On the interest of ambipolar materials for gas sensing

Publication date: 1 April 2018
Source:Sensors and Actuators B: Chemical, Volume 258
Author(s): Amélie Wannebroucq, Seydou Ouedraogo, Rita Meunier-Prest, Jean-Moïse Suisse, Mabinty Bayo, Marcel Bouvet
Based on the electrochemical properties of a series of metallophthalocyanines this article shows that the phthalocyanine bearing four alkoxy groups and twelve fluorine atoms behaves approximately as those with eight fluorine atoms. This indicates that the electron-donating effect of one alkoxy group balances the electro-withdrawing effect of one fluorine atom. We engaged three metallophthalocyanines, namely the octafluoro copper phthalocyanine, Cu(F8Pc), an octaester metallophthalocyanine and a phthalocyanine bearing four alkoxy groups and twelve fluorine atoms, Zn(T4F12Pc), in building original conductometric transducers that are Molecular Semiconductor – Doped Insulator heterojunctions (MSDIs) in association with the highly conductive lutetium bisphthalocyanine, LuPc2. Whereas the octaester derivative and Zn(T4F12Pc) exhibited a negative response to ammonia, as expected for p-type materials, Cu(F8Pc) exhibited a particular behavior. At low humidity levels, 30 and 10% rh, the current of the Cu(F8Pc)/LuPc2 MSDI decreases, similarly to p-type devices, but at higher relative humidity values, 70% rh, the current increases under ammonia, which is the signature of a n-type behavior. This ambipolar behavior is unique amongst semiconducting sensing materials. This work opens the way to the study of ambipolar materials as sensing materials for the development of a new type of conductometric gas sensors.

Graphical abstract

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