Mechanism for interaction between gases and Phthalocyanine films

Phthalocyanines (Pcs) have been identified as promising candidates for electro-chemical gas sensors. They show potential for chemical selectivity via manipulation of the metal center and substitution of functional groups on the organic ring. However, for a given analyte and Pc, it is not clear which properties define the strength of response. To address this issue, we measured time-dependent current responses, of cobalt and metal free Pc, at constant voltage during exposure to various analyte vapor doses. The current in the device reduces with dosing; the response is linear with concentration and is found to follow first order kinetics. We show that the response is dominated by analyte interactions with the central Pc cavity; coordination strength governs CoPc responses, and hydrogen bonding ability governs H$_{2}$Pc responses. A model for the phthalocyanine electrical response and binding with analytes will be discussed.