Silver Anchored Polyaniline@Molybdenum Disulfide Nanocomposite (Ag/Pani@MoS) for Highly Efficient Ammonia and Methanol Sensing under Ambient Conditions: A Mechanistic Approach.

We report the synthesis of silver anchored and para toluene sulfonic acid (TSA) doped polyaniline/molybdenum disulfide nanocomposite (TSA/Ag-Pani@MoS) for highly reproducible room temperature detection of ammonia and methanol. Pani@MoS was synthesized by in situ polymerization of aniline in the presence of MoS nanosheets. The chemical reduction of AgNO in the presence of Pani@MoS led to the anchoring of Ag to Pani@MoS and finally doping with TSA produced highly conductive TSA/Ag-Pani@MoS. Morphological analysis showed Pani-coated MoS along with the observation of Ag spheres and tubes well anchored to the surface. Structural characterization by X-ray diffraction and X-ray photon spectroscopy showed peaks corresponding to Pani, MoS and Ag. The DC electrical conductivity of annealed Pani was 11.2 and it increased to 14.4 in Pani@MoS and finally to 16.1 S/cm with the loading of Ag. The high conductivity of ternary TSA/Ag-Pani@MoS is due to Pani and MoS π-π* interactions, conductive Ag, as well as the anionic dopant. The TSA/Ag-Pani@MoS also showed better cyclic and isothermal electrical conductivity retention than Pani and Pani@MoS owing to the higher conductivity and stability of its constituents. The ammonia and methanol sensing response of TSA/Ag-Pani@MoS showed better sensitivity and reproducibility than Pani@MoS owing to the higher conductivity and surface area of the former. Finally, a sensing mechanism involving chemisorption/desorption and electrical compensation is proposed.