Uncovering Metastable α-Ag2MoO4 Phase Under Ambient Conditions. Overcoming High Pressures by 2,3-Bis(2-pyridyl)pyrazine Doping

The study of metastable phases has been elusive due to their propensity to convert to the stable phase. In this work, 3-bis(2-pyridyl)pyrazine (dpp)-doping was successfully used to relieve the high pressures required for the formation of metastable α-Ag2MoO4. α-Ag2MoO4 spheres were prepared via solution-phase precipitation under ambient conditions with the addition of dpp. While the properties of β-Ag2MoO4 have been well-studied, the difficulty in preparing the α-phase has limited its investigations to theoretical calculations. The overdue synthesis of α-Ag2MoO4 allowed empirical snapshots of its electronic and optical properties. The spheres show absorption in the visible/near-IR regions, and the band gap was determined to be 1.26 eV. Unlike β-Ag2MoO4, which is known to decay into Ag filaments on electron irradiation, the α-Ag2MoO4 spheres maintain their structural and electronic integrity. The inclusion of dpp into the crystal lattice is used to explain the experimental observations.