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.

We are thankful for the financial support of the Spanish Ministry of Science and Innovation MICINN, Project MAT-2009-13569; the European Research Council, under the Marie Curie Career Integration Grant program (FP7-PEOPLE-2011-CIG), Grant Agreement PCIG09-GA-2011-291877; and Industry Program from the Basque Government: Saiotek project (S-PE10UN65, S-PE11UN64 and S-PE12UN140). LGH acknowledges Ministerio de Economía y Competitividad for a Juan de la Cierva contract and VMM for Gobierno Vasco IT339-10 (2012) contracts.

Peer Reviewed