Recent advances in the photophysical detection and delivery of singlet oxygen

Singlet oxygen (1O2) is an important reactive oxygen species (ROS) in chemistry, medicine, and human physiology. It has significant real-world applications in photodynamic therapy (PDT) and organic transformations. However, its adoption in biological systems has been minimal due to a lack of efficient probes for detecting, quantifying, imaging, and delivering 1O2 in physiological conditions. This review will discuss current developments of probes and molecular carriers (MC) of 1O2. The developments in their molecular design and mechanism documented in the literature have been discussed. Most probes and carriers are molecular dyads bearing a 1O2-specific binding unit (BU) and a signaling unit (SU). The BUs of probes and carriers comprise motifs like acene, alkene, furan, pyrrole, imidazole, and 2-pyridone. Based on the signaling mode, these probes could be divided into four categories: absorption-based, colorimetric, photoluminescent, and chemiluminescent. Furthermore, we elaborated on the factors determining their efficiency and identified the unexplored areas with massive potential. This review could be a useful reference for the future development of 1O2 tools.