Detection of volatile organic compounds: The role of tetrapyrrole pigment-oriented thin films

The interaction between some ambient reactive compounds and organic or inorganic thin layers can cause variations in the physicochemical properties of the chemically interactive layers. Molecules in the gas phase, which are adsorbed onto the surface or absorbed in the bulk of the thin layer, generally modify the electrical, optical, or mass properties of the sensitive material, giving rise to a number of different kinds of chemical sensors based on different working principles. Metallophthalocyanines (MPcs) and metalloporphyrins (MPPs) represent a large family of functional pi macrocycle materials with high chemical and thermal stability. Their general structures are shown in Figure 3.1. These compounds are the object of great interest to chemists, physicists, and industrial scientists because of their potential role in emerging technologies, including photoconductors, organic light-emitting diode, photovoltaic cell, thin- lm transistors, gas sensors, and biosensors [1]. These compounds, usually in their thin- lm forms, interact with some inorganic gases such as H2S, HCl, Cl2, NH3, or NOx by absorption onto the sensing layer. Several review articles regarding these related sensing applications are available [2-4]. However, recent efforts have been made on these sensitive compounds to detect various volatile organic compounds (VOCs), such as aromatic compounds, alcohols, amines, and so forth [5-7]. In this chapter, we emphasize on the sensing properties of VOCs.