Toward singlet oxygen delivery at a measured rate: a self-reporting photosensitizer.

A Bodipy-based energy transfer cassette with a singlet oxygen reactive linker between the donor and acceptor modules has an interesting emergent property, if the acceptor module is also a photosensitizer. Singlet oxygen produced by the photosensitizer reacts rapidly with the molecule itself to liberate the energy donor, resulting in an enhanced fluorescence emission. The result is a self-reporting photosensitizer providing an assessment of the singlet oxygen production rate under the operational conditions.