Elham S. Aazam

H2 Production with Low CO Selectivity from Photocatalytic Reforming of Glucose on Ni/TiO2-SiO2

Nano-sized Ni particles on TiO2-SiO2 were synthesized by the two methods of photo-assisted deposition (PAD) and impregnation. H2, which is a promising energy carrier, with a low CO concentration was produced by the photocatalytic reforming of glucose (a model biomass) on the Ni/TiO2-SiO2 catalyst. The supported Ni enhanced the rate of H2 production while it suppressed CO selectivity. The catalysts were characterized by X-ray diffraction, X-ray absorption fine structure, transmission electron microscope, and nitrogen adsorption analysis. Both H2 production and CO selectivity were strongly dependent on the preparation method, and PAD-Ni/TiO2-SiO2 was the better catalyst for H2 production with the lowest CO concentration.

Synthesis and characterization of P-doped TiO 2 thin-films for photocatalytic degradation of butyl benzyl phthalate under visible-light irradiation

P-doped TiO2 (PTIO) thin-films with different P contents were prepared using a sol-gel method. The thin-film samples were characterized using various techniques. The photocatalytic activity was evaluated by decomposing butyl benzyl phthalate under visible-light irradiation. The results showed that the transformation of anatase to the rutile phase was inhibited and grain growth of TiO2 was prevented by P doping. The results confirm that the doped P atoms existed in two chemical forms, and those incorporated in the TiO2 lattice may play a positive role in photocatalysis. The high photocatalytic activities of the PTIO thin-films may be the result of extrinsic absorption through the creation of oxygen vacancies, rather than excitation of the intrinsic absorption band of bulk TiO2. The PTIO can be recycled with little depression of the photocatalytic activity. After six cycles, the photocatalytic activity of the PTIO film was still higher than 98%.

Aggregation of Congo red with surfactants and Ag-nanoparticles in an aqueous solution.

Self aggregation, sorption, and interaction of Congo red, with cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), Ag(+) ions and silver nanoparticles have been determined spectrophotometrically. Congo red self-aggregation was identified from UV-visible spectra due to the shrinkage in an absorption band at 495 nm. The shape of the absorbance spectrum changed entirely with increasing [Congo red] but wavelength maxima remain unchanged. The molar absorptivity was found to be 9804 mol(-1) dm(3) cm(-1) at 495 nm. Absorption spectra of Congo red with Ag(+) ions show an isosbestic point. The complex formation constant and difference in absorption coefficients were found to be 8.5 × 10(4) mol(-1) dm(3) and 11,764 mol(-1) dm(3) cm(-1), respectively. Silver nano-particles could not be used for the catalytic degradation of Congo red because it results in the formation of a strong complex with them. Sodium dodecylsulfate did not show any significant interaction with this dye. Congo red was also used as a probe to determine the critical micellar concentration of CTAB.

Synthesis of copper/nickel nanoparticles using newly synthesized Schiff-base metals complexes and their cytotoxicity/catalytic activities

Transition metal complexes compounds with Schiff bases ligand representing an important class of compounds that could be used to develop new metal-based anticancer agents and as precursors of metal NPs. Herein, 2,3-bis-[(3-ethoxy-2-hydroxybenzylidene)amino]but-2-enedinitrile Schiff base ligand and its corresponding copper/nickel complexes were synthesized. Also, we reported a facile and rapid method for synthesis nickel/copper nanoparticles based on thermal reduction of their complexes. Free ligand, its metal complexes and metals nanoparticles have been characterized based on elemental analysis, transmission electron microscopy, powder X-ray diffraction, magnetic measurements and by various spectroscopic (UV-vis, FT-IR, (1)H NMR, GC-MS) techniques. Additionally, the in vitro cytotoxic activity of free ligand and its complexes compounds were assessed against two cancer cell lines (HeLa and MCF-7 cells)and one healthy cell line (HEK293 cell). The copper complex was found to be active against these cancer cell lines at very low LD50 than the free ligand, while nickel complex did not show any anticancer activity against these cell lines. Also, the antibacterial activity of as-prepared copper nanoparticles were screened against Escherichia coli, which demonstrated minimum inhibitory concentration and minimum bactericidal concentration values lower than those values of the commercial Cu NPs as well as the previous reported values. Moreover, the synthesized nickel nanoparticles demonstrated remarkable catalytic performance toward hydrogenation of nitrobenzene that producing clean aniline with high selectivity (98%). This reactivity could be attributed to the high degree of dispersion of Ni nanoparticles.

A dimeric copper coumarin complex: synthesis and crystal structure of [{Cu(4-methyl-7-(salicylideneamino)coumarin)2}2]

A binuclear copper complex [{Cu(L)2}2], C68H48Cu2N4O12C (where L is 4-methyl-7-(salicylideneamino)coumarin), has been synthesized and characterized using elemental analysis, molar conductance measurements, and infrared, ultraviolet and ESR spectrosopy. The molecular structure of title compound, determined by single-crystal X-ray diffraction studies, reveals that the two symmetric Cu(L)2 units are associated into a dimer by rather long Cu...O bonds. The Cu(II) ions are bridged via the phenolic oxygen of one of the monomers and have distorted trigonal bipyramidal conformation geometry. Within each monomer the two methylsubstituted coumarin skeletons are trans to one another, but adopt a parallel arrangement with respect to the other monomer. Only half of the complex molecule can be found in the asymmetric unit, Z′ = 0.5, the other half is generated by the symmetry centre.

