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Employing high-yield production of layered materials by liquid-phase exfoliation, molybdenum disulfide (MoS₂) dispersions with large populations of single and few layers were prepared. Electron microscopy verified the high quality of the two-dimensional MoS₂ nanostructures. Atomic force microscopy analysis revealed that ∼39% of the MoS₂ flakes had thicknesses of less than 5 nm. Linewidth and frequency difference of the E¹_2g and A_1g Raman modes confirmed the effective reduction of flake thicknesses from the bulk MoS₂ to the dispersions. Ultrafast nonlinear optical (NLO) properties were investigated using an open-aperture Z-scan technique. All experiments were performed using 100 fs pulses at 800 nm from a mode-locked Ti:sapphire laser. The MoS₂ nanosheets exhibited significant saturable absorption (SA) for the femtosecond pulses, resulting in the third-order NLO susceptibility Imχ⁽³⁾ ∼ 10^–15 esu …