Optical spectra of a novel polyoxometalate occluded within modified MCM-41

The novel polyoxometalate ([(Eu2PW10O38)(4)(W3O8(H2O)(2)(OH)(4))](22-)), also referred to herein as Eu8P4W43, has been immobilized inside the channels of MCM-41 mesoporous molecular sieve material by means of the incipient wetness method. For proper host-guest interaction, amine groups were introduced into the system as a result of an aminosilylation procedure. A stable and integrated Eu8P4W43 polyoxometalate was shown to be formed inside the channels of the modified MCM-41. The products were characterized by XRD, UV-vis absorption, emission, Raman excitation, Raman, and P-31 solid-state NMR measurements. Infrared and Raman spectra of the polyoxometalate/MCM-41 composite systems are interpreted as showing spectral shifts due to site induced electrostatic interactions. The photoluminescent behavior of the composite at room temperature indicates a characteristic Eu3+ emission pattern corresponding to D-5(0)-F-7(J) transitions. A strong photoluminescence suggests the potential utility of the polyoxometalate as a luminescent material.