The nonlinear optical property of few-layered MoS₂ nanoplatelets synthesized by the hydrothermal exfoliation method was investigated from the visible to the near-infrared band using lasers. Both open-aperture Z-scan and balanced-detector measurement techniques were used to demonstrate the broadband saturable absorption property of few-layered MoS₂. To explore its potential applications in ultrafast photonics, we fabricated a passive mode locker for ytterbium-doped fibre laser by depositing few-layered MoS₂ onto the end facet of optical fiber by means of an optical trapping approach. Our laser experiment shows that few-layer MoS₂-based mode locker allows for the generation of stable mode-locked laser pulse, centered at 1054.3 nm, with a 3-dB spectral bandwidth of 2.7 nm and a pulse duration of 800 ps. Our finding suggests that few-layered MoS₂ nanoplatelets can be useful nonlinear optical material for laser photonics devices, such as passive laser mode locker, Q-switcher, optical limiter, optical switcher and so on.

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.

Two-dimensional transition metal dichalcogenides (TMDs) have attracted lots of interest because of their potential for electronic and optoelectronic applications. Atomically thin TMD flakes were believed capable to scroll into nanoscrolls (NSs) with distinct properties. However, limited by mechanical strength and chemical stability, production of high-quality TMD NSs remains challenging. Here, we scroll chemical vapor deposition-grown monolayer TMD flakes into high-quality NSs in situ in 5 s with a nearly 100% yield by only one droplet of ethanol solution. An obvious photoluminescence is demonstrated in NSs and the self-encapsulated structure makes NSs more insensitive to external factors in optical and electrical properties. Furthermore, based on the internal open topology, NSs hybridized with a variety of functional materials have been fabricated, which is expected to confer TMD NSs with additional properties and functions attractive for potential application.

No abstract