Moisture-Resistant Gas Sensor Derived from ZIF-8/Layered Double Hydroxide/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> Nanocomposites for Trace Isopropanol Detection
Yuxiang Qin, Haiyang Gui, Yinan Bai, Xie Jing
Abstract
Layered double hydroxides (LDHs) are recently gaining scientific attention in the gas sensor field. However, the general layer-stacking of two-dimensional (2D) materials significantly limits the performance of LDHs-based gas sensors due to the resulting reduction of gas-active sites. To address the issue, we designed and successfully constructed a nanocomposite of ZIF-8/LDHs/Ti3C2Tx via a sequential induced growth of LDHs and ZIF-8 on the 2D Ti3C2Tx nanosheets. The achieved ZIF-8/LDHs/Ti3C2Tx nanocomposite exhibits the uniform coverage of hexagonal ZIF-8 particles on LDHs/Ti3C2Tx. In the nanocomposite, the ZIF-8 particles grown with Zn atoms in LDHs as the core sites form a tight ternary heterostructure with LDHs and Ti3C2Tx, and a two-dimensional electron gas (2DEG) region with high conductivity is generated during an isopropanol (IPA)-sensing process. Benefiting from the modification of ZIF-8 and the generation of 2DEG, the gas adsorption sites and effective conductive pathway are prominently increased, which is crucial for the improvement of gas-sensing performance. Resultantly, the as-fabricated ZIF-8/LDHs/Ti3C2Tx sensor can detect rarefied IPA at the sub-ppm level with a theoretical limit of detection of 9 ppb; it shows a response value of 61.82 toward 50 ppm IPA at room temperature (RT), which is about 27 times boost in contrast to LDHs/Ti3C2Tx. Notably, the ZIF-8/LDHs/Ti3C2Tx sensor still shows a significant response (5.12) toward 2.5 ppm IPA under high relative humidity (85 %RH) at RT. The gas-sensing mechanism was clarified from the heterostructure effect, adsorption energy calculation, and morphology promotion. Above all, this research provides a route to explore the application potential of LDHs-based nanocomposites in both atmospheric and breath IPA detection.