Improvement of Raman Spectra of SAPO-5 by Chromium(III)-Induced Luminescence Quenching

Addition of small amounts of Cr(N03)3 x 9 H20 during the hydrothermal synthesis of SAPO-5 produced pseudooctahedrally coordinated chromium(III) species within the unidimemsional channel system of the molecular sieve. A broad intense photoluminescence that occurs in the visible region upon 532 nm photoexcitation of calcined SAPO-5 is efficiently quenched in Cr-SAPO-5 allowing for unobstructed detection of Raman scattering spectra. The photoluminescence quenching mechanism appears to involve an energy transfer from the molecular sieve photoexcited surface states to the metastable chromium(III) 2E state, giving rise to the well-known chromium(III) 2E - 4A2 luminescence at 696 nm.