Photochemically gated protonation effected by intramolecular hydrogen bonding: Towards stable fluorescence imaging in polymer films

A photoacid-induced non-destructive fluorescence image in a polymer film is achieved by the photochemically gated protonation of a basic fluorophore (HPQ), effected by the intramolecular hydrogen bond via the controlled basicity of the quinoline ring. The Figure shows a non-degraded fluorescence image (top, using HPQ) after successive readouts, and, for comparison, a degraded image using the conventional hydrogen-bond-free analogue (lower, MPQ).