Optical and Electrical Properties of Size-Controlled Cu–7,7',8,8'-Tetracyanoquinodimethane Nanocrystals

Abstract

We report the optical and electrical properties of Cu–TCNQ (TCNQ = 7,7',8,8'-tetracyanoquinodimethane) nanocrystals (NCs) fabricated by previously reported chemical reduction reprecipitation methods. The size of the resulting NCs ranges from 50 nm to 10 µm along the long axis. Raman experiment, X-ray photoelectron spectroscopic experiment, and elemental analysis reveal that these NCs have few TCNQ dianions due to the excess amount of Cu. The absorption of interband transition in the near-infrared region shows a blue shift, and the band gap increases with decreasing NC size. The obtained NCs show high electric conductivity, compared with typical Cu–TCNQ microcrystals, and multistep switching due to the existence of TCNQ dianions.