Abstract
A highly sensitive self-powered humidity sensor has been realized from AuNPs hybrid black zinc oxide (ZnO) nanorods prepared through a sol-gel method. XRD pattern reveals that both ZnO and ZnO/AuNPs exhibit a wurtzite structure. ZnO/AuNPs nanorods grow in a vertical alignment, which possesses high uniformity and forms dense arrays with a smaller diameter than that of ZnO nanoparticles. All ZnO/AuNPs and pure black ZnO show lower band gap energy than the typically reported 3.34 eV of pure ZnO. Furthermore, the band gap of ZnO/AuNPs nanocomposites is effectively influenced by the amount of AuNPs. The humidity sensing tests clearly prove that all the ZnO/AuNPs humidity sensors exhibit much higher response than that of ZnO sensors, and the sensitivity of such ZnO/AuNPs nanorods (6 mL AuNPs) display a change three orders higher than that of pure ZnO with relative humidity (RH) ranging from 11% to 95% at room temperature. The response and recovery time of the ZnO/AuNPs are 5.6 s and 32.4 s, respectively. This study of the construction of semiconductor/noble metal sensors provides a rational way to control the morphology of semiconductor nanomaterials and to design a humidity sensor with high performance.
Highlights
Humidity sensors for detecting relative humidity (RH) are very important in many fields of technology and our daily life, such as industrial production, public transportation, health care and food storage [1,2,3]
Au nanoparticles (AuNPs) hybrid black zinc oxide (ZnO) nanorods manufactured through a sol-gel method
The X-ray diffraction measurements (XRD) patterns reveal that both ZnO and ZnO/AuNPs exhibit a wurtzite structure
Summary
Humidity sensors for detecting relative humidity (RH) are very important in many fields of technology and our daily life, such as industrial production, public transportation, health care and food storage [1,2,3]. Resistive-type humidity sensors have received considerable attention due to their high sensitivity, good linearity, operating stability and direct current electrical conductivity. Resistive-type humidity sensors make frequent use of the main categories of humidity sensing materials, which are ceramics, carbon materials, polymers, and metal oxide semiconductors [7,8,9]. Among these materials, metal oxide semiconductors are the most common material type used for humidity sensors on account of their ease of fabrication, and controllable size and morphology. Of the many metal oxide semiconductor materials, ZnO has attracted considerable attention for use in the fabrication of RH sensors.
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