title: Protoporphyrin IX-Functionalized AgSiO2Core-Shell Nanoparticles: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production.
abstract: Metal-enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the viewpoint of dye fluorescence and photoactivity. Herein, protoporphyrin IX (PpIX) is grafted onto the surface of silver core silica shell NPs in order to investigate the effect of silver (Ag) localized surface plasmon resonance (LSPR) on PpIX fluorescence and PpIX singlet oxygen (1O2) production. Using two Ag core sizes, we report a systematic study of these photophysical processes as a function of silica (SiO2) spacer thickness, LSPR band position and excitation wavelength. The excitation of Ag NP LSPR, which overlaps the PpIX absorption band, leads to the concomitant enhancement of PpIX fluorescence and1O2production independently of the Ag core size, but in a more pronounced way for larger Ag cores. These enhancements result from the increase in the PpIX excitation rate through the LSPR excitation and decrease when the distance between PpIX and Ag NPs increases. A maximum fluorescence enhancement of up to 14-fold, together with an increase in photogenerated1O2production of up to five times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating.
authors.affiliation: GRASP-Biophotonics, Département de Physique, B5a, Université de Liège, Belgium.
authors.forename: Marjorie
authors.initials: M
authors.lastname: Lismont
authors.affiliation: GRASP-Biophotonics, Département de Physique, B5a, Université de Liège, Belgium.
authors.forename: Laurent
authors.initials: L
authors.lastname: Dreesen
authors.affiliation: Laboratoire de Génie chimique-Nanomatériaux, Catalyse, Electrochimie, B6a, Université de Liège, Liège, Belgium.
authors.forename: Benoît
authors.initials: B
authors.lastname: Heinrichs
authors.affiliation: Laboratoire de Génie chimique-Nanomatériaux, Catalyse, Electrochimie, B6a, Université de Liège, Liège, Belgium.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Páez