Multi-Photon Excitation

By Multi-Photon Excitation (MPE) we mean the simultaneous absorption of two or more long wavelength photons followed by fluorescence emission from the lowest excited state.

The goal of this CFS long-term project is to study the basic principles and biochemical applications of MPE.MPE offers a localized excitation in fluorescence microscopy and an enhanced photoselection in spectroscopy.

We applied MPE to study:

• Spectroscopic properties and images of stained DNA
• Tyrosine, Tryptophon and Proteins
• DPH-labeled membranes
• Detection of anti-cancer drugs in blood
• Ru and Re metal ligand complexes

We also demonstrated a two-color two-photon excitation with synchronized UV and NIR beams. Recently we used MPE to observe a UV fluorescence from saturated hydrocarbons and cholesterol analogues. We also applied MPE in High Throughput Screening (HTS).

Figure 1: Emission intensity of p-terphenyl with NIR (750 nm), UV (375 nm) and combined (375 and 750 nm) excitation.

Figure 2: Emission spectra of p-terphenyl with 250 nm excitation and with 2C2P excitation at 375 and 750 nm.