Two-Part Surfactant-Assisted\nExfoliation of Hexagonal\nBoron Nitride Nanosheets to Obtain Highly Stable Two-Dimensional Nanomaterial\nDispersions

Printable dielectric materials that exhibit high dielectric\nconstants\nand low losses at high frequencies are needed for additive manufacturing\nof electronic devices. One promising nanomaterial for use in such\nsystems is hexagonal boron nitride (hBN). This 2D nanomaterial is\ninsulating due to its wide band gap and has a dielectric constant\nranging from 2 to 4, making it an ideal candidate for applications\nincluding gate dielectrics, capacitors, and passivation layers in\n2D nanoelectronics. However, stabilizing the dispersion of hBN nanosheets\nfor printing applications while minimizing the reliance on toxic solvents\nand excessive surfactants remains a challenge. Many of the prevailing\nexfoliation techniques are time-consuming and resource-intensive.\nThis work explores a two-part, surfactant-assisted mechanical exfoliation\nmethod to obtain stable hBN nanosheet dispersions from bulk hBN in\na relatively short period, using ball milling followed by probe sonication.\nExfoliation of hBN nanosheets assisted by various concentrations (from\n0 to 1 wt %) of Triton X −100 was explored. The yield of each\nmixture was quantified by thermogravimetric analysis (TGA), and a\nmaximum yield of 18.4% was achieved using 1 wt % surfactant. Colloidal\nstability was examined by using UV–vis spectroscopy, and solutions\nwere found to remain stable for up to 30 days. The quality and size\nof the nanosheets were assessed using X-ray diffraction, scanning\nelectron microscopy, and atomic force microscopy. The dielectric properties\nof the obtained nanosheets were measured using a vector network analyzer\nat microwave frequencies, and the real permittivity of the nanosheets\nranged from 2.1 to 3.7 with varying concentrations of surfactant used\nin the synthesis. Furthermore, the nanosheets were found to be insulating\nand to have low dielectric loss tangents ranging from 0.012 to 0.014.\nThe two-part, surfactant-assisted mechanical exfoliation technique\nrequires much lower processing time than sonication alone and results\nin highly stable dispersions. The resulting hBN nanosheets exhibited\ntunable real permittivity and low dielectric loss, positioning these\nmaterials as promising options for dielectric ink formulations.