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The use of pulsed laser-induced dewetting (PLiD) is reported as a novel approach in the fabrication of Au nanoparticle (NP) catalytic arrays for the growth of Si nanowires (NWs) by chemical vapor deposition using Si[Cl.sub.4] in the presence of [H.sub.2]. On polished Si substrates, PLiD generates Au NP catalysts with long-range order and narrow size distributions. It has been shown that the monodispersed distribution of Au NPs provides consistent diameter control of the as-grown Si NWs. A systematic exploration of the Si NW synthesis time, temperature, and gas flow rates illustrates a level of tunability in terms of morphology, be it arrayed or entangled Si NWs, with varying experimental parameters. An investigation of the effect of growth temperature also showed that Si NWs can be synthesized at temperatures as low as 700 [degrees]C when using Si[Cl.sub.4] as the precursor. The use of porous Si substrates enabled direct observation of the diameter-dependent growth due to the simultaneous presence of three Au NP size distributions. Growth from the small- and medium-sized Au NP catalysts occurred first, followed by that from the large-sized Au NPs, which was only observed at extended times or high Si[Cl.sub.4] flow rates. The delayed onset of growth from the large-sized Au NPs is due to the longer time to achieve Si super-saturation of larger catalyst NPs. The morphology and diameter control of the as-grown Si NWs reported in this work makes this approach potentially useful toward applications such as nanoelectronics, sensors, and lithium ion battery electrodes depending on the desired morphology. Key words: silicon nanowires, chemical vapor deposition, diameter control, Au nanoparticle catalysts, pulsed laser-induced dewetting, 1. Introduction Silicon nanowires (NWs) have been identified as a promising material for a wide range of applications including nanoelectronics, (1,2) biological (3) and chemical (4) sensors, photovoltaic devices, (5,6) [...]

The density functional theory was used to calculate the reaction mechanism and selectivity of nonmetallic single-atom catalysts, such as N, O, and P, doped on graphene in the direct dehydrogenation of propane (PDH). Our results show that the rate-controlling step in PDH varies with the doping atom. We also found that N, O, and P nonmetallic single-atom-doped graphene catalysts showed relatively low adsorption performance for propane and the active site was the C atom adjacent to N, O, and P, rather than the doped atom itself. Interestingly, for the O-doped graphene catalysts, which can reduce the reaction energy harrier hy searching for multiple transition states, and the more transition states in the reaction path, the lower the energy harrier for the reaction rate-controlling step. Finally, the results show that the energy harrier of P-doped propane direct dehydrogenation reflecting the speed control step is the lowest, which is 44.32 kcal*[mol.sup.-1], and the energy barrier of deep dehydrogenation is 53.08 kcal*[mol.sup.-1]; so it has good selectivity. Therefore, the P-doped graphene catalyst has a promising application as a nonmetallic catalyst for the direct PDH, which provides the possibility for the design of cheap and environmentally friendly catalysts. Key words: propane, DFT, direct dehydrogenation, nonmetallic catalyst, graphene, 1. Introduction Propylene occupies an important position in the modern chemical industry and is the main chemical raw material for producing polypropylene, acrylonitrile, and acrylic fibers. (1) With the worldwide [...]

Author(s): Nuntaporn Moonrungsee [sup.1], Somkid Pencharee [sup.2], Jaroon Junsomboon [sup.3], Jaroon Jakmunee [sup.4], Nipat Peamaroon [sup.1] Author Affiliations: (1) grid.443781.d, Department of Chemistry, Faculty of Science and Technology, Rambhai Barni [...], A simple and low cost colorimetric procedure using an Android smartphone was developed for determination of copper(II) in copper supported silica catalysts. The developed software was installed in a smartphone for measuring the intensity of the blue color produced by the reaction between copper(II) and 2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene in an acidic solution. More than one sample can be measured by taking only one photo shot. Under the selected conditions, the linear range from 0 to 5 mg/L was obtained with the detection and quantitation limits of 0.04 and 0.13 mg/L, respectively. The method provided a good precision with the percent relative standard deviation values less than 5%. The percent recoveries were in the range of 97-104%. The results corresponded well with those obtained by atomic absorption spectrophotometry. This developed method is convenient, rapid and simple with an uncomplicated device.

The introduction of single-site catalysts and the use of multiple reactors in the polyolefins industry has opened new routes to design resins with the desirable microstructure to optimize performance in [...]

