Self-assembled layer-by-layer deposition of ultrathin graphene membranes for high performance gas separation

In this contribution, a new layer-by-layer (LbL) deposition approach is demonstrated for the preparation of ultrathin graphene membranes out of graphene flakes suspension, and it is based on the van der Waals force principle. Specifically, this new LbL process allow a repeated deposition using only one type of graphene suspension, without any intentional functionalization, crosslinkers or alternate deposition of graphene or GO with opposite charge states, and the adhesion of the next graphene layer is achieved by van der Waals force. By using a double self-assembly (DSA) process, graphene flakes can be self-assembled to a densely packed single layer of graphene flakes (SLGFs), and subsequently deposited on porous ceramic substrates. The DSA process allows precise control of the number of layer stacks, or insertion of any 2D or nanoparticles to prepare mixed matrix membranes. Therefore, the thickness of the membranes can be easily adjusted. It is demonstrated that a closed graphene membrane can be obtained after a 5 times deposition, and the membranes prepared by multilayer deposition of SLGFs can be used as molecular sieves for gas separation. The single gas permeance properties of graphene membranes deposited on α-Al2O3 ceramic substrates have been characterized after 5 (5L), 8 (8L) and 11 layers (11L) deposition of graphene.