bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards New Molecular Photocatalysts for CO2 Reduction: Photo‐Induced Electron Transfer versus CO Dissociation within [Os(NN)(CO)2Cl2] Complexes
Authors: Chauvin Jérôme , Lafolet Frédéric , Chardon‐Noblat Sylvie , Deronzier Alain , Jakonen Minna , Haukka Matti 
Published: March 2011

AbstractOptical excitation in the visible region of trans‐(Cl)‐[Os(bpy)(CO)2Cl2] (bpy=2,2′‐bipyridine; C1) and trans‐(Cl)‐[Os(dmbpy)(CO)2Cl2] (dmbpy=4,4′‐dimethyl 2,2′‐bipyridine; C2) is known to induce the common CO dissociation reaction. However, the quantum yield of the reactions is less than 0.15, although C1 and C2 display pronounced photoluminescence in the visible region at room temperature with a lifetime of few tens of nanoseconds. Taking into account the characteristics of their emitting state, we have investigated the capability of C1 and C2 to act as a photosensitiser in redox reactions in different solvents (MeCN, PrCN and DMF). The efficient oxidation and reduction of both complexes under continuous irradiation in the presence of a sacrificial electron acceptor or donor is reported here. The photo‐induced transformations and the nature of the resulting compounds were analysed by UV/Vis and IR spectroscopies and cyclic voltammetry. Photo‐induced oxidation of C1 and C2 leads to the corresponding monocarbonyl oxidised species, whereas photo‐induced reduction under argon leads mainly to the formation of the corresponding Os‐bonded molecular wires P1 and P2 after exchange of two electrons associated with the loss of two chloro ligands. The chemical yield of the latter reaction (around 65 %) becomes quantitative by adding [Ru(bpy)3]2+ as an external redox photosensitiser. This behaviour has been used to photocatalyse the two electron, two proton conversion of CO2 to CO. Turnover numbers (TON) of 11.5 and 19.5 have been obtained respectively for C1 and C2 after 4.5 h of irradiation under CO2 in DMF with triethanolamine as the electron donor. TON can be slightly increased by adding [Ru(bpy)3]2+ to the solution.
Ti/Pd Bimetallic Systems for the Efficient Allylation of Carbonyl Compounds and Homocoupling Reactions
Authors: Millán Alba , Campaña Araceli G. , Bazdi Btissam , Miguel Delia , Álvarez de Cienfuegos Luis , Echavarren Antonio M. , Cuerva Juan M. 
Published: March 2011

AbstractThe allylation, crotylation and prenylation of aldehydes and ketones with stable and easily handled allylic carbonates is promoted by a Ti/Pd catalytic system. This Ti/Pd bimetallic system is especially convenient for the allylation of ketones, which are infrequent substrates in other related protocols, and can be carried out intramolecularly to yield five‐ and six‐membered cyclic products with good stereoselectivities. In addition, Ti/Pd‐mediated reductions and Würtz‐type dimerisation reactions can be readily carried out from allyl carbonates and carboxylates.
Thermal Activation of NH Bonds by Transition‐metal Oxide Cations: Does a Hierarchy Exist in the First Row?
Authors: Kretschmer Robert , Zhang Xinhao , Schlangen Maria , Schwarz Helmut 
Published: March 2011

