Polyoxometalates—A Novel Surface Stabilizer for Optically Tunable 2D Systems

2D van der waals systems have attracted significant interest across multi-disciplinary fields ranging from sensors, optical filters, and structurally responsive composites. Access to these materials is paramount for technology development. Technologies that facilitate and expand methods to stabilize monolayers, disperse them into a wide array of matrices (i.e. solvents, polymers) is desirable for facile integration into current bulk manufacturing methods. Despite the advances made in the last decade, access to many systems is limited by liquid phase exfoliation techniques (i.e. H₂O/Surfactant) where surface corrosion, oxidation, hydrolysis are common challenges. In this regard, we demonstrate that polyoxometalates (POMs) can meet exfoliation and stabilization challenges for layered van der waals heterostructures. This is exemplified in their ubiquitous ability to stabilize and exfoliate layered transition metal dichalcogenides (LTMDs); surface adsorption of POMs provide coulombic repulsion between individual layers in bulk crystallites and facilitate gentle delamination without the use of mechanical forces, minimizing surface defects and crystallite scission. POMs can further impart charge transfer to the LTMD surface resulting in tunable absorption edges for modular optics; this is further demonstrated via tuning the affinity of the POM to the LTMD surface to allow adaptive optical responses. The mechanism of surface adsorption, exfoliation, and stabilization can be transferred to colloidal systems outside of LTMDs (graphene, CIPs, MXenes) creating a general exfoliant for robust colloidal 2D systems.