Two-step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter

A new two-step procedure for the synthesis of MoS2 nanotubes using lead as a growth promoter is reported. In the first step, molybdenum suboxide nanowhiskers containing a small amount of lead atoms were created by exposing a pressed MoS2+Pb mixture to highly compressed shock-heated argon gas, with estimated temperatures exceeding 9900 K. In the second step, these molybdenum suboxide nanowhiskers served as templates for the sulfidization of the oxide into MoS2 nanotubes (by using H2S gas in a reducing atmosphere at 820 degrees C). Unlike the case of WS2 nanotubes, the synthesis of a pure phase of MoS2 nanotubes from molybdenum oxide has proven challenging, due mostly to the volatile nature of the latter at the high requisite reaction temperatures (>800 degrees C). In contrast, the nature and apparent reaction mechanism of the method reported herein are amenable to future scale-up. The high-temperature shockwave system should also facilitate the synthesis of new nanostructures from other layered materials.

Mechanochemical Synthesis of Amide Functionalized Porous Organic Polymers

Two porous organic polymers decorated with the amide functionality were synthesized mechanochemically and their properties were compared with the ones prepared by conventional solution mediated method. All the POPs were subjected to gas and water vapor sorption studies. The mechanochemically synthesized POPs have less surface area and show moderate adsorption properties compared to the solution mediated POPs. The amide based POPs show remarkable stability in water and concentrated acids.

Design and synthesis of new low band gap organic semiconductors for photovoltaic applications

Donor-acceptor (D-A) conjugated polymers have attracted a good deal of attention in recent years. In D-A systems, the introduction of electron withdrawing groups reduces E-g by lowering the LUMO levels whereas, the introduction of electron donating groups reduces E-g by raising the HOMO levels. Also, conjugated polymers with desired HOMO and LUMO energy levels could be obtained by the proper selection of donor and acceptor units. Because of this reason, D-A conjugated polymers are emerging as promising materials particularly for polymer light emitting diodes (PLEDs) and polymer solar cells (PSCs). We report the design and synthesis of four new narrow band gap donor-acceptor (D-A) conjugated polymers, PTCNN, PTCNF, PTCNV and PTCNO, containing electron donating 3,4-didodecyloxythiophene and electron accepting cyanovinylene units. The effects of further addition of electron donating and electron withdrawing groups to the repeating unit of a D-A conjugated polymer (PTCNN) on its optical and electrochemical properties are discussed. The studies revealed that the nature of D and A units as well as the extent of alternate D-A structure influences the optical and the electrochemical properties of the polymers. All the polymers are thermally stable up to a temperature of 300 degrees C under nitrogen atmosphere. The electrochemical studies revealed that the polymers possess low-lying HOMO energy levels and low-lying LUMO energy levels. In the UV-Vis absorption study, the polymer films displayed broad absorption in the wavelength region of 400-700 nm. The polymers exhibited low optical band gaps in the range 1.70 - 1.77 eV.

Synthesis of self-light-scattering wrinkle structured ZnO photoanode by sol-gel method for dye-sensitized solar cells

A special morphological zinc oxide (ZnO) photoanode for dye-sensitized solar cell was fabricated by simple sol-gel drop casting technique. This film shows a wrinkled structure resembling the roots of banyan tree, which acts as an effective self scattering layer for harvesting more visible light and offers an easy transport path for photo-injected electrons. These ZnO electrode of low thickness (similar to 5 mu m) gained an enhanced short-circuit current density of 6.15 mA/cm(2), open-circuit voltage of 0.67 V, fill factor of 0.47 and overall conversion efficiency of 1.97 % under 1 sun illumination. This shows a high conversion efficiency and a superior performance than that of ZnO nanoparticle-based photoanode (eta similar to 1.13 %) of high thickness (similar to 8 mu m).

