Direct dyes containing two urea groups

A series of asymmetrically substituted amphiphilic phthalocyanines have been synthesized. They have been deposited as Langmuir¯Blodgett films onto glass and/or glass substrates bearing aluminum interdigitated electrode patterns. The films show fast response to NO2 with almost complete recovery at room temperature. It is indicated that layer ordering and molecular packing within the LB films are important factors determined the gas-sensing properties.