Abstract: In this study, a rapid and convenient synthesis of quinolines was developed. The reaction involves a one-pot synthesis of pyranoquinoline derivatives from aldehyde, malonitrile, and 8-hydroxyquinoline using DABCO as [...]

Hybrid composite of polyaniline metal oxide composite, polyaniline-dodecyl hydrogen sulfate salt with ferric oxide, was prepared for the first time via simple one-step process of oxidizing aniline with ferric tris(dodecyl sulfate). Ferric tris(dodecyl sulfate) acts as an oxidant, emulsifier, dopant for polyaniline and also source of ferric oxide. Polyaniline salt composites were prepared via aqueous, emulsion, and interfacial polymerization pathways. Polyaniline salt composite was successfully demonstrated as polymer based solid acid catalysts in the ring-opening polymerization of ζ-caprolactone for the first time. This methodology gave low molecular weight poly(ζ-caprolactone) (MW-4035) with highly crystalline polymer of flower petals like morphology in 52 wt% yield (with respect to the amount of ζ-caprolactone used). Advantages of this methodology are the use of easily synthesizable, easily handlable, recyclable, cheaper, and eco-friendly nature of the catalyst., INTRODUCTION In the large field of nanotechnology, conducting polymer matrix based metal oxide nano composites have become a prominent area of current research and development. Composite materials are especially important [...]

Although the chemical and biotechnology industries have preferred to use continuous-flow systems because of their high productivity and efficiency, fine chemical production has been conducted using batch systems because the [...], Chemical manufacturing is conducted using either batch systems or continuous-flow systems. Flow systems have several advantages over batch systems, particularly in terms of productivity, heat and mixing efficiency, safety, and reproducibility (1-4). However, for over half a century, pharmaceutical manufacturing has used batch systems because the synthesis of complex molecules such as drugs has been difficult to achieve with continuous-flow systems (5, 6). Here we describe the continuous-flow synthesis of drugs using only columns packed with heterogeneous catalysts. Commercially available starting materials were successively passed through four columns containing achiral and chiral heterogeneous catalysts to produce (R)-rolipram (7), an anti-inflammatory drug and one of the family of γ-aminobutyric acid (GABA) derivatives (8). In addition, simply by replacing a column packed with a chiral heterogeneous catalyst with another column packed with the opposing enantiomer, we obtained antipole (S)-rolipram. Similarly, we also synthesized (R)-phenibut, another drug belonging to the GABA family. These flow systems are simple and stable with no leaching of metal catalysts. Our results demonstrate that multistep (eight steps in this case) chemical transformations for drug synthesis can proceed smoothly under flow conditions using only heterogeneous catalysts, without the isolation of any intermediates and without the separation of any catalysts, co-products, by-products, and excess reagents. We anticipate that such syntheses will be useful in pharmaceutical manufacturing.

Abstract: Solid niobium oxide treated with phosphoric acid (NbP) was used as a heterogeneous catalyst in the protection of a series of aliphatic alcohols as tetrahydropyranyl (THP) derivatives. Protection of [...]

The article deals with the preparation and characterization of a series of functional polycyanurate (PCN) films obtained from bisphenol E dicyanate (BDECy) by thermal cyclotrimerization in the presence of four different catalysts. Thermal, structural, and dielectrical analyses of PCN films are performed as well as some physical properties such as solubility, adhesion, hardness, and contact angle measurements are studied. Fourier transform infrared spectroscopy results reveal that cyclotri-merized structure is formed from BDECy not only in the presence of catalyst but also free of catalyst. While 55.5% of BDECy is cylotrimerized without catalyst, the conversion of BDECy into triazine significantly increases and reaches to 82.1% and 84.8% for PCNPh1-2 and PCNPh3-2, respectively. Thermogravimetric analysis results reveal that PCN films prepared in the presence of catalyst are thermally stable up to 240 C and exhibit two degradation steps. Dielectric constant and dielectri-cal breakdown strength of the PCN film cyclotrimerized with 1 wt% phenol as catalyst are found to be 3.16 at 1 MHz and 194 kV/mm, respectively, while the catalyst-free PCN film has the dielectric constant of 4.92 at the same frequency. On the other hand, chemical stability, hardness, and adhesion properties of the prepared films are found to be excellent. POLYM. ENG. SCI., 53:662-670, 2013. [C] 2012 Society of Plastics Engineers, INTRODUCTION In the last decades, polycyanurates (PCNs) have attracted much interest due to their excellent thermal stability, low dielectric constant (ζ), high glass transition temperature (Tg) (1-3), improved flame resistance [...]

