Monodisperse size-controlled 1T'-WS2 nano-monolayers with high colloidal stability

The difference between in-plane and out-of-plane bonding energy of transition metal dichalcogenides has provided the possibility of isolating single layers. A one step synthesis protocol to produce size-controlled single layers has always been challenging. Here we developed a new colloidal synthesis to produce monodisperse size-controlled 1T'-WS2 nano-monolayers with outstanding colloidal stability by using 1-octadecanethiol as the coordinating agent. Changes in the reaction time and amount of coordinating agent regulate the mean size of the nanosheets. We investigated the effect of octadecanethiol and injection rate on the dispersion and mean-size, using UV-Vis spectroscopy, X-ray diffraction techniques, and transmission electron microscopy. Furthermore, thermogravimetric analysis and Fourier transform infrared spectroscopy allow for ligands detection and analysis at the surface of the nanosheets. These results open a new pathway to synthesize, control and explore the properties of nanoscale transition metal dichalcogenides.