Hot electron migration from gold nanoparticle to an organic molecule enhances luminescence and photosensitization properties of a pH activatable plasmon-molecule coupled nanocomposite

The luminescence and photosensitization properties of a plasmon-molecule coupled nanocomposite is tuned by varying the pH of the medium. The mechanistic insights of improved luminescence and photosensitized singlet oxygen generation are investigated and explored for the selective detection and killing of cancer cells. • A stimuli-responsive plasmon-molecule coupled nanocomposite containing gold nanoparticles and a naphthalidenimine-boron complex was prepared. • Luminescence and photosensitization properties of the nanocomposite was tuned by varying the pH of the medium. • Ultrafast spectroscopy revealed that hot electron migration from gold to molecule improved the luminescence and photosensitization properties of the nanocomposite. • Nanocomposite was used to selective detect and kill cancer cells. Plexcitonic hybrids - comprised of metal nanoparticles and molecular aggregates - have unique photophysical properties. Modulation of plextonic interactions to achieve strong coupling via external stimuli such as pH has the potential to be used for studying cellular properties in biological systems. Here, we show that plasmon-molecule coupling can be tuned by varying the pH which further improves the luminescence and photosensitization properties of a nanocomposite containing gold nanoparticles and a naphthalidenimine-boron complex. Ultrafast spectroscopy affirmed that photoexcited hot-electron transfer from gold to the dye molecule enhanced the luminescence of the nanocomposite. Moreover, it is assumed that the increased charge carriers at the edge of the molecular singlet state endorsed intersystem crossing and aided the generation of singlet oxygen. Furthermore, the pH-sensitive luminescence of nanocomposite allowed for the differentiation of normal and cancerous cells.