Interaction of nitrogen dioxide with sulfonamide-substituted phthalocyanines: Towards NO2 gas sensor

Abstract

Much of life requires fast, cheap and reliable gas sensors. As nitrogen dioxide is a toxic and environmentally polluting gas, produced by humans in excess, to be able to monitor and detect it is necessary. One of the way to manufacture cheap and reliable gas sensors sensitive to nitrogen dioxide is to use soluble organic materials as the sensing media. In this paper, we study the properties of soluble sulfonamide-substituted zinc and metal-free phthalocyanines. The sensing capabilities of these materials are discussed in detail. We have found that Zn sulfonamide-substituted phthalocyanine (Pc) forms a charge transfer complex with nitrogen dioxide, which results in a change of absorption spectrum and an increase of electrical conductivity as much as two orders of magnitude. On the other hand, metal-free Pc does not form the complex and its interaction with nitrogen dioxide is based on weak Van-der-Waals forces. The absorption spectrum does not change and the electrical conductivity slightly decreases during nitrogen dioxide exposure. We have also found that these materials, unlike literature reported derivatives, are reversibly sensitive to nitrogen dioxide at room temperature. This opens a great potential for the fabrication of cheap and reliable gas sensors.