Controlled Production of MoS₂ Full‐Scale Nanosheets and Their Strong Size Effects

Abstract

The production of 2D nanosheets (2D NSs) with all sizes (1–100 nm) and few (<10) layers is highly desired but remains great challenge. Herein, the top‐down production of molybdenum disulfide (MoS2) NSs with wide‐range (161–10 nm) controlled sizes is reported. Considering the recently achieved MoS2 quantum sheets (QSs) with sizes of ≈2 nm, full‐scale NSs of MoS2 are successfully produced. The top‐down method combines silica‐assisted ball‐milling and sonication‐assisted solvent exfoliation. Ball‐milling with controlled time enables the production of multiscale NSs with varying distributions, which are then precisely separated by cascade centrifugation. Multiple spectroscopic techniques reveal the dramatic size dependence, indicating prominent quantum confinement and edge effects of the MoS2 NSs. The NSs‐poly(methyl methacrylate) (PMMA) hybrid thin films demonstrate strong size effects in nonlinear saturation absorption (NSA). Both (absolute) modulation depths and saturation intensities can be broadly modulated by simple variation of the NS sizes. With the sizes down from 161 to 10 nm, the modulation depths are increased from 27.0% to 51.3% and the saturation intensities are decreased from 33 419 to 21.2 kW cm−2 (3341.9–2.12 nJ cm−2). The work greatly facilitates the mass production and full exploration of 2D NSs with all sizes.

In-depth first-principle study on novel MoS2 polymorphs

“…We calculated the effective masses for the semiconductor (group A) polymorphs to conrm the ndings in the band structures. In general, the effective masses of electrons and holes are relevant for the mobility, electrical resistivity, quantum connement, 46,47 and free-carrier optical response in semiconductor materials. For the rst time, effective masses are presented for seven different polymorphs of MoS 2 and are shown in Table 2.…”

Structural Stability of Bilayer MoS2 in Ambient Air

“…In this paper, we report on the structural stability of preheated and as-grown BL and thicker-layer MoS 2 films in ambient air. The films are grown using CVD on SiO 2 substrates and studied using atomic force microscopy (AFM), and Raman and PL spectroscopies.BL and thicker-layer MoS 2 and other TMD films, nanosheets, [12] and nanostructures, [13] although having indirect band gaps, have attracted considerable interest because of their useful properties. For example, BLs and thicker-layers have higher electrical conductivities than MLs due to their higher density of states and more effective screening of impurities in the substrate.…”

“…BL and thicker-layer MoS 2 and other TMD films, nanosheets, [12] and nanostructures, [13] although having indirect band gaps, have attracted considerable interest because of their useful properties. For example, BLs and thicker-layers have higher electrical conductivities than MLs due to their higher density of states and more effective screening of impurities in the substrate.…”

Toward layered MoS2 anode for harvesting superior lithium storage

“…This excellent storage response with a negligible Li ion diffusion limit is due to the surface area offered by nanosheets of fewer than 10 layers with adequate interlayer and interplanar spacing. 26 Nevertheless, agglomeration of the nanosheets has been shown to compromise the electrochemical performance of the cell in numerous cases. [27][28][29][30][31][32][33] Thus, an effective synthesis is essential for fabricating high performance MoS 2 anodes.…”

“…There are various bottom-up 34 and top-down 35 approaches to produce MoS 2 but attaining a few layers of nanosheets continued to be a massive challenge through the years. 26 Generally, the bottom-up approach requires an extreme energy intensive post-treatment under stringent conditions, making it a least preferred process. 36,37 In spite of low yields, the top-down approach is commonly preferred on account of the bulk material abundance.…”