Anisotropic fluorescence materials: Effect of the synthesis conditions over the incorporation, alignment and aggregation of Pyronine Y within MgAPO-5

In order to prepare a highly fluorescent anisotropic material, different hydrothermal synthesis conditions have been studied in an attempt to favor the incorporation of the fluorescing dye Pyronine Y as monomeric species within the large-pore nanoporous aluminophosphate MgAPO-5 (AFI-type structure) during its crystallization (one-pot synthesis). Valuable information regarding the dye orientation, molecular distribution and aggregation behaviour inside the nanochannels of MgAPO-5 as a function of the gel composition has been obtained using the FLIM technique (Fluorescence Lifetime Imaging Microscopy). DFT-based calculations of the different dye species occluded within the nanochannels of MgAPO-5 allowed us to explain the properties of the newly synthesised composite materials. Our results show that although H-aggregates can fit within the MgAPO-5 channels, their presence can be reduced by varying the synthesis parameters, in particular by decreasing the template and PY concentration and increasing Mg content.

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► The fluorescing dye Pyronine Y is encapsulated in MgAPO-5 (AFI) by crystallization inclusion.
► Gel composition influences the incorporation, alignment and aggregation of the dye in the material.
► A high incorporation of monomeric dye species produce materials with improved optical properties.
► Low dye loadings in the AFI crystals results in the incorporation of a high amount of monomeric species.
► At high loadings, the dye forms H-type aggregates that quench the fluorescence of the materials.