Ultrathin Porous Hydrocarbon Membranes Templated by Nanoparticle Assemblies

Porous polymer membranes are widely desired as catalyst supports, sensors, and active layers for separation membranes. We demonstrate that electron beam irradiation of freely suspended gold or Fe3O4 nanoparticle (NP) monolayer sheets followed by wet chemical etching is a high-fidelity strategy to template two-dimensional (2D) porous cross-linked hydrocarbon membranes. This approach, which relies on secondary electrons generated by the NP cores, can further be used to transform three-dimensional (3D) terraced gold NP supercrystals into 3D porous hydrocarbon membranes. We utilize electron tomography to show how the number of NP layers (monolayer to pentalayer) controls attenuation and scattering of the primary e-beam, which in turn determines ligand cross-link density and 3D pore structure. Electron tomography also reveals that many nanopores are vertically continuous because of preferential sintering of NPs. This work demonstrates new routes for the construction of functional nanoporous media.

Automated summary

By using electron beam irradiation of gold or Fe3O4 nanoparticle monolayer sheets followed by wet chemical etching, it is possible to template 2D porous hydrocarbon membranes and transform gold nanoparticle supercrystals into 3D porous hydrocarbon membranes. The control of nanoparticle layers and vertical continuity of nanopores are demonstrated using electron tomography. This work presents new routes for the construction of functional nanoporous media.