Two-dimensional (2D) materials are promising candidates for nanoscale wear-protective coatings. The mechanisms governing their tribological behaviour (i.e., friction and wear) are material-dependent. In this work, we use atomistic molecular dynamics simulations to investigate nanoscale sliding, friction, and lithographic tracks in two 2D materials, graphene and MoS2, both placed on a SiO2 substrate. Our results reveal fundamentally different deformation mechanisms in the two materials, where deformation comes as a consequence of applied normal load. MoS2 deforms via the formation of a stable out-of-plane pucker beneath the contact, enabling efficient absorption and elastic redistribution of mechanical energy within the coating as well as simultaneous reduction of plastic deformation of the underlying material. Wear prevention in the substrate comes at the cost of localised damage to the MoS2 layer along the sliding path once it reaches the rupture point. On the contrary, graphene exhibits strongly localised deformation due to its high in-plane stiffness and atomic thickness, leading to plastic deformation of the underlying material and mitigating layer damage. These findings provide clear design guidelines for 2D coatings in nanotribological applications, and highlight layered materials, such as MoS2, as particularly effective for wear protection.

Proton exchange membrane fuel cells (PEMFCs) require polymer electrolytes that combine high proton conductivity with mechanical robustness. Although Nafion remains the industry standard, the mechanisms linking its performance to hydration and nanoscale structural organization remain unclear. In this work, we employ molecular dynamics simulations to elucidate how these factors control membrane properties at the molecular level, with particular emphasis on backbone ordering in both amorphous and crystalline Nafion configurations. A central contribution of this study is the development and validation of a highly accurate force field for the hydronium ion (H₃O⁺) based on density functional theory calculations. This model enables detailed characterization of proton–water interactions, hydrogen-bonding statistics, and the energetic landscape governing charge transport within the membrane. Using this new potential, we systematically investigate how structural ordering affects density, hydration, and water-channel formation. Water-clustering analysis reveals distinct hydration-dependent regimes: at low water content, isolated clusters dominate; at intermediate hydration, larger clusters form and percolate preferentially in crystalline systems; and at high hydration, continuous water networks span the simulation domain. Such well-connected pathways are crucial for facilitating efficient proton transport via the Grotthuss mechanism. Complementary Voronoi tessellation analysis demonstrates that highly ordered (crystalline) backbones consistently exhibit higher densities than disordered (amorphous) counterparts across all hydration levels, as spatial ordering enables more efficient packing of the hydrophobic polymer matrix. 1 Overall, our results establish a direct link between membrane nanostructure, hydration dynamics, and transport properties. By integrating force-field development with detailed structural and energetic analyses, this work provides a robust framework for the rational design of next-generation polymer electrolyte membranes with enhanced performance for fuel cells and related electrochemical technologies. Acknowledgments The authors acknowledge funding from the European Union’s Horizon Europe research and innovation program under the Marie Sklodowska-Curie project BLESSED grant agreement No - 101072578. References: [1] Jovanović, M.; Bernhard, N.; Baldofski, M.; Rybicki, M.; Dašić, M.; Stanković, I., Linking Density and Nanoscale Crystallinity to Hydration in Nafion PEMFC Membranes: Insights From Experiment and Molecular Dynamics Simulations, Small Structures, , DOI: 10.1002/sstr.202500573 Figure 1: Comparison between experimental data, the analytic model (bold line) and densities obtained in simulations in hydrated Nafion. The various structural configurations obtained via MD simulations within the scope of this study: amorphous (blue shaded region), semi-crystalline (green shaded region), and crystalline (orange shaded region). Figure 1

Water is omnipresent in nanoscale systems, yet its collective dynamics and impact on emerging electronics remain poorly understood. Here, we investigate the role of water molecule dynamics in the ferroelectric response of graphene nanoribbon devices. Our findings demonstrate that the collective dynamics of water molecules stabilize the ferroelectric effect. We find that a minimum bi-layer thickness is required for the temperature stability of the ferroelectric effect. In contrast, mono-layer ribbons show a 70% shrinkage of the hysteresis window between 120 and 400 K. Using a combination of electrical transport measurements and molecular dynamics simulations, we conclude that water molecules bridging between graphene nanoribbon layers stabilize the formation of water clusters via intermolecular Coulomb interactions, driving a robust ferroelectric behavior and remnant polarization observed at the device level. This work lays the foundations for exploiting water dynamics in next-generation ferroelectric heterostructures, with direct implications for neuromorphic computing and memory devices.

