Heterogeneous optochemical VOC sensing layers selected by ESI-mass spectrometry

Spin-coated films of 29H,31H-tetra-4-(2,4-di-tert-amylphenoxy)phthalocyanine (H2Pc) and [κP,μ-κS-(dppeS)Pt(CH3)]2[BF4]2 have been used as sensing layers deposited in thin film form for the detection of VOCs. The sensing behaviour of the blend was predicted on the basis of mass spectrometric determinations performed on H2Pc/Pt-complex solutions, by monitoring the formation of gas-phase ions at the electrospray interface. The addition of small amounts of acetonitrile produced a [M + 41]+ peak whereas the addition of similar amounts of methanol, ethanol and isopropyl alcohol did not give the corresponding [M + ROH]+ species. These results were confirmed by sensing tests. A pure phthalocyanine optosensing element did not show relevant selectivity. Conversely, the heterogeneous sensing layer obtained by spin-coating deposition of a Pt-complex/H2Pc blend allowed the sensing of acetonitrile vapours with respect to the above mentioned alcohols.