Fast and reversible acid sensor based on Porphycene

Nano-sensors devices, particularly if targeted for biological purposes, require a fine control of the properties at the molecular length scale. By means of UV-Vis-NIR optical spectroscopies (absorption, emission, and surface differential reflectivity) and surface microscopies (i.e. AFM) we prove that porphycene thin films show a spectacular chromatic change when exposed to acid vapors observed not only in transmission mode but even in reflectivity one on ultra-thin film on opaque substrates. Porphycene optical properties are recovered in few seconds and without any thermal annealing. AFM analyses correlate the film morphologies with the acid reactivity.