Enhanced gas-sensing properties of ZnO nanorods encapsulated in an Fe-doped ZnO shell

Abstract

Encapsulated ZnO nanorod arrays synthesized on glass substrates by a two-step route, hydrothermal followed by dip-coating. It was found that the encapsulating process increases the rods diameter from ~20 to ~ 40nm without any significant effects on the microstructure even by Fe doped ZnO encapsulated layer. Optical studies indicated a reduction in the band gap of encapsulated nanorods. The electrical measurements illustrated a remarkable resistance reduction due to encapsulation process especially in the encapsulated ZnO nanorod film with Fe doped-ZnO shell layer. The gas sensing properties of the sensors were systematically investigated to ethanol vapor at different concentrations and temperatures up to 270 °C. An optimum operational temperature was found for each sensor in which high sensitivity and fast recovery obtained. The response was improved from 11.7 to 19 by Fe doping on the ZnO encapsulated nanorod at constant 500 ppm concentration of ethanol. The response threshold also decreased by encapsulating at 165 °C.