The enhancement of oxygen sensitivity of ZnO macropore film by functionalizing with azo pigment

Abstract

Azo–ZnO hybrid films were prepared by functionalizing the ZnO macropore films with azo pigment (1,1′-(biphenyl-4,4′-diylbis(diazene-2,1-diyl))dinaphthalen-2-ol). Scanning electronic microscopy, current–voltage, UV-Vis absorption spectroscopy and Kelvin probe were used to characterize these films. The oxygen sensing characteristics of hybrid films and pure ZnO film were measured under the irradiation of UV light. The results show that the sensitivity of hybrid film is about 500 times higher than that of pure ZnO film. The high sensitivity to oxygen of hybrid films is mainly attributed to the increasing of the photo-generated electron concentration. Enhanced photo-induced charge separation after functionalization is confirmed by the pattern of transient photovoltage. Our results demonstrate that the functionalization with azo pigment is a promising approach to enhance the oxygen sensitivity of ZnO under the irradiation of UV light.