Since the early 1990s when the preparation of MCM-41 was first reported, host-guest systems based on mesoporous materials started attracting increasing interest. In the last decades mesostructured silicas were investigated as hosts for different kind of guest molecules, ranging from drugs and bioactive molecules for controlled release to luminescent compounds for technological and biomedical applications. Lots of efforts are devoted to the preparation of smart materials, in particular stimuli responsive materials in which the functional features of the system can be monitored and switched on and off through an external stimulus. This work is focused on the preparation of versatile mesoporous nanoreservoirs functionalized with innovative fluorescent moieties which allows the monitoring and tracking of drug delivery processes along tissutal and cellular pathways. A new series of pH responsive fluorescent molecules were developed based on the general structure shown above. Different functional groups were introduced in order to explore and compare different routes for the preparation of the MCM41-fluorophore hybrid. Physical adsorption, post-synthesis grafting and co-condensation methods were used and the resulting hybrids characterized. Photophysical performances were evaluated by UV-Vis absorption and emission spectroscopies, the latter augmented by fluorescence lifetimes measurements, which allows a better understanding of the fluorophore location and distribution within the hybrid. The new series of prepared fluorophores with interesting pH responsive features showed high absorptivity and quantum yield, only slightly affected by the nature of the substituent in R1 position. These molecules were used for the preparation of MCM41-fluorophore hybrids exploring different preparation strategies, such as physical adsorption, post-synthesis grafting and co-condensation methods, which led to hybrids with different levels of occupancy of the mesopores due to a different loading level and distribution of the dyes within the mesoporous material, depending on the preparation methods.
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