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Free keywords:
Cr:AlPO4-5;
molecular sieve;
single crystal absorption spectroscopy;
CCD array spectrometer
Abstract:
Large Cr:AlPO4-5 single crystals have been characterized by microcrystal absorption spectros copy using a CCD array spectrometer and a fiber optics technique. For Cr3+ in AlPO4-5 crystals a polarization-dependent absorption is observed. This indicates an anisotropic coordination of Cr3+ distorted by the molecular sieve structure. Polarized absorption measurements on Cr: AlPO4-5 crystals loaded with p-nitrodimethyl aniline (pNDMA) and with p-nitroaniline (pNA) show a strong alignment of the guest molecules in the pore system parallel to the straight channels. The reduced ability to adsorb large molecules into the channels of the Cr:AlPO4-5 crystals supports the hypothesis of the nonframework incorporation of Cr3+.
