What does the following mean?

Rhodamine B is a useful fluorochrome for medical histology due to its fluorescent properties in ultraviolet light. It ejects an electron onto TiO2, which is then scavenged by O2 forming the O2- radical anion. This anion ultimately becomes the OH radical. A pH-independent process degrades Rhodamine B in TiO2 dispersions containing no dodecylbenzenesulfonate. The compound has been incorporated in a FRET system based on lanthanide-doped nanoparticles for monitoring biological effects.

What is the chemical process for Rhodamines?