Synthesis of novel azo-bridged phthalocyanines and their toluene vapour sensing properties

The novel azo-bridged phthalocyanines (Pcs) were synthesised to extend the conjugation effect on the Pc molecules because the classic oxo-bridge has limited the electron delocalisation. The effect of the long-range electron orbital delocalisation on the toluene vapour sensing properties of azo-bridged Pcs based chemiresistor-type sensors were investigated in this work. The effect of humidity on the toluene vapour detection capabilities of the spin coated films has also been investigated. The results showed that the presence of water vapour, functioning as the interference gas, led to the lowering of the toluene response of the sensors in humid atmosphere. Comparing gas-sensing properties of the azo- and oxo-briged Pcs, it was found that toluene sensitivities of the azo-bridged Pcs are higher than those of oxo-bridged homologous. Further, we determined that both the central metal atom and bridging unit on the Pc molecules are the critical parameters in the toluene vapour adsorption.