A new sandwich-type diphthalocyanine as a potential optical transducer for NO2 detection

Bis(phthalocyaninato)titanium(IV) (Ti(Pc)(2)), a sandwich-type metal diphthalocyanine, is used as a chemical transducer for the optical detection of nitrogen dioxide. The optical properties of this chemical transducer after its immobilization on controlled pore glass (CPG) by a casting from a Ti(Pc)(2) solution in alpha-chloronaphthalene are described. This compound is characterized by three well-defined absorption bands in the visible region (lambda = 506, 675 and 720 nm) which undergo spectral changes in the presence of nitrogen dioxide. Two different optodes were manufactured and characterized. A plastic flat reflector is used as a solid support placed in front of an optical fibre bundle, and Ti(Pc)(2) is immobilized on CPG that was previously embedded in the plastic reflector either by casting or by sublimation. The characterization of the developed optodes in terms of sensitivity, reversibility and response time is described. (C) 1998 Elsevier Science S.A. All rights reserved.