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 . Based on these premises, this work is focused on the preparation of versatile mesoporous nanoreservoirs functionalized with innovative fluorescent moieties to allow the monitoring and tracking of pH changes associated with inappropriate cell functions, cellular pathways and drug delivery processes [2,3]. The use of a mesoporous silica as matrix for pH sensing fluorophores provides brighter and more stable systems with respect to dyes alone . To this aim a new series of pH responsive fluorescent molecules, based on the general structure shown in the picture, were developed. Different functional groups and structures were introduced in order to explore and compare different routes for the preparation of the MCM41-fluorophore hybrid, with the final goal to obtain different work-range pH sensig luminescent hybrid systems, working at wavelength higher then 600nm. At this stage of the work, one of the developed dye was selected for grafting on mesoporous MCM-41 nanoparticles, by reaction with amino groups anchored to the silica surface. This contribution thus include the preliminary results on the photophysical performances of the selected fluorofore, before and after anchoring on the silica substrate. More in detail, UV-Vis absorption and emission spectroscopies measurement were performed on both systems at different pHs, and the hybrid material was characterized about textural, morphological and structural properties (BET, TGA, XRD, TEM etc.). The results suggest interesting performances of the developed fluorophore, in terms of pH-sensing, emission intensity and Stoke shift. These properties are substantially mantained after inclusion in the hybrid material. Further work is in progress for the optimization and upscale of the material, including spectroscopic measurements for a better understanding of the fluorophore location and distribution within the hybrid and more accurate pH titration analysis.
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