One Dimensional Segregated Single AU Sites on Step-Rich ZnO Ladder for Ultrasensitive NO <sub>2</sub> Sensors

Here we develop a freestanding ladder-like ZnO surface with abundant unsaturated step defects, which could efficiently anchor Au1 sites with one dimensional assembling for the ultrasensitive NO2 detection. The dimension of obtained ZnO hexagonal ladder could be precisely controlled through reasonably regularizing the nucleation and growth rate. Following a layer-by-layer growth mode, the obtained ZnO would adopt the step-rich evolution. These ladder-like structure could provide abundant unsaturated step defects along with their curved edge profiles to serve as susceptible centers to site-selectively immobilize isolated Au1 species (Au1-ZnO). The obtained Au1-ZnO catalysts exhibit an outstanding NO2 sensing response (12.6 to 300 ppb) at a low operating temperature (150 °C). The proposed step-induced strategy will broaden the rational design of special sites-trapped supported metal catalysis for gas sensors.