We report an experimental investigation regarding the entrapping of O2 molecules inside various silica nano–structured systems having specific surfaces from 50 to 1000 m2/g. By recording Raman spectra and NearInfrared O2 emission we studied the O2 content per mass unit. Our data show that the internal voids of thesenanostructured systems can trap O2 molecules diffusing from the surrounding air or from a pure O2atmosphere, whereas the concentration of O2 that can be trapped in the silica near–surface layer is at leastone order of magnitude lower. This low ability is consistently observed in non–porous and porous silicananoparticles and in mesoporous silica systems. Furthermore, we observed that the O2 emission appears inthe measurements recorded for mesoporous systems as the MCM41 after thermal treatment at 1000 °Cwhen the mesoporous structure collapses, as proved by the variations of the Raman spectra. Consideringthe high variability in structure and morphology of the ensemble of investigated samples we suggest that thefact that the thin near–surface layer of silica has a low ability in trapping O2 molecules is a general propertyof the silica high specific surface systems.
|Numero di pagine||6|
|Stato di pubblicazione||Published - 2014|
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