Sonochemical degradation of textile dyes in aqueous solution using sulphate radicals activated by immobilized cobalt ions

Decolorisation of dye solutions by cobalt activated persulphate and ultrasonication has been investigated. Rhodamine B, Methylene Blue dye (basic dyes) and Acid orange II, Acid scarlet red 3R (acid dyes) were used as model compounds in this study. Immobilized cobalt ions, activated the persulphate to form highly reactive sulphate radicals. The degradation studies were conducted with only persulphate (PS), cobalt activated persulphate (PS + Co), persulphate + ultrasonication (PS + US) and cobalt activated persulphate + ultrasonication (PS + US + Co). The decolorisation efficiency were in the order of PS < PS + Co < PS + US < PS + US + Co for all the four dye solutions. The effect of pH, dosage of persulphate as well as catalyst and contact time was investigated. Under the optimum condition, the decolorisation obeyed first-order kinetics. Nearly 90–97% of decolorisation was achieved with COD and TOC removal of about 65–73% and 53–62%, respectively, were achieved within an hour.     

Electrical rectification from a fullerene[60]-dyad based metal-organic-metal junction

Langmuir-Blodgett monolayer films of C60-didodecyloxybenzene dyad, with a C60 acceptor and didodecyloxybenzene donor, exhibit rectification with high rectification ratios of 87-158 at 3 V.     

Versatile,metal free and temperature-controlled g-C3N4 as a highly efficient and robust photocatalyst for the degradation of organic pollutants

Research on Chemical Intermediates - In the present study, we report novel graphitic carbon nitride (g-C3N4) nanosheets at different calcination temperatures viz 500&nbsp;°C,...     

Impact of FRET between Molecular Aggregates and Quantum Dots

Energy transfer has been employed in third‐generation solar cells for the conversion of light into electrical energy. Long‐range nonradiative energy transfer from semiconductor quantum dots (QDs) to fluorophores has been demonstrated by using CdS QDs and thiophene?BODIPY (boron dipyrromethene, abbreviated as TG2). TG2 shows a broad photoluminescence (PL) spectrum, which varies with concentration. At very low concentrations, monomeric units are present; then, upon increasing the concentration, these monomers form a mixed (J‐/H‐)aggregated state. Energy transfer between the CdS QDs and TG2 was confirmed by separately investigating the interactions between CdS and the monomer of TG2 and between CdS and the aggregated states of TG2. Size‐dependent PL quenching confirmed that nonradiative Förster resonance energy transfer (FRET) from photoexcited CdS QDs to the J‐aggregate state of TG2 was the major energy‐relaxation channel, which occurred on the timescale of hundreds of fs. These results have broad applications in the field of light harvesting based on the assembly of molecular aggregates.     

Phytochemical constituents from dietary plant Citrus hystrix

Chemical investigation of the fruit peel of dietary plant Citrus hystrix offered two new flavones 5,6,4′-trihydroxypyranoflavone I and 5,4′-dimethyl-6-prenylpyranoflavone XIII besides 11 known compounds. The structures of all compounds were elucidated with the aid of suitable analytical methods like 1D, 2D-NMR, mass and single crystal X-ray analysis. An X-ray crystal study of compound II was done for the first time and the compounds I–VI, XI and XII are hitherto not reported from this plant. Biological studies revealed that compound I found to have a good antidiabetic and antiacetylcholinesterase activities meanwhile compounds II, III and V showed a significant free radical scavenging ability as well as antioxidant capacity. In addition, compounds I, IV, V and VI showed cytotoxicity against U87, A549 and MCF-7 cells. Overall, the new compound I showed valuable bioactive properties. Due to insufficient quantity of compound XIII, biological studies were not done.     

