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Abstract: A series of CeO2–CaO nanocomposite oxides were synthesized by the amorphous citrate method and characterized by TGA, XRD, UV–Vis-DRS, SEM and TEM experimental techniques. The XRD analysis indicated the presence of a substitutional type solid solution for ceria rich composite oxides whereas for the calcium oxide rich composite oxides, the presence of crystalline CaO was observed along with the solid solution phase. Fourier line profile analysis of the broadened X-ray diffraction profiles revealed the presence of small nanocrystallites of the mixed oxides with size in the range of 5–25nm. UV–Vis-DRS study of the composite oxide showed well dispersion of the ceria in the CaO matrix. The characteristic reflections from the low coordinated surface Ce4+ ions were observed in the UV study along with a blue shift in the absorption edge for samples containing up to 20mol% ceria. The direct band gaps calculated from the UV spectra were found to be in the range of 3.45–3.66eV. The composite oxide materials were found to be porous and spongy in nature observed from the SEM analysis. TEM study of the CeO2(20%)–CaO material indicated the presence of well dispersed mixed oxide nanoparticles in a continuous CaO matrix. The Ce–Ca–O nanocomposite oxides were used as an environmentally benign catalyst for the multicomponent one pot synthesis of 2-amino-2-chromenes by multicomponent condensation of aryl aldehydes, α-naphthol and malononitrile in aqueous media. The nanocomposite oxides were found to be highly efficient for the synthesis of structurally diverse aminochromenes with excellent yield and purity. [Copyright &y& Elsevier]

Abstract: A series of MoO3–ZrO2 nanocomposite oxides with MoO3 content in the range of 2–20mol% were prepared by solution combustion method. Three different fuels namely urea, glycine and hexamethylenetetramine (HMTA) were used for the preparation of MoO3–ZrO2 oxides. For the sake of comparison, the MoO3–ZrO2 composite oxides were also prepared by impregnation of zirconia with molybdenum salt precursor and subsequent heat treatment. The synthesized nanomaterials were characterized by XRD, SEM, TEM and UV–vis spectroscopic technique. XRD study indicated selective stabilization of the tetragonal phase of zirconia in the presence of MoO3. The method of preparation was found to be crucial for the phase composition of zirconia in the composite oxide. The crystallite size and rms stain were calculated from the Fourier line shape analysis of the broadened X-ray diffraction profiles. With increase in the MoO3 content, the crystallite size of the tetragonal zirconia phase was found to be decreased. TEM study indicated the presence of small nanoparticles with size in the 5–10nm range. UV–vis study of the composite oxide materials revealed well dispersion of the molybdenum oxide component in the form of monomer, dimers and nanoclusters in the zirconia matrix. The nature of fuel was found to be crucial in determining the morphology and shape of the particles. [Copyright &y& Elsevier]

Nanocrystalline orthorhombic gallium ferrite (GFO) has been synthesized by a sol–gel method. The synthesized powder has been characterized by TG/DTA, XRD, TEM, FTIR and nitrogen adsorption isotherm. In the present study we report an excellent ethanol vapour sensitivity of nanocrystalline GaFeO 3 at concentrations down to 1 ppm making the sensors suitable for application in food industries. Interestingly in contrast to the market available consumers breath analyser based on tin dioxide, GaFeO 3 -based sensor is immune to moisture (present in breath) and acetone vapour (an interfacing agent for diabetics). Such gallium ferrite based sensors can be used to make potential interference free breath analyser for real-life applications. In addition, such sensors being highly selective and do not show any cross-sensitivity towards moisture, methanol and carbon monoxide like those based on tin dioxide. [ABSTRACT FROM AUTHOR]