AbstractThe thermal reactions of first‐row transition‐metal oxide cations [MO]+ (M=Sc–Ni, Zn) with ammonia have been studied by gas‐phase experiments and computational methods. The activation of NH bonds is brought about by the monoxides of the middle and late 3d metals Mn–Ni and Zn. The two primary reaction channels correspond to dehydration, which leads to [M(NH)]+, and hydrogen‐atom abstraction to form [M(OH)]+. Oxygen‐atom transfer from [MO]+ to NH3 to produce neutral or ionized hydroxylamine was observed as a minor channel for some of the late transition‐metal oxides. The computational analysis of these reactions, which was aimed at elucidating the reaction mechanisms and to uncover possible periodic trends across the first row, have been performed for the couples [MO]+/NH3 (M=Sc–Zn). Dehydration is found to be endothermic for the oxides of scandium to vanadium and exothermic for the other systems. Hydrogen‐atom abstraction becomes exothermic starting with [MnO]+ and, finally, oxygen‐atom transfer is feasible for the cationic oxides of nickel to zinc.
Novel Cinnamyl Hydroxyamides and 2‐Aminoanilides as Histone Deacetylase Inhibitors: Apoptotic Induction and Cytodifferentiation Activity
Authors: Valente Sergio , Tardugno Maria , Conte Mariarosaria , Cirilli Roberto , Perrone Andrea , Ragno Rino , Simeoni Silvia , Tramontano Anna , Massa Silvio , Nebbioso Angela , Miceli Marco , Franci Gianluigi , Brosch Gerald , Altucci Lucia , Mai Antonello 
Published: March 2011

AbstractFour novel series of cinnamyl‐containing histone deacetylase (HDAC) inhibitors 1–4 are described, containing hydroxamate (1 and 3) or 2‐aminoanilide (2 and 4) derivatives. When screened against class I (maize HD1‐B and human HDAC1) and class II (maize HD1‐A and human HDAC4) HDACs, most hydroxamates and 2‐aminoanilides displayed potent and selective inhibition toward class I enzymes. Immunoblotting analyses performed in U937 leukemia cells generally revealed high acetyl‐H3 and low acetyl‐α‐tubulin levels. Exceptions are compounds 3 f–i, 3 m–o, and 4 k, which showed higher tubulin acetylation than SAHA. In U937 cells, cell‐cycle blockade in either the G2/M or G1/S phase was observed with 1–4. Five hydroxamates (compounds 1 h–l) effected a two‐ to greater than threefold greater percent apoptosis than SAHA, and in the CD11c cytodifferentiation test some 2‐aminoanilides belonging to both series 2 and 4 were more active than MS‐275. The highest‐scoring derivatives in terms of apoptosis (1 k, 1 l) or cytodifferentiation (2 c, 4 n) also showed antiproliferative activity in U937 cells, thus representing valuable tools for study in other cancer contexts.
Genetic variation in the transforming growth factor‐β signaling pathway and survival after diagnosis with colon and rectal cancer
Authors: Slattery Martha L. , Lundgreen Abbie , Herrick Jennifer S. , Wolff Roger K. , Caan Bette J. 
Published: March 2011

AbstractBACKGROUND:The transforming growth factor‐β (TGF‐β) signaling pathway is involved in many aspects of tumorigenesis, including angiogenesis and metastasis. The authors evaluated this pathway in association with survival after a diagnosis of colon or rectal cancer.METHODS:The study included 1553 patients with colon cancer and 754 patients with rectal cancer who had incident first primary disease and were followed for a minimum of 7 years after diagnosis. Genetic variations were evaluated in the genes TGF‐β1 (2 single nucleotide polymorphisms [SNPs]), TGF‐β receptor 1 (TGF‐βR1) (3 SNPs), smooth muscle actin/mothers against decapentaplegic homolog 1 (Smad1) (5 SNPs), Smad2 (4 SNPs), Smad3 (37 SNPs), Smad4 (2 SNPs), Smad7 (11 SNPs), bone morphogenetic protein 1 (BMP1) (11 SNPs), BMP2 (5 SNPs), BMP4 (3 SNPs), bone morphogenetic protein receptor 1A (BMPR1A) (9 SNPs), BMPR1B (21 SNPs), BMPR2 (11 SNPs), growth differentiation factor 10 (GDF10) (7 SNPs), Runt‐related transcription factor 1 (RUNX1) (40 SNPs), RUNX2 (19 SNPs), RUNX3 (9 SNPs), eukaryotic translation initiation factor 4E (eiF4E) (3 SNPs), eukaryotic translation initiation factor 4E‐binding protein 3 (eiF4EBP2) (2 SNPs), eiF4EBP3 (2 SNPs), and mitogen‐activated protein kinase 1 (MAPK1) (6 SNPs).RESULTS:After adjusting for American Joint Committee on Cancer stage and tumor molecular phenotype, 12 genes and 18 SNPs were associated with survival in patients with colon cancer, and 7 genes and 15 tagSNPs were associated with survival after a diagnosis of rectal cancer. A summary score based on “at‐risk” genotypes revealed a hazard rate ratio of 5.10 (95% confidence interval, 2.56‐10.15) for the group with the greatest number of “at‐risk” genotypes; for rectal cancer, the hazard rate ratio was 6.03 (95% confidence interval, 2.83‐12.75).CONCLUSIONS:The current findings suggest that the presence of several higher risk alleles in the TGF‐β signaling pathway increase the likelihood of dying after a diagnosis of colon or rectal cancer. Cancer 2011;. © 2011 American Cancer Society.
Study of the Efficiency of UV and Visible‐Light Photocatalytic Oxidation of Methanol on Mesoporous RuO2–TiO2 Nanocomposites
Authors: Ismail Adel A. , Robben Lars , Bahnemann Detlef W. 
Published: March 2011

