Electrochemical deposition of praseodymium oxide on tin-doped indium oxide as a thin sensing film

Fabrication of a thin praseodymium oxide film is of great technological interest in sensor, semiconducting, and ceramic industries. It is shown for the first time that an ultrathin layer of praseodymium oxide can be deposited on tin-doped indium oxide surface (ITO) by applying a negative sweeping voltage (cathodic electrodeposition) to the aqueous solution containing Pr(NO3)(3) and H2O2 using cyclic voltammetry, followed by annealing the film at 500 S C for 1 h. X-ray diffraction suggested that the predominant phase of the film is Pr6O11 and atomic force microscopy and scanning electron microscopy characterizations indicated that this film is assembled with a monolayer coverage of spherical praseodymium oxide nanoparticles packed closely on the ITO surface. AC impedance measurements of the thin Pr6O11 film on ITO also revealed that the composite material displays a much higher electrical conductivity compared to the pure ITO. As a result, the material could suitably be used as a new chemical sensor. (c) 2006 The Electrochemical Society.

Layer-by-layer deposition of praseodymium oxide on tin-doped indium oxide (ITO) surface

Praseodymium oxide as a thin film of controllable layer is known to display many unique physiochemical properties, which can be useful to ceramic, semiconductive and sensor industries. Here in this short paper, we describe a new chemical method of depositing praseodymium oxide on tin-doped indium oxide (ITO) surface using a layer-by-layer approach. The process is carried out by dipping the ITO in solutions of adsorbable polycationic chitosan and alkaline praseodymium hydroxide Pr(OH)(3) alternatively in order to build up the well-defined multi-layers. XRD suggests that the predominant form of the oxide is Pr6O11, obtained after heat treatment of the deposited ITO in static air at 500 degrees C. Microscopic studies including AFM, TEM and SEM indicate that the deposited oxide particles are uniform in size and shape (cylindrical), mesoporous and the thickness of the film can be controlled. AC impedance measurements of the deposited materials also reveal that the oxide layers display a high electrical conductivity hence suitable for sensor uses. (c) 2006 Elsevier B.V. All rights reserved.

Synthesis and fabrication of a thin film containing silica-encapsulated face-centered tetragonal FePt nanoparticles

Self-assembly of monodisperse, silica-encapsulated, face-centered tetragonal FePt nanoparticles forms closely packed 2D arrays (see figure). Placing monodisperse FePt nanoparticles in silica nanocapsules allows the transition from a disordered face-centered cubic phase to a ferromagnetic crystalline face-centered tetragonal structure at elevated temperature without severe sintering. These materials are potential candidates for the generation of ultrahigh-density magnetic recording media.

Film-forming polymers containing in the main-chain dibenzo crown ethers with aliphatic (C-10-C-16), aliphatic-aromatic, or oxyindole spacers

Novel, linear, soluble, high-molecular-weight, film-forming polymers and copolymers in which main-chain crown ether units alternate with aliphatic (C-10-C-16) units have been obtained for the first time from aromatic electrophilic substitution reactions of crown ethers by aliphatic dicarboxylic acids followed by reduction of the carbonyl groups. The crown ether unit is dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, or dibenzo-30-crown-10; the aliphatic spacer is derived from a dicarboxylic acid (sebacic, 1,12-dodecanedicarboxylic, hexadecanedioic or 1,4-phenylenediacetic acids). The reactions were performed at 35 degrees C in a mixture of methanesulfonic acid (MSA) with phosphorus pentoxide, 12:1 (w/w), (Eaton's reagent). The carbonyl groups in the polyketones obtained were completely reduced to methylene linkages by treatment at room temperature with triethylsilane in a mixture of trifluoroacetic acid and dichloromethane. Polymers containing in the main chain crown ethers alternating with oxyindole fragments were prepared by one-pot condensation of crown ethers with isatin in a medium of Eaton's reagent. A possible reaction mechanism is suggested. According to IR and NMR analyses, the polyacylation reactions lead to the formation of isomeric (syn/anti-substituted) crown ether units in the main chain. The polymers obtained were soluble in the common organic solvents, and flexible transparent films could be cast from the solutions. DSC and X-ray studies of the polymers with "symmetrical" crown ethers reveal the presence of the endotherms corresponding to the supramolecular assemblies.

Effects of endogenous flour lipids on the quality of short-dough biscuits

Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of short-dough (shortcake type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat, but without endogenous lipid. Short-dough biscuits baked from defatted flour had smaller diameters, and were flatter, denser and harder than control biscuits. Defatted flour shortcake doughs exhibited different rheological behaviour from the control samples, showing higher storage and loss moduli (G' and G" values), ie higher viscoelasticity. Functionality was restored when total non-starch flour lipids were added back to defatted flour. The polar lipid fraction had a positive effect in restoring flour quality whereas the non-polar lipid fraction had no effect. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics. A study of the microstructure of defatted biscuits revealed that their gluten protein was more hydrated and developed than the gluten of the control biscuits. This conclusion was supported by the higher water absorption of the defatted gluten. (C) 2004 Society of Chemical Industry.

Effects of resistant starch type III polymorphs on human colon microbiota and short chain fatty acids in human gut models

This study probed the possible effects of type III resistant starch (RS) crystalline polymorphism on RS fermentability by human gut microbiota and the short chain fatty acids production in vitro. Human fecal pH-controlled batch cultures showed RS induces an ecological shift in the colonic microbiota with polymorph B inducing Bifidobacterium spp. and polymorph A inducing Atopobium spp. Interestingly, polymorph B also induced higher butyrate production to levels of 0.79 mM. In addition, human gut simulation demonstrated that polymorph B promotes the growth of bifidobacteria in the proximal part of the colon and double their relative proportion in the microbiota in the distal colon. These findings suggest that RS polymorph B may promote large bowel health. While the findings are limited by study constraints, they do raise the possibility of using different thermal processing to delineate differences in the prebiotic capabilities of RS, especially its butryrogenicity in the human colon.