Humidity sensors based on ZnO/TiO2 core/shell nanorod arrays with enhanced sensitivity

Abstract

Highly aligned arrays of ZnO/TiO(2) core/shell nanorods were fabricated on glass substrates by hydrothermal growth of ZnO nanorods cores followed by the deposition of anatase TiO(2) shells in a sol-gel process. The characterization of these composite materials with scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and transmission emission microscopy (TEM) points to the formation of crystalline ZnO nanorod cores that are coated with anatase TiO(2) shells. Humidity sensors based on these core/shell nanorod arrays exhibit outstanding sensitivities with capacitances varying from 10(1) to 10(6) pF over a relative humidity (RH) range of 11%-95% at room temperature, which is 1.5 and 3 orders of magnitude higher than that of pristine TiO(2) films and ZnO nanorods, respectively. Complex impedance analysis indicated that the enhanced humidity sensitivity is probably due to the high surface/volume ratio of this core/shell material in combination with the remarkable hydrophilicity of the TiO(2) shell. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t 2 AbstractHighly aligned arrays of ZnO/TiO 2 core/shell nanorods were fabricated on glass substrates by hydrothermal growth of ZnO nanorods cores followed by the deposition of anatase TiO 2 shells in a sol-gel process. The characterization of these composite materials with scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and transmission emission microscopy (TEM) points to the formation of crystalline ZnO nanorod cores that are coated with anatase TiO 2 shells. Humidity sensors based on these core/shell nanorod arrays exhibit outstanding sensitivities with capacitances varying from 10 6 to 10 1 pF over a relative humidity (RH) range of 11% -95% at room temperature, which is 1.5 and 3 orders of magnitude higher than that of pristine TiO 2 films and ZnO nanorods, respectively.Complex impedance analysis indicated that the enhanced humidity sensitivity is probably due to the high surface/volume ratio of this core/shell material in combination with the remarkable hydrophilicity of the TiO 2 shell.

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