Two-Dimensional La2CoO4 Perovskite Oxide Enabled by Phonon-Resonance-Driven Exfoliation for High-Performance Gas Sensing

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.