Extending photocatalytic activity of TiO2 nanoparticles to visible region of illumination by doping of cerium

Cerium-doped Titanium dioxide (TiO(2)) nanoparticles are prepared by sol-gel method. Doping shifts the UV absorption edge of TiO(2) to the visible region, making it efficient for visible light photocatalysis. Incorporation of cerium decreases the effective band gap of TiO(2) and increases the Urbach energy levels. At the dopant concentrations of 0.015 and 0.025 mol the luminescence intensity increases compared to undoped TiO(2); however, the luminescence is quenched at 0.035 mol. Quenching of luminescence indicates efficient separation of charge carriers. Undoped TiO(2) is showing poor performance in the photocatalytic degradation of methyl orange under visible light. However, on cerium doping its photoactivity is increased, and is drastically enhanced at 0.035 mol of cerium. Further increase in Ce(3+) doping level to 0.045 mol results in the reduction of the photodegradation of the dye. On UV irradiation, entire samples show good photocatalytic activity up to 30 min, but their efficiency decreases when irradiation time is increased to 45 min. Irradiation for longer time results in negative charging of the TiO(2) surface with migrating electrons. The negatively charged surface repels the OH(-) ion and O(2) molecule from adsorbing on its surface thus decreasing the availability of hydroxyl and superoxide radical for dye degradation.     

Efficient synthesis of methyl carbamate via Hofmann rearrangement in the presence of TsNBr2

An efficient method has been developed for the synthesis of carbamates from the corresponding amides via the Hofmann rearrangement using N,N-dibromo-p-toluenesulfonamide (TsNBr₂) in the presence of DBU in methanol. The reaction goes into completion in 10–20 min at 65 °C to produce the corresponding carbamate in excellent yield.     

Synthesis of some novel functionalized dihydropyrido[2,3-d]pyrimidines via an one-pot three-component reaction catalysed by InCl3

Some novel functionalized dihydropyrido[2,3-d]pyrimidine derivatives 4 were synthesized using a one-pot three-component reaction of 6-aminouracils 1, aryl aldehydes 2 and 3-cyanoacetyl indole 3 using InCl₃ as catalyst.     

Carbon-13 NMR relaxation and transitions in polymers

High-resolution proton-decoupled carbon-13 nuclear magnetic resonance relaxation parameters have been obtained as a function of temperature for a set of completely amorphous polymers, semicrystalline polymers, and a series of ethylene–vinyl acetate copolymers. With these samples the nature of the glass temperature, other postulated amorphous transitions, and the β transition were investigated. For the completely amorphous polymers, the average correlation times depend on temperature according to the Williams–Landel–Ferry relation. Spectral collapse occurs at temperatures whose ratio to T_g is in the range 1.2–1.4 and corresponds to a correlation time of about 10^?7s. The loss of resolvable spectra is demonstrated to be a consequence of experimental methods and is not due to the occurrence of another amorphous transition. Both the methylene and methine carbons can be resolved for the ethylenevinyl acetate copolymers. Although the correlation time for the methylene carbon is continuous and resolvable through the β transition region, the methine branch-point resonance is lost. The implication of these results to the molecular nature of the β transition is discussed.     

Aza-Michael Addition of Amines to α,β-Unsaturated Compounds Using Molecular Iodine as Catalyst

Aza-Michael adducts are obtained in very good yields by the conjugate addition of aliphatic amines to α,β-unsaturated compounds using molecular iodine as catalyst in dichloromethane at room temperature. Aromatic amines were found to be reactive under reflux in toluene.     

A vanadyl complex grafted to periodic mesoporous organosilica: a green catalyst for selective hydroxylation of benzene to phenol

Selective benzene hydroxylation: A periodic mesoporous organosilica embedded with a vanadyl(IV) acetylacetonate complex has been synthesized through a co-condensation method. This system is a catalyst for direct hydroxylation of benzene to phenol, presenting a selectivity of 100?% towards the phenol formation as well as an excellent catalytic recyclability (see scheme).     

Iron carbonyl complex containing bis[2‐(diphenylphosphino)phenyl]ether enhancing efficiency in the palladium‐catalyzed Suzuki–Miyaura reaction

The reaction of [Fe₃(CO)₁₂] with bis[2‐(diphenylphosphino)phenyl]ether (DPEphos) in refluxing THF afforded a mononuclear complex, [Fe(CO)₄(η¹‐P‐DPEphos)] (1), as major product and a binuclear complex, [Fe₂(CO)₆(μ‐CO)(μ‐P,P‐DPEphos)] (2), as minor product respectively. The DPEphos ligand acts as a terminal P‐donor in complex 1 and a bridging P,P‐donor in complex 2. Complexes 1 and 2 were characterized by elemental analysis, fast atom bombardment mass spectrometry, FT‐IR, ¹H and ³¹P{¹H} NMR spectroscopy. The structure of complex 1 has been tentatively assigned by density functional theory calculations and its analogy with reported complexes. Combination of complex 1 and PdCl₂ furnished an active catalyst for the Suzuki–Miyaura cross‐coupling reactions of various aryl halides with arylboronic acids. Interestingly, under the same experimental condition, complex 1/PdCl₂ as catalyst showed superior activity over the DPEphos/PdCl₂ system. Copyright © 2012 John Wiley & Sons, Ltd.     

Alga-mediated facile green synthesis of silver nanoparticles: Photophysical,catalytic and antibacterial activity

A facile, convenient and green method has been employed for the synthesis of silver nanoparticles (AgNPs) using dried biomass of a green alga, Chlorella ellipsoidea. The phytochemicals from the alga, as a mild and non-toxic source, are believed to serve as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of a surface plasmon resonance band at 436 nm and energy dispersive X-ray spectroscopy. The transmission electron microscopy images showed the nanoparticles to be nearly spherical in shape with different sizes. A dynamic light scattering study revealed the average particle size to be 220.8 ± 31.3 nm. Fourier transform infrared spectroscopy revealed the occurrence of alga-derived phytochemicals attached to the outer surface of biogenically accessed silver nanoparticles. The powder X-ray diffraction study revealed the face-centred cubic crystalline structure of the nanoparticles. The as-synthesized biomatrix-loaded AgNPs exhibited a high photocatalytic activity for the degradation of the hazardous pollutant dyes methylene blue and methyl orange. The catalytic efficiency was sustained even after three reduction cycles. A kinetic study indicated the degradation rates to be pseudo-first order with the degradation rate being 4.72 × 10⁻² min⁻¹ for methylene blue and 3.24 × 10⁻² min⁻¹ for methyl orange. The AgNPs also exhibited significant antibacterial activity against four selected pathogenic bacterial strains.     

Effect of E × B electron drift and plasma discharge in dc magnetron sputtering plasma

Study of electron drift velocity caused by Etimes B motion is done with the help of a Mach probe in a dc cylindrical magnetron sputtering system at different plasma discharge parameters like discharge voltage, gas pressure and applied magnetic field strength. The interplay of the electron drift with the different discharge parameters has been investigated. Strong radial variation of the electron drift velocity is observed and is found to be maximum near the cathode and it decreases slowly with the increase of radial distance from the cathode. The sheath electric field, E measured experimentally from potential profile curve using an emissive probe is contributed to the observed radial variation of the electron drift velocity. The measured values of the drift velocities are also compared with the values from the conventional theory using the experimental values of electric and magnetic fields. This study of the drift velocity variation is helpful in providing a useful insight for determining the discharge conditions and parameters for sputter deposition of thin film.