High yield synthesis of boron-based nanosheets

Abstract

We present the chemical exfoliation of magnesium diboride (MgB 2 ) by employing organic chelating agents for synthesising boron-based nanosheets in high yield. MgB 2 is a promising parent material towards realising quasi-2D forms of boron, owing to its unique layered constitution: graphenic boron planes interleaved with hexagonal arrays of Mg atoms. Chelating agents can selectively extract the interlayer Mg from MgB 2 in water, to form Mgchelant complexes. The loss of Mg results in delamination of MgB 2 into boron-based nanosheets. This approach is further improved by rational choice of chelants with greater affinity for Mg and tuning the optimal pH for metal complexation, thereby leading to a better yield of nanosheets. These boron-based nanosheets have been explored for their candidacy as a new class of inorganic fillers in a polymeric matrixpolyvinyl alcohol (PVA). The mechanical and thermal properties of these boron-based nanosheet-PVA nanocomposite films have been studied.

Progress, Challenges, and Opportunities in the Synthesis, Characterization, and Application of Metal-Boride-Derived Two-Dimensional Nanostructures

“…They found that the reaction between MgB 2 and water is an ion-exchange process between protons and Mg cations, followed by a hydrolysis reaction . James et al introduced an alternative chelation-assisted route to delaminate MgB 2 and AlB 2 by selectively removing the Mg and Al atoms using a suitable chelating agent (Figure b). , All the above studies explored exfoliation of MgB 2 crystals in aqueous media, resulting in functionalized magnesium-deficient boron-based nanosheets with an empirical formula Mg 1– x B 2 H y O z with nanosheet thickness varying from ∼1.5 to 6 nm. It is noteworthy that the change in structure, composition, and the presence of functional groups (hydrides, oxides, and hydroxides) increased the band gap energy of MgB 2 from 2.2 meV and 7.2 meV to 4.49 eV, transforming it to an insulating material .…”

“…Many known metal-boride-derived 2D nanostructures could potentially display high mechanical strength. However, the study of their mechanical properties is in its incipient stages. ,,,, Metal-boride-derived 2D nanostructures can be utilized as advanced nanofillers to improve the strength of various polymer composites and as protective nanocoatings.…”

“…This is attributed to the multicentered bonding nature of boron, which leads to a rich variety of metal-boride properties. Several metal borides have been predicted to exist in 2D forms, some of which have also been experimentally realized (as represented in Figure a). − During the past few years, several top-down and bottom-up approaches have been proposed and developed to realize the 2D forms of metal borides, − adding a new facet to the rich science of these materials. For example, the enhanced accessibility to surface active sites in planar forms endows a state-of-the-art catalytic activity to metal-boride-derived 2D nanomaterials. − These nanostructures are also finding applications in areas not conventionally envisaged for such materials, such as hydrogen generation, rechargeable energy storage, and sensors. − Recently, several computational studies have also sought to explain the effect of two-dimensionality on their electronic and thermal transport properties. ,,,,− …”

“…In this Perspective, we present concrete examples where the unique structures of the main group and transition-metal-boride-derived 2D nanostructures result in unusual electrical, superconducting, photonic, mechanical, and catalytic properties. ,,− The flexibility, strength, and optoelectronic properties of metal-boride-derived 2D nanostructures make them ideal candidates for various applications in sensing, electronics, catalysis, energy harvesting, ion transport, superconductivity, hydrogen generation, and storage. ,,,,,,,,,,− We note that one of the main barriers to commercial adoption of these materials is the lack of scalable and controlled synthetic methods. In addition, the ultrathin nature of the layers poses unique challenges for detailed structural characterization. ,,,,,, We emphasize the need for detailed structure–function relationships to tune the physical and chemical properties and tailor them for specific applications. ,,,,,,− ,− ,− ,,− …”

2D boron nanosheet architectonics: opening new territories by smart functionalization

“…76 OH functionalization can be simply achieved by immersing or fabricating boron nanosheets within aqueous solutions. 43,[77][78][79][80] In 2017, Kondo et al prepared hydroxyl-functionalized boron nanosheets (B-OH) by an ion exchange reaction in water. 79 The ion-exchange reaction between protons in water and some of the Mg cations was followed by a hydrolysis reaction between the HB and water, producing H 2 and Mg-decient hydroxylfunctionalized boron sheets.…”