Silver Anchored Polyaniline@Molybdenum Disulfide Nanocomposite (Ag/Pani@MoS(2)) 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 (pTSA) doped polyaniline/molybdenum disulfide nanocomposite (pTSA/Ag-Pani@MoS(2)) for highly reproducible room temperature detection of ammonia and methanol. Pani@MoS(2) was synthesized by in situ polymerization of aniline in the presence of MoS(2) nanosheets. The chemical reduction of AgNO(3) in the presence of Pani@MoS(2) led to the anchoring of Ag to Pani@MoS(2) and finally doping with pTSA produced highly conductive pTSA/Ag-Pani@MoS(2). Morphological analysis showed Pani-coated MoS(2) 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(2,) and Ag. The DC electrical conductivity of annealed Pani was 11.2 and it increased to 14.4 in Pani@MoS(2) and finally to 16.1 S/cm with the loading of Ag. The high conductivity of ternary pTSA/Ag-Pani@MoS(2) is due to Pani and MoS(2) π–π* interactions, conductive Ag, as well as the anionic dopant. The pTSA/Ag-Pani@MoS(2) also showed better cyclic and isothermal electrical conductivity retention than Pani and Pani@MoS(2,) owing to the higher conductivity and stability of its constituents. The ammonia and methanol sensing response of pTSA/Ag-Pani@MoS(2) showed better sensitivity and reproducibility than Pani@MoS(2) owing to the higher conductivity and surface area of the former. Finally, a sensing mechanism involving chemisorption/desorption and electrical compensation is proposed.