Two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) have attracted much interest in the past decade. Herein, we present an all-physical top-down method for the scalable production of the intrinsic TMD quantum sheets (QSs). The phases of the TMDs (e.g., 2H-MoSe₂, 2H-WSe₂, and T_d-WTe₂) remain stable during the transformation from bulk to QSs. However, phase transition (from T_d to 2H) is detected in MoTe₂. Such phase-modulation by size-reduction has never been reported before. The TMD QSs can be well dispersed in solvents, resulting in remarkable photoluminescence with excitation wavelength-, concentration-, and solvent-dependence. Meanwhile, the TMD QSs can be readily solution-processed into hybrid thin films, which demonstrate exceptional nonlinear saturation absorption (NSA). Notably, 2H-MoTe₂ QSs in poly(methyl methacrylate) show extremely high NSA performance with (absolute) modulation depth up to 46.6% and saturation intensity down to 0.81 MW·cm⁻². Our work paves the way towards quantum-sized TMDs.

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.

Hetero-nanostructures of plasmonic metals and semiconductors have attracted increasing attention in the field of photocatalysis. However, most of the hetero-nanostructured catalysts are randomly arranged and therefore require comprehensive structural design for optimizing their properties. Herein, we report the robust construction of hierarchical hetero-nanostructures where gold (Au) nanorods and molybdenum disulfide (MoS₂) quantum sheets (QSs) are integrated in highly ordered arrays. Such construction is achieved through porous anodic alumina (PAA) template-assisted electrodeposition. The as-fabricated hetero-nanostructures demonstrate exciting electrocatalysis towards hydrogen evolution reaction (HER). Both plasmon-induced hot-electron injection and plasmonic scattering/reabsorption mechanisms are determinative to the enhanced electrocatalytic performances. Notably, broadband photoresponses of HER activity in the visible range are observed, indicating their superiority compared with random systems. Such integrated hetero-nanoelectrodes could provide a powerful platform for conversion and utilization of solar energy, meanwhile would greatly prompt the production and exploration of ordered nanoelectrodes.

Platinum (Pt)-based electrocatalyst with low Pt content and high electrocatalytic performance is highly desired in fuel cell applications. Herein, we demonstrated that platinum-nickel (Pt-Ni) nanowires with an average composition of PtNi₃ and a fishbone structure can be readily synthesized and used as an efficient electrocatalyst toward methanol oxidation reaction (MOR). The PtNi₃ fishbone-like nanowires (PtNi₃-FBNWs) present features such as richer Pt on the surface than in the bulk, high-index facets on the rough surface, and polyhedral facets at the ends of side chains. Such compositional and structural features could be determinative to the enhanced performance in the electrocatalysis of MOR. Compared with commercial 20% Pt/carbon black (Pt/C), the specific activity and mass activity of the PtNi₃-FBNWs are enhanced by approximately 4.76 and 3.02 times, respectively. The stability of electrocatalysis is significantly improved as well. Such comprehensive enhancement indicates that the PtNi₃-FBNWs would be a promising candidate toward MOR in fuel cells.