Second Generation Nanostructured Metal Oxide Matrices to Increase the Thermal Stability of CO and NO2 Sensing Layers Based on Iron(II) Phthalocyanine

An iron(II) phthalocyanine (FePc) complex solubilized by decylamine (DA) and benzylamine (BA) is incorporated into a nanoparticulate metal oxide matrix to develop optical sensor films sensitive to NO2 and CO. Eleven amine solvents have been tested as N‐donor ligands that permit ligand exchange with the gas molecules. We have systematically investigated the suitability of different N‐donor ligands, studied the thermal stability of the NO2‐ and CO‐sensing films at 4, 25, 60, and 80 °C by photometry, and corroborated our findings by using NMR experiments. A satisfactory thermal stability of the films has not been obtained for chemically unmodified nanoparticulate metal oxide matrices. We have therefore developed a second generation of nanostructured metal oxide supports that show increased thermal stability and adequate sensitivity to NO2 and CO. These novel nanostructured matrices have been chemically modified using amines, alumina oligomers, and/or anti‐gas‐fading agents. These components have been integrated into the metal oxide matrices to avoid degradation of the optical films and to preserve their sensitivity. Second‐generation optical gas sensors based on iron(II) phthalocyanine incorporated within nanostructured metal oxide matrices have been developed. The figure shows the structure of the active complex overlaid on NMR spectra used to determine the mechanism of its activity. Modification of the nanostructured support with amines, alumina oligomers, and anti‐gas‐fading agents leads to enhanced thermal stability while retaining sensitivity to CO and NO2.