bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elemental Distribution and Thermoelectric Properties of Layered Tellurides 39R‐M0.067Sb0.667Te0.266 (M=Ge, Sn)
Authors: Schneider Matthias N. , Fahrnbauer Felix , Rosenthal Tobias , Döblinger Markus , Stiewe Christian , Oeckler Oliver 
Published: December 2011

AbstractThe isostructural phases 39R‐Ge0.067Sb0.667Te0.266 (R$\bar 3$m, a=4.2649(1), c=75.061(2) Å) and 39R‐Sn0.067Sb0.667Te0.266 (R$\bar 3$m, a=4.2959(1), c=75.392(2) Å) were prepared by quenching stoichiometric melts of the pure elements and subsequent annealing at moderate temperatures. Their structures are comparable to “superlattices” synthesized by layer‐by‐layer deposition onto a substrate. These structures show no stacking disorder by electron microscopy. The structure of the metastable layered phases are similar to that of 39R‐Sb10Te3 (equivalent to Sb0.769Te0.231), which contains four A7 gray‐arsenic‐type layers of antimony alternating with Sb2Te3 slabs. Joint refinements on single‐crystal diffraction data using synchrotron radiation at several K edges were performed to enhance the scattering contrast. These refinements show that the elemental distributions at some atom positions are disordered whereas otherwise the structures are long‐range ordered. The variation of the elemental concentration correlates with the variation in interatomic distance. Z‐contrast scanning transmission electron microscopy (HAADF‐STEM) on 39R‐Ge0.067Sb0.667Te0.266 confirms the presence of concentration gradients. The carrier‐type of the isostructural metal (A7‐type lamellae)‐semiconductor heterostructures (Ge/Sn‐doped Sb2Te3 slabs) varies from n‐type (Ge0.067Sb0.667Te0.266) to p‐type (Sn0.067Sb0.667Te0.266). Although the absolute values of the Seebeck coefficient reached about 50–70 μV/K and the electrical conductivity is relatively high, the two isotypic phases exhibit a maximal thermoelectric figure of merit (ZT) of 0.06 at 400 °C as their thermal conductivity (κ≈8–9.5 W/mK at 400 °C) lies interestingly in between that of antimony and pure Sb2Te3.
Platinum(II)–Bis(aryleneethynylene) Complexes for Solution‐Processible Molecular Bulk Heterojunction Solar Cells
Authors: Dai Feng‐Rong , Zhan Hong‐Mei , Liu Qian , Fu Ying‐Ying , Li Jin‐Hua , Wang Qi‐Wei , Xie Zhiyuan , Wang Lixiang , Yan Feng , Wong Wai‐Yeung 
Published: December 2011

AbstractFour new solution‐processible small‐molecular platinum(II)–bis(aryleneethynylene) complexes consisting of benzothiadiazole as the electron acceptor and triphenylamine and/or thiophene as the electron donor were conveniently synthesized and characterized by physicochemical and computational methods, and utilized as the electron‐donor materials in the fabrication of solution‐processed bulk heterojunction (BHJ) solar cells. The effect of different electron‐donor groups in these small molecules on the optoelectronic and photovoltaic properties was also examined. The optical and time‐dependent density functional theory studies showed that the incorporation of stronger electron‐donor groups significantly enhanced the solar‐absorption abilities of the complexes. These molecular complexes can serve as good electron donors for fabricating BHJ devices by blending them with the [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM) as the electron acceptor. The best power conversion efficiency of 2.37 % was achieved with the open‐circuit voltage of 0.83 V, short‐circuit current density of 7.10 mA cm−2 and fill factor of 0.40 under illumination of an AM 1.5 solar‐cell simulator. The spin‐coated thin films showed p‐channel field‐effect charge transport with hole mobilities of up to 2.4×10−4 cm2 V−1 s−1 for these molecules. The present work illuminates the potential of well‐defined organometallic complexes in developing light‐harvesting small molecules for efficient power generation in organic photovoltaics implementation.
Spreading and Stability of a Thin Droplet on a Heated Rotating Plate
Authors: Boettcher Konrad E. R. , Ehrhard Peter 
Published: December 2011

