Photocatalytic studies under visible light irradiation using nanosized β-Bi2O3 are reported. β-Bi2O3 nanoparticles are prepared starting from the well-defined bismuth oxido cluster [Bi38O45(OMc)24(DMSO)9]⋅2 DMSO⋅7 H2O (OMc=O2CC3H5) using a straightforward hydrolysis and annealing protocol. Powder X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV/Vis spectroscopy and nitrogen adsorption measurements (using the Brunauer-Emmett-Teller (BET) theory) are used for the characterization of the as-prepared β-Bi2O3. By time-dependent annealing, the crystallite size can be controlled between (17±2) nm and (45±5) nm with BET surface areas of 7 to 29 m(2) g(-1). The indirect band gap of the as-prepared β-Bi2O3 amounts to (2.15±0.05) eV. The decomposition rates for rhodamine B (RhB) solutions are in the range of 2.46×10(-5) to 4.01×10(-4) s(-1) and depend on the crystallite size, amount of catalyst and concentration of RhB. Photocorrosion experiments have shown the formation of Bi2O2CO3 after several catalytic cycles. However, the catalyst can be recycled to phase-pure β-Bi2O3 nanoparticles by annealing for one hour under argon atmosphere at 380 °C. Furthermore, the photocatalytic activity of as-prepared β-Bi2O3 nanoparticles for the decomposition of phenol, 4-chlorophenol, 2,4-dichlorphenol, 4-nitrophenol, triclosan and ethinyl estradiol is demonstrated.

Metastable β-Bi2O3 Nanoparticles with Potential for Photocatalytic Water Purification Using Visible Light Irradiation

In this work, we investigate the impact of the solvation environment on single-walled carbon nanotube (SWCNT) photoluminescence quantum yield and optical transition energies (Eii) using a highly charged aryleneethynylene polymer. This novel surfactant produces dispersions in a variety of polar solvents having a wide range of dielectric constants (methanol, dimethyl sulfoxide, aqueous dimethylformamide, and deuterium oxide). Because a common surfactant can be used while maintaining a constant SWCNT–surfactant morphology, we are able to straightforwardly evaluate the impact of the solvation environment upon SWCNT optical properties. We find that (i) the SWCNT quantum yield is strongly dependent on both the polarity and electrophilicity of the solvent and (ii) solvatochromic shifts correlate with the extent of SWCNT solvation. These findings provide a deeper understanding of the environmental dependence of SWCNT excitonic properties and underscore that the solvent provides a tool with which to modulate SWCNT...

Effect of Solvent Polarity and Electrophilicity on Quantum Yields and Solvatochromic Shifts of Single-Walled Carbon Nanotube Photoluminescence

Surface functionalization of a series of nanosized iron oxide particles (average diameter around 6 nm) with oleic acid was realized in this study. The aim is to suspend the surface-functionalized nanoparticulated materials in insulating mineral oil and evaluate their colloidal stability as a function of time. Nanoparticulated samples presenting stoichiometry close to maghemite were obtained by oxidation of a freshly precipitated magnetite sample. Systematic variations observed in the Fe3+/Fe2+ ratio, average particle size, and lattice constant were attributed to differences in oxidation route and oxidation condition employed. Morphological, compositional, thermal, optical and magnetic characterization techniques were used in the investigation of native (P, PN1, PN2, POX1, POX3, and POX7) and surface-functionalized (POA, PN1OA, PN2OA, POX1OA, POX3OA, and POX7OA) samples. While suspending the oleic-acid-coated nanosized iron oxide particles in insulating mineral oil, the best colloidal stability was achieve...

