Growth of Nanocrystals in a Single Crystal of Different Materials: A Way of Giving Function to Molecular Crystals

We have recently found that organic conductors Ag(DR)2 (DR = 2,5-disubsituted-N,N′-dicyanoquinone diimine; substituent (R) = CH3, Cl, Br, I) irreversibly vary their electrical and magnetic properties by UV irradiation. By selecting the irradiation conditions (wavelengths, temperature, atmosphere, duration), one can accurately control the physical properties from metallic to insulating behavior while retaining their crystal structures. In order to clarify the mechanism of the conductivity change in the case of R = Cl, Br, and I, structure analysis of the irradiated crystals has been carried out. Transmittance electron microscopy and X-ray single crystal structure analysis clarified that the Ag(DCl)2 crystals after 72 h irradiation (375 nm) contained single crystals of nearly three-dimensionally ordered AgCl (0.9 in mole fraction) with varying dimensions (∼1−50 nm). Owing to such a unique hybrid crystal structure, a highly nonlinear current−voltage characteristic unlike any existing electronic devices is observed on irradiated single Ag(DCl)2 crystals.