Graphene doping continues to gather momentum because it enables graphene properties to be tuned, thereby affording new properties to, improve the performance of, and expand the application potential of graphene. Graphene can be chemically doped using various methods such as surface functionalization, hybrid composites (e.g., nanoparticle decoration), and substitution doping, wherein C atoms are replaced by foreign ones in the graphene lattice. Theoretical works have predicted that graphene could be substitutionally doped by aluminum (Al) atoms, which could hold promise for exciting applications, including hydrogen storage and evolution, and supercapacitors. Other theoretical predictions suggest that Al substitutionally doped graphene (AlG) could serve as a material for gas sensors and the catalytic decomposition of undesirable materials. However, fabricating Al substitutionally doped graphene has proven challenging until now. Herein, we demonstrate how controlled-flow chemical vapor deposition (CVD) implementing a simple solid precursor can yield high-quality and large-area monolayer AlG, and this synthesis is unequivocally confirmed using various characterization methods including local electron energy-loss spectroscopy (EELS). Detailed high-resolution transmission electron microscopy (HRTEM) shows numerous bonding configurations between the Al atoms and the graphene lattice, some of which are not theoretically predicted. Furthermore, the produced AlG shows a CO₂ capturability superior to those of other substitutionally doped graphenes.

There is ongoing research in freestanding single-atom thick elemental metal patches, including those suspended in a two-dimensional (2D) material, due to their utility in providing new structural and energetic insight into novel metallic 2D systems. Graphene pores have shown promise as support systems for suspending such patches. This study explores the potential of Sn atoms to form freestanding stanene and/or Sn patches in graphene pores. Sn atoms were deposited on graphene, where they formed novel single-atom thick 2D planar clusters/patches (or membranes) ranging from 1 to 8 atoms within the graphene pores. Patches of three or more atoms adopted either a star-like or close-packed structural configuration. Density functional theory (DFT) calculations were conducted to look at the cluster configurations and energetics (without the graphene matrix) and were found to deviate from experimental observations for 2D patches larger than five atoms. This was attributed to interfacial interactions between the graphene pore edges and Sn atoms. The presented findings help advance the development of single-atom thick 2D elemental metal membranes.

Single atoms are the ultimate minimum size limit for catalysts. Graphene, as an exciting, ultimately thin (one atom thick) material can be imaged in a transmission electron microscope with relatively few imaging artefacts. Here, we directly observe the behavior of single Cr atoms in graphene mono- and di-vacancies and, more importantly, at graphene edges. Similar studies at graphene edges with other elemental atoms, with the exception of Fe, show catalytic etching of graphene. Fe atoms have been shown to both etch and grow graphene. In contrast, Cr atoms are only observed to induce graphene growth. Complementary theoretical calculations illuminate the differences between Fe and Cr, and confirm single Cr atoms as superior catalysts for sp2 carbon growth.

Graphene oxide shows great promise as a material for biomedical applications, e.g., as a multi-drug delivery platform. With this in view, reports of studies on the interaction between nanosized graphene oxide flakes and biological cells are beginning to emerge. However, the number of studies remains limited, and most used labeled graphene oxide samples to track the material upon endocytosis. Unfortunately, the labeling process alters the surface functionality of the graphene oxide, and this additional functionalization has been shown to alter the cellular response. Hence, in this work we used label-free graphene oxide. We carefully tracked the uptake of three different nanoscale graphene oxide flake size distributions using scanning/transmission electron microscopy. Uptake was investigated in undifferentiated human monocyte cells (THP-1) and differentiated macrophage cells. The data show clear size dependence for uptake, such that larger graphene oxide flakes (and clusters) are more easily taken up by the cells compared to smaller flakes. Moreover, uptake is shown to occur very rapidly, within two min of incubation with THP-1 cells. The data highlights a crucial need for cellular incubation studies with nanoparticles, to be conducted for short incubation periods as certain dependencies (e.g., size and concentration) are lost with longer incubation periods.