Inverted vortex fluidic exfoliation and scrolling of hexagonal-boron nitride†
Exfoliation or scrolling of hexagonal boron nitride (h-BN) occurs in a vortex fluidic device (VFD) operating under continuous flow, with a tilt angle of −45° relative to the horizontal position. This new VFD processing strategy is effective in avoiding the build-up of material that occurs when the device is operated using the conventional tilt angle of +45°, where the h-BN precursor and scrolls are centrifugally held against the wall of the tube. At a tilt angle of −45° the downward flow aided by gravity facilitates material exiting the tube with the exfoliation of h-BN and formation of h-BN scrolls then optimized by systematically varying the other VFD operating parameters, including flow rate and rotational speed, along with concentration of h-BN and the choice of solvent. Water was the most effective solvent, which enhances the green chemistry metrics of the processing.