International audienceNanocomposites have been processed following a wet-impregnation approach, by confined growth of nanoparticles of the spin crossover complex [Fe(Htrz)2(trz)](BF4) within pre-formed transparent mesoporous silica monoliths of well controlled porosity. The obtained materials were studied using numerous characterisation techniques to define the interplay between the porosity of the host matrix, the structure and morphology of the in situ elaborated nanoparticles, and the spin crossover properties of the composite. Transmission electron micrographs show monodisperse spherical nanoparticles of mean diameter 3.2(5) nm, homogeneously distributed within the pores of the silica monolith. Magnetic measurements, temperature dependent infrared, Raman, and M¨ossbauer spectroscopy confirm the spin transition behaviour of the nanocomposite, with a room temperature bistability and 65 K wide hysteresis

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We report on the optical spectroscopy of monolithic fiber preform prepared from nanoporous bismuth-doped silica glass. The experiments reveal the existence of at least two different types of active centers and clearly demonstrate that the presence in the glass matrix of other dopant is not necessary to obtain the near-IR photoluminescence connected to Bismuth.