CONICET | Buscador de Institutos y Recursos Humanos

We describe a method based on a cagedfluorescent molecule that can act as a chemical two-photonprobe. It is composed of an organic fluorophore and aruthenium−bipyridine complex that acts as a photoremovablequencher. For the fluorophore to be emissive, two independentphotons must act on the molecule: the first photon frees thefluorescent ligand from the Ru complex and the second photonexcites the fluorescence. In this two-photon regime, theemission is not proportional to the excitation intensity butrather to its second power, as in traditional two-photonsystems based on ultrashort pulsed high-power lasers. Thisquadratic relationship implies a much higher spatial precisionon the z-axis when the probe is used in a microscopytechnique. The chemical nature of the two-photon excitationmechanism allows the use of inexpensive low-power lasers.