by co-precipitation. The influence of pH on the structure of Bi12TiO20 was studied in the pH range of 3–10. The sillenite structure was characterized using XRD and FTIR. The photo-degradation reaction of 4-nitrophenol (4-NP) was used to study photocatalytic activity of Bi12TiO20 as a function of the preparation pH. The rate of decomposition was followed by UV-vis and TOC. The beginning concentration of 4-NP, 44 ppm, decreased to less than 1 ppm within 30 min for all prepared catalysts. It was found that the decomposition rate constant of Bi12TiO20 is six times higher than those of either TiO2 or Bi2O3 under the same conditions. [Copyright &y& Elsevier]

Examines use of supersonically injected pulses of phosphine to achieve uniform and high levels of in situ n-type doping in silicon during molecular beam epitaxy. Application of highly doped semiconductor regions spectroscopy profiles in silicon-doped with phosphine; Results of measured Hall electron concentrations and mobilities.

Focuses on a study which investigated ultraviolet light induced changes in polyimide liquid-cyrstal alignment films. Experimental procedure; Experimental results; Discussion.

Abstract: Silatrane synthesized from inexpensive oxide precursor, silica and TEA was used as the precursor for MCM-41 synthesis at low temperature because of its stability in aqueous solutions. Using cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB) as a template, the resulting meso-structure mimics the liquid crystal phase. Varying the surfactant concentration, ion concentration and temperature of the system, changes the structure of the liquid crystal phase, resulting in different pore structures and surface area. After heat treatment, very high surface area mesoporous silica was obtained and characterized using XRD, BET and TEM. XRD and TEM results show a clear picture of hexagonal structure. The surface area is extraordinarily high, up to more than 2400m2 g−1 at a pore volume of 1.29cm3 g−1. However, the pore volume is up to 1.72cm3 g−1 when the surface area is greater than 2100m2 g−1. [Copyright &y& Elsevier]

Abstract: TS-1 zeolite with high Ti loading was successfully synthesized from low-cost and moisture-stable precursors, titanium glycolate and silatrane, using microwave heating. The effect of composition, viz. tetrapropylammonium ion (TPA+), NaOH, H2O, and reaction conditions, viz. aging time, reaction temperature, and reaction time, was studied. The Si:Ti mole ratios were varied from 100.00 to 5.00 and the extent to which Ti is incorporated into the zeolite framework was evaluated. The TS-1 samples were characterized by XRD, FT-IR, S.E.M. and DR-UV, and confirmed the fingerprint of MFI type zeolite. A small amount of extra-framework titanium dioxide was also identified at a Si:Ti mole ratio of 5.0. Photocatalytic decomposition of 4-nitrophenol (4-NP) was used to test the catalytic activity of the TS-1 samples. All samples showed high catalytic efficiency, which increased with Ti loading. [Copyright &y& Elsevier]

Cubic-phase CeO2 with high surface area was prepared using sol–gel process. The effect of sol–gel parameters, viz. HCl:alkoxide and water:alkoxide molar ratios, indicated that the gelation time increased with acid concentration and the lowest gelation time was found at 55 water:alkoxide molar ratio. The XRD patterns of cerium dioxide at different calcination temperature (300–800°C) and times (1–7h) showed increasing crystallinity as a function of temperature and time, while the scanning electron microscope (SEM) micrographs showed the agglomeration of crystallites to form large particle cerium dioxide at higher calcination temperatures. The Brunauer–Emmett–Teller (BET) specific surface area increased with decreasing the HCl:alkoxide and water:alkoxide molar ratios, calcination temperature and time. The highest surface area was obtained at 0.8:1:55 HCl:alkoxide:water molar ratio and 400°C calcination for 1h (180m2/g). The viscoelastic properties of different HCl:alkoxide ratio solutions were studied using oscillatory shear. The fractal dimension determined from the frequency-scaling exponent of the modulus at the gel point indicated a dense critical gel structure at high HCl ratio and tight structure at low amount of acid. The gel strength increased as a function of acid molar ratio and the 0.8 molar ratio gave the highest gel strength. [Copyright &y& Elsevier]

