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21.
Ghosh R Shen X Villegas JC Ding Y Malinger K Suib SL 《The journal of physical chemistry. B》2006,110(14):7592-7599
Manganese oxide octahedral molecular sieves having 2 x 2 tunnel structure (OMS-2) and synthesized by different methods were used for studying styrene oxidation with tert-butyl hydroperoxide (TBHP) as the oxidant. The catalytic activity of the as-synthesized OMS-2 materials was investigated. The physical and chemical properties of the OMS-2 materials are related to their activity in styrene oxidation. This particular study emphasizes the acid-base properties and the porous nature of these materials, and their role in styrene oxidation. Results of styrene oxidation reveal that acidity coupled with high porosity play a crucial role in these catalytic reactions. A desired acidity coupled with pore volume found in OMS-2 synthesized by reflux methods (OMS-2(R)) and high-temperature methods (OMS-2(HT)) produces materials with higher styrene conversion and styrene oxide selectivity when compared with OMS-2 synthesized by solvent free (OMS-2(S)), microwave (OMS-2(MW)), or hydrothermal methods (OMS-2(HY)). Transition metal doped OMS-2 catalysts show better selectivity of styrene oxide when compared to their undoped catalysts. 相似文献
22.
A simple one-pot method has been developed to deposit discreet nanometer line formations on silicon substrates without any surface pretreatment starting with vanadium pentoxide sol-gels. These vanadium suspensions were made by hydrolyzing amorphous V2O5 in water. The properties of the vanadium clusters were determined through X-ray diffraction, elemental analyses, pH calculations, and concentration calculations. Morphology of the lines was examined with optical microscopy, atomic force microcoscopy, and scanning electron microscopy. Infrared spectroscopy was used to inspect the organic components. The vanadium sol-gel used formed discreet and regular lines with high reproducibility and on the same order of magnitude as other patterning techniques. Previous research with a low solubility, 8 g/L, metal oxide for line, ring, or helix formation has not been found in the literature; this work could lead to novel applications of metal oxides such as porous catalysts, battery materials, and resistive electronic materials. 相似文献
23.
Ligand‐Assisted Co‐Assembly Approach toward Mesoporous Hybrid Catalysts of Transition‐Metal Oxides and Noble Metals: Photochemical Water Splitting 下载免费PDF全文
Dr. Ben Liu Chung‐Hao Kuo Jiejie Chen Zhu Luo Srinivas Thanneeru Dr. Weikun Li Wenqiao Song Sourav Biswas Prof. Steven L. Suib Prof. Jie He 《Angewandte Chemie (International ed. in English)》2015,54(31):9061-9065
A bottom‐up synthetic approach was developed for the preparation of mesoporous transition‐metal‐oxide/noble‐metal hybrid catalysts through ligand‐assisted co‐assembly of amphiphilic block‐copolymer micelles and polymer‐tethered noble‐metal nanoparticles (NPs). The synthetic approach offers a general and straightforward method to precisely tune the sizes and loadings of noble‐metal NPs in metal oxides. This system thus provides a solid platform to clearly understand the role of noble‐metal NPs in photochemical water splitting. The presence of trace amounts of metal NPs (≈0.1 wt %) can enhance the photocatalytic activity for water splitting up to a factor of four. The findings can conceivably be applied to other semiconductors/noble‐metal catalysts, which may stand out as a new methodology to build highly efficient solar energy conversion systems. 相似文献
24.
Ching S Kriz DA Luthy KM Njagi EC Suib SL 《Chemical communications (Cambridge, England)》2011,47(29):8286-8288
Reactions between MnSO(4) and KMnO(4) in the presence of carboxylic acids provide a facile, one-pot route to nanostructured manganese oxides with high surface areas. Acetic and propionic acid induce formation of hierarchical nanosphere morphologies whereas butyric acid promotes assembly of hollow spheres. The materials are active catalysts for CO oxidation. 相似文献
25.
