1,8-Diazafluoren-9-one

1,8-Diazafluoren-9-one (DFO) is an aromatic ketone first synthesized in 1950. It is used to find fingerprints on porous surfaces. It makes fingerprints glow when they are lit by blue-green light.

DFO reacts with amino acids present in the fingerprint to form highly fluorescent derivatives. Excitation with light at ~470 nm results in emission at ~570 nm.