DETECTION OF LOW HYDROGEN CONCENTRATIONS BY A CU-PC SENSOR

A hydrogen sensor based on copper phthalocyanine (Cu-Pc) with palladiu m admixture was prepared. The sensor material is obtained by mixing pa lladium acetate and Cu-Pc (1:8) and adding semiconductor-grade acetone . The doped Cu-Pc was printed on interdigitated Pt electrodes supporte d by an Al2O3 substrate. The detection limit of the sensor is well bel ow 1 ppm H-2 at an operating temperature of 95 degrees C; the response and recovery times are about 1 min, depending on the temperature and gas concentration. An H-2 concentration of 30 ppm leads to a conductan ce decrease of 44% compared with the clean air value. Changes in relat ive humidity between 0 and 100% lead to conductance changes of less th an 6%; admixture of 48 ppm CO increases the conductance by only 5%. Th e increase in the sensor conductance on admixture of NO2 is comparable to vacuum-evaporated Cu-Pc thin film sensors. From the direction of r esistance changes on admixture of NO2, it is obvious that Cu-Pc with P d admixture remains a p-type conductor. The response mechanism of the sensor may be explained by a spillover of atomic hydrogen from Pd clus ters onto the Pc film and subsequent reaction with adsorbed oxygen.