Phase/size dual controlled 2D semiconductor In₂X₃ (X = S, Se, Te) for saturable absorption modulation

The production of two-dimensional nanosheets (2D NSs) with all sizes (1–100 nm) and few (< 10) layers is highly desired but far from satisfactory. Herein, we report an all-physical top-down method to produce indium chalcogenide (In₂X₃ (X = S, Se, Te)) NSs with wide-range (150–3.0 nm) controlled sizes. The method combines silica-assisted ball-milling and sonication-assisted solvent exfoliation to fabricate multiscale NSs with varying distributions, which are then precisely separated by cascade centrifugation. Multiple characterization techniques reveal that the as-produced In₂X₃ NSs are intrinsic and defect-free and remain β-phase during the whole process. The redispersions of In₂X₃ NSs exhibit prominent excitation wavelength-, solvent-, concentration-, and size-dependent photoluminescence. The NSs-poly(methyl methacrylate) (PMMA) hybrid thin films demonstrate strong size effects in nonlinear saturation absorption. The absolute modulation depths of 35.4%, 43.3%, 47.2% and saturation intensities of 1.63, 1.05, 0.83 MW·cm⁻² (i.e., 163, 105, and 83 nJ·cm⁻²) are derived for the In₂S₃, In₂Se₃, and In₂Te₃ quantum sheets, respectively. Our method paves the way for mass production and full exploration of full-scale 2D NSs.