Reversible encapsulation of silver nanoparticles into the helix of amylose (water soluble starch)

Natural biodegradable polymeric starch capped Ag-nanoparticles (AgNPs) were prepared by using extract of Dioscorea deltoidea in the presence of starch. UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, and digital images were used to determine the morphology and chemical composition of the as prepared AgNPs. The kinetics and morphology of the nano-materials (spherical, rod, triangular, irregular, truncated triangular, hexahedral, mono-dispersed, and aggregated) were discussed in terms of the [extract], [Ag+], and [starch]. Iodometric titration was used to confirm the reversible encapsulation of the AgNPs inside the helical structure of amylose. TEM images also suggest that the morphology of the encapsulated AgNPs entirely changes in comparison with the non encapsulated AgNPs. The starch functionalized AgNPs could be used for drug delivery, with the nucleation and aggregation controlled through fusogenic behaviour.

Synthesis of new microbial pesticide metal complexes derived from coumarin-imine ligand.

A series of metal complexes of zinc(II), cadmium(II), copper(II), nickel(II) and palladium(II) have been synthesized from coumarin-imine ligand, 8-[(1E)-1-(2-aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate, [HL]. The structures of the complexes were proposed in the light of their spectroscopic, molar conductance, magnetic and thermal studies. The ligand coordinated in a tridentate manner through the azomethine nitrogen, the phenolic oxygen and the amine nitrogen and all complexes were non-electrolytes with different geometrical arrangements around the central metal ion. Photoluminescence data unambiguously showed remarkable fluorescence enhancement to Zn(2+) over other cations. The antimicrobial screening tests revealed that copper(II) complex exhibited the highest potency and its minimum inhibitory concentration on the enzymatic activities of the tested microbial species was determined. No toxin productivity was detected for all tested toxigenic species upon the exposure of copper complex.

(Dimethyl sulfoxide-κO){4,4',6,6'-tetra-tert-butyl-2,2'-[1,2-dicyano-ethene-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato-κO,N,N',O'}zinc(II) acetonitrile monosolvate.

The Zn atom in the title acetonitrile solvate, [Zn(C34H42N4O2)(C2H6OS)]·CH3CN, exists in a distorted square-pyramidal geometry with the basal plane defined by the N2O2 atoms of the tetradentate Schiff base and with the dimethyl sulfoxide O atom in the apical position. The tetradentate mode of coordination of the Schiff base ligand leads to a five-membered ZnN2C2 chelate ring which adopts an envelope conformation with the Zn atom at the flap, and two six-membered ZnOC4N chelate rings, one of which is approximately planar (r.m.s. deviation = 0.054 Å) but the other has significant puckering (r.m.s. deviation = 0.203 Å).

Eco-friendly green synthesis of Ag@Fe bimetallic nanoparticles: Antioxidant, antimicrobial and photocatalytic degradation of bromothymol blue

Silver-iron bimetallic nanoparticles (BMNPs) were synthesized by using AgNO3 and Fe(NO3)3 as an Ag/Fe source in presence of Palm dates fruit. Upon addition of extract to a solution of Ag+ and Fe3+, a prefect transparent stable dark brown color appears with in a few minuets at room temperature. In order to conform the nature of resulting color, UV-visible spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) techniques were used. The absence of surface plasmon resonance (SPR) peaks in the entire UV-visible region suggests the formation of silvercore-ironshell BMNPs. The obtained nanoparticles were used as a catalyst for the degradation of bromothymol blue (BTB) in absence and presence of sunlight. The degradation kinetics was studied in presence of electron acceptors and scavengers, such as hydrogen peroxide, ammonium oxalate, ammonium per sulphate, benzoquinone, isopropyl alcohol, n-butanol, potassium bromate and potassium iodide. Radical trapping experiments demonstrates that active holes (h+) and generated hydroxy radical are primary species involved in H2O2 assisted catalytic degradation process. The free-radical scavenging, antioxidant and antimicrobial activities were determined for extract and BMNPs. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities were found to increase with increasing the amounts of extract. The silver-iron showed good invitro antibacterial activities against human pathogens.

Seedless synthesis of nanocomposites, optical properties, and effects of additives on their surface resonance plasmon bands

The work describes an easy seedless competitive chemical reduction method for the synthesis of Ag@Au/Ag bimetallic nanoparticles by mixing AgNO3, HAuCl4 and cysteine. Transmission electron microscope (TEM) images show that the large number of irregular, cross-linking, and aggregated Ag@Au/Ag are formed in a reaction mixture (HAuCl4+AgNO3+cysteine), whereas flower-like nanocomposites are obtained in presence of cetyltrimethylammonium bromide (CTAB), which acted as a shape-directing agent. Optical images reveal that the initially reaction proceeds through formation of purple color, which changes into dark brown color with the reaction time, indicating the formation of Ag@Au/Ag nanocomposites. The Ag+ has strong tendency to form complex with cysteine. Firstly, the reduction of Ag+ ions to Ag0 occurred by the HS group of the cysteine-Ag complex. Secondly, AuCl4- ions adsorbed on the positive surface of Ag0, which undergoes reduction by potential deposition, and leads to the formation of Ag@Au/Ag bimetallic nanoparticles. Inorganic electrolytes (NaCl, NaBr, NaNO3 and Na2SO4) have significant impact on the stability and aggregation of Ag@Au/Ag nanocomposites.