Graphite Surface Research Articles

Nonadiabatic Proton-Coupled Electron Transfer at a Graphitic Surface Immobilized Cobalt Porphyrin

Nonadiabatic Proton-Coupled Electron Transfer at a Graphitic Surface Immobilized Cobalt Porphyrin

Green synthesis of magnetic graphene