Optical spectroscopy on Se clusters and chains confined in zeolites.

The incorporation of selenium into the supercages of zeolite Y leads to the formation of Se(8) rings and distorted Se chains in a ratio which is influenced by the nature of the zeolitic cations. Here we review Raman (including resonance Raman) and UV/vis absorption spectroscopy results on Se encapsulated into a number of cation-exchanged faujasite zeolites. Both rings and chains give rise to characteristic Raman bands. In particular, low-frequency Raman bands are attributed to localized vibrations in ordered segments of distorted chains. The UV/vis absorption spectra indicate an opening of the band gap of selenium upon confinement in these zeolites. This can be reversed through electronic interaction with zeolite cations.