Thin layer porphyrinogen for alcohol-vapor optical sensors

Thin films of meso-octaethylporphyrinogen with different thickness were deposited on suitable substrates by Langmuir-Blodgett deposition technique in order to realize optical-sensitive active layers using Surface Plasmon Resonance (SPR) technique as transduction methodology. Analysis of the morphology of the sensing layers was performed by Atomic Force Microscopy. In particular, such coatings were tested for the detection of alcohol vapors such as ethanol, methanol and isopropanol. This resulted in a reversible shift in the resonance depth and angular position of the SPR curves, depending on the interactions between the sensing layers and the alcohol vapor molecules. Different sensitivity and rate of response for different alcohol molecules were found and analyzed. Measurements of the sensing response towards successive expositions of the sensing layers to methanol, ethanol and isopropanol vapors were performed in order to analyze the discrimination properties of the active layers towards the analytes.