Rapid exfoliation of well-defined vermiculite nanosheets via ultrasound-triggered limited space shear for pollutant adsorption

Well-defined vermiculite (VMT) nanosheets possessing desirable physicochemical properties are highly attractive for a variety of uses. But a significant obstacle still stands in the way of their quick, scalable, sustainable, and economical preparation. Herein, we report an ultrasound-assisted confined shear exfoliation strategy based on a shear-cut collision mechanism. This method enables the efficient and controllable delamination of ultrathin VMT nanosheets through the synergistic action of ultrasonic vibration, shear, and collision forces. Nanosheet yield and size distribution can be finely tuned by adjusting the confined gap, rotational speed, and collision intensity, with the confined gap as the dominant parameter. Interestingly, reducing the rotation space enhances exfoliation efficiency, increasing productivity tenfold over conventional ball milling. Moreover, the use of water as the exfoliation medium eliminates the need for post-separation steps associated with salt-based solvents. The resulting colloidal dispersion remains stable for over six months. The as-obtained VMT nanosheets demonstrate outstanding adsorption capacity toward methylene blue (MB) and can be readily regenerated without aggregation. This green, high-yield exfoliation route offers a universal platform for scalable production of VMT and other two-dimensional layered materials.