Insights into the Exfoliation Process of V(2)O(5)·nH(2)O Nanosheet Formation Using Real-Time (51)V NMR

[Image: see text] Nanostructured hydrated vanadium oxides (V(2)O(5)·nH(2)O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V(2)O(5)·nH(2)O nanosheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V(2)O(5)·nH(2)O nanosheets from the V(2)O(5) and VO(2) precursors in real time using solution- and solid-state (51)V NMR. Solution-state (51)V NMR showed that the aqueous solution contained mostly the decavanadate anion [H(2)V(10)O(28)](4–) and the hydrated dioxovanadate cation [VO(2)·4H(2)O](+), and during the exfoliation process, decavanadate was formed, while the amount of [VO(2)·4H(2)O](+) remained constant. The conversion of the solid precursor V(2)O(5), which was monitored with solid-state (51)V NMR, was initiated when VO(2) was in its monoclinic forms. The dried V(2)O(5)·nH(2)O nanosheets were weakly paramagnetic because of a minor content of isolated V(4+). Its solid-state (51)V signal was less than 20% of V(2)O(5) and arose from diamagnetic V(4+) or V(5+).This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials.