Chemochromism\nand Tunable Acoustic Phonons in Intercalated\nMoO<sub>3</sub>: Ag‑, Bi‑, In‑, Mo‑, Os‑,\nPd‑, Pt-, Rh-, Ru-, Sb-, and W‑MoO<sub>3</sub>

Intercalation of several elements (Ag, Bi, In, Mo, Os,\nPd, Pt,\nRh, Ru, Sb, and W) is used to chemically alter a wide range of properties\nof two-dimensional layered α-MoO<sub>3</sub>. Intercalation\nmodifies acoustic phonons and elastic constants, as measured with\nBrillouin scattering. Intercalation alters electronic bandgaps, color,\nstructure, Raman shifts, and electron binding energies. Optical chemochromism\nis demonstrated with intercalants changing the color of MoO<sub>3</sub> from transparent to brilliant blue (In, Mo, Os, and Ru) and orange\n(Ag). Correlations are investigated among material properties. There\nis evidence that in-plane longitudinal stiffness <i>c</i><sub>11</sub> correlates with changes in the bandgap, while various\nRaman modes appear to be connected to a variety of properties, including\nshear modulus <i>c</i><sub>55</sub>, Mo binding energies,\nlattice constants, and the preferred crystal structure of the intercalant.\nThe results indicate a surprising degree of complexity, suggesting\n competition among multiple distinct mechanisms and interactions involving\nspecific intercalant species.