Photochemical versus Thermal Synthesis of Cobalt Oxyhydroxide Nanocrystals

Photochemical methods facilitate the generation, isolation, and study of metastable nanomaterials having unusual size, composition, and morphology. These harder-to-isolate and highly reactive phases, inaccessible using conventional high-temperature pyrolysis, are likely to possess enhanced and unprecedented chemical, electromagnetic, and catalytic properties. We report a fast, low-temperature and scalable photochemical route to synthesize very small (~3 nm) monodisperse cobalt oxyhydroxide (Co(O)OH) nanocrystals. This method uses readily and commercially available pentaamminechlorocobalt(III) chloride, [Co(NH3) 5Cl]Cl2, under acidic or neutral pH and proceeds under either near-UV (350 nm) or Vis (575 nm) illumination. Control experiments showed that the reaction proceeds at competent rates only in the presence of light, does not involve a free radical mechanism, is insensitive to O 2, and proceeds in two steps: (1) Aquation of [Co(NH3) 5Cl] 2+ to yield [Co(NH3) 5(H2O)] 3+, followed by (2) slow photoinduced release of NH3 from the aqua complex. This reaction is slow enough for Co(O)OH to form but fast enough so that nanocrystals are small (ca. 3 nm). The alternative dark thermal reaction proceeds much more slowly and produces much larger (~250 nm) polydisperse Co(O)OH aggregates. UV-Vis absorption measurements and ab initio calculations yield a Co(O)OH band gap of 1.7 eV. Fast thermal annealing of Co(O)OH nanocrystals leads to Co3O4 nanocrystals with overall retention of nanoparticle size and morphology. Thermogravimetric analysis shows that oxyhydroxide to mixed-oxide phase transition occurs at significantly lower temperatures (up to T = 64 degrees C) for small nanocrystals compared with the bulk

Taking care of our health: research tackling Europe's grand challenge of future health issues

Europeans have never been healthier than they are today. Yet although European countries have experienced a continuous improvement of their overall health situation, our increasing wealth has paradoxically become a driving force of new health problems. Aging and unhealthy lifestyles are leading to new health risks. From an increase in incidence in some non-communicable diseases, to neurodegenerative and mental disorders, we are increasingly faced with new types of ‘maladies of prosperity’. Combined with rising health expectations and technological progress, they also threaten the financial sustainability of our health-care systems. If left unaddressed, these trends are likely to evolve into the health crises of tomorrow. To tackle these challenges, the report argues for increasing research on costly diseases, personalization of treatments, targeted and cost-reducing innovations, health inequalities and sustainability of health-care systems. Our report is complemented by a GeoRisQ Monitor, which assesses the health challenges affecting European countries. It does so by taking a closer look at how these countries fare with respect to three risk factors: (i) Unhealthy Lifestyles; (ii) Aging; and, (iii) Environmental Degradation. The Monitor can be accessed by clicking here

Direct Low-Temperature Deposition of Crystallized CoOOH Films by Potentiostatic Electrolysis.

Cobalt oxide films were deposited onto nickel electrodes from 25 up to 90°C at a constant potential of 0.5 V vs. SCE from a pH 7.4 nitrate solution containing Co(II). Above 60°C, scanning electron microscopy and X-ray diffraction (XRD) experiments reveal that the films are constituted of crystallized grains. At 90°C the crystallite size is measured at ca. 34 nm. XRD experiments show that the crystallized product is composed of CoOOH, and Raman spectroscopy shows the formation of this compound between 40 and 90°C. Between room temperature and 90°C, the deposition rate is increased by an order of magnitude and the deposit crystallization has a favorable effect on the faradaic deposition efficiency. It may also favor the mechanical stability in temperature of this deposit when used as cobalt oxide-based protective coating of the molten carbonate fuel cell nickel cathode

Gastrointestinal: Ano-popliteal fistula in Crohn's disease

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