Investigation of the Molecular Surface Coating on the Stability of Insulating Magnetic Oils

Fine tuning of a solvatochromic fluorophore for selective determination of Fe3+: a new type of benzimidazole-based anthracene-coupled receptor

The work describes the interactions of nanosilver (NAg) with bacterial cell envelope components at a molecular level and how this associates with the reactive oxygen species (ROS)-mediated toxicity of the nanoparticle. Major structural changes were detected in cell envelope biomolecules as a result of damages in functional moieties, such as the saccharides, amides, and phosphodiesters. NAg exposure disintegrates the glycan backbone in the major cell wall component peptidoglycan, causes complete breakdown of lipoteichoic acid, and disrupts the phosphate-amine and fatty acid groups in phosphatidylethanolamine, a membrane phospholipid. Consistent with the oxidative attacks, we propose that the observed cell envelope damages are inflicted, at least in part, by the reactive oxygen radicals being generated by the nanoparticle during its leaching process, abiotically, without cells. The cell envelope targeting, especially those on the inner membrane phospholipid, is likely to then trigger the rapid generation of lethal levels of cellular superoxide (O2•-) and hydroxyl (OH•) radicals herein seen with a model bacterium. The present study provides a better understanding of the antibacterial mechanisms of NAg, whereby ROS generation could be both the cause and consequence of the toxicity, associated with the initial cell envelope targeting by the nanoparticle.

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Nanosilver Targets the Bacterial Cell Envelope: The Link with Generation of Reactive Oxygen Radicals.

The thermodynamics of complexation of transition and lanthanide ions by 3-(α-carboxymethylaminobenzyli-denehydrazino)-5,6-diphenyl-1,2,4 triazine (HipHt)

Solvent effects on the electronic spectra of dicyanobis(1,10-phenanthroline)iron(II) have been investigated in thirteen
 pure solvents and twenty binary solvent mixtures. In pure solvents, the shifts of the νmax values are found to
 depend on more than one of the known solvent parameters (AN, α, β, DN and π*). AN, α and π* are found to be the most important
 solvent parameters, exerting a considerable effect on the solvatochromic shifts of the title complex. The preferential
 solvation of dicyanobis(1,10-phenanthroline)iron(II) in binary solvent mixtures has been investigated by monitoring
 the metal–ligand charge transfer band of the indicator complex. Organic solvents are preferred near the
 indicator complex in aqueous binary solvent mixtures (negative deviation), except in regions rich in
 MeCN, Me2CO and 1,4-dioxane, where water molecules are preferred over the organic component (dual behavior). However,
 the indicator complex is preferentially solvated by the component which has the higher acceptor number
 in non-aqueous binary solvent mixtures. Negative deviation was observed in binary mixtures of CHCl3
 and Me2CO with alcohols and positive deviation in mixtures of CHCl3 with THF, DMSO and Me2CO. Different criteria were
 considered to evaluate the extent of preferential solvation in different solvent mixtures, iz., the local molar fraction
 (XAL), the excess function (ΔX), the iso-solvation point (XBiso) and the preferential solvation constant (KA/B). The preferential
 solvation
 data have been linearly
 correlated with the different solvent parameters.

Preferential solvation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Preparation and characterization of a novel system of CdS nanoparticles embedded in borophosphate glass matrix

The values of the Lewis acidity parameter (acceptor number) for acceptor compounds (ANν) and twenty binary solvent mixtures (ANm) were estimated using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex. The acceptor number values for the acceptor compounds (ANν) are linearly correlated with the Taft constant (σTaft) and the formation constant values. On the other side, ANm values for binary solvent mixtures over the whole composition range of the mixture are correlated with the other solvent parameters and equilibrium data. These correlations suggest the importance of the present ANm values to correlate the reaction rates, and may be used as an aid in the interpretation of equilibrium studies in solvent mixtures. Equilibrium constants, for the stepwise interaction of one or two acceptor ligand molecules with Fe(phen)2(CN)2 in DMF solution at 25 °C to form adducts, Fe(phen)2(CN)2(A)n, have been evaluated using a spectrophotometric technique. The equilibrium constants obtained were correlated with the values of the dissociation constant (pKa), acceptor number, and σTaft of the acceptor ligands.

Lewis acidity parameter for binary solvent mixtures and adduct formation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Mohamed A.M. Mahmoud

Papers

The thermodynamics of complexation of transition and lanthanide ions by 3-(α-carboxymethylaminobenzyli-denehydrazino)-5,6-diphenyl-1,2,4 triazine (HipHt)

Preferential solvation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Preparation and characterization of a novel system of CdS nanoparticles embedded in borophosphate glass matrix

Lewis acidity parameter for binary solvent mixtures and adduct formation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Thermo-kinetic theoretical studies on pyrolysis of dimethoxymethane fuel additive