Chemical Two-Photon Fluorescence
- Publication date
- 2015
- Publisher
Abstract
We
describe a method based on a caged fluorescent molecule that
can act as a chemical two-photon probe. It is composed of an organic
fluorophore and a ruthenium–bipyridine complex that acts as
a photoremovable quencher. For the fluorophore to be emissive, two
independent photons must act on the molecule: the first photon frees
the fluorescent ligand from the Ru complex and the second photon excites
the fluorescence. In this two-photon regime, the emission is not proportional
to the excitation intensity but rather to its second power, as in
traditional two-photon systems based on ultrashort pulsed high-power
lasers. This quadratic relationship implies a much higher spatial
precision on the <i>z</i>-axis when the probe is used in
a microscopy technique. The chemical nature of the two-photon excitation
mechanism allows the use of inexpensive low-power lasers