Moisture-Resistant Gas Sensor Derived from ZIF-8/Layered Double Hydroxide/Ti₃C₂T_x Nanocomposites for Trace Isopropanol Detection

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.