2D Zn/ZnO via solid–liquid interfacial engineering for room temperature optoelectronic gas sensing

Abstract

Solid–liquid interface reactions offer a promising route for synthesizing two-dimensional (2D) metal oxides. Here, we demonstrate the in situ formation of Zn-nanoparticle-decorated 2D ZnO sheets through the simple sonication treatment of solid Zn metal in a pure aqueous environment. In this synthetic system, dissolved oxygen in water enables the mild surface oxidation of a solid Zn substrate, while the intrinsic lattice mismatch between metallic Zn and ZnO generates interfacial tensile strain, which ultimately promotes the exfoliation of ultrathin 2D ZnO nanosheets. Residual parent Zn that is incompletely oxidized during the reaction can grow in situ and firmly anchor to the surface of ZnO nanosheets, thereby achieving the natural construction of Zn/ZnO metal–semiconductor heterostructures. The resulting Zn/ZnO heterostructure forms Mott–Schottky contacts at the metal–semiconductor interface, leading to a built-in electric field that facilitates the efficient separation of photogenerated electron–hole pairs. Leveraging their optical absorption in the blue-to-ultraviolet range, the heterostructure exhibits remarkable room-temperature NO₂ sensing under purple-light illumination. A response magnitude of up to 705.3% is achieved toward 10 ppm NO₂, along with reversible and dynamic responses across a range of concentrations. Additionally, the sensor exhibits excellent repeatability, high selectivity, and a low detection limit of 50 ppb. This study demonstrates the potential of solid–liquid interfacial engineering for constructing metal–semiconductor heterostructures and advancing light-assisted high-performance gas sensing technologies.