Self-assembly of Chloro-Bridged Arene-Ruthenium Based Rectangle: Synthesis, Structural Characterization and Sensing Study

Self-assembly of a chloro-bridged half-sandwich p-cymene ruthenium(II) complex Ru-2(mu-Cl-2)(eta(6)-p-cymene)(2)Cl-2] 1 with linear ditopic donor L; trans-1,2-bis(4-pyridyl) ethylene] in presence of 2 eq. AgNO3 in CH3CN yielded a chloro-bridged molecular rectangle 2. The rectangle 2 was isolated as nitrate salt in high yield (90 %) and characterized by infra-red, H-1 NMR spectroscopy including ESI-MS analyses. Molecular structure of 2 was determined by single crystal X-ray diffraction study The diffraction analysis shows that 2 adopts a tetranuclear rectangular geometry with the dimensions of 5.51 angstrom x 13.29 angstrom and forming an infinite supramolecular chain with large internal porosity arising through multiple pi-pi and CH-pi interactions between the adjacent rectangles. Furthermore, rectangle 2 is used as selective receptor for phenolic-nitroaromatic compounds such as picric acid, dinitrophenol and nitrophenol.

Bioremediation and lipid synthesis through mixotrophic algal consortia in municipal wastewater

Algae grown in outdoor reactors (volume: 10 L and depth: 20 cm) were fed directly with filtered and sterilised municipal wastewater. The nutrient removal efficiencies were 86%, 90%, 89%, 70% and 76% for TOC, TN, NH4-N, TP and OP, respectively, and lipid content varied from 18% to 28.5% of dry algal biomass. Biomass productivity of similar to 122 mg/l/d (surface productivity 24.4 g/m(2)/d) and lipid productivity of similar to 32 mg/l/d were recorded. Gas chromatography and mass spectrometry (GC-MS) analyses of the fatty acid methyl esters (FAME) showed a higher content of desirable fatty acids (bearing biofuel properties) with major contributions from saturates such as palmitic acid C16:0; similar to 40%] and stearic acid C18:0; similar to 34%], followed by unsaturates such as oleic acid C18:1(9); similar to 10%] and linoleic acid C18:2(9,12); similar to 5%]. The decomposition of algal biomass and reactor residues with an exothermic heat content of 123.4 J/g provides the scope for further energy derivation. (C) 2014 Elsevier Ltd. All rights reserved.

Synthesis, characterization and reactivity studies of electrophilic ruthenium(II) complexes: a study of H-2 activation and labilization

Reaction of 2,2'-bipyridine (bpy) with dinuclear complexesRuCl(dfppe)(mu-Cl)(3)Ru(dmso-S)(3)](dfppe = 1,2-bis(dipentafluorophenyl phosphino)ethane (C6F5)(2)PCH2CH2P(C6F5)(2); dmso = dimethyl sulfoxide) (1) or RuCl(dfppe)(mu-Cl)(3)RuCl(dfppe)] (2) affords the mononuclear species trans-RuCl2(bpy)(dfppe)] (3). Using this precursor complex (3), a series of new cationic Ru(II) electrophilic complexes RuCl(L)(bpy)(dfppe)]Z] (L = P(OMe)(3) (5), PMe3 (6), CH3CN (7), CO (8), H2O (9); Z = OTf (5, 6, 7, 8), BAr4F (9) have been synthesized via abstraction of chloride by AgOTf or NaBAr4F in the presence of L. Complexes 5 and 6 were converted into the corresponding isomeric hydride derivatives RuH(PMe3)(bpy)(dfppe)]OTf] (10a, 10b) and RuH(P(OMe)(3))(bpy)(dfppe)]OTf] (11a, 11b) respectively, when treated with NaBH4. Protonation of the cationic monohydride complex (11a) with HOTf at low temperatures resulted in H-2 evolution accompanied by the formation of either solvent or triflate bound six coordinated species Ru(S)(P(OMe)(3))(bpy)(dfppe)]OTf](n) (S = solvent (n = 2), triflate (n = 1)] (13a/13b); these species have not been isolated and could not be established with certainty. They (13a/13b) were not isolated, instead the six-coordinated isomeric aqua complexes cis-(Ru(bpy)(dfppe)(OH2)(P(OMe)(3))]OTf](2) (14a/14b) were isolated. Reaction of the aqua complexes (14a/14b) with 1 atm of H-2 at room temperature in acetone-d(6) solvent resulted in heterolytic cleavage of the H-H bond. Results of the studies on H-2 lability and heterolytic activation using these complexes are discussed. The complexes 3, 5, 11a, and 14a have been structurally characterized.

Stepwise Crystallization: Illustrative Examples of the Use of Metalloligands Cu-6(mna)(6)](6-) and (Ag-6(Hmna)(2)(mna)(4)](4-) (H(2)mna=2-Mercapto Nicotinic Acid) in the Formation of Heterometallic Two- and Three-Dimensional Assemblies with brucite, pcu, and sql Topologies

Three new inorganic coordination polymers, {Mn(H2O)(6)]-Mn-2(H2O)(6)](Cu-6(mna)(6)]center dot 6H(2)O}, 1, {Mn-4(OH)(2)(H2O)(10)] (Cu-6(mna)6]center dot 8H(2)O}, 2, and {Mn-2(H2O)(5)]Ag-6(Hmna)(2)(mna)(4)]center dot 20H(2)O}, 3, have been synthesized at room temperature through a sequential crystallization route. In addition, we have also prepared and characterized the molecular precursor Cu-6(Hmna)(6)]. Compounds 1 and 3 have a two-dimensional structure, whereas 2 has a three-dimensional structure. The formation of 2 has been achieved by minor modification in the synthetic composition, suggesting the subtle relationship between the reactant composition and the structure. The hexanudear copper and silver duster cores have Cu center dot center dot center dot Cu and Ag center dot center dot center dot Ag distances close to the sum of the van der Waals radii of Cu1+ and Ag1+, respectively. The connectivity between Cu-6(mna)(6)](6-) cluster units and Mn2+ ions gives rise to a brucite related layer in 1 and a pcu-net in 2. The Ag-6(Hmna)(2)(mna)(4)](4-) cluster in 3, on the other hand, forms a sql-net with Mn2+. Compound 1 exhibits an interesting and reversible hydrochromic behavior, changing from pale yellow to red, on heating at 70 degrees C or treatment under a vacuum. Electron paramagnetic resonance studies indicate no change in the valence states, suggesting the color change could be due to changes in the coordination environment only. The magnetic studies indicate weak antiferromagnetic behavior. Proton conductivity studies indicate moderate proton migrations in 1 and 3. The present study dearly establishes sequential crystallization as an important pathway for the synthesis of heterometallic coordination polymers.

Iminodiacetic acid functionalized polypyrrole modified electrode as Pb(II) sensor: Synthesis and DPASV studies

An electrochemical lead ion sensor has been developed by modification of carbon paste electrode (CPE) using polypyrrole functionalized with iminodiacetic acid (IDA-PPy) containing carboxyl group. The electrochemical response of Pb2+ ion on the IDA-PPy modified CPE has been evaluated and the controling parameters have been optimized using differential pulse anodic stripping voltammetry (DPASV). The IDA-PPy modified CPE shows a linear correlation for Pb2+ concentrations in the range of 1 x 10(-6) to 5 x 10(-9) M and the lower detection limit of Pb2+ has been found to be 9.6 x 10(-9) M concentration. Other tested metal ions, namely Cu2+, Cd2+, Co2+, Hg2+, Ni2+ and Zn2+, do not exhibit any voltammetric stripping response below 1 x 10(-7) M concentration. However, the Pb2+ response is affected in the presence of molar equivalents or higher concentrations of Cu2+, Cd2+ and Co2+ ions in binary systems with Pb2+, consequent to their ability to bind with iminodiacetic acid, while Hg2+, Ni2+ and Zn2+ do not interfere at all. A good correlation has been observed between the lead concentrations as analyzed by DPASV using IDA-PPy modified CPE and atomic absorption spectrophotometry for a lead containing industrial effluent sample. (C) 2014 Elsevier Ltd. All rights reserved.

