3D flower-like architectures assembled by ZnO porous nanosheets with higher surface area for enhanced lower temperature NO2 gas sensors

Abstract

It is essential to detect nitrogen dioxide (NO₂) in air, which is hazardous to human health, with accuracy and convenience. According to our prior findings, ZnO responds quickly to NO₂ gas. However, it continues to suffer from interference caused by high temperatures and low response values. In this study, we synthesized porous (surface area: ∼35 and average pore size: ∼19 nm) ZnO nanosheets assembled into a 3D flower-like structure using the conventional hydrothermal method to investigate their NO₂ gas sensing properties. The fundamental structural transformation process for 3D porous ZnO is studied in depth. The as-made 3D porous ZnO flower-like structure gas sensors have good gas-sensing capability to 4 ppm NO₂ at 135 °C, with a high response value (96), a rapid response/recovery time (50/6 s), a low detection limit (100 ppb), a long-term stability (35 days), and great selectivity. The relevant gas sensing mechanism is discussed in depth. This simple method clarifies the design of sensing materials by building a three-dimensional framework for very effective target gas.