Etching of transition metal dichalcogenide monolayers into nanoribbon arrays

Two-dimensional transition metal dichalcogenide (TMDC) nanoribbons are reported to exhibit interesting properties distinctly different from their 2D analogues, including a change of transport properties depending on the edge structure, enhanced exciton correlation effect and thermoelectric property. Here we report a successful preparation method for large arrays of 2D TMDC nanoribbons without a template, using a reducing agent aqueous etchant. This method is a simple and tuneable way for generating TMDC (e.g. MoS2 and MoSe2) nanoribbons from CVD grown 2D TMDCs on Si/SiO2 through liquid phase mechano-chemical reaction. The reducing agent converts Mo(iv) from the defect sites to a lower oxidation state, thus expanding the defects. Water acts as a detaching and tearing medium that pulls the TMDC flake into nanoribbons. The area of conversion, density, and aspect ratio of the nanoribbons can be tuned by concentration and potency of the etchant. The 2D nanoribbons possess high structural integrity, zigzag edges with chalcogen termination, and an increase of bandgap when ribbon width decreases. This method allows a scalable approach for 2D nanoribbons to be prepared for various applications.