Abstract:
Graphene has generated enormous research prospects over the last decade owing to its atomic thin sheet structure that has enabled newer thresholds in several physico-chemical properties. Recently significant efforts have been directed towards synthesizing inorganic analogues of graphene which offer a rich prospect for fundamental and applied science. Boron being the immediate neighbor of carbon in the periodic table, offers a curious case to be explored in the search for nanostructures isostructural to graphene. Currently, there exists no experimental evidence detailing synthesis of 2-D nanostructures based on boron honeycomb lattice. This thesis reports a chemical method that we developed to synthesize nanosheets based on boron honeycomb lattice. This method involves ultra-sonication assisted exfoliation of layered magnesium diboride in water. This simple sonochemical route results in a colloidal dispersion of chemically modified MgB2 nanosheets which were characterized for their morphology and chemical nature. Field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) pattern and zeta particle size analysis revealed that the MgB2 nanosheets had average effective diameters of ~7–50 μm and average thickness of less than 10 nm. Chemical characterization using Fourier transform infrared (FTIR) spectroscopy, zeta potential analysis and energy-dispersive X-ray (EDX) spectroscopy suggests that the chemically modified MgB2 nanosheets (CMMBs) exhibit a substantial degree of hydroxyl functional groups. This functionalization stabilizes the colloidal dispersion by facilitating a net negative charge on the surface of nanosheets. The concentration of ionized groups present on the nanosheets was quantified by acid-base titration at different pH values. At pH 7, the nanosheets exhibit a net negative charge. The discovery of nanosheets comprising boron honeycomb lattice could serve as an important advance in the science of two-dimensional inorganic nanomaterials. These nanosheets are expected to provide an avenue to tap the availability of boron at the atomic level and their functionalized surface is expected to facilitate the attachment of chemical/biological moieties, providing rich potential to fabricate and study several unprecedented constructs.