Room-temperature efficient NO2 gas sensors fabricated by porous 3D flower-like ZnAl-layered double hydroxides

Abstract

Three-dimensional (3D) flower-like zinc and aluminum-sodium dodecyl sulfate-layered double hydroxides (ZnAl-SDS-LDHs) intercalated by anions were prepared using a simple one-step hydrothermal method. Making use of urea as a precipitant and SDS as a template agent affords samples with intriguing ultra-thin nanosheets. Amongst them, the sample ZAS-2, synthesized with the Zn : Al molar ratio of 2 : 1, possessed nanosheets only 3.2 nm thick, with an average pore diameter of 3–12 nm, and a large specific surface area of 85.5 m² g⁻¹. At room temperature (25 °C) and a relative humidity of 26%, ZAS-2 exhibited a very rapid response/recovery time and 28.6 response to 100 ppm NO₂. Its fabricated sensor was endowed with good selectivity, high stability and low detection limit. The outstanding activity was mainly attributed to the unique microstructure of newly-synthesized ZAS materials that are composed of ultra-thin nanosheets along with plenty of embedded pores, and to the increased large specific surface area; all together promoting gas diffusion and adsorption. In addition, the coupling effect between hydroxyls and hydrogens of water adsorbed on the surface of LDH laminates further provides a static channel for efficient and fast carrier transport. Therefore, the heterostructure constructed by Zn(OH)₂ and Al(OH)₃ was beneficial for gas sensing performance.