MoS2@PANI composite for highly sensitive ammonia gas sensing at room temperature

Reliable gas sensor is obligatory for accurate detection of ammonia gas concentration in many fields. In this paper, a MoS 2 @PANI (polyaniline) composite prepared by a simple in-situ polymerization process of polyaniline on MoS 2 matrix was applied as the ammonia sensing material. Characterizations of SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope), EDS (Energy-Dispersive X-ray Spectroscopy), XRD (X-ray Diffraction) and BET (Brunauer-Emmett-Teller) were carried out to confirm the information of surface morphology, element, crystallography, and specific surface area of the prepared materials. The MoS 2 @PANI-based sensor showed tunable n-to-p response to ammonia gas depending on the doping content of PANI. The prepared MoS 2 @PANI sensor exhibited a fast response and recovery (16 s/41 s) to 100 ppm of ammonia gas with response value of 4.24 at room temperature. It was demonstrated for satisfying selectivity, repeatability, and stability. Specifically, the XPS (X-ray Photoelectron Spectroscopy) in vacuum and in-situ XPS in ammonia atmosphere was carried out and analyzed to investigate intuitive and powerful evidence for the gas sensing mechanism. On one hand, the coordination interactions between the PANI and MoS 2 during the in-situ oxidative polymerization of aniline was demonstrated by formation of Mo-N bond. On the other hand, the existence and function of multiple adsorption sites in the ammonia sensing process was also confirmed. Based on these advantages of the sensor, a portable and visual device by integrating the wireless signal connection, the prepared sensor, and the mobile phone was designed for the real-time monitoring and timely warning of ammonia concentration. The improved sensing performance and probable sensing mechanism elucidated can provide helpful reference for the development of room-temperature responsive ammonia gas sensors.