AbstractMesoporous RuO2–TiO2 nanocomposites at different RuO2 concentrations (0–10 wt %) are prepared through a simple one‐step sol–gel reaction of tetrabutyl orthotitanate with ruthenium(III) acetylacetonate in the presence of an F127 triblock copolymer as structure‐directing agent. The thus‐formed RuO2–TiO2 network gels are calcined at 450 °C for 4 h leading to mesoporous RuO2–TiO2 nanocomposites. The photocatalytic CH3OH oxidation to HCHO is chosen as the test reaction to examine the photocatalytic activity of the mesoporous RuO2–TiO2 nanocomposites under UV and visible light. The photooxidation of CH3OH is substantially affected by the loading amount and the degree of dispersion of RuO2 particles onto the TiO2, which indicates the exclusive effect of the RuO2 nanoparticles on this photocatalytic reaction under visible light. The measured photonic efficiency ξ=0.53 % of 0.5 wt % RuO2–TiO2 nanocomposite for CH3OH oxidation is maximal and the further increase of RuO2 loading up to 10 wt % gradually decreases this value. The cause of the visible‐light photocatalytic behavior is the incorporation of small amounts of Ru4+ into the anatase lattice. On the other hand, under UV light, undoped TiO2 shows a very good photonic efficiency, which is more than three times that for commercial photocatalyst, P‐25 (Evonik–Degussa); however, addition of RuO2 suppresses the photonic efficiency of TiO2. The proposed reaction mechanism based on the observed behavior of RuO2–TiO2 photocatalysts under UV and visible light is explored.
Crystallization field and rate study for the formation of single phase sodium‐potassium and potassium clinoptilolite
Authors: Güvenir Ö. , Kalıpçılar H. , Çulfaz A. 
Published: March 2011

AbstractReproducible synthesis of clinoptilolite as the single crystalline phase was achieved in the narrow crystallization field at or around the nominal batch composition of 2.1(Na2O+K2O):Al2O3:10SiO2:110H2O at 140 °C. Clinoptilolites of high purity were crystallized in the pure sodium or mixed sodium‐potassium cation systems. Partial replacement of hydroxyl anions with the salts of carbonates or chlorides also yielded clinoptilolite as the single crystalline phase although at lower crystallization rates. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Managing gas purity in epitaxial growth
Authors: Succi M. , Pirola S. , Ruffenach S. , Briot O. 
Published: March 2011