AbstractFür die Ausbreitung eines dünnen rotierenden Tropfens wird, unter Ausnutzung der Schmierfilmapproximation, eine Entwicklungsgleichung zur Beschreibung der Position der freien Grenzfläche abgeleitet. Die dynamische Benetzung wird mit dem empirischen Tanner'schen Gesetz beschrieben und die Modellierung mit Experimenten aus der Literatur verglichen. Eine lineare Störungsanalyse liefert die instabilen Moden und das Einsetzen von Fingerbildung während der Ausbreitung. Betrachtet wird auch Konvektion aufgrund der temperaturabhängigen Oberflächenspannung und Dichte sowie deren Stabilität.
Electrochemiluminescence of SDBS‐Ru(bpy)32+‐CPM System and Its Application
Authors: Li Lijun , Gao Wenyan , Huang Wenyi , Cai Zhuo , Hu Dachun , Li Yanqing 
Published: December 2011

AbstractWhen the concentration of dodecyl benzene sulfonic acid sodium salt (SDBS) is 0.7 mmol·L−1, the electrochemical and electrochemiluminescence (ECL) intensity of Ru(bpy)32+‐chlorpheniramine maleate (CPM) system at the Au electrode were studied. The results showed that compared with the absence of SDBS, enhancement of the ECL intensity was 14‐fold at Au electrode. Base on this, an ECL method was established for efficient and simple determination of CPM at Au electrode. Under the optimum experimental condition, the enhanced ECL intensities had good linear relationship with the concentration of CPM in the range of 1.0×10−4–1.0×10−7 mol·L−1, and a linear regression equation was obtained as follows: I (counts)=48.805×106c+394.03 (r=0.9975), the detection limit for CPM was 1.4×10−8 mol·L−1. The RSD for 5 times determinations of 1.0×10−5 mol·L−1 CPM was 3.2%. The results of recovery test were between 96.3%–102.5%, and the RSD of recovery test (n=5) was 2.7%. In addition, eleven kinds of tertiary amines‐Ru(bpy)32+ systems were investigated in the absence and presence of SDBS. The results showed that the enhancement of SDBS on ECL intensity of tertiary amines‐Ru(bpy)32+ systems was universal.
Theoretical Study of the Radical Scavenging Activity of Shikonin and Its Derivatives
Authors: Jin Ruifa , Li Jie 
Published: December 2011

AbstractA series of shikonin derivatives have been designed and their radical scavenging activity has been characterized by the B3LYP/6‐31+G(d) approach. The hydrogen bond properties of the studied structures were investigated using the atoms in molecules (AIM) theory. The calculated results reveal that the hydrogen bond is important for good scavenging activity. The introduction of electron‐drawing (electron‐donating) groups increases (decreases) the scavenging activities of radical and radical cations of shikonin derivatives. Shikonin derivatives appear to be good candidates for the single‐electron‐transfer mechanism, particularly for N(CH3)2 derivative. Taking this system as an example, we present an efficient method for the investigation of radical scavenging activity from theoretical point of view. With the current work, we hope to highlight the radical scavenging activity of hydroxynaphthoquinones derivatives and stimulate the interest for further studies and exploitation in pharmaceutical industry.
Synthesis, Structure Elucidation and H+/K+‐ATPase Inhibitory Activity of Bisabolangelone Reduction Derivatives
Authors: Huang Nianyu , Chen Lei , Liao Zhaojiang , Fang Hubiao , Wang Junzhi , Zou Kun 
Published: December 2011

