Aqueous dispersions of highly luminescent boron-rich nanosheets by the exfoliation of polycrystalline titanium diboride.

Titanium diboride (TiB2) is a layered inorganic material composed of graphenic boron sheets alternating with titanium cations. Here we report the exfoliation of bulk titanium diboride (TiB2) to yield aqueous dispersions of two-dimensional (2D), boron-rich nanosheets. The delamination was realized by subjecting the pristine material to repeated cycles of shear-force grinding in aqueous medium followed by ultrasonication. The physico-chemical characterisation of the nanosheets has registered a significant decrease in the titanium-to-boron atomic ratio (i.e., with boron-rich stoichiometry) as compared to the pristine material. The aqueous dispersed boron-rich nanosheets were found to be highly photoluminescent with a quantum yield of about 13%, unlike the pristine material, which has no luminescence traits. To the best of our knowledge, this is the first successful exfoliation of a 2D material realized from bulk polycrystalline TiB2. The synthesis of stable, water-dispersible nanosheets with a high boron-to-titanium ratio may be an important step in the journey of 2D, boron-based nanosheet fabrication.