Solvothermal route to S-deficient CoS nanoplates and their cathodoluminescence and magnetic properties.

A facile solvothermal method was developed to fabricate CoS nanoplates using ethylenediamine as solvent. The microstructure characterizations indicate that the CoS nanoplates have well-crystalline hexagonal phase and regular hexagonal or pentagonal shape. The XPS and ICP-AES measurements confirm the chemical composition of nanoplates is S-deficient CoS0.921. Cathodoluminescence spectra of both a large area of the nanoplates and individual nanoplate show broad emission bands centered at 615 nm. Magnetic measurements including magnetization dependence of temperature and magnetic hysteresis loops reveals that the CoS nanoplates exhibit room-temperature ferromagnetic behavior. It is found that intrinsic point defects mainly as V(s), Co(i) and/or the complex defects of V(s) and Co(i) should be responsible for both the broad emission band and the unique ferromagnetism.