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.