Tailoring Multi-Walled Carbon Nanotubes into Graphene Quantum Sheets.

Transformation of carbon nanotubes (CNTs) into sub-10 nm pieces is highly required but remains great challenge. Herein, we report a robust strategy capable of mechanically tailoring pristine multi-walled carbon nanotubes (MWCNTs) into graphene quantum sheets (M-GQSs) with extremely high yield of up to 44.6 wt%. The method combines silica-assisted ball-milling and sonication-assisted solvent exfoliation therefore enables reproducible high-yield production of M-GQSs directly from MWCNTs. Remarkable solvent diversity and extraordinary solvability (up to 7 mg/mL) are demonstrated facilitating the solution processing of the M-GQSs. The M-GQSs are essentially monolayers with intrinsic curvature, which could be determinative to their outstanding performances in both dispersions and thin films. Besides the excitation wavelength-, concentration-, and solvent-dependent photoluminescence (PL) in dispersions, the solid-state fluorescence and exceptional nonlinear saturation absorption (NSA) in thin films are demonstrated. Particularly, NSA with relative modulation depth up to 46 % and saturation intensity down to 1.53 MW/cm2 are achieved in M-GQSs/poly(methyl methacrylate) (PMMA) hybrid thin films with loading content of merely 0.2 wt%. Our method opens up a new avenue toward conversion and utilization of CNTs.