Design and synthesis of a novel pH sensitive core and peripherally 1,8-naphthalimide-labeled PAMAM dendron as light harvesting antenna

The system surface was labeled with blue emitting 1,8-naphthalimide “donor” dyes capable of absorbing light and efficiently transferring the energy to a single yellow-green emitting 1,8-naphthalimide “acceptor” dye. The overlap between the blue emission of the donor and the absorbance of the acceptor (focal dye) was >70%. Due to the energy transfer from the periphery to the focal 1,8-naphthalimide chromophore (67%) the core fluorescence (λex = 360 nm) was enhanced >36 times. It was also found that the novel light harvesting system displayed sensitive fluorescence signaling over a wide pH scale, which was ascribed to photoinduced electron transfer from the dendron bone to the blue emitting periphery. In acidic media the electron transfer was “switched off” and, in turn, the periphery emission was “switched on”, resulting in energy transfer enhancement to the focal chromophore up to 92%. This indicates the high potential of the novel light harvesting system as an efficient pH hemosensing material.