Au10(TBBT)10: the Begining and the End of Aun(TBBT)m Nanoclusters

Gold(I) thiolate compounds (i.e. Au^I-SR) are important precursors for the synthesis of atomically precise Au_n(SR)_m nanoclusters. However, the nature of the Au^I-SR precursor remains elusive. Here, we report that the Au₁₀(TBBT)₁₀ complex is a universal precursor for the synthesis of Au_n(TBBT)_m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au₁₀(TBBT)₁₀ complex is also found to be re-generated through extended etching of the Au_n(SR)_m nanoclusters with excess of TBBT thiol and O₂. The formation of well-defined Au₁₀(TBBT)₁₀ complex, instead of polymeric Au^I-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au₁₀(TBBT)₁₀ is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au₅(TBBT)₅ rings. The photophysical property of Au₁₀(TBBT)₁₀ complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au₁₀(TBBT)₁₀ precursor improves the efficiency of the synthesis of the Au_n(TBBT)_m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.     

In vitro study of magnesium-calcite biomineralization in the skeletal materials of the seastar Pisaster giganteus

The mechanisms of formation of biogenic magnesium-rich calcite remain an enigma. Here we present ultrastructural and compositional details of ossicles from the seastar Pisaster giganteus (Echinodermata, Asteroidea). Powder X-ray diffraction, infrared spectroscopy and elemental analyses confirm that the ossicles are composed of magnesium-rich calcite, whilst also containing about 0.01 % (w/w) of soluble organic matrix (SOM) as an intracrystalline component. Amino acid analysis and N-terminal sequencing revealed that this mixture of intracrystalline macromolecules consists predominantly of glycine-rich polypeptides. In vitro calcium carbonate precipitation experiments indicate that the SOM accelerates the conversion of amorphous calcium carbonate (ACC) into its final crystalline product. From this observation and from the discovery of ACC in other closely related taxa, it is suggested that substitution of magnesium into the calcite lattice through a transient precursor phase may be a universal phenomenon prevalent across the phylum echinodermata.     

Peristaltic transport of a Newtonian fluid in a vertical asymmetric channel with heat transfer and porous medium

The problem of peristaltic flow of a Newtonian fluid with heat transfer in a vertical asymmetric channel through porous medium is studied under long-wavelength and low-Reynolds number assumptions. The flow is examined in a wave frame of reference moving with the velocity of the wave. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The analytical solution has been obtained in the form of temperature from which an axial velocity, stream function and pressure gradient have been derived. The effects of permeability parameter, Grashof number, heat source/sink parameter, phase difference, varying channel width and wave amplitudes on the pressure gradient, velocity, pressure drop, the phenomenon of trapping and shear stress are discussed numerically and explained graphically.     

Bilayer vesicles as precursors for spherical fractal aggregates from the self-assembly of a C60-fullerene-dyad in polar solvent

Spherical fractal aggregates of approximately 10 microm were formed from a pi-electronic amphiphile, C(60)-didodecyloxybenzene dyad when extracted from THF into water, necessitating a critical dielectric constant epsilon > or =30 in binary THF-water mixtures. Molecular dynamics simulations revealed the unit cluster to such a form involves an aggregation number approximately 90 with predominant soft associative molecular interactions which corroborated the octadecahedral model proposed for the cluster growth.     

Pulsatile blood flow in large arteries: comparative study of Burton’s and McDonald’s models

To get a clear picture of the pulsatile nature of blood flow and its role in the pathogenesis of atherosclerosis, a comparative study of blood flow in large arteries is carried out using the two widely used models, McDonald＇s and Burton＇s models, for the pressure gradient. For both models, the blood velocity in the lumen is obtained analytically. Elaborate investigations on the wall shear stress （WSS） and oscillatory shear index （OSI） are carried out. The results are in good agreement with the available data in the literature. The superiority of McDonald＇s model in capturing the pulsatile nature of blood flow, especially the OSI, is highlighted. The present investigation supports the hypothesis that not only WSS but also OSI are the essential features determining the pathogenesis of atherosclerosis. Finally, by reviewing the limitations of the present investigation, the possibility of improvement is explored.