We report the synthesis of Tm 3+ /Yb 3+ /Er 3+ -doped Lu 3 Ga 5 O 12 nanocrystals prepared by a simple sol-gel method exhibiting bright white light following excitation with lower energy near-infrared light (λ exc ) 980 nm) via an upconversion process. The combination of upconverted blue (from Tm 3+ ), green, and red (from Er 3+ ) emissions resulted in the white luminescence, which is intense and visible to the naked eye at a laser power less than 30 mW (3.4 W/cm 2 ). The calculated Commission internationale de l′éclairage (CIE) color coordinates, which is the standard reference for defining colors, fall well within the white region and shift only slightly with the incident laser powers indicating that the material might be promising for the development of devices such as white light lasers and LEDs.

Carbon-supported, promoted Ru-based catalysts for ammonia synthesis proved to be interesting substitutes for the traditional Fe-based ones. A debate recently arose on the active state of promoters, mainly Cs and Ba, and on the effect of the latter on Ru active sites. In the present work a set of Ba-, Cs-and K-promoted samples has been characterised by various techniques. Higher H2 and O2 uptakes have been observed during reduction and chemisorption, respectively, on Cs-and K-promoted samples supported on graphitised carbon. No evidence of this has been observed with samples supported on active carbon. This is in line with the hypothesis of alkaline promoters partial reduction under the ammonia synthesis conditions, favoured by the formation of graphite intercalation compounds. Furthermore, some suggestions are here introduced on the beneficial role of Ba, especially in increasing the support resistance to methanation.Finally, the efficacy of catalyst activation was found to depend on the nature of Ru precursor. Indeed, a prolonged activation at relatively high temperature is usually needed with chloride precursors, to remove the counterion, a poison for the catalyst, whereas less dramatic conditions are required for different precursors, such as nitrosylnitrate.

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