Precise gradient separation of nanoparticles using reduced graphene oxide-polyoxomolybdate membranes

The purification and size sieving of nanoparticles (NPs) represents a significant scientific challenge. Herein, the rGO-polyoxometalates (POMs = PMo₁₂, Mo₁₃₂ and Mo₃₆₈) membranes were fabricated successfully via a simple and scalable POMs-assisted in-situ photoreduction strategy. When the mass ratio of rGO to PMo₁₂ was 1:30, the resultant rGO-PMo₁₂ membranes with highly ordered and uniform nanochannels of 1.0 nm can be obtained, which showed an accurate carbon quantum dots (CQDs) separation with a cut-off size approximately 1.0 nm. Further increase of the size of the interlayered POMs from PMo₁₂ (1.0 nm), {Mo₁₃₂} (2.9 nm) to {Mo₃₆₈} (3.8 nm), the resultant rGO-PMo₁₂, rGO-Mo₁₃₂ and rGO-Mo₃₆₈ exhibited precise gradient separation of CQDs and Au nanoparticles by size exclusion effect. The results pave a promising way to construct new two-dimensional (2D) membranes for highly efficient size-selective separation.