Nanoparticle-mediated singlet oxygen generation from photosensitizers

We report on the modification of the efficiency of singlet oxygen generation in photosensitizers conjugated to dielectric (CeF₃) and metal (Au) nanoparticles in water. The conjugates were formed with two photosensitizers, verteporfin and Rose Bengal. Quantitative analysis of the singlet oxygen generation demonstrated that the conjugation of the photosensitizer to a nanoparticle increases the efficiency of the photosensitizers to produce singlet oxygen in water. The singlet oxygen quantum yield of UV-sensitized verteporfin increases by a factor of 1.45 and 1.64 for CeF₃-verteporfin and Au-verteporfin conjugates respectively compared to unconjugated verteporfin. Furthermore, Au-Rose Bengal conjugates also demonstrated enhanced singlet oxygen yield when sensitized at the plasmonic wavelength of 532 nm. We quantitatively explain these findings by the electric field enhancements around the nanoparticles.