Improved Erlenmeyer Synthesis with 5-Thiazolone and Catalytic Mn(II) Acetate. Crystal Structure Confirmation of the Reaction Stereochemistry

2-Phenylthiazolin-5-one (5, a thioazlactone) condenses with various aldehydes in the presence of the mild base Mn(II) acetate as catalyst in CH2Cl2 solution. This leads to the corresponding Erlenmeyer reaction products (6) in excellent yields in the case of aromatic aldehydes and moderate yields in others. The mildness of the reaction conditions is apparently enabled by the aromaticity of the (putative) intermediate thiazolone anion. The structure and stereochemistry (Z) of the product derived from i-BuCHO was confirmed by single crystal X-ray diffraction. This study overcomes key limitations of the classical Erlenmeyer synthesis and also introduces the relatively nontoxic Mn(II) acetate as a reagent in heterocyclic chemistry.

Synthesis and antiproliferative activity of imidazo2,1-b]1,3,4]thiadiazole derivatives

A series of 2,5,6-substituted imidazo2,1-b]1,3,4]thiadiazole derivatives have been prepared and were tested for antiproliferative activity on cancer cells at the National Cancer Institute. Results showed that molecules with a benzyl group at position 2, exhibited an increase in activity for the introduction of a formyl group at the 5 position. The compound 2-benzyl-5-formyl-6-(4-bromophenyl)imidazo 2,1-b]1,3,4]thiadiazole 22 has been chosen for understanding the mechanism of action by various molecular and cellular biology studies. Results obtained from cell cycle evaluation analysis, analysis of mitochondrial membrane potential and Annexin V-FITC by flow cytometric analysis, ROS production and expression of apoptotic and DNA-repair proteins suggested that compound 22 induced cytotoxicity by activating extrinsic pathway of apoptosis, however, without affecting cell cycle progression. (C) 2014 Elsevier Ltd. All rights reserved.

Azide and Alkyne Terminated Polybutadiene Binders: Synthesis, Cross-linking, and Propellant Studies

In composite solid propellants, the fuel and oxidizer are held together by a polymer binder. Among the different types of polymeric binders used in solid propellants, hydroxyl terminated polybutadiene (HTPB) is considered as the most versatile. HTPB is conventionally cured using isocyanates to form polyurethanes. However, the incompatibility of isocyanates with energetic oxidizers such as ammonium dinitramide and hydrazinium nitroformate, the short pot life of the propellant slurry, and undesirable side reactions with moisture are limiting factors which adversely affect the mechanical properties of HTPB based propellant. With an aim of resolving these problems, HTPB was chemically transformed to azidoethoxy carbonyl amine terminated polybutadiene and propargyloxy carbonyl amine terminated polybutadiene by adopting appropriate synthesis strategies and characterizing them by spectroscopic and chromatographic techniques. This is the first report on 1,3-dipolar addition reaction involving azide and alkyne end groups for cross-linking HTPB. The blend of these two polymers underwent curing under mild temperature (60 degrees C) conditions through 1,3-dipolar cycloaddition reaction resulting in triazoletriazoline networks. The curing parameters were studied using differential scanning calorimetry. The kinetic parameter, viz., activation energy, was computed to be 107.6 kJ/mol, the preexponential factor was 2.79 x 10(12) s-(1), and the rate constant at 60 degrees C was computed to be 3.64 x 10-(5) s-(1). The cure profile at a given temperature was predicted using the kinetic parameters. Rheological studies revealed that the gel time for curing through the 1,3-dipolar addition is 280 min compared to 120 min for curing through the urethane route. The mechanical properties of the resultant cured polybutadiene network were superior to those of polyurethanes. The cured triazolinetriazole polymer network exhibited biphasic morphology with two glass transitions (T-g) at -56 and 42 degrees C in contrast to the polyurethane which exhibited a single transition at -60 degrees C. This was corroborated by associated morphological changes observed by scanning probe microscopy. The propellant processed using this binder has the advantages of improved pot life as indicated by the end of the mix viscosity which is 165 Pas as compared with 352 Pas for the polyurethane system along with a slow build- up rate. The mechanical properties of the propellant are superior to polyurethane with an improvement of 14% in tensile strength, 22% enhancement in elongation at break, and 12% in modulus.

