Optical sensing properties of CoTPP thin films deposited by glow-discharge-induced sublimation

Thin porphyrin assemblies, widely used as sensing materials in different kinds of transducers, are usually produced through chemical deposition techniques. In this work a new physical technique named glow-discharge-induced sublimation (GDS) has been employed for the production of cobalt 5,10,15,20 meso-tetraphenyl porphyrin (CoTPP) thin films. For comparison, CoTPP coatings have been also produced by vacuum evaporation and spin coating procedures. The inspection of the surface morphology with a scanning electron microscope evidenced the very high surface roughness of the GDS samples. Optical measurements performed in ethanol-vapour-containing nitrogen flux highlighted that the responses of the GDS films were one order of magnitude more intense than those of the films deposited through spin coating and vacuum evaporation techniques. Moreover, the GDS films exhibited very short response times (t50 = 12 s and t90 = 72 s) and fast and complete recovery.