Graphene/poly(ethylene terephthalate) composite membranes for ultrafiltration

Graphene/poly(ethylene terephthalate) composite membranes for ultrafiltration

Jsch

Membranes with specific barrier structures can be used in a wide range of applications, for, e.g., ultrafiltration, dialysis, or gas separation [1]. For all these applications the selective barrier should be as thin and robust as possible. Because of its infinitesimal thickness of 3 Å, great mechanical strength, impermeability for gases and liquids, and chemical inertness, the quasi 2D material graphene seems to be the ideal material for a selective barrier [2]. With porous graphene, because of negligible wall interactions, one could achieve very high transport rates (permeabilities) in filtering applications.

The aim of this work is to produce an ultrafiltration membrane which consists of a selective barrier of perforated monolayer graphene on top of a porous polymer support and to demonstrate its superior performance. Several approaches had been made to produce a perforated graphene membrane, for instance by focused electron beam ablation, ultraviolet-induced oxidative etching, or oxygen plasma etching [3]. Because all these techniques have intrinsic problems [3], another approach is used in this project. First, large area CVD graphene is transferred from copper foil onto a polymer film (polyethylene terephthalate, PET). This composite is irradiated by swift heavy ions (SHI, 6-1500 MeV), which perforate the whole composite. Due to its high energy the SHI form atomic pores directly in the graphene. In the polymer support a latent ion track is formed. After irradiation the composite is treated with NaOH solution to form pores in the polymer out of the latent ion tracks while graphene is inert on the etchant. The pore diameter in the graphene layer depends on the irradiation conditions and is in the range from 2 to 10 nm; each pore is aligned with a larger one in the PET support. Potential applications of those composite membranes are special separation problems like protein fractionation.

The work is done in close collaboration with physicist, and main current tasks of the group are developing suited composite preparation protocols, reducing the defect density in the graphene layer and characterizing the barrier properties of the resulting composite membranes [4].

References

  1. M. Ulbricht, Polymer 2006, 47, 2217
  2. P. Sun, K. Wang, H. Zhu, Adv. Mater. 2016, 28, 2287
  3. L. Huang, M. Zhang, C. Li, G. Shi, J. Phys. Chem. Lett. 2015, 6, 2806
  4. L. Madauß, J. Schumacher, M. Ghosh, O. Ochedowski, J. Meyer, H. Lebius, B. Ban-d'Etat, M. E. Toimil-Molares, C. Trautmann, R. G. H. Lammertink, M. Ulbricht, M. Schleberger, Nanoscale 2017, 9, 10487

Funding

The work is part of a collaborative project (NU-TEGRAM) within the FLAG-ERA JTC 2015 program of the European Union, and it receives funding from the German Research Council (DFG, Ul 113/10-1).

Contact:
Jens Schumacher