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The discovery of graphene has led to a rising interest in seeking quasi two-dimensional allotropes of several elements and inorganic compounds. Boron, carbon’s neighbour in the periodic table, presents a curious case in its ability to be structured as graphene. Although it cannot independently constitute a honeycomb planar structure, it forms a graphenic arrangement in association with electron-donor elements. This is exemplified in magnesium diboride (MgB 2 ): an inorganic layered compound comprising boron honeycomb planes alternated by Mg atoms. Till date, MgB 2 has been primarily researched for its superconducting properties; it hasn’t been explored for the possibility of its exfoliation. Here we show that ultrasonication of MgB 2 in water results in its exfoliation to yield few-layer-thick Mg-deficient hydroxyl-functionalized nanosheets. The hydroxyl groups enable an electrostatically stabilized aqueous dispersion and create a heterogeneity leading to an excitation wavelength dependent photoluminescence. These chemically modified MgB 2 nanosheets exhibit an extremely small absorption coefficient of 2.9 ml mg −1  cm −1 compared to graphene and its analogs. This ability to exfoliate MgB 2 to yield nanosheets with a chemically modified lattice and properties distinct from the parent material presents a fundamentally new perspective to the science of MgB 2 and forms a first foundational step towards exfoliating metal borides.

Layered boron compounds have attracted significant interest in applications from energy storage to electronic materials to device applications, owing in part to a diversity of surface properties tied to specific arrangements of boron atoms. Here we report the energy landscape for surface atomic configurations of MgB 2 by combining first-principles calculations, global optimization, material synthesis and characterization. We demonstrate that contrary to previous assumptions, multiple disordered reconstructions are thermodynamically preferred and kinetically accessible within exposed B surfaces in MgB 2 and other layered metal diborides at low boron chemical potentials. Such a dynamic environment and intrinsic disordering of the B surface atoms present new opportunities to realize a diverse set of 2D boron structures. We validated the predicted surface disorder by characterizing exfoliated boron-terminated MgB 2 nanosheets. We further discuss application-relevant implications, with a particular view towards understanding the impact of boron surface heterogeneity on hydrogen storage performance. Layered boron compounds attract enormous interest in applications. This work reports first-principles calculations coupled with global optimization to show that the outer boron surface in MgB 2 nanosheets undergo disordering and clustering, which is experimentally confirmed in synthesized MgB 2 nanosheets.

Two-dimensional (2D) materials have sought intensive research attention from diverse scientific disciplines due to their unique and exciting properties. The most well-known 2D material is graphene that finds applications in various physical and life sciences fields. There has been a surge in the protocols available to synthesize graphene during the last two decades. Furthermore, several of these protocols have been revisited to improve the quality and yield of graphene that has resulted in a large body of literature. Young researchers, however, may not be entirely aware of these approaches. This review attempts to highlight the synthesis schemes that students and researchers could quickly adopt—even those having limited access to sophisticated tools. This review focuses on the top-down synthesis schemes that use low-end readily available equipment, benefitting the inexperienced and under-equipped researchers. This review's primary goal is to reach out to the young students, researchers, and technocrats working in diverse fields (not limited to nanoscience), to provide them with a roadmap for graphene synthesis. We will also present students entering academia with exciting applications that can be undertaken in university laboratories and high schools. Graphical abstract

The discovery of graphene showcased anability to isolate atomic thin sheet from layered graphite, and presented a precedent to the scientific community for exploring a similar possibility in other layered materials. Magnesium diboride (MgB2), which has metal atoms sandwiched in between boron honeycomb planes, represents an ionic layered material isostructural to intercalated graphite. We show that ultrasonication of MgB2 in ionic liquid (1-butyl-3-methyl imidazolium tetrafluoroborate)results in a stable dispersion of few-layer-thick boron based nanosheets. Furthermore, these nanosheets (∼3-6 µm wide, ∼2 nm thick) are found to exhibit an optical band-gap of ∼3.3eV alongwith excitation wavelength dependent photoluminescence.

Nanoscale materials invite immense interest from diverse scientific disciplines as these provide access to precisely understand the physical world at their most fundamental atomic level. In concert with this aim of enhancing our understanding of the fundamental behavior at nanoscale, this dissertation presents research on three nanomaterials: Gold nanoparticles (GNPs), Graphene and ultra-thin Boron Nitride sheets (UTBNSs). The three-fold goals which drive this research are: incorporating mobility in nanoparticle based single-electron junction constructs, developing effective strategies to functionalize graphene with nano-forms of metal, and exfoliating ultrathin sheets of Boron Nitride. Gold nanoparticle based electronic constructs can achieve a new degree of operational freedom if nanoscale mobility is incorporated in their design. We achieved such a nano-electromechanical construct by incorporating elastic polymer molecules between GNPs to form 2-dimensional (2-D) molecular junctions which show a nanoscale reversible motion on applying macro scale forces. This GNP-polymer assembly works like a molecular spring opening avenues to maneuver nano components and store energy at nano-scale. Graphene is the first isolated nanomaterial that displays single-atom thickness. It exhibits quantum confinement that enables it to possess a unique combination of fascinating electronic, optical, and mechanical properties. Modifying the surface of graphene is extremely significant to enable its incorporation into applications of interest. We demonstrated the ability of chemically modified graphene sheets to act as GNP stabilizing templates in solution, and utilized this to process GNP composites of graphene. We discovered that GNPs synthesized by chemical or microwave reduction stabilize on graphene-oxide sheets to form snow-flake morphologies and bare-surfaces respectively. These hybrid nano constructs were extensively studied to understand the effect and nature of GNPs’ interaction with graphene, and applied to address the challenge of dispersing bare-surfaced GNPs for efficient liquid-phase catalysis. We also revisited the functionalization of graphene and present a non-invasive surface introduction of interfaceable moieties. Isostructural to graphene, ultrathin BN sheet is another atomic-thick nanomaterial possessing a highly diverse set of properties inconceivable from graphene. Exfoliating UTBNSs has been challenging due to their exceptional intersheet-bonding and chemical-inertness. To develop applications of BN monolayers and evolve research, a facile lab-scale approach was desired that can produce processable dispersions of BN monolayers. We demonstrated a novel chlorosulfonic acid based treatment that resulted in protonation assisted layer-by-layer exfoliation of BN monolayers with highest reported yields till date. Further, the BN monolayers exhibited extensively protonated N centers, which are utilized for chemically interfacing GNPs, demonstrating their ability to act as excellent nano-templates. The scientific details obtained from the research shown here will significantly support current research activities and greatly impact their future applications. Our research findings have been published in ACS Nano, Small, Journal of Physical Chemistry Letters, MRS Proceedings and have gathered >45 citations.