AbstractNine bisabolangelone reduction derivatives were synthesized and separated as potential anti‐ulcer agent. Their structures were characterized by 2D NMR, IR, ESI‐MS, elemental analysis and single‐crystal X‐ray diffraction analysis. Preliminarily H+/K+‐ATPase activity evaluation indicated that all the target compounds had a certain inhibitory effect, and compounds II and IV exhibited the better inhibitory activity against H+/K+‐ATPase than bisabolangelone and the commercial omeprazole with the IC50 of 23.21 and 65.32 μmol/L, respectively. The initial structure‐activity analysis suggested that the presence of carbonyl group in six‐membered ring and double bond in side‐chain seemed to be necessary to the activity.
A New Nanocatalytic Spectrophotometric Assay for Cationic Surfactant Using Phosphomolybdic Acid‐Formic Acid‐Nanogold as Indicator Reaction
Authors: Jiang Zhiliang , Qin Huimin , Liang Aihui 
Published: December 2011

AbstractIn the pH 7.4 Na2HPO4‐NaH2PO4 buffer solution, the cationic surfactant (CS) interacted with nanogold particles (NG) to form NG aggregations (NGA) that resulted in its color changing from wine red to blue‐violet. NG has a strong catalysis on the formic acid‐phosphomolybdic acid (PMo) colored reaction, but that of the NGA catalysis is weak. With the increase of CS concentration, the NGA increased and the NG decreased, the catalysis decreased and the absorption value at 700 nm decreased linearly. The concentrations of 6.25–250 nmol/L tetradecyl dimethyl benzyl ammonium chloride (TDBAC), 0.625–250 nmol/L cetyltrimethyl ammonium bromide (CTMAB) and 12.5–500 nmol·L−1 dodecyldimethylbenzyl ammonium chloride (DDBAC) had good linear responses to the decreased absorption value (ΔA700 nm), with molar absorption coefficients of 2.2×106, 2.1×106 and 9×105 L·mol−1·cm−1 respectively. This method was simple, highly sensitive and low‐cost.
Methenamine as an Efficient Ligand for Copper‐catalyzed Coupling of Phenols with Aryl Halides
Authors: Qian Cunwei , Zong Qianshou , Fang Dong 
Published: December 2011

AbstractEmploying methenamine as a new supporting ligand, the copper‐catalyzed coupling reactions of aryl bromides or aryl iodides with various phenols successfully proceeded in good yields under mild conditions. A series of diaryl ethers were obtained with excellent yields in the presence of K3PO4 and copper(I) salt.
Orthogonal Enzymatic Reactions to Control Supramolecular Hydrogelations
Authors: Chen Guoqin , Ren Chunhua , Wang Ling , Xu Bing , Yang Zhimou 
Published: December 2011

AbstractEnzyme‐responsive hydrogels have great potential in applications of controlled drug release, tissue engineering, etc. In this study, we reported on a supramolecular hydrogel that showed responses to two enzymes, phosphatase which was used to form the hydrogels and esterase which could trigger gel‐sol phase transitions. The gelation process and visco‐elasticity property of the resulting gel, morphology of the nanostructures in hydrogel, and peptide conformation in the self‐assembled nanostructure were characterized by rheology, transmission electron microscope (TEM), and circular dichroism (CD), respectively. Potential application of the enzyme‐responsive hydrogel in drug release was also demonstrated in this study. Though only one potential application of drug release was proved in this study, the responsive hydrogel system in this study might have potentials for the applications in fields of cell culture, controlled‐drug release, etc.
Influence of Temperatures on the Tautomerism of the N‐(1H‐imidazoline‐2‐yl)‐1H‐benzimidazol‐2‐amine and Investigation of Its Electrochemical Behaviour
Authors: Servi Süleyman , Genc Murat , Saydam Sinan 
Published: December 2011

