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

摘要

By maintaining alpha-Ag(DM)(2) (DM = C10H8N4) around room temperature (RT) ( 155 degrees 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.