IN THE FORTHCOMING U.S. presidential and congressional campaigns, I guarantee that we will hear, and not just once, the stock characterization of a candidate as 'a catalyst for change.' You [...]

Nonisothermal crystallization behavior of linear and long chain branched (LCB) polyethylene (PE) samples having similar molecular weight but different long-chain branching densities (LCBD) up to 0.44 C per 1000 carbons was investigated using differential scanning calorimetry (DSC) at various scanning rates. The LCB PE samples were prepared in our high-temperature, high-pressure continuous stirred-tank reactor (CSTR) system using the constrained geometry catalyst. The existence of LCB was found to affect the PE crystallization behavior considerably. The enthalpy of crystallization and the ultimate degree of crystallinity decreased with the increase of LCBD. At the relatively low cooling rates, the small amount of LCB promoted nucleation but restrained chain movement and reduced the crystal growth rate. There was ~ 17% of crystallinity generated from a secondary crystallization. The energy barrier became significant with the LCB structure, resulting in chain diffusion limitations and lower LCB PEs overall crystallization rates than their linear counterpart. POLYM. ENG. SCI., 52:21-34, 2012. © 2011 Society of Plastics Engineers, INTRODUCTION Polyethylene (PE) is one of the largest polymer products in the global market. Various grades of PEs have become commercially available with the aid of substantial developments in catalysis [...]

In this study, we developed an automatic protein hydrolysis system using strong cation-exchange resins as solid acid catalysts. Examining several kinds of inorganic solid acids and cation-exchange resins, we found that a few cation-exchange resins worked as acid catalysts for protein hydrolysis when heated in the presence of water. The most efficient resin yielded amounts of amino acids that were over 70% of those recovered after conventional hydrolysis with hydrochloric acid and resulted in amino acid compositions matching the theoretical values. The solid-acid hydrolysis was automated by packing the resin into columns, combining the columns with a high-performance liquid chromatography system, and heating them. The amino acids that constitute a protein can thereby be determined, minimizing contamination from the environment. 10.1021/ac101718x

Continuous, on-site monitoring of personal exposure levels to occupational chemical hazards in ambient air is a longstanding analytical challenge. Such monitoring is required to institute appropriate health measures but is often limited by the time delays associated with batch air sampling and the need for off-site instrumental analyses. In this work, we report on the first attempt to use the catalytic properties of perfluorosulfonic acid (PSA) membranes to obtain a rapid, selective, and highly sensitive optical response to trimellitic anhydride (TMA) in the gas phase for portable sensor device application. TMA is used as starting material for various organic products and is recognized to be an extremely toxic agent by the National Institute for Occupational Safety and Health (NIOSH). Resercinol dye is shown to become immobilized in PSA membranes and diffusionally constrain an orange brown product that results from acid-catalyzed reaction with more rapidly diffusing TMA molecules. FTIR, UV/ vis, reaction selectivity to TMA versus trimellitic acid (TMLA), and homogeneous synthesis are used to infer 5,7- dihydroxyanthraquinone-2-carboxylic acid as the acylation product of the reaction. The color response has a sensitivity to at least 3 parts per billion (ppb) TMA exposure and, in addition to TMLA, excludes maleic anhydride (MA) and phthalic anhydride (PA). Solvent extraction at long limes is used to determine that the resorcinol extinction coefficient in 1100 EW PSA membrane has a value of 1210 [m.sup.2]/g at 271.01 nm versus a value of 2010 [m.sup.2]/g at 275.22 nm in 50 vol% ethanol/water solution. The hypsochromic wavelength shift and reduced extinction coefficient suggest that the polar perfluorosulfonic acid groups in the membrane provide the thermodynamic driving force for diffusion and immobilization. At a resorcinol concentration of 0.376 g/L in the membrane, a partition coefficient of nearly unity is obtained between the membrane and solution concentrations and a maximum conversion rote of one ambient TMA molecule for every two membrane-immobilized resorcinol molecules is observed in 15 min. 10.1021/ac101356j

