Photoactivation and Detection of Photoexcited Molecules and Photochemical Products

Aerobic photoactivation of photosensitizing dye molecules can lead to the formation of oxygen radicals, singlet oxygen and other partially reduced oxygen species, collectively called reactive oxygen species (ROS), which are responsible for photodynamic damage and the accompanying cytotoxicity. This review briefly describes basic photophysical phenomena involved in the formation of electronically excited states and photochemical processes that play a key role in the generation of ROS. Physicochemical properties of the excited states of the photosensitizing dye molecules and of ROS, particularly their chemical reactivity with selected substrate molecules, as well as major spectroscopic and analytical methods used for the detection and characterization of reactive intermediates involved in photodynamic phenomena, are critically discussed in this paper.