Polyamidoamine dendrimers based on silica nanoparticles have been prepared, then the fluorescein was bonded onto the surface of such dendrimers. The photophysical behavior of different generations was studied carefully by using fluorescence spectroscopy in solid state, aqueous suspension or acetone suspension. An excimer fluorescent emission was observed for the lowest generation (G0F), and fluorescein-fluorescein complex fluorescent emissions were observed for the first generation (G1F) and the second-generation (G2F). The different photophysical behaviors in various suspension indicated that the hydrogen-bonding interaction was crucial to form either excimer or fluorescein-fluorescein complex. These results will be important and beneficial for design and development of this system used as a core-shell fluorescent sensor of nanosilica.

Key words: fluorescein, silica nanoparticle, hydrogen bonding, excimer, ground-state complex, fluorescent sensor