Chemistry at the Solid-Gas Interface: Direct Crystalline Thin-Film to Thin-Film Chemical Transformation

Single-crystal to single-crystal transformation is an elegant example of altering a crystalline solid-state of matter to a solid-state with a different chemical identity. Herein, we present an alluring example of thin-film to thin-film transformation of metal-organic to metal-halide by exploring chemistry at the solid-gas interface. Exposure of crystalline AgTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) thin-film to iodine (I-2) vapor and subsequent washing with chloroform (CHCl3) generated crystalline AgI (silver iodide) thin-film. The chemical transformation AgTCNQ -> AgI was so rapid that it took place within 2 min at ambient conditions. Reversible structural phase transition in the thin-film of AgI (beta-phase <-> alpha-phase) was further captured in variable temperature X-ray diffraction patterns, which appears promising for superionic conductivity and pyroelectricity applications.