VB2-Derived Nanosheets Synthesized via Dissolution-Recrystallization and Their Chemical Modification for Enhanced NIR Absorption

Abstract

Vanadium diboride (VB2), a layered ceramic comprising of vanadium atoms between boron honeycomb planes, has sought a renewed attention on account of its promising properties for energy storage and catalysis. The layered structure of VB2 also presents a possibility to yield two-dimensional counterparts. This aspect, however, has remained largely unexplored. In this work, we show that bulk VB2 can be transformed into a colloidal dispersion of quasi-2D nanostructures by a simple chemical approach. We found that a mere 1% aqueous H2O2 solution can result in the complete dissolution of VB2 crystals into prenucleation clusters, which subsequently recrystallize in a nonclassical manner to form sheet-like structures (∼2–5 μm wide and ∼5–15 nm thick). The resultant nanosheets exhibit a vanadium-rich stoichiometry (∼1.84:2) along with surface oxy-functionalization having vanadium in the +4 and +5 states. We further show that these nanosheets are chemically active- they undergo reduction in the presence of ascorbic acid, which results in a distinct color change of the colloidal dispersion from bright yellow through deep blue to eventually light blue. These chemically modified nanosheets exhibit enhanced absorbance in the near-infrared region. This work is the first study demonstrating the feasibility of VB2 to yield sheet-like nanostructures.