Mechanism of spatially resolved photochemical control of the resistivity of a molecular crystalline solid

摘要

By maintaining alpha-Ag(DM)_2 (DM velence C_(10)H_8N_4) around room temperature (RT) (l55 deg C) during ultraviolet-visible (UV-vis) irradiation, a series of photochemical products named beta was obtained. The solid beta was comprised of structurally different compounds. All of the solid beta phases share the original chemical formula of Ag(DM)_2 and exhibit semiconducting behaviour, yet they differ from each other in their XRD patterns. They are divided into two phases: beta_ 1 and beta_2. Compared with the XRD pattern of the alpha phase, the beta_1 phase exhibited XRD peaks at the same 2 theta-angles but with different relative intensities, while the beta_2 phase exhibited totally different XRD patterns from those of the alpha or beta_1 phases. The actual composition of a particular solid of 'beta' phase is dependent upon irradiation time, and can be controlled continuously. Around RT, the alpha phase exhibits metallic conductivity, while the beta_1 and beta_2 phases are suggested to be semiconductors. As a result, one can continuously and finely control the electrical resistivity of Ag(DM)_2 by UV irradiation to modify it into a mixture of alpha, beta_1 and/or beta_2 phases.