AbstractSynthesis of N‐(1H‐imidazoline‐2‐yl)‐1H‐benzimidazol‐2‐amine was carried out under microwave irradiation (MWI) conditions. Dynamic 1H NMR investigation of N‐(1H‐imidazoline‐2‐yl)‐1H‐benzimidazol‐2‐amine compound was reported at temperature range of 223–333 K in DMF‐d7. Some physical parameters, such as coalescence temperature (Tc), the free energy of activation (ΔG∗︁) and rate constant (k) values were calculated from its 1H NMR spectra at various temperatures. Electrochemical feature of this compound was investigated by cyclic (CV) and square wave voltammetry (SWV).
Theoretical Study of the Mechanism of Cycloaddition Reaction between Silylene Silylene (H2SiSi:) and Acetone
Authors: Wang Zhina , Shi Leyi , Li Yongqing , Lu Xiuhui 
Published: December 2011

AbstractThe mechanism of the cycloaddition reaction between singlet silylene silylene (H2SiSi:) and acetone has been investigated with the CCSD (T)//MP2/6‐31G∗︁ method. According to the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction channels. The present rule of this reaction is that the [2+2] cycloaddition reaction of the two π‐bonds in silylene silylene (H2SiSi:) and acetone leads to the formation of a four‐membered ring silylene (E3). Because of the unsaturated property of Si: atom in E3, it further reacts with acetone to form a silicic bis‐heterocyclic compound (P7). Simultaneously, the ring strain of the four‐membered ring silylene (E3) makes it isomerize to a twisted four‐membered ring product (P4).
Synthesis, Insecticidal Assay and Molecular Docking Study of Novel Neonicotinoids N‐Oxide Analogues
Authors: Zhang Wenwen , Fan Yefeng , Yu Tao , Xu Zhiping , Xu Xiaoyong , Cheng Jiagao , Li Zhong 
Published: December 2011

AbstractEight novel neonicotinoids N‐oxide analogues were designed and synthesized. All the compounds have been identified by 1H NMR and HRMS. The N‐oxide analogues exhibit high insecticidal activity against cowpea aphids (Aphis craccivora) at 250 mg·L−1. The influence of N‐oxide formation on the biological activity was elucidated by computational chemical study, and it indicated that the water bridge hydrogen bonding network was broken due to the influence of the O atom connected with the pyridine ring.
A DFT Study on the Structure and Properties of Cu/Cr2O3 Catalyst
Authors: Zhang Minhua , Li Ruzhen , Yu Yingzhe 
Published: December 2011

AbstractUsing DFT method, the stable adsorption configurations of Cu4 cluster on Cr2O3 (0001) surface were investigated. The regular tetrahedron structure and the planar structures were considered as the initial adsorption configuration of Cu4 cluster, respectively. The adsorption energies of the two structures were also calculated. The simulation result indicated that the adsorption energy of the regular tetrahedron structure was higher than that of the planar structure, and thus the regular tetrahedron structure was confirmed to be the stable adsorption configuration for Cu4 cluster on Cr2O3 (0001) surface. Moreover, it was observed that the Cu4 cluster showed the definite stable adsorption sites on Cr2O3 (0001) surface, namely 3‐fold O sites. During the adsorption process of Cu4 cluster onto Cr2O3 (0001) surface, the Cu4 cluster could bond with more Cr or O atoms on the surface, and the apparent charge transfer also occurred correspondingly. Meanwhile, the Cu4 cluster and Cr2O3 (0001) surface would bond in the form of local polarization to enhance the stability of adsorption configuration.
N‐Heterocyclic Carbene‐Catalyzed [2+2+2] Annulation of Allenoates with Trifluoromethylketones
Authors: Sun Lihui , Wang Tong , Ye Song 
Published: December 2011

AbstractIn contrast with the reported phosphine‐ and DABCO‐catalyzed [3+2] and [2+2] annulation of allenoates with trifluoromethylketone, the [2+2+2] annulation of allenoates and two molecules of trifluoromethylketone was found under the condition of N‐heterocyclic carbene catalysis.
CITIES – ein europäisches Projekt
Authors: Bader Hans Joachim , Gros Leo , Maciejowska Iwona 
Published: December 2011

