Sensors based on double-decker rare earth phthalocyanines

Phthalocyanines are interesting materials for sensing applications because their physicochemical properties are susceptible to be modified by the presence of certain molecules. Among the large family of the phthalocyanines, the sensing properties of double-decker phthalocyanines (which are sandwich-type complexes where a lanthanide metal is co-ordinated with two phthalocyanine rings) are of special interest due to their unique physicochemical properties. Their high intrinsic semiconductivity and their rich electrochemical and electrochromic behaviour, facilitate enormously the measurement of the changes in the physicochemical properties caused by the environment. In spite of their remarkable sensing behaviour, bisphthalocyanines have not been so extensively studied as sensitive materials as the parent monophthalocyanine compounds. This is due to the difficulty of the synthesis and purification processes, and to the fact that these compounds are not commercially available. In this paper, the sensing devices constructed using rare earth bisphthalocyanines are revised (including sensors foe electronic noses and electronic tongues) and their advantages discussed.