D. Dettmann, M. Panighel, N. Preetha Genesh et al.

Ullmann coupling is a widely used reaction for the on-surface growth of low-dimensional carbon nanomaterials. The irreversible nature of this reaction prevents the “self-healing” of defects, and a detailed knowledge of its mechanism is therefore essential to enable the growth of extended ordered structures. However, the dynamics of the Ullmann polymerization remain largely unexplored, as coupling events occur on a timescale faster than conventional scanning probe microscopy imaging frequencies. Here, we reveal the dynamics of these surface events using high-speed variable-temperature scanning tunneling microscopy (STM) (10 frames per second). Performing the measurements at the onset reaction temperatures provides an unprecedented description of the evolution of organometallic (OM) and covalent surface species during the Ullmann polymerization of para-dibromobenzene on Cu(110). Our results demonstrate the existence of an intermediate OM phase with Cu adatoms that inhibits the polymerization. These observations now complete the picture of the pathways of on-surface Ullmann polymerization, which includes the complex interplay of the phenylene moieties and metal atoms. Our work demonstrates the unique capability of high-speed STM to capture the dynamics of molecular self-assembly and coupling.

L. Boulbet-Friedelmeyer, G. Pécastaings, C. Labrugère-Sarroste, et al.

Graphene in water is electrically charged in most conditions. The level of charge can be large enough to stabilize single (or few) layer graphene colloidal dispersions in water, without the need of using any other additive. In this work, potentiometric titration, isothermal titration calorimetry, electrokinetic measurements, Density Functional Theory calculations, Raman Spectroscopy, and direct force measurements using Atomic Force Microscopy to investigate this charge and explore its origin are combined. The body of data collected suggests that this charge is a consequence of the interaction between water ions (hydroxide and hydronium) and graphene, and can be conveniently tuned (in magnitude and sign) by changing the pH of water.

T. Omiya, A. Cavaleiro, N. Figueiredo, R. Gouttebaron, A. Felten, F. Ferreira

This study examines the integration of ionic liquids (ILs) with gadolinium diamond-like carbon (Gd-DLC) films as a means of addressing the environmental drawbacks associated with conventional additives, such as zinc dialkyldithiophosphates. Tribological testing initially revealed that higher concentrations of gadolinium in the DLC resulted in improved wear resistance. Further observation of the wear tracks confirmed no corrosion typically seen in steel under bromide-containing ILs, thereby demonstrating the protective capabilities of Gd-DLC. Advanced surface analysis techniques revealed that increased gadolinium content enhances phosphate adsorption, resulting in the generation of protective tribofilms. These findings indicate that Gd-DLC and ILs have the potential to develop sustainable and efficient lubrication systems, significantly enhancing both performance and environmental compatibility of mechanical applications.