AbstractEs gibt nur wenige europäischer Ansätze, über die Grenzen einzelner Mitgliedsländer der Europäischen Union hinaus Impulse für die Fortbildung von Chemielehrern zu geben. Aus diesem Grund fanden sich im Rahmen des COMENIUS‐Projekts CITIES (Chemistry and Industry for Teachers in European Schools) Partner aus Hochschulen, Wissenschaftlichen Gesellschaften und Vertretungen von Arbeitgebern und Arbeitnehmern der Chemischen Industrie aus Großbritannien, Polen, Tschechien, Deutschland, Frankreich und Spanien zusammen. Die Gruppe erstellte eine gemeinsame, über das Internet zugängliche Plattform für die Chemielehrerfortbildung, auf der alle von den Partnern eingebrachten Materialien eingestellt werden.
Experimental Designs Applied to Desorption of Dichromate Ions after Separation and Preconcentration from Natural and Industrial Water by Modified Nano‐Alumina
Authors: Sayar Omid , Abadi Iman Jabbari Zahir , Sadeghi Omid , Zhad Hamid Reza Lotfi Zadeh , Tavassoli Najmeh 
Published: December 2011

AbstractNano‐alumina modified by 9‐aminoacridine was used as a sorbent for separation and determination of dichromate ions from water. Statistical method, based on surface response design, has been used for the optimization of dichromate ions elution from 9‐aminoacridine nano‐alumina. The adsorbed dichromate ions were found to be eluted quantitatively with 0.8 mol L−1 KCl in 1.6 mol L−1 NaOH which optimized by response surface design. Under optimum conditions, the accuracy, precision (relative standard deviation, RSD%) and R‐square of the method were calculated as >98, <3, and >94%, respectively. Remarkable agreement between experimental and theoretical data was confirmed the predicted assumption. The method was applied to the simultaneous determination of dichromate in natural and industrial water samples. We also examined the retention of dichromate anions in the presence of Cl−, ${\rm NO}_{3}^{- } $, and ${\rm SO}_{4}^{2- } $ anions at pH 3.
Improving Soil Enzyme Activities and Related Quality Properties of Reclaimed Soil by Applying Weathered Coal in Opencast‐Mining Areas of the Chinese Loess Plateau
Authors: Li Hua , Shao Hongbo , Li Weixiang , Bi Rutian , Bai Zhongke 
Published: December 2011

AbstractThere are many problems for the reclaimed soil in opencast‐mining areas of the Loess Plateau of China such as poor soil structure and extreme poverty in soil nutrients and so on. For the sake of finding a better way to improve soil quality, the current study was to apply the weathered coal for repairing soil media and investigate the physicochemical properties of the reclaimed soil and the changes in enzyme activities after planting Robinia pseucdoacacia. The results showed that the application of the weathered coal significantly improved the quality of soil aggregates, increased the content of water stable aggregates, and the organic matter, humus, and the cation exchange capacity of topsoil were significantly improved, but it did not have a significant effect on soil pH. Planting R. pseucdoacacia significantly enhanced the activities of soil catalase, urease, and invertase, but the application of the weathered coal inhibited the activity of catalase. Although the application of appropriate weathered coal was able to significantly increase urease activity, the activities of catalase, urease, or invertase had a close link with the soil profile levels and time. This study suggests that applying weathered coals could improve the physicochemical properties and soil enzyme activities of the reclaimed soil in opencast‐mining areas of the Loess Plateau of China and the optimum applied amount of the weathered coal for reclaimed soil remediation is about 27 000 kg hm−2.
On the Accuracy of DFT Methods in Reproducing Ligand Substitution Energies for Transition Metal Complexes in Solution: The Role of Dispersive Interactions
Authors: Jacobsen Heiko , Cavallo Luigi 
Published: December 2011

