Syn–anti conformation switching of a bis-porphyrin derivative at the air–water interface and in the solid state as an effective tool for chemical sensing

A Langmuir film of bis(zinc octaethylporphyrin) (ZnPP) was characterised at the air–water interface and its syn–anti conformation switching induced upon addition of aromatic amines was studied by infrared and UV–vis reflection spectroscopic methods. The highly specific interaction of ZnPP with aromatic amines was maintained even after the floating film was transferred onto solid supports by the Langmuir– Schaefer (LS) technique, enabling us to selectively sense aromatic amines at concentrations as low as 20 ppb. Furthermore, LS ZnPP active layer selectivity was evaluated in the presence of aliphatic amines.