Transition-metal dichalcogenides like molybdenum disulphide have attracted great interest as two-dimensional materials beyond graphene due to their unique electronic and optical properties. Solution-phase processes can be a viable method for producing printable singlelayer chalcogenides. Molybdenum disulphide can be exfoliated into monolayer flakes using organolithium reduction chemistry; unfortunately, the method is hampered by low yield, submicron flake size and long lithiation time. Here we report a high-yield exfoliation process using lithium, potassium and sodium naphthalenide where an intermediate ternary Li x MX n crystalline phase (X ¼ selenium, sulphur, and so on) is produced. Using a two-step expansion and intercalation method, we produce high-quality single-layer molybdenum disulphide sheets with unprecedentedly large flake size, that is up to 400 mm 2 . Single-layer dichalcogenide inks prepared by this method may be directly inkjet-printed on a wide range of substrates.

A molecular‐scale gap array is introduced into a single‐layer graphene sheet by a lithographic dash‐line cutting process. Electrically active molecules are then covalently wired into these point contacts in high yield, thus forming stable molecular devices that for example are able to reversibly switch their conductance by chemical treatment.

Low-voltage, low-cost, high-performance monolayer field-effect transistors are demonstrated, which comprise a densely packed, long-range ordered monolayer spin-coated from core-cladding liquid-crystalline pentathiophenes and a solution-processed high-k HfO2 -based nanoscale gate dielectric. These monolayer field-effect transistors are light-sensitive and are able to function as reporters to convert analyte binding events into electrical signals with ultrahigh sensitivity (≈10 ppb).