AbstractThe performance of a series of density functionals when tested on the prediction of the phosphane substitution energy of transition metal complexes is evaluated. The complexes FeBDA and RuCOD (BDA=benzylideneacetone, COD=cyclooctadiene) serve as reference systems, and calculated values are compared with the experimental values in THF as obtained from calorimetry. Results clearly indicate that functionals specifically developed to include dispersion interactions usually outperform other functionals when BDA or COD substitution is considered. However, when phosphanes of different sizes are compared, functionals including dispersion interactions, at odd with experimental evidence, predict that larger phosphanes bind more strongly than smaller phosphanes, while functionals not including dispersion interaction reproduce the experimental trends with reasonable accuracy. In case of the DFT‐D functionals, inclusion of a cut‐off distance on the dispersive term resolves this issue, and results in a rather robust behavior whatever ligand substitution reaction is considered.
Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules
Authors: Blaudeck Thomas , Zenkevich Eduard I. , Abdel‐Mottaleb Mohamed , Szwaykowska Klementyna , Kowerko Danny , Cichos Frank , von Borczyskowski Christian 
Published: December 2011

AbstractFunctional dye molecules, such as porphyrins, attached to CdSe quantum dots (QDs) through anchoring meso‐pyridyl substituents, form quasi‐stable nanoassemblies. This fact results in photoluminescence (PL) quenching of the QDs both due to Förster resonance energy transfer (FRET) and the formation of non‐radiative surface states under conditions of quantum confinement (non‐FRET). The formation process is in competition with the ligand dynamics. At least two timescales are found for the formation of the assemblies: 1) one faster than 60 s attributed to saturation of empty attachment sites and 2) one slower than 600 s, which is attributed to a reorganisation of the tri‐n‐octylphosphine oxide (TOPO) ligand shell. Finally, this process results in almost complete exchange of the TOPO shell by porphyrin dye molecules. Following a Stern–Volmer analysis, we established a microscopic description of PL quenching and assembly formation. Based on this formalism, we determined the equilibrium constant for assembly formation between QDs and the pyridyl‐functionalised dye molecules to be ${K \approx 10^5 - 10^7 }$ M−1, which is several orders of magnitude larger than that of the TOPO ligands. Our results give additional insights into the non‐FRET PL quenching processes involved and show that the QD surface is inhomogeneous with respect to the involved attachment and detachment processes. In comparison with other methods, such as NMR spectroscopy, the advantage of our approach is that ligand dynamics can be investigated at extremely low ratios of dye molecules to QDs.
Water‐Soluble Monodispersed Lanthanide Oxide Submicrospheres: PVP‐Assisted Hydrothermal Synthesis, Size‐Control and Luminescence Properties
Authors: Cui Ying , Lai Xiaoyong , Li Li , Hu Zhudong , Wang Shuo , Halpert Jonathan E. , Yu Ranbo , Wang Dan 
Published: December 2011

AbstractWe report a facile hydrothermal synthetic route to prepare a class of monodispersed lanthanide‐based compound submicrospheres with controllable size, which employs raw lanthanide oxides as starting material, urea as precipitator and poly(N‐vinyl‐2‐pyrrolidone) (PVP) as surfactant. Dependent on the intrinsic properties of respective lanthanide, the resulting products could be in the form of oxide, hydroxide or basic carbonate. These lanthanide hydroxides or basic carbonates can be easily transformed into their corresponding oxides by calcination, retaining the same morphology and size dispersion. The formation mechanism of these lanthanide‐based compound submicrospheres is investigated and PVP plays a critical role in forming uniform and well‐dispersed products. Furthermore, this method could be extended to a binary system by using two kinds of lanthanide oxides as starting material, resulting in doped‐type lanthanide oxide submicrospheres (such as Y2O3:Eu3+). The Y2O3:Eu3+ submicrospheres exhibit nearly uniform spherical morphology and narrow size distribution as well as good water solubility and sharp spectral emission at 610 nm (corresponding to the 5D0–7F2 transition of Eu3+). This makes them attractive materials for applications in fields such as fluorescent lamps, field emission displays (FEDs) or LCDs, or as biomedical labels and molecular probes.