Efficient generation of singlet oxygen due to localized surface plasmon resonance of silver nanoparticles in rose bengal–silver nanoparticle composite films

Abstract

Abstract The effect of silver nanoparticles (AgNP) on the generation of singlet oxygen (1O2*) using rose bengal (RB) as a photosensitizer for photodynamic therapy (PDT) was examined by measuring the phosphorescence spectra of 1O2* from RB-AgNP composite film and RB film on glass plates in CCl4. 1O2* was successfully detected by direct observation of the characteristic 1O2* phosphorescence around 1275 nm in two films. The excitation spectra of 1O2* in the two films were in agreement with the that of RB in film or in solution. The results indicate that the generation of 1O2* is ascribed to a PDT type Ⅱ reaction. The phosphorescence intensity of 1O2* in RB-AgNP composite film was larger than that in RB film. The enhancement of the phosphorescence intensity of 1O2* is most likely attributable to the strong electric fields due to the localized surface plasmon resonance of AgNP aggregates.