Strong interest in graphene oxide (GO) over the past decades has resulted in significant advances toward numerous applications and progress in understanding its chemistry. A rather broad community of scientists is involved in GO research including specialists in chemistry, physics, life, and materials sciences. While this diversity is a strength, common characterization techniques, such as Raman spectroscopy, FTIR, XPS, and XRD are often misused and inconsistently interpreted. Errors in data processing and analysis often invalidate key conclusions made in research papers. In many cases, experimental data provided in different studies are difficult to compare due to the lack of standardized ways of interpretations. The purpose of this review is to clarify common misunderstandings and errors in GO characterization by the four above-mentioned methods and to provide useful recommendations for best practices in data acquisition, processing, and interpretation. It also aims to offer guidance for new researchers entering the field of GO. The review is based on the authors' extensive experience in the field. By promoting standardized approaches, this review seeks to improve data comparability, enhance reliability in GO research, and establish a solid foundation for analyzing the structure and reactivity of GO-based materials.

Wet-chemical oxidation of graphite in a mixture of sulfuric acid with a strong oxidizer, such as potassium permanganate, leads to the formation of graphene oxide with hydroxyl and epoxide groups as the major functional groups. Nevertheless, the reaction mechanism remains unclear and the source of oxygen is a subject of debate. It could theoretically originate from the oxidizer, water, or sulfuric acid. In this study, we employed 18O and 17O labeled reagents to experimentally elucidate the reaction mechanism and, thus, determine the origin of oxo-functional groups. Our findings reveal the multifaceted roles of sulfuric acid, acting as a dispersion medium, a dehydrating agent for potassium permanganate, and an intercalant. Additionally, it significantly acts as a source of oxygen next to manganese oxides. Through ¹⁷O solid-state magic-angle spinning (MAS) NMR experiments, we exclude water as a direct reaction partner during oxygenation. With labeling experiments, we conclude on mechanistic insights, which may be exploited for the synthesis of novel graphene derivatives.

Functionalization of pristine graphene by hydrogen and fluorine is well studied, resulting in graphane and fluorographene structures. In contrast, functionalization of pristine graphene with iodine has not been reported. Here, the functionalization of graphene with iodine using photochemical activation is presented, which is thermally reversible at 400 °C. Additional dispersive dominant Raman modes that are probed by resonance Raman spectroscopy are observed. Additionally, iodinated graphene is probed by Kelvin probe force microscopy and by transport measurements showing p‐doping surpassing non‐covalent iodine doping by charge transfer‐complex formation. The emergent Raman modes combined with strong p‐doping indicate that iodine functionalization is distinct from simple iodine doping. A reaction mechanism based on these findings is proposed, identifying the large size of iodine atoms as the probable cause governing regiochemically controlled addition due to steric hinderance of reactive sites. The modification of the electronic structure is explained by the confinement of 1D trans‐oligoene chains between sp³‐defects. These results demonstrate the uniqueness of iodine reactivity toward graphene and the modification of the electronic structure of iodinated graphene, highlighting its dependence on the spatial arrangement of substituents.