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Surface chemistry and interface interactions profoundly influence the properties of two‐dimensional (2D) materials and heterostructures. Therefore, developing methods to precisely control surfaces and interfaces is crucial for harnessing the properties and functions of 2D materials and heterostructures. Here, we developed a facile approach to tuning the interface distance and properties of graphene/MoS2 heterostructures (G/MoS2) by varying the functional groups attached to the surface of graphene bottom layer. We systematically investigated how different functionalized graphene bottom layers affect the interlayer distance, coupling between the interlayers, and optical properties of resulting G/MoS2 heterostructures. Our findings indicate that both the size and electron‐withdrawing/donating properties of functional groups are pivotal in regulating charge transport properties, with size playing a particularly decisive role. Our approach demonstrates an efficient and flexible pathway to regulate the interlayer spacing and charge transport, highlighting the potential of engineering interface chemistry in optimizing properties of van der Waals heterostructures. [ABSTRACT FROM AUTHOR]

Many organic dyes are fluorescent in solution. In the solid state, however, quenching processes often dominate, hampering material science applications such as light filters, light‐emitting devices, or coding tags. We show that the dimethylene‐cyclopropanide scaffold can be used to form two structurally different types of chromophores, which feature fluorescence quantum yields up to 0.66 in dimethyl sulfoxide and 0.53 in solids. The increased fluorescence in the solid state for compounds bearing malonate substituents instead of dicyanomethide ones is rationalized by the induced twist between the planes of the cyclopropanide core and a pyridine ligand. [ABSTRACT FROM AUTHOR]

Stacked graphene oxide (GO) proton membranes are promising candidates for use in energy devices due to their proton conductivity. Identification of through‐plane channels in these membranes is critical but challenging due to their anisotropic nature. Here, we present an electrochemical reduction method for identifying and quantifying through‐plane proton channels in GO membranes. The simplicity lies in the operando optical observation of the change in contrast as GO is electrochemically reduced. Here, we find three proton‐dominated three‐phase interfaces, which are critical for the reduction reactions of GO membranes. Based on these findings, a method is proposed to identify and quantify through‐plane channels in stacked GO proton membranes using a simple three‐electrode device in combination with real‐time imaging of the membrane surface. [ABSTRACT FROM AUTHOR]

The photochemical reaction of iodine and graphene induces strong new Raman modes due to the formation of trans‐oligoene substructures in graphene domains. This unique reactivity was demonstrated before on defect‐free graphene, however leaving the influence of e. g. carbon vacancies, unexplored. Here, we investigate the photochemical reaction applied on graphene with varying average distances of lattice defects and statistically analyze the characteristic Raman modes which develop with the iodination reaction. We show that the iodination reaction does not lead to Raman‐active defects and thus, the newly formed trans‐oligoene substructures do not contribute to the D‐mode of graphene. A statistical analysis reveals the correlation between the average distance of lattice defects and the intensity of the v1‐mode. For defective graphene with average defect distances below ~1 nm no new Raman modes evolve, which is the lower limit of the substructure size probed at 532 nm and explains why this observation was not possible before using common graphene oxide as graphene source. [ABSTRACT FROM AUTHOR]

Electrostatic potentials strongly affect molecular energy levels and charge states, providing the fascinating opportunity of molecular gating. Their influence on molecular vibrations remains less explored. Here, we investigate ethyl‐diaminodicyanoquinone molecules on a monolayer of MoS2 on Au(111) using scanning tunneling and atomic force microscopy and spectroscopy. These molecules exhibit a large dipole moment in gas phase, which is found to (partially) persist on the MoS2 monolayer. The self‐assembled structures consist of chains, where the dipoles of neighboring molecules are aligned antiparallel. Thanks to the decoupling efficiency of the molecular states from the metal by the MoS2 interlayer, vibronic states of the molecules are resolved, which vary in intensity depending on the molecular surrounding. We suggest that the vibrations are strongly damped by electrostatic interactions with the environment. [ABSTRACT FROM AUTHOR]

Oxo‐graphene nanoribbons (oxo‐GNRs) can be prepared by the oxidative unzipping of single‐walled carbon nanotubes. We present an orthogonal functionalization method for the functionalization of the rims and the π‐surface, respectively, what is only possible due to the high rim portion in oxo‐GNRs. In particular, X‐ray photoelectron spectroscopy could be used to follow the reaction and detect the marker atoms contained in the addends. We propose that the reported orthogonal functionalization strategy can also be applied on other oxo‐functionalized carbon materials, such as graphene quantum dots, or reduced graphene oxide flakes. [ABSTRACT FROM AUTHOR]

Surface chemistry and interface interactions profoundly influence the properties of two-dimensional (2D) materials and heterostructures. Therefore, developing methods to precisely control surfaces and interfaces is crucial for harnessing the properties and functions of 2D materials and heterostructures. Here, we developed a facile approach to tuning the interface distance and properties of graphene/MoS 2 heterostructures (G/MoS 2 ) by varying the functional groups attached to the surface of graphene bottom layer. We systematically investigated how different functionalized graphene bottom layers affect the interlayer distance, coupling between the interlayers, and optical properties of resulting G/MoS 2 heterostructures. Our findings indicate that both the size and electron-withdrawing/donating properties of functional groups are pivotal in regulating charge transport properties, with size playing a particularly decisive role. Our approach demonstrates an efficient and flexible pathway to regulate the interlayer spacing and charge transport, highlighting the potential of engineering interface chemistry in optimizing properties of van der Waals heterostructures., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Many organic dyes are fluorescent in solution. In the solid state, however, quenching processes often dominate, hampering material science applications such as light filters, light-emitting devices, or coding tags. We show that the dimethylene-cyclopropanide scaffold can be used to form two structurally different types of chromophores, which feature fluorescence quantum yields up to 0.66 in dimethyl sulfoxide and 0.53 in solids. The increased fluorescence in the solid state for compounds bearing malonate substituents instead of dicyanomethide ones is rationalized by the induced twist between the planes of the cyclopropanide core and a pyridine ligand., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

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 17 O 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.