SL Mironov E Skorova G Taschenberger N Hartelt VO Nikolaev MJ Lohse S Kügler 《BMC neuroscience》2009,10(1):29-11
Background
cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca2+ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before. 相似文献26.
PF Hendrix SL Lachnicht MA Callaham X Zou 《Rapid communications in mass spectrometry : RCM》1999,13(13):1295-1299
Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
27.
K. J. Jordan S. L. Suib 《Journal of polymer science. Part A, Polymer chemistry》2000,38(19):3690-3696
The statistical product distribution for a linear polydisperse polymer of finite molecular weight was included into the statistical analysis for a system undergoing random chain scission showing the effect of volatilization of species other than monomer. Two sets of equations were derived. One set is for the nonvolatile fraction; the other is for the volatile fraction. Within each set there are three equations, one for the number of polymer molecules, the second for the molar (or number) fraction, and the third for the weight fraction of polymer molecules containing a specific number of repeat units. As degradation proceeds the polydispersity index should converge to a value of 1 rather than 2, which has been reported previously. The expected effects of polydispersity, number‐average degree of polymerization, and volatility were treated individually, and we determined that the molecular weight of a polymer has no theoretical influence on the product distribution. As for the effect of volatility, we determined that only the volatile product distribution would change. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3690–3696, 2000 相似文献
28.
Li WN Yuan J Gomez-Mower S Sithambaram S Suib SL 《The journal of physical chemistry. B》2006,110(7):3066-3070
A new and facile route is reported to manipulate the self-assembly synthesis of hierarchically ordered Rb-OMS-2 and pyrolusite with an interesting flowerlike morphology by a direct and mild reaction between rubidium chromateand manganese sulfate without any organic templates. The crystal forms, morphologies, and tunnel sizes of the obtained OMS materials can be controlled. A mechanism for the growth of manganese dioxides with flowerlike architectures was proposed. The obtained products exhibit potential for use in catalysis and other applications. 相似文献
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30.
Jian Luo Steven L. Suib Yuji Hayashi Hiroshige Matsumoto 《Research on Chemical Intermediates》2000,26(9):849-874
Plasma-induced water splitting at atmospheric pressure has been studied with a novel fan-type Pt reactor and several tubular-type
reactors: an all-quartz reactor, a glass reactor, and three metal reactors with Pt. Ni, and Fe as electrodes. Reaction products
have been analyzed by using GC (gas chromatography) and Q-MS (quadrupole mass spectrometry). Optical emission spectroscopic
studies of the process have been carried out by employing a CCD (charge-coupled device) detector. Water splitting with tubular
quartz and glass reactors is probably non-catalytic. However, a heterogeneous catalytic function of surface of metal electrodes
has been observed. The variation of hydrogen yield (YH) and energy efficiency (Ee) with operational parameters such as input voltages (Uin), flow rates of carrier gas (FHe), and concentrations of water (CW) has been examined. Plasma-induced water splitting can be described with a kinetic equation of-dCw/dt = kCW
0.2. The rate constants at 3.25 kV are 2.8 × 10−4, 3.5 × 10−3, and 3.4 × 10−2 mol0.8L−0.8 min−1 for tubular glass reactor, a tubular Pt reactor, and a fan-type Pt reactor, respectively. A CSTR (continuous-stirred tank
reactor) and PFR (piston-flow reactor) model have been applied to a fan-type reactor and tubular reactor, respectively. A
mechanism on the basis of optical emission spectroscopic data has been obtained comprising the energy transfer from excited
carrier gas species to water molecules, which split via radicals of HO·, O·, and H· to form H2 and O2. The fan-type Pt reactors exhibit highest activity and energy efficiency among the reactors tested. Higher yields of hydrogen
are achieved at higher input voltages, low flow rates, and low concentrations of water (YH = 78 % at Uin of 3.75 kV, FHe of 20 mL/min, and CW of 0.86 %). The energy efficiency exhibits an opposite trend (Ee = 6.1 % at Uin of 1.25 kV, FHe of 60 mL/min and CW of 3.1 %). 相似文献