Experimental and numerical studies were performed to investigate the simultaneous reduction in N[O.sub.x]and CO for stoichiometric diesel combustion with a three-way catalyst. A single-cylinder engine was used for the experiments and KIVA simulations were used in order to characterize the combustion efficiency and emissions of throttled stoichiometric diesel combustion at 0.7 bar boost pressure and 90 MPa injection pressure. In addition, the efficiency of emission conversion with three-way catalysts in stoichiometric diesel combustion was investigated experimentally. The results showed CO and N[O.sub.x]emissions can be controlled with the three-way catalyst in spite of the fact that CO increases more at high equivalence ratios compared with conventional diesel combustion (i.e., lean combustion). At a stoichiometric operation, the three-way catalyst reduced CO and N[O.sub.x] emissions by up to 95%, which achieves lower emissions compared with conventional diesel combustion or low temperature diesel combustion, while keeping better fuel consumption than a comparable gasoline engine. [DOI: 10.1115/1.4000290] Keywords: group-hole nozzles, GHN, stoichiometric diesel combustion, fuel economy, N[O.sub.x]emission reduction

The hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme is assembled on Au electrodes. It reveals bioelectrocatalytic properties and electrocatalyzes the reduction of [H.sub.2][O.sub.2]. The bioelectrocatalytic functions of the hemin/G-quadruplex DNAzyme are used to develop electrochemical sensors that follow the activity of glucose oxidase and biosensors for the detection of DNA or low-molecular-weight substrates (adenosine monophosphate, AMP). Hairpin nucleic structures that include the G-quadruplex sequence in a caged configuration and the nucleic acid sequence complementary to the analyte DNA, or the aptamer sequence for AMP, are immobilized on Au-electrode surfaces. In the presence of the DNA analyte, or AMP, the hairpin structures are opened, and the hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme structures are generated on the electrode surfaces. The bioelectrocatalytic cathodic currents generated by the functionalized electrodes, upon the electrochemical reduction of [H.sub.2][O.sub.2], provide a quantitative measure for the detection of the target analytes. The DNA target was analyzed with a detection limit of 1 x [10.sup.-12] M, while the detection limit for analyzing AMP was 1 x [10.sup.-6] M. Methods to regenerate the sensing surfaces are presented. 10.1021/ac100095u

Traditional homogeneous water oxidation catalysts are plagued by instability under the reaction conditions. We report that the complex [[[Co.sub.4][([H.sub.2]O).sub.2][([PW.sub.9][O.sub.34]).sub.2]].sup.10- ], comprising a [Co.sub.4][O.sub.4] core stabilized by oxidatively resistant polytungstate ligands, is a hydrolytically and oxidative[y stable homogeneous water oxidation catalyst that self-assembles in water from salts of earth-abundant elements (Co, W, and P). With [[Ru[(bpy).sub.3]].sup.3+] (bpy is 2,2'-bipyridine) as the oxidant, we observe catalytic turnover frequencies for [O.sub.2] production [greater than or equal to]5 [s.sup.-1] at pH = 8. The rate's pH sensitivity reflects the pH dependence of the four-electron [O.sub.2]-[H.sub.2]O couple. Extensive spectroscopic, electrochemical, and inhibition studies firmly indicate that [[[Co.sub.4][([H.sub.2]O).sub.2][([PW.sub.9][O.sub.34]).sub.2]].sup.10-] is stable under catalytic turnover conditions: Neither hydrated cobalt ions nor cobalt hydroxide/oxide particles form in situ. 10.1126/science.1185372

Pt-Ag nanoparticles were prepared on a glassy carbon (GC) surface by pulsed electrodeposition and tested using cyclic voitammetry and scanning electrochemical microscopy (SECM) with respect to their possible use as catalyst material for oxygen reduction in 400 mM HCl solution. For comparison, a Pt catalyst was investigated under similar conditions. The redox competition mode of scanning electrochemical microscopy (RC-SECM) was adapted to the specific conditions caused by the presence of CI ions and used to visualize the local catalytic activity of the Pt-Ag deposits. Similarly prepared Pt deposits were shown to dissolve underneath the SECM tip. Pt-Ag composites showed improved long-term stability toward oxygen reduction as compared with Pt even under multiple switching off to open-circuit potential in 400 mM HCl. 10.1021/ac902620g