Ultrasensitive ethanol sensor based on nano-Ag&ZIF-8 co-modified SiNWs with enhanced moisture resistance

Abstract

Silicon nanowires (SiNWs) is considered as one of the most promising candidates for gas sensing application due to its capability of operating at room temperature (20 °C) and compatibility with modern semiconductor process. However, there still remains a challenge that SiNWs is poorly sensitive to volatile organic compounds (VOCs). In this study, we reveal that the co-decoration of zeolite imidazole frameworks-8 (ZIF-8) and Ag nanoparticles can improve the gas-sensing response to ethanol and enhance the humidity resistance at 20 °C. Due to the inversion modulation introduced by nano-Ag modificaiton and the enhanced gas adsorption provided by ZIF-8 modification, the resultant co-decorated sensor of ZIF-8&[email protected] shows obviously enhanced response upon exposure to ethanol with wide concentration range. It meanwhile exhibits a practical capability to sense rarefied ethanol vapor low to 125 ppb at 20 °C and relative humidity of 25 %. Especially, the sensor exhibits a low limit of detection of 5.45 ppb of ethanol vapor. When working at high humidity of 85 %, the developed ZIF-8&[email protected] sensor still remain a significant response. The superior moisture resistance performance is clarified by first-principles caculations to be highly related to the hydrophobicity characteristic of the modified ZIF-8 and the hygroscopic center formed by Ag nanoparticles. A resistance model was proposed to demonstrate the enhanced sensing response of the ZIF-8&[email protected] Further, a two-level moisture resistance mechanism is demonstrated based on the first-principles caculations and the unique microstructure of ZIF-8&[email protected] The beneficial effect of ZIF-8&nano-Ag co-modification demonstrated in present work suggest an effective strategy for developing superior gas sensors capable of sensitive detection of VOCs with strong stability in humditiy ambient.