Two‐Dimensional La <sub>2</sub> CoO <sub>4</sub> Perovskite Oxide Enabled by Phonon‐Resonance‐Driven Exfoliation for High‐Performance Gas Sensing
Yi Liang, Zhong Li, Tao Tang, Yinfen Cheng, Xinyi Hu, Jinghao Zhuang, Ang Li, Y. W. Liu, Qingguo Feng, Mengdi Wang, Guiwu Liu, G. Chen, Fanli Meng, Jian Zhen Ou
Abstract
ABSTRACT Strong electron‐phonon interactions in layered Ruddlesden‐Popper (RP) phase oxides, such as La 2 CoO 4 , present a major challenge for accessing their 2D counterparts. Here, we present a rapid and efficient exfoliation strategy that leverages the resonance between ultrasonic phonon waves and the intrinsic vibrational frequency of La‐O bonds within the rock‐salt interlayer, which are responsible for the strong electron‐phonon coupling. By applying a continuous phonon wave at this resonant frequency, bulk La 2 CoO 4 is exfoliated into 2D nanosheets within minutes. This process is significantly faster than conventional ion‐insertion‐based chemical exfoliation methods, which typically require several days. The resulting 2D‐La 2 CoO 4 possesses abundant surface dangling bonds and pronounced surface charge redistribution, enabling highly sensitive NO 2 detection at room temperature under visible light excitation. The sensor demonstrates an ultra‐low detection limit of 5 ppb and a high response magnitude of 86.67% toward 1 ppm NO 2 , along with excellent selectivity, humidity resistance, and long‐term stability for up to 60 days. This work not only introduces a phonon‐resonance‐driven exfoliation strategy for layered oxides but also showcases the potential of 2D RP phase materials with undercoordinated surface sites for high‐performance room‐temperature gas sensing.