Electron Storage in Monolayer Tungstate Nanosheets Produced via a Scalable Exfoliation Method

Inorganic nanosheet materials with atomic thinness have been widely studied as (photo)catalytic materials due to their unique electronic states and surface structures. One scalable and reproducible method of producing monolayer nanosheets is a top-down approach based on the exfoliation of layered parent compounds using an alkylammonium solution as a surfactant. However, H₂W₂O₇ layered tungstates dissolve in basic aqueous solutions, making them unsuitable for the exfoliation process. This work proposes a scalable method to obtain monolayer WO₃ nanosheets with a very high external field responsiveness. This work shows that H₂W₂O₇ topochemically swells in a concentrated octylamine (C₈N₁₇NH₂) aqueous solution with a concentration above the solubility of octylamine in water. Water was added for exfoliation of the liquid crystalline phase into isolated W₂O₇^2- nanosheets with octylammonium (C₈N₁₇NH₃⁺) protection. Crystalline WO₃ nanosheets on the n-Si substrate obtained with calcination exhibited electron richness in the conduction band due to static electron transfer at the interface.