Correlation between optical characteristics and NO2 gas sensing performance of ZnO nanorods under UV assistance

Abstract

In this research, we present the ZnO nanorods synthesized through the simple route of the hydrothermal method. The ZnO nanorods were developed through the application of only zinc acetate Zn(CH₃COO)₂ and ammonia solution, NH4OH, in the hydrothermal process at 150^oC for 10 hours. The size of the ZnO nanorods was defined as approximately 300 nm in diameter and 1-2 µm in length. The fabrication of sensors was achieved through drop-coating of synthesized ZnO nanorods on Al₂O₃ substrates integrated with Au electrodes. Subsequent to the process of sintering done at 500^oC for different durations, ZnO nanorod-based sensors were investigated when exposed to NO2 gas (1.5, 2.5, and 5 ppm) at room temperature under continuous UV-LED (385 nm) illumination. The correlation between NO₂ gas sensing performance and the optical property of the ZnO nanorods is discussed in detail. Herein, the defect concentration, particularly `in the surface region of the ZnO nanorods could be modified through sintering, and this indicates its importance in the reduction of responserecovery times and enhancement of high sensitivity to NO₂ gas.