Highly Luminescent and Optically Switchable Hybrid Material by One-Pot Encapsulation of Dyes into MgAPO-11 Unidirectional Nanopores

Abstract

In this work a highly fluorescent hybrid material with strong anisotropic response is obtained by “one-pot” synthesis. The system is based on the “in situ” encapsulation of two chromophores, acridine (AC) and pyronine Y (PY), with similar molecular structure but perpendicular dipole moment vectors, into the 1D-nanochannels of MgAPO-11 aluminophosphate crystals (AEL structure). This non-diffusional-limited synthetic approach allows the filling of very long channels, reducing considerably the time of sample preparation (>10 μm rectangular-like AEL particles), as well as a perfect fit between the molecular and channel dimensions, avoiding the leakage of the guest dyes and any Davidov coupling. As a consequence, both dyes are embedded only in momomeric units and preferentially aligned with their long molecular axes along the channels. Interestingly, the less bulky nature of AC without pendant groups leads to a much stronger incorporation with respect to PY (48:1), enabling an efficient FRET process between them. The final solid hybrid material shows fluorescent quantum yields higher than the respective dyes in diluted solution together with blue (AC)/green (PY) fluorescence color switching depending on the direction of the polarizers upon UV light excitation.