Mesoporous nanocrystalline titanium dioxide was prepared via the sol–gel technique using titanium glycolate as precursor in 1 M HCl solution at various HCl:H2O ratios. XRD analysis indicates the anatase phase forms at calcination temperatures in the range 600–800 °C. From the average grain sizes, we deduce that the nucleation rate dominates the kinetics at lower temperature, and growth rate becomes the controlling factor at higher temperature for materials prepared at HCl:H2O ratios of 0.28 and 0.33. At higher volume ratios, the growth rate appears to be the dominant factor at all temperatures. The highest specific surface area (BET) obtained was 125 m2/g at the HCl:H2O ratio of 0.28. A small decrease of specific surface area was observed from low to high acid ratio and a substantial decrease from lower to higher temperature. The material calcined at 800 °C was found to consist primarily of spherical particles with diameters smaller than 1 μm. Application of the Winter rheological criteria for the gel point indicates that the gelation time increases with increase of the HCl:H2O volume ratio. The fractal dimension of the critical gel cluster decreases with acid ratio, whereas the gel strength increases with acid ratio. Thus, increase of acidity leads to a less dense but stronger network structure. [Copyright &y& Elsevier]

We describe here the use of liquid-feed flame spray pyrolysis (LF-FSP) to produce high surface area, nonporous, mixed-metal oxide nanopowders that were subsequently subjected to high-throughput screening to assess a set of materials for deNOx catalysis and hydrocarbon combustion. We were able to easily screen some 40 LF-FSP produced materials. LF-FSP produces nanopowders that very often consist of kinetic rather than thermodynamic phases. Such materials are difficult to access or are completely inaccessible via traditional catalyst preparation methods. Indeed, our studies identified a set of Ce1-xZrxO2 and Al2O3-Ce1-xZrxO2 nanopowders that offer surprisingly good activities for both NOx reduction and propane/propene oxidation both in high-throughput screening and in continuous flow catalytic studies. All of these catalysts offer activities comparable to traditional Pt/Al2O3 catalysts but without Pt. Thus, although Pt-free, they are quite active for several extremely important emission control reactions, especially considering that these are only first generation materials. Indeed, efforts to dope the active catalysts with Pt actually led to lower catalytic activities. Thus the potential exists to completely change the materials used in emission control devices, especially for high-temperature reactions as these materials have already been exposed to 1500 °C; however, much research must be done before this potential is verified. [ABSTRACT FROM AUTHOR]

We designed and successfully implemented the use of in situ-synthesized 45-mer oligonucleotide DNA microarrays (XeoChips) for genome-wide expression profiling of Burkholderia xenovorans LB400, which is among the best aerobic polychlorinated biphenyl degraders known so far. We conducted differential gene expression profiling during exponential growth on succinate, benzoate, and biphenyl as sole carbon sources and investigated the transcriptome of early-stationary-phase cells grown on biphenyl. Based on these experiments, we outlined metabolic pathways and summarized other cellular functions in the organism relevant for biphenyl and benzoate degradation. All genes previously identified as being directly involved in biphenyl degradation were up-regulated when cells were grown on biphenyl compared to expression in succinate-grown cells. For benzoate degradation, however, genes for an aerobic coenzyme A activation pathway were up-regulated in biphenyl-grown cells, while the pathway for benzoate degradation via hydroxylation was up-regulated in benzoate-grown cells. The early-stationary-phase biphenyl-grown cells showed similar expression of biphenyl pathway genes, but a surprising up-regulation of C1 metabolic pathway genes was observed. The microarray results were validated by quantitative reverse transcription PCR with a subset of genes of interest. The XeoChips showed a chip-to-chip variation of 13.9%, compared to the 21.6% variation for spotted oligonucleotide microarrays, which is less variation than that typically reported for PCR product microarrays. [ABSTRACT FROM AUTHOR]

We report, for the first time, temperature-dependent intersubband absorption data in doped pseudomorphic InxGa1-xAs/Al0.4Ga0.6As (0≤x≤0.15) multiquantum wells. In this composition range the absorption resonance varies in the range 6–7 μm for 50 Å wells, which agrees extremely well with theoretical calculations. [ABSTRACT FROM AUTHOR]

Far-infrared absorption spectra have been measured for molecular beam epitaxial InAs/Al0.36Ga0.64Sb multiquantum wells by Fourier transform infrared spectroscopy using light incident normal to the layers. The special band lineup for this heterostructure system causes an overlap of the electron and hole states. The measured absorption peak varies in the wavelength range of 5–10 μm in the temperature range of 100–300 K. [ABSTRACT FROM AUTHOR]