Nanostructured mixed ZnO and CdO thin film for selective ethanol sensing

Nanostructured mixed zinc oxide (ZnO) and cadmium oxide (CdO) thin films were prepared using spray pyrolysis technique under optimized deposition condition using zinc acetate dihydrate and cadmium acetate dihydrate as precursors. The X-ray diffraction (XRD) pattern confirmed the polycrystalline nature of the films. A combination of cubic (CdO) and hexagonal wurzite (ZnO) phase was observed for the film deposited with 0.04 M and 0.06 M precursor concentration of zinc and cadmium salts respectively. From scanning electron micrograph (SEM) uniform distribution of spherical shaped nanograins was observed. The sensing behavior of as deposited films toward various concentrations of volatile organic compounds (VOCs) responsible for off-flavors in milk/fish namely ethanol and trimethyl amine (TMA) were investigated at an optimized operating temperature of 373 K. The film deposited with 0.04 M and 0.06 M of ZnO and CdO precursor was found to be highly selective toward ethanol in a mixed environment. Hence, mixed oxide based sensor element can be effectively used in the sensor array of electronic nose for real time milk/fish quality assessment.

Graphical abstract(a) SE Micrograph of mixed oxide thin film (b) Response of the mixed oxide thin film based sensor element toward various concentrations of ethanol and TMAFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► An optimized mixed ZnO and CdO thin film processing was established. ► Mixed oxide films are composed of wurtzite ZnO and rock salt CdO crystallite phases. ► Selectivity toward ethanol was found to be appreciable in mixed environment.