Selective etching of Aluminium towards the synthesis of AlB₂ derived aqueous dispersion of luminescent boron-based Nanosheets

The selective extraction of metal atoms interspersed between the boron layers in the bulk metal diboride crystals - which are layered ionic solids akin to ion-intercalated graphene - offer a promising route for fabricating boron-based two-dimensional nanosystems. This study introduces an eco-friendly and cost-effective synthesis method utilizing the non-toxic citric acid and the green oxidant- hydrogen peroxide, to selectively etch aluminum atoms from the layered aluminium diboride crystals in powder form. Performed under ambient conditions with simple magnetic stirring, this synthesis route is both sustainable and scalable for industrial use. The resulting non-stochiometric, free-standing, aluminium diboride-derived, highly boron-rich nanostructures were found to be chemically functionalized with hydroxyl, hydride and oxide functional groups. In addition to endowing excellent dispersion stability, the surface moities created defect centers in the nanosheets, which, in turn, accounted for excellent photoluminescence properties. Thus, this synthesis process provides an opportunity to harness the astounding capabilities of boron in its nanodomain.