Proton exchange membrane fuel cells (PEMFCs) powered by hydrogen are promising for a wide range of energy‐conversion applications, with Nafion remaining the most widely used membrane material. Here, by comparing experimental data and molecular dynamics (MD) simulation results, we examine how a measurable property, the density, relates to the structure of Nafion at different water contents (λ). Voronoi tessellation and free‐volume analysis of MD results confirm that crystallinity and effective density are strongly correlated, highlighting the role of structural ordering. Further analysis of water clustering reveals isolated molecules at low hydration, while percolating networks form at higher λ, particularly within crystalline systems. Simultaneously, the density of confined water exhibits variations reaching values up to ≈1.2 g/cm3. We propose a model that bridges experimental and molecular observations by quantitatively linking water uptake to density variations, offering a predictive framework for optimising hydration and transport in membranes. Understanding how membranes with varying levels of crystallinity respond to changes in water content helps translate nanoscale mechanisms into practical designs for industrial PEMFCs.

This study explores the challenges associated with translating electrical characteristics of individual two-dimensional semiconductor nanosheets into a network of partially overlapping sheets. Such systems typically suffer from high-energy barriers required to overcome the junctions formed between the adjacent nanosheets, and consequently quench the current passing through the network. We use in-operando Kelvin probe force microscopy to image electrostatic potential profiles during the operation of MoS2 nanosheet network transistors. Direct imaging of the potential drops allows us to distinguish contributions from individual nanosheets and those from junctions, correlated by the junction-related potential drops with the network morphology. A diagram-based model is developed to describe the system numerically and to estimate the current path formation probabilities. Finally, a correlation with the integral electrical characteristics of the nanosheet-based transistors is made using a robust Y-function approach. It is shown that the total junction resistance is well estimated by the proposed equivalent circiut model.

Low-energy light ion beams are an essential resource in lithography for nanopatterning magnetic materials and interfaces due to their ability to modify the structure and properties of metamaterials. Here we create ferromagnetic/non-ferromagnetic heterostructures with a controlled layer thickness and nanometer-scale precision. For this, hydrogen ion (H+) irradiation is used to reduce the antiferromagnetic nickel oxide (NiO) layer into ferromagnetic Ni with lower fluence than in the case of helium ion (He+) irradiation. Our results indicate that H+ chemical affinity with oxygen is the primary mechanism for efficient atom remotion, as opposed to He+ irradiation, where the chemical affinity for oxygen is negligible.

Understanding atomic friction within a liquid environment is crucial for engineering friction mechanisms and characterizing surfaces. It has been suggested that the lattice resolution of friction force microscope in liquid environments stems from a dry contact state, with all liquid molecules expelled from the area of closest approach between the tip and substrate. Here, we revisit this assertion by performing in-depth friction force microscopy experiments and molecular dynamics simulations of the influence of surrounding water molecules on the dynamic behavior of the nanotribological contact between an amorphous SiO2 probe and a monolayer MoS2 substrate. An analysis of simulation and experimental stick-slip patterns demonstrates the entrapment of water molecules at the contact interface. These trapped water molecules behave as an integral component of the probe and participate in its interaction with the substrate, affecting the dynamics of the probe and preventing long slips. Significantly, surrounding water from the capillary or layer exhibits a replenishing effect, acting as a water reservoir during sliding. This phenomenon facilitates the preservation of lattice-scale resolution across a range of applied normal loads.

We present a numerical investigation of the influence of water content on the dynamic properties of a family of phosphonium-based room-temperature ionic liquids. The study presents a compelling correlation between structural changes in water-ionic liquid solutions and thermodynamic and transport properties across diverse systems. The results for phosphonium ionic liquids are compared with 1-butyl-3-methylimidazolium hexaphosphate ([bmim]PF6) as a reference. Through this approach, phosphonium cation structure-related characteristics can be identified and placed within the broader context of ionic liquids. These insights are underpinned by observed changes in interaction energy, boiling point, diffusion rate, and viscosity, highlighting the crucial role of water molecules in weakening the strength of interactions between ions within the ionic liquid. The investigation also explains temperature-dependent trends in phosphonium cations, showing that alkyl group length and molecular symmetry are important tuning parameters for the strength of Coulomb interactions. These results contribute to a refined understanding of phosphonium ionic liquid behavior in the presence of water, offering valuable insights for optimizing their use in diverse fields.

The electrolyte intercalation mechanism facilitates the insertion and extraction of charge into the electrode material in rechargeable batteries. Aluminum fluoride (AlF3) has been used as an electrolyte in rechargeable aluminum batteries with graphite electrodes, demonstrating improved reversibility of battery charging and discharging processes; however, the intercalation mechanism of this neutral molecule in graphite is so far unknown. In this work, we combine scanning tunneling microscopy (STM) in ultrahigh vacuum conditions, calculations based on density functional theory, and large-scale molecular dynamics simulations to reveal the mechanism of AlF3 intercalation in highly oriented pyrolytic graphite (HOPG). We report the formation of AlF3 molecule clusters between graphite layers and their self-assembly by graphene buckling-mediated interactions and explain the origin and distribution of superficial blisters in the material. Our findings have implications for understanding the relationship between the mobility and clustering of molecules and the expansion of the anode material. This, in turn, paves the way for future enhancements in the performance of energy storage systems.

The interaction mechanisms of water with nanoscale geometries remain poorly understood. This study focuses on behaviour of water clusters under varying external electric fields with a particular focus on molecular ferroelectric devices. We employ a two-fold approach, combining experiments with large-scale molecular dynamics simulations on graphene nanoribbon field effect transistors. We show that bilayer graphene nanoribbons provide stable anchoring of water clusters on the oxygenated edges, resulting in a ferroelectric effect. A molecular dynamics model is then used to investigate water cluster behaviour under varying external electric fields. Finally, we show that these nanoribbons exhibit significant and persistent remanent fields that can be employed in ferroelectric heterostructures and neuromorphic circuits.

The physics of dynamic friction on water molecule contaminated surfaces is still poorly understood. In line with the growing interest in hydrophobic contact for industrial applications, this paper focuses on friction mechanisms in such interfaces. As a commonly used material, contact with graphite is considered in a twin-fold approach based on experimental investigations using the circular mode atomic force microscopy technique combined with molecular dynamic simulations. We demonstrate that an intuitive paradigm, which asserts that water molecules are squeezed out of a hydrophobic contact, should be refined. As a consequence, we introduce a mechanism considering a droplet produced within the sliding nanocontact by the accumulation of water adsorbed on the substrate. Then we show that a full slip regime of the droplet sliding on the hydrophobic substrate explains the experimental tribological behavior.

We study the stabilisation of clusters and lattices of cuboidal particles with long-ranged magnetic dipolar and short-ranged surface interactions. Two realistic systems were considered: one with magnetisation oriented in the [001] crystallographic direction and the other with magnetisation along the [111] direction. We have studied magnetic nanocube clusters first in the limit of T = 0 K intending to elucidate the structural genesis of low energy configurations and then analysed finite-temperature behaviour of the same systems in simulations. Our results demonstrate that dipolar coupling can stabilise nanoparticle assemblies with cubic, planar, and linear arrangements seen previously in experiments. While attractive surface energy supports the formation of super-cubes, repulsion results in the elongated structures in the form of rods and chains. We observe the stabilisation of the ferromagnetic planar arrangements of the cubes standing on their corners and in contact over edges. We illustrate that minimal energy structures depend only on the size of the assembly and balance of surface repulsion and magnetic dipolar coupling. The presented results are scalable to different particle sizes and material parameters.

Poly(methyl methacrylate)-Fullerene (PMMA/C-60) nanocomposites, with different concentrations of C(60)molecules (0.025 wt.%, 0.05 wt.%, 0.075 wt.% and 0.1 wt.%), were synthesized and characterized by Magnetic Force Microscopy and UV-VIS spectroscopy. Characterization had two main objectives: to identify C(60)molecules in the PMMA/C(60)complex and to evaluate the order of PMMA and C(60)molecules in it. Since the structural properties of PMMA/C(60)complex depend on the arrangement of methyl methacrylate (MMA) and C(60)molecules, it can be concluded that the structure of the complex directly correlates to the ratio of an unpaired/paired electrons within the material. To investigate the influence of different concentrations of fullerene molecules in PMMA on the attraction and the repulsion forces in material, based on paired and unpaired electrons, and ultimately on the complex structural and optical properties, Magnetic Force Microscopy was used. Investigation showed that PMMA/C(60)complex with 0.025 wt.% concentration of C(60)has the best structural and optical properties for applications in ophthalmology, and may be used as a new material for spectacles. UV-VIS Spectroscopic analysis in domain of 380 to780 nm showed that PMMA material with 0.025 wt.% concentration of C(60)reduces UV and high blue energy light for more than 60% and in new spectral scenario ratio of blue and green spectra is changed.

Correction for ‘A platform for nanomagnetism – assembled ferromagnetic and antiferromagnetic dipolar tubes’ by Igor Stanković et al., Nanoscale, 2019, DOI: 10.1039/c8nr06936k.

Under typical operation of internal combustion engines, the conditions inside the combustion chamber vary significantly. Temperature can range from 300 K to values higher than 2000 K, while pressure ranges from atmospheric to values higher than 10 MPa [1]. The piston reciprocates with a sinusoidal velocity variation with speeds varying from zero to over 20 m/s. The time required for one revolution of the engine is of the order of 10−2 s, while the total distance travelled by the piston over this period is of the order of 0.2 m. Such scales are typically modelled using continuum mechanics simulations. However, such simulations cannot provide the physical insight which is necessary for understanding the molecule–dependent processes that affect the tribological phenomena. Therefore, we have found a solution which includes the coarse grain MD setup which can, inter alia, provide useful insights to lubrication mechanisms of piston ring–cylinder liner contact in automotive engines.

in-flight assembly of magnetic particles into macroscopic chains Lluis Balcells,† Igor Stanković,∗,‡ Zorica Konstantinović,¶ Aanchal Alagh,† Victor Fuentes,† Laura López-Mir,† Judit Oró,† Narcis Mestres,† Carlos Garćıa,§ Alberto Pomar,† and Benjamin Mart́ınez† †Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain ‡ Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, 11080 Belgrade, Serbia. ¶Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia §Departamento de F́ısica & Centro Cient́ıfico Tecnológico de Valparáıso-CCTVal, Universidad Técnica Federico Santa Maŕıa, Av. España 1680, Casilla 110-V, Valparáıso, Chile.

We report an interesting case where magnetic phenomena can transcend mesoscopic scales. Our system consists of tubes created by the assembly of dipolar spheres. The cylindrical topology results in the breakup of degeneracy observed in planar square and triangular packings. As far as the ground state is concerned, the tubes switch from circular to axial magnetization with increasing tube length. All magnetostatic properties found in magnetic nanotubes, in which the dipolar interaction is comparable to or dominant over the exchange interaction, are reproduced by the dipolar tubes including an intermediary helically magnetized state. Besides, we discuss the antiferromagnetic phase resulting from the square arrangement of the dipolar spheres and its interesting vortex state.

Knowing the interactions controlling aggregation processes in magnetic nanoparticles is of strong interest in preventing or promoting nanoparticles' aggregation at wish for different applications. Dipolar magnetic interactions, proportional to the particle volume, are identified as the key driving force behind the formation of macroscopic aggregates for particle sizes above about 20 nm. However, aggregates' shape and size are also strongly influenced by topological ordering. 1-D macroscopic chains of several micrometer lengths are obtained with cube-shaped magnetic nanoparticles prepared by the gas-aggregation technique. Using an analytical model and molecular dynamics simulations, the energy landscape of interacting cube-shaped magnetic nanoparticles is analysed revealing unintuitive dependence of the force acting on particles with the displacement and explaining pathways leading to their assembly into long linear chains. The mechanical behaviour and magnetic structure of the chains are studied by a combination of atomic and magnetic force measurements, and computer simulation. The results demonstrate that [111] magnetic anisotropy of the cube-shaped nanoparticles strongly influences chain assembly features.

We present a theoretical study of the influence of the molecular geometry of the cation on the response of ionic liquids (ILs) to confinement and mechanical strain. The so-called tailed model includes a large spherical anion and asymmetric cation consisting of a charged head and a neutral tail. Despite its simplicity, this model recovers a wide range of structures seen in ILs: a simple cubic lattice for small tails, a liquid-like state for symmetric cation-tail dimers, and a molecular layer structure for dimers with large tails. A common feature of all investigated model ILs is the formation of a fixed (stable) layer of cations along solid plates. We observe a single anionic layer for small gap widths, a double anionic layer for intermediate ones, and tail-to-tail layer formation for wide gaps. The normal force evolution with gap size can be related to the layer formed inside the gap. The low hysteretic losses during the linear cyclic motion suggest the presence of strong slip inside the gap. In our model the specific friction is low and the friction force decreases with tail size.

Two-dimensional (2D) materials are envisaged as ultra-thin solid lubricants for nanomechanical systems. So far, their frictional properties at the nanoscale have been studied by standard friction force microscopy. However, lateral manipulation of nanoparticles is a more suitable method to study the dependence of friction on the crystallography of two contacting surfaces. Still, such experiments are lacking. In this study, we combine atomic force microscopy (AFM) based lateral manipulation and molecular dynamics simulations in order to investigate the movements of organic needle-like nanocrystallites grown by van der Waals epitaxy on graphene and hexagonal boron nitride. We observe that nanoneedle fragments - when pushed by an AFM tip - do not move along the original pushing directions. Instead, they slide on the 2D materials preferentially along the needles' growth directions, which act as invisible rails along commensurate directions. Further, when the nanocrystallites were rotated by applying a torque with the AFM tip across the preferential sliding directions, we find an increase of the torsional signal of the AFM cantilever. We demonstrate in conjunction with simulations that both, the significant friction anisotropy and preferential sliding directions are determined by the complex epitaxial relation and arise from the commensurate and incommensurate states between the organic nanocrystallites and the 2D materials.