In-depth properties analysis of ZnAl2O4/ZnO micro-nanostructures

This manuscript presents characterization of ZnAl2O4/ZnO micro-nanostructures of their morphological, chemical, structural and sensing properties. The ZnO micro-nanostructures obtained using flame transport synthesis were covered with ZnAl2O4 nanodots by chemical approach. Morphological, chemical and structural properties have been investigated using SEM, EDX and XRD, respectively. Scanning electron microscopy investigation shows the formation of micro-nanostructures of different morphologies, namely tetrapods and nanowires, covered with nanodots. The EDX study revealed the chemical composition of the micro-nanostructures, confirming the presence of Al on the micro-nanostructures’ surfaces too.The XRD pattern of the studied micro-nanostructures shows the presence of ZnO and ZnAl2O4 crystalline phases in the grown material. A single ZnAl2O4/ZnO nanostructure was integrated into a device by FIB/SEM and tested to a series of gases at different operating temperatures, demonstrating selectivity to 100 ppm hydrogen gas andresponse value of ~1.2 up to ~3.65 at 20 °C and 150 °C, respectively. A sensing mechanism to hydrogen gas was proposed, involving free electrical charge transfer between ZnO wire and ZnAl2O4 nanodots. Based on the knowledge gained, optimization of hydrogen gas sensors using the methods and nanomaterials presented herein is envisioned.