Metallic molybdates are of great importance for their potential use as catalysts of selective nature. The synthesis of the β-NiMoO4 phase is not simple and has been approached employing different methods; however, combustion synthesis has never been proposed before. This work describes the synthesis of nanometric β-NiMoO4 powders from mixtures of Ni (II) and Mo (VI) acetylacetonates as cation precursors and urea as fuel. The characterization of the as-prepared combustion product showed that the combustion synthesis provides a straightforward method for the achievement of β-NiMoO4. This phase, prepared by this method, is stable at room temperature in the absence of NiO. The as-prepared powders are nanometric (∼6 nm as observed by TEM) and have a specific surface area of 31 ± 7 m2/g. Both parameters are crucial for an enhancement of its catalyst activity. As the β-NiMoO4 phase is not stable at room temperature its preparation is discussed taking into account its evolution with temperature and the synthesis conditions which promote metastable phases due to a high exothermic energy release followed by a rapid cooling. The electrical conductivity is determined in air as a function of temperature and discussed in relation with the phase transition that takes place promoted by temperature.

Titanium oxide has antiinflammatory activity and tunable electrochemical behavior that make it an attractive material for the fabrication of implantable devices. The most stable composition is TiO2 and occurs mainly in three polymorphs, namely, anatase, rutile, and brookite, which differ in its crystallochemical properties. Here, we report the preparation of rutile surfaces that permit good adherence and axonal growth of cultured rat cerebral cortex neurons. Rutile disks were obtained by sinterization of TiO2 powders of commercial origin or precipitated from hydrolysis of Ti(IV)-isopropoxide. Commercial powders sintered at 1300-1600 degrees C produced rutile surfaces with abnormal grain growth, probably because of impurities of the powders. Neurons cultured on those surfaces survived in variable numbers and showed fewer neurites than on control materials. On the other hand, rutile sintered from precipitated powders had less contaminants and more homogenous grain growth. By adjusting the thermal treatment it was possible to obtain surfaces performing well as substrate for neuron survival for at least 10 days. Some surfaces permitted normal axonal elongation, whereas dendrite growth was generally impaired. These findings support the potential use of titanium oxide in neuroprostheses and other devices demanding materials with enhanced properties in terms of biocompatibility and axon growth promotion.

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