Speaker
Description
Ultrathin and thin graphene oxide (GO) membranes with well-defined in-plane nanopores are promising for separation, sensing, molecular transport, and nanofluidic applications. A versatile route to fabricate such porous GO architectures is heavy-ion irradiation in the high electronic energy loss ($S_e$) regime or with intermediate-$S_e$ ions at grazing incidence ($1-10^\circ$). The resulting nanopores are well-defined and uniformly distributed, with partially restored sp$^2$-hybridized carbon around the pore periphery and oxygen-containing functional groups at the pore edges. This unique pore structure is expected to enhance mass transport through laminar membranes. However, controlled nanopore formation using intermediate-$S_e$ ions at normal incidence remains poorly understood, with previous studies reporting somehow contradictory results.
In view of the planned restart of the UNILAC accelerator with medium-intensity ion beams up to Xe, we will present a critical review of GO nanoperforation in this regime together with results from our recent pilot experiments at GANIL.
High-resolution TEM combined with EELS mapping of suspended single- and few-layer GO revealed that, compared with the high-$S_e$ regime, the resulting nanopores were generally smaller, less uniform in size, and created with lower efficiency. A similar trend was observed for supported GO membranes (100$-$500 nm thick), as evidenced by SAXS measurements and SEM imaging of the surface. The ion track halo extended to a radius of $\sim$10 nm and, with increasing distance from the track center, exhibited a gradual decrease in functionalization density and progressive restoration of the sp$^2$-hybridized carbon lattice.
Finally, we stress the role of GO chemical composition (functional group density, group types, and defect density) in governing the threshold conditions for nanopore formation.
This research was funded by the National Science Centre, Poland grant No. 2025/09/X/ST11/00589.