The influence of ZnO-Sensor modification by porphyrins on to the character of sensor response to volatile organic compounds

The influence of modification of semi conductive ZnO and SnO₂ sensors by porphyrins and their metal complexes on the parameters of sensor response to volatile organic compounds, ethanol, acetone and benzene, was analyzed. The concentration of volatile organic compounds (c _i ) varied in the range of 1–200 ppm. The sensor response was characterized by specific sensitivity γ _i = 100ΔR _i /R ₀ c _i , where ΔR _i = R _i − R ₀, R _i and R ₀ are measurable and initial resistance of the sensitive sensor layer correspondingly. It was established that the modification of sensors by porphyrins caused changes in sensor response and first of all decrease of ZnO sensor temperature at which the threshold of sensitivity is achieved (as used at this method c _i ^min = 0.1 ppm) from 300 to 100°C. It also caused a change in sing of the parameter γ, which was of importance for creating “electronic nose” sensor systems. It was shown also, that the modification of ZnO sensor by metal complexes of porphyrin did not change sensor response parameters.