A novel tungsten trioxide (WO3)/ITO porous nanocomposite for enhanced photo-catalytic water splitting

Hybrid nanocomposite films of ITO-coated, self-assembled porous nanostructures of tungsten trioxide (WO(3)) were fabricated using electrochemical anodization and sputtering. The morphology and chemical nature of the porous nanostructures were studied by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS), respectively. The photoelectrochemical (PEC) properties of WO(3) porous nanostructures were studied in various alkaline electrolytes and compared with those of titania nanotubes. A new type of alkaline electrolyte containing a mixture of NaOH and KOH was proposed for the first time to the best of our knowledge and shown to improve the photocurrent response of the photoanodes. Here, we show that both the WO(3) nanostructures and titania nanotubes (used for comparison) exhibit superior photocurrent response in the mixture of NaOH and KOH than in other alkaline electrolytes. The WO(3) porous nanostructures suffered from surface corrosion resulting in a huge reduction in the photocurrent density as a function of time in the alkaline electrolytes. However, with a protective coating of ITO (100 nm), the surface corrosion of WO(3) porous nanostructures reduced drastically. A tremendous increase in the photocurrent density of as much as 340% was observed after the ITO was applied to the WO(3) porous nanostructures. The results suggest that the hybrid ITO/WO(3) nanocomposites could be potentially coupled with titania nanotubes in a multi-junction PEC cell to expand the light absorption capability in the solar spectrum for water splitting to generate hydrogen.     

A fitted numerical method for parabolic turning point singularly perturbed problems with an interior layer

The objective of this paper is to construct and analyze a fitted operator finite difference method (FOFDM) for the family of time‐dependent singularly perturbed parabolic convection–diffusion problems. The solution to the problems we consider exhibits an interior layer due to the presence of a turning point. We first establish sharp bounds on the solution and its derivatives. Then, we discretize the time variable using the classical Euler method. This results in a system of singularly perturbed interior layer two‐point boundary value problems. We propose a FOFDM to solve the system above. Through a rigorous error analysis, we show that the scheme is uniformly convergent of order one with respect to both time and space variables. Moreover, we apply Richardson extrapolation to enhance the accuracy and the order of convergence of the proposed scheme. Numerical investigations are carried out to demonstrate the efficacy and robustness of the scheme.     

Propriétés de permutabilité avec certaines restrictions

Sans résumé     

Iodine-catalyzed allylation of 1,3-dicarbonyl compounds with allylic alcohols at room temperature

A highly efficient iodine-catalyzed allylation of 1,3-dicarbonyl compounds with a wide variety of allylic alcohols has been developed. The reaction is operationally straightforward and proceeds under very mild conditions at room temperature in good to excellent yields (up to 99%) and regioselectivity.     

Microchemical investigation of medicinal plants. V

Summary The spectral analysis of the yellow compound isolated from the seeds ofC. Bignonioides was carried out to further investigate its structure. The presence of two methoxyl groups, two hydroxyl groups, and an ,-unsaturated carbonyl is firmly established. It is not possible at this time to substantially confirm whether the carbonyl is an aromatic aldehyde or a six-membered ring ketone. The molecular formula, C₁₇H₁₄O₆ (11 sites of unsaturation and/or rings), is established. The compound does not contain any methyl or methylene groups. The location of one methoxyl and one hydroxyl closer to an electronegative group (i. e. a furanoic oxygen) is indicated. The hydroxyl groups are not located ortho to the carbonyl.The compound has a polynuclear aromatic structure. The evidence indicates one ring is 1,2,3,4-tetra substituted. Another ring may be 1,2,3,5-tetrasubstituted or 1,3,5-trisubstituted. A heteroaromatic group (e. g. furan) may also be present.Further work is in progress to elucidate the structure of the compound.

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Zusammenfassung Die Spektralanalyse der gelben, aus Catalpasamen isolierten Verbindung wurde zwecks weiterer Untersuchung ihrer Struktur durchgeführt. Die Anwesenheit zweier Methoxylgruppen, zweier Hydroxylgruppen und einer,-ungesättigten Carbonylgruppe wurde sichergestellt. Bis jetzt ist nicht zu entscheiden, ob letztere einer aromatischen Aldehydgruppe oder einem sechsgliedrigen cyklischen Keton zugehört. Die Summenformel C₁₇H₁₄O₆ mit elf ungesättigten Bindungen und/oder Ringen wurde nachgewiesen. Die Verbindung enthält keine Methyl- oder Methylengruppen. Die Lokalisation einer Methoxyl- und einer Hydroxylgruppe in der Nähe einer elektronegativen Gruppe (das heißt, eines furanoiden Sauerstoffs) ist erkennbar. Die Hydroxylgruppen stehen zur Carbonylgruppe nicht ino-Stellung.Die Verbindung hat polynukleare aromatische Struktur. Ein Ring ist in den Stellungen 1, 2, 3 und 4 substituiert, ein weiterer in den Stellungen 1, 2, 3 und 5 oder nur in 1, 3 und 5. Eine heterocyklische Gruppe (z. B. Furan) dürfte anwesend sein. Die Untersuchungen werden fortgesetzt.

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For Part IV see Mikrcohim. Acta [Wien]1968, 1085.