Rollover-Preventive Force Synthesis at Active Suspensions in a Vehicle Performing a Severe Maneuver With Wheels Lifted Off

Among the intelligent safety technologies for road vehicles, active suspensions controlled by embedded computing elements for preventing rollover have received a lot of attention. The existing models for synthesizing and allocating forces in such suspensions are conservatively based on the constraints that are valid until no wheels lift off the ground. However, the fault tolerance of the rollover-preventive systems can be enhanced if the smart/active suspensions can intervene in the more severe situation in which the wheels have just lifted off the ground. The difficulty in computing control in the last situation is that the vehicle dynamics then passes into the regime that yields a model involving disjunctive constraints on the dynamics. Simulation of dynamics with disjunctive constraints in this context becomes necessary to estimate, synthesize, and allocate the intended hardware realizable forces in an active suspension. In this paper, we give an algorithm for the previously mentioned problem by solving it as a disjunctive dynamic optimization problem. Based on this, we synthesize and allocate the roll-stabilizing time-dependent active suspension forces in terms of sensor output data. We show that the forces obtained from disjunctive dynamics are comparable with existing force allocations and, hence, are possibly realizable in the existing hardware framework toward enhancing the safety and fault tolerance.

Relaxor behaviour in BaBi4Ti4O15 ceramics fabricated using the powders obtained by mechanochemically assisted synthesis route

Mechanochemically activated reactants were found to facilitate the synthesis of fine powders comprising 200-400 nm range crystallites of BaBi4Ti4O15 at a significantly lower temperature (700 A degrees C) than that of solid-state reaction route. Reactants (CaCO3, Bi2O3 and TiO2) in stoichiometric ratio were ball milled for 48 h to obtain homogeneous mixture. The evolution of the BaBi4Ti4O15 phase was systematically followed using X-ray powder diffraction (XRD) technique. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to probe its structural and microstructural details. The electron diffraction studies established the presence of correlated octahedral rotations and associated long-range polar ordering. High-resolution TEM imaging nevertheless revealed structural inhomogeneities leading to intergrowth defects. Dense BaBi4Ti4O15 ceramics with an average grain size of 0.9 mu m were fabricated using mechanochemically assisted synthesized powders at relatively low temperature (1000 A degrees C). The effect of grain size on the dielectric and relaxor behaviour of BaBi4Ti4O15 ceramics was investigated. Fine-grained ceramics (average grain size similar to 0.9 mu m) showed higher diffusion in phase transition, lower temperature of phase transition, lower Vogel-Fulcher freezing temperature and higher activation energy for the polarization reversal than those for coarse-grained ceramics (average grain size similar to 7 mu m) fabricated via the conventional solid-state reaction route.

Friedel-Crafts Arylation of a-Hydroxy Ketones: Synthesis of 1,2,2,2-Tetraarylethanones

Friedel-Crafts arylation of a-hydroxy ketones such as 2-hydroxy- 1,2,2-triarylethanones has been achieved with a variety of arenes and heteroarenes in the presence of Lewis or Bronsted acids. Both sterically hindered and unhindered 1,2,2,2-tetrarylethanones are formed in good to excellent yields by using a stoichiometric amount of triflic acid. The intermediacy of an a-keto carbenium ion has been proposed.