Reverse microemulsion in situ crystallizing growth of ZnO nanorods and application for NO2 sensor

One-dimensional ZnO nanorods with needle-like morphology have been synthesized by a reverse microemulsion in situ crystallizing process. Pseudo-ternary phase diagrams in quaternary component systems of sodium dodecyl sulphate/n-hexanol/n-heptane/water were presented to select the appropriate reaction conditions, and studied the effect of alcohol chain length, surfactant/co-surfactant ratio and temperature on microemulsion stability. The crystal structure, morphology and size of obtained products have been characterized by XRD, FE-SEM and HR-TEM. The results show the ZnO nanorods have a hexagonal wurtzite structure with an aspect ratio (length/diameter) over 57. The sensing test results show that the nanoneedles exhibits high response and selectivity to NO2 in the presence of CO and CH4 at optimum operating temperature of 120 °C, which results from its high aspect ratio, well dispersion and high crystallinity. The response is further enhanced by loading of Pd, which can be attributed to electronic and chemical sensitization effect.