Photoinduced charge transfer in the supramolecular structure based on toroid polyoxomolibdate Mo138 and xanthene dye – Rhodamine-B

Abstract

The new supramolecular structure based on the toroid nanoclustered giant polyoxomolybdate (POM) Mo138 and xanthene dye (rhodamine-B) was synthesized by a self-assembly technique in solution and was extracted in the solid state for the first time. Fluorescence studies of this structure have shown a very effective energy transfer (conditioned by the charge transfer and/or fluorescence resonance energy transfer mechanisms) from a dye molecule to a nanocluster under excitation by visible light (522 and 558nm). The promotion of potential catalytic properties of polyoxomolybdate or revealing nonlinear optical properties could be expected there due to the presence of MoV and MoVI sites in Mo138. Raman-spectroscopy showed significant changes for vibrating bands of the rhodamine-B conditioned by the energy transfer. Investigations of the supramolecular structure by zeta-potential and size distribution measurements allowed us to determine an interaction mechanism between the components in solution. Spatial location of dye molecules on the polyoxomolybdate surface and the integrity of nanocluster Mo138 in the supramolecular structure were found by FTIR-spectroscopy. The calculation of HOMO–LUMO electron transition of rhodamine-B by the Time-Dependent Density Functional Theory (TDDFT) technique revealed the potential overlapping between molecular orbitals of adsorbed dye molecules and POM’s surface. That is well-correlated with the overlapping of fluorescence and absorption spectrums of rhodamine-B and the nanocluster respectively.