Ultrasound-Assisted Facile Green Synthesis of Hexagonal Boron Nitride Nanosheets and Their Applications

In this study, a facile, novel, ecofriendly method has been demonstrated for the fabrication of hexagonal boron nitride nanosheets (h-BNNs) by ultrasound-assisted exfoliation of h-boron nitride (h-BN) using various extracts of plant materials. Plant extract can be used for nanoparticle synthesis by acting as a reducing, capping, and stabilizing agent. Similarly, plant extract can function as a green surfactant by adsorbing on the surface of h-BN and, by weakening the interlayer interaction, slowly exfoliating h-BN in the form of layer h-BNNs. The product of exfoliation was confirmed by characterization with UV–visible spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Phytoexfoliated h-BNNs were applied for the removal of both cationic and anionic dyes from water, as an antioxidant, and to improve mechanical properties of biobased polyurethane composites. Stable dispersibility of h-BNNs in water was confirmed via stability experiments. Compared to that of the pristine h-BN and the control (h-BNNs synthesized using isopropanol), the plant-material-synthesized h-BNNs showed higher removal efficiency for both cationic and anionic dyes. Improved radical scavenging activities and mechanical properties in castor oil-based polyurethane composites were also shown. This novel and facile approach provides a convenient strategy for stable and scalable exfoliation of h-BN, which might find wide applications in different fields.