Surface plasmon-photosensitizer resonance coupling: an enhanced singlet oxygen production platform for broad-spectrum photodynamic inactivation of bacteria.

Singlet oxygen plays a critical role in a great number of applications including photodynamic therapy of cancers, photodynamic inactivation of microorganisms, photooxidation, and photodegradation of polymers. Herein we demonstrate a general platform to improve singlet oxygen production via resonance coupling between surface plasmon and photosensitizers. By loading photosensitizers into mesoporous silica containing silver nanoparticles, strong resonance coupling between the photosensitizers and the silver core markedly increases the singlet oxygen production, by up to three orders of magnitude in some cases. It is observed that the more spectral overlap between the surface plasmon resonance spectrum of the silver core and the photosensitizers' absorption spectra, the greater the singlet oxygen production. The as-synthesized hybrids have shown exceptionally high photoinactivation efficiency against both Gram-positive and Gram-negative bacteria. This work establishes a general platform to improve singlet oxygen production and to develop more effective and efficient hybrid photosensitizers for broad-spectrum photodynamic inactivation of bacteria.