Plasmonic nanoparticles can strongly interact with adjacent photosensitizer molecules, resulting in significant alteration of their singlet oxygen (1O2) production. In this work, we report the next generation of metal-enhanced 1O2 nanoplatforms exploiting the lightning rod effect, or plasmon hot spots, in anisotropic (non-spherical) metal nanoparticles. We describe the synthesis of Rose Bengal decorated silica-coated silver nanocubes (Ag@SiO2-RB NCs) with silica shell thicknesses ranging from 5 to 50 nm based on an optimized protocol yielding highly homogeneous Ag NCs. Steady-state and time-resolve 1O2 measurements demonstrate not only the silica shell thickness dependence on the metal-enhanced 1O2 production phenomenon, but also the superiority of this next generation of nanoplatforms. A maximum enhancement of 1O2 of approximately 12-fold is observed with a 10 nm silica-shell, which is amongst the largest 1O2 production metal enhancement factor ever reported for a colloidal suspension of nanoparticles. Finally, the Ag@SiO2-RB NCs were benchmarked against Ag@SiO2-RB nanospheres previously reported by our group, and the superior 1O2 production of Ag@SiO2-RB NCs resulted in improved antimicrobial activities in photodynamic inactivation experiments using both gram-positive and -negative bacteria model strains.
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