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New organic devices including a heterojunction between a semiconducting molecular material (MS)--lutetium bisphthalocyanine (LuPc2)--and a doped insulator (DI)--copper phthalocyanine (Cu(F(n)Pc), where n = 0, 8, 16)--are designed and studied as transducers for redox-active species sensing.

In this review molecular field-effect transistors are described and compared with their gate-modified inorganic counterparts. The different processes involved in gas sensing are summarized. The advantages of transistors on resistors are demonstrated. The sensitivity of molecular field-effect transistors to strong oxidizing species, for example ozone, is detailed and compared with their sensitivity to humidity and volatile organic compounds. Application to ozone monitoring in urban atmospheres is also described.

Solution processed thin films of an amphiphilic tris(phthalocyaninato) rare earth triple-decker complex, Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)], have been prepared from three different methods: self-assembly (SA) annealed in solvent vapor, quasi-Langmuir-Shäfer (QLS) and drop casting methods. In particular, we successfully developed a simple QLS process for fabricating ordered multilayers with a good thickness control. The films prepared from three different methods were characterized by a wide range of methods including electronic absorption spectra, IR, X-ray diffraction, atomic force microscopy (AFM), and current-voltage (I-V) measurements. J-type aggregates have been formed with the increasing degree of order of molecular stacking Cast < QLS < SA films. Moreover, the gas sensing behavior of the three types of films was investigated towards ozone in the 8-300 ppb range. Unexpectedly good sensitive, stable and reproducible responses to O(3) gas are obtained for these kinds of ultra-thin solution processed films in a fast response/recovery cycle of only 1/4 min. The response of Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)] films is linearly correlated to the ozone concentration. The interaction between the Eu(2)[Pc(15C5)(4)](2)[Pc(OC(10)H(21))(8)] films and different ozone concentrations was found to follow first-order kinetics. Strikingly, QLS films showed the most stable response and the largest average sensor response rate constant among the three types of films.

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