The influence of ammonia, chlorine and nitrogen dioxide on chloro-aluminium phthalocyanine thin films

Abstract Amperometric gas sensors were prepared by thermal evaporation of a chloro-aluminium phthalocyanine (ClAlPc) thin film onto inter-digital gold electrodes with 100 μm spacing. The behaviour of these thin films on exposure to NO 2 , Cl 2 and NH 3 gases and the suitability of ClAlPc as a material for use in a practical gas sensors was investigated with zero grade air as the reference atmosphere. A change in resistivity of the ClAlPc thin film sensors was observed on exposure to ammonia and chlorine at several different temperatures. In particular, it was found that on increasing the temperature, the sensitivity of the ClAlPc thin film decreases a little, but the reversibility is greatly enhanced. This means that ClAlPc based toxic gas sensors could operate at lower temperatures than their mono-phthalocyanine counterparts. The temperature of maximum sensitivity ( T max ) and the minimum temperature for good reversibility ( T min ) have been determined for ClAlPc sensors ‘doped’ with Cl 2 and NO 2 . It was found that these characteristic temperatures can provide information on the concentration and the nature of the gas to which the sensor is exposed and so could perhaps be used to distinguish between the different adsorbed species. Activation energies for conduction were also measured in the presence of the test gases.

[1]  R. A. Collins,et al.  Gas sensitivity of some metal phthalocyanines , 1988 .

[2]  D. Kohl,et al.  Problems and possibilities of oxidic and organic semiconductor gas sensors , 1985 .

[3]  R. A. Collins,et al.  Electrical characteristics of planar phthalocyanine thin film gas sensors , 1987 .

[4]  T. A. Jones,et al.  A highly sensitive NO2 sensor based on electrical conductivity changes in phthalocyanine films , 1984 .

[5]  A. Pauly,et al.  Interaction of NO2 with copper phthalocyanine thin films. II: Application to gas sensing , 1992 .

[6]  W. Göpel,et al.  Lead phthalocyanine (PbPc) as a prototype organic material for gas sensors: comparative electrical and spectroscopic studies to optimize O2 and NO2 sensing , 1989 .

[7]  R. A. Collins,et al.  The influence of oxygen on the electrical properties of monoclinic lead phthalocyanine , 1993 .

[8]  John D. Wright,et al.  Gas adsorption on phthalocyanines and its effects on electrical properties , 1989 .

[9]  S. C. Thorpe,et al.  Fast response metal phthalocynanine-based gas sensors , 1989 .

[10]  R. A. Collins,et al.  Spectral response of monoclinic and triclinic lead phthalocyanine to nitrogen dioxide , 1995 .

[11]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[12]  M. Sakaguchi,et al.  The Phase Transition Phenomenon in Metal Phthalocyanine Crystals , 1980 .

[13]  R. A. Collins,et al.  The effects of humidity on phthalocyanine NO2 and NH3 sensors , 1990 .

[14]  G. G. Roberts,et al.  Study of Localized Levels in Semi-Insulators by Combined Measurements of Thermally Activated Ohmic and Space-Charge-Limited Conduction , 1969 .