AbstractThe development of high brightness LEDs is being studied worldwide due to the expectation to replace present light sources because of the higher efficiency and estimated lifetime. The deposition of the epitaxial layers is the most critical step of the LED manufacturing process and has to be carried‐out in well controlled conditions to get the necessary uniformity of the epitaxial layers and the proper cleanliness. The most common technology to grow the epitaxial layers is MOVPE, a technology that requires a large quantity of gas to transport the precursors into the process reactor. Control of the cleanliness of the gases used during the process (hydrogen, ammonia, arsine, etc) is necessary to obtain highly efficient and reproducible devices. However, even the use of the cleanest gas source cannot avoid the introduction of impurities when the gas is used in the process reactor. In fact there are several causes that can degrade the actual purity level: the degree of emptiness of the source cylinder, improper procedures during the change out of the cylinder or outgassing from the components in the gas distribution system. These effects can be even worse in research centers where the gas consumption is low and not continuous. A common way to get rid of the above mentioned problems is the adoption of point of use purifiers. Results showing the improvements in the gas quality by adopting point of use purifiers will be presented and discussed. The differences between some widely used hydrogen purification technologies in the compound semiconductor applications will also be evaluated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of calcium phosphates by vapour diffusion in highly concentrated ionic micro‐droplets
Authors: Iafisco M. , Delgado‐López J. M. , Gómez‐Morales J. , Hernández‐Hernández M. A. , Rodríguez‐Ruiz I. , Roveri N. 
Published: March 2011

AbstractIn this work we have used the sitting drop vapour diffusion technique, employing the “crystallization mushroom ” to analyze the evolution of calcium phosphate crystallization in micro‐droplets containing high initial concentrations of Ca2+ and HPO42‐. The decomposition of NH4HCO3 solution produces vapours of NH3 and CO2 which diffuse through the droplets containing an aqueous solution of Ca(CH3COO)2 and (NH4)2HPO4. The result is the increase of pH by means of the diffusion of NH3 gas and the doping of the calcium phosphate with CO32‐ ions by means of the diffusion of CO2 gas. The pH of the crystallization process is monitored and the precipitates at different times are characterized by XRD, FTIR, TGA, SEM and TEM techniques. The slow increase of pH and the high concentration of Ca2+ and HPO42‐ in the droplets induce the crystallization of three calcium phosphate phases: dicalcium phosphate dihydrate (DCPD, brushite), octacalcium phosphate (OCP) and carbonate‐hydroxyapatite (HA). The amount of HA nanocrystals with needle‐like morphology and dimensions of about 100 nm, closely resembling the inorganic phase of bones, gradually increases, with the precipitation time up to 7 days, whereas the amount of DCPD, growing along the b axis, increases up to 3 days. Then, DCDP crystals start to hydrolyze yielding OCP nanoribbons and HA nanocrystals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of substrate and film thickness on structural, optical and electrical properties of ZnO thin films
Authors: Gopalakrishnan N. , Balakrishnan L. , Latha K. , Gowrishankar S. 
Published: March 2011

AbstractTransparent Zinc Oxide (ZnO) thin films have been grown on Si (100) and Sapphire (0001) substrates by RF magnetron sputtering for different growth time intervals (10, 30 and 60 min) to study the substrate and thickness effects. All the films have been grown at a substrate temperature of 450 °C. It has been found that the average growth rate on Si (100) substrate (8.6 nm/min) is higher than that on Sapphire (0001) substrate (2.6 nm/min) in an identical growth condition which clearly shows the virtual role of substrates. The lower growth rate on Sapphire (0001) suggests that the increasingly ordered and uniform growth due to less lattice mismatch. The grown films have been characterized by X‐ray diffraction (XRD), Reflectance, Photoluminescence (PL) and Hall measurements. The XRD result (FWHM) reveals that for lower growth time, the films grown on Si (100) is better than on Sapphire (0001). Conversely, for higher growth time, the films grown on Sapphire (0001) is better than on Si (100). The variation of strain behavior due to thickness on both substrates has been justified by UV‐Vis reflectance, photoluminescence and Hall effect measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOCVD of Vertically Aligned ZnO Nanowires Using Bidentate Ether Adducts of Dimethylzinc
Authors: Ashraf Sobia , Jones Anthony C. , Bacsa John , Steiner Alexander , Chalker Paul R. , Beahan Peter , Hindley Sarah , Odedra Rajesh , Williams Paul A. , Heys Peter N. 
Published: March 2011

AbstractThe dimethylzinc‐bidentate ether adducts [Me2Zn(1,4‐dioxane)] (1), [Me2Zn(1,2‐dimethoxyethane)] (2) and [Me2Zn(1,4‐thioxane)] (3) are used as precursors for the growth of vertically aligned zinc oxide (ZnO) nanowires (NWs) by liquid‐injection, metal‐organic (MO)CVD. The ZnO NWs are deposited on Si(111) and F‐doped SnO2/glass substrates in the absence of a seed catalyst. The precursors (1) and (2) are used to deposit ZnO NWs at substrate temperatures of 450 °C and 500 °C, whilst higher deposition temperatures of 550–600 °C are necessary to obtain ZnO NWs using (3). X‐ray diffraction (XRD) data show that the NWs grown from all three adduct precursors are deposited in the wurtzitic ZnO phase. Room‐temperature photoluminescence (PL) data for the ZnO NWs grown using (1) and (2) show an intense peak at 3.28 eV due to near band‐edge emission with a very low intensity of defect‐related green luminescence at 2.42 eV. In contrast, room‐temperature PL data for the ZnO NWs deposited using (3) is dominated by deep centre, defect‐related emission at 2.42 eV. Auger electron spectroscopy (AES) shows that the ZnO films deposited from (1) and (2) are high purity with no detectable carbon, but the ZnO films grown from (3) are contaminated with sulfur (1 at.‐%). Single‐crystal X‐ray structures show that (1) is polymeric containing bridging 1,4‐dioxane ligands while (2) is a monomeric complex featuring a chelating 1,2‐dimethoxyethane ligand. The wide [Me‐Zn‐Me] bond angles in (1) and (2) (152.0(3)° and 154.5(2)°, respectively) suggest moderately weak [Me2Zn]‐ligand interactions. Complex (3) is polymeric and exhibits nearly linear [Me‐Zn‐Me] bond angles, indicative of much weaker [Me2Zn]‐ligand interactions.
Forest, climate and water issues in Europe
Authors: Bredemeier Michael 
Published: March 2011

AbstractThe particular European perspective on current forest and water issues is outlined in three focal areas: water supply, water quality, and water‐related hazards. Much of the synopsis relies on contributions brought together within the European COST consortium ‘Forest management and the water cycle’, which is operating from 2007 to 2011. Under the currently projected climate change (CC) scenarios for Europe, the humidity gradient across the sub‐continent from moist Northwest to dry Southeast will probably intensify, bringing about potentially more flooding problems at the ‘wet end’, and more drought and related problems (wildfires, salination) at the ‘dry end’. Careful planning of management is essential wherever tradeoff situations between forest growth and water yield emerge. The water quality issue in Europe is not as pressing as it was a few decades ago. Much has been achieved on account of successful water‐ and air‐pollution control. Particularly, the acidification pressure on forest soils and their water‐related systems was much relieved, due to strongly declining acidic deposition over the past 30 years. Forests and their appropriate management for optimizing water retention can support flood control, but with clear limitations under very strong and catastrophic events. The contribution to flood control is more important under ‘normal’ conditions than under extremes. Important controls are infiltration capacity and the status of water saturation prior to the rain event, i.e. the still available storage capacity. The safeguarding of water quality is seen as the most important single aspect among forest‐water relations. Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis and Characterization of Platinum(II) Complexes with a Diazenecarboxamide‐Appended Picolyl‐Triazole Ligand
Authors: Urankar Damijana , Pevec Andrej , Košmrlj Janez 
Published: March 2011

AbstractThe coordination of the diazenecarboxamides, which were functionalized with the 1‐(2‐picolyl)‐1H‐1,2,3‐triazole moiety 1, to platinum(II) were studied, where K2[PtCl4] and cis‐[PtCl2(DMSO)2] were used as the platinum sources. The picolyl‐triazole (pictri) binding unit enabled chelation to the metal centre through the 1,2,3‐triazole N2 and the pyridyl nitrogen atoms under mild reaction conditions. When cis‐[PtCl2(DMSO)2] was used, with CH2Cl2 or CH3CN as the reaction solvents, the pure, stable diamminedichloridoplatinum(II) complexes 2 were isolated by filtration in 39 to 83 % yield. The products were structurally characterized in solution by 1H, 13C and 195Pt NMR spectroscopy. The 195Pt NMR chemical shifts for 2 appear in the region of –2203 to –2207 ppm. The structure of complex 2a was confirmed by single‐crystal X‐ray crystallography. The formation of the platinum complexes 2 was monitored using NMR spectroscopy. The complexation with cis‐[PtCl2(DMSO)2] in [D7]dmf proceeded through several intermediates, as indicated by the 195Pt NMR spectra with resonances in the range of –3055 to –2907 ppm. Similarly, the reaction of cis‐[PtCl2(DMSO)2] with diazenecarboxamide, which was functionalized with the nonchelating 1‐(2‐aminoethyl)‐1,2,3‐triazole derivative, was examined by NMR spectroscopy.
Performance of Dye‐Sensitized Solar Cells Based on MWCNT/TiO2–xNx Nanocomposite Electrodes
Authors: Guo Wei , Shen Yihua , Wu Liqiong , Gao Yurong , Ma Tingli 
Published: March 2011

AbstractMultiwall carbon nanotube (MWCNT) fibrils were introduced into TiO2–xNx photoelectrodes to enhance charge collection efficiency as charge‐transport pathways. For comparison, we also synthesized MWCNT/TiO2 nanocomposites to fabricate dye‐sensitized solar cells (DSCs). The effect of MWCNTs on the photovoltaic performance of the DSCs was studied in detail. The performance of DSCs based on MWCNT/TiO2–xNx differs significantly from that of MWCNT/TiO2 photoelectrodes. A high energy conversion efficiency of 7.66 % was achieved in the dye‐sensitized MWCNT/TiO2 nanocomposites solar cells. The results show that remarkable enhancement of ca. 33 % and ca. 40 % in the conversion efficiency (η) and short‐circuit photocurrent density (Jsc), respectively, occurrs for the DSCs based on MWCNT/TiO2 than those made of pure TiO2 electrodes. The energy conversion efficiency of DSCs based on TiO2–xNx electrodes was 6.98 %, which is similar to that of MWCNT/TiO2–xNx DSCs (6.88 %–5.17 %). We also investigated the charge collection efficiency, electron transport, electron lifetime, and photocurrent transient behavior by electrochemical analysis. The introduced MWCNTs exhibit a smaller sheet resistance and electron transfer resistance, as well as a longer electron lifetime. A 20 % enhancement in the charge collection efficiency is achieved in the nanocomposite DSCs.
The U28 Nanosphere: What's Inside?
Authors: Nyman May , Rodriguez Mark A. , Alam Todd M. 
Published: March 2011

AbstractPolyoxometalate‐like behavior of actinyl‐peroxide anions in aqueous alkaline media has been recently unveiled in the form of more than 20 reported crystal structures of clusters, each with 20–60 uranyl polyhedra composing capsule‐like topologies. There is now opportunity to fully develop this new polyoxometalate (POM) family to include redox behavior, non‐aqueous chemistry, complex materials from cluster building blocks, cluster‐counterion interactions, etc. To pursue these opportunities, reliable syntheses rooted in an understanding of cluster assembly processes are imperative. To this end, using the U28 nanosphere [UO2(O2)1.5]28 as an example, we report high yield syntheses of a series of four U28 salts that feature different templating cations (K, Rb, Cs) and anions [uranyl monomer, Nb(O2)4 and Ta(O2)4]. The key to assembly and stability of U28 is both 1) synthetic conditions that are not extreme or dynamic, and 2) templating cations and anions that ideally match each other and the topology of the capsule interior. U28 salts are characterized in the solid‐state by powder and single‐crystal X‐ray diffraction and infrared spectroscopy. Furthermore, Cs‐templated U28 is re‐dissolved and characterized by 133Cs NMR; providing information on solution stability, and revealing the interaction of the internal templating Cs+ with the central templating anion. While Cs+ internal to the cluster remains inside when U28 is dissolved in a Na salt solution, the internal K+ will rapidly exchange with Na+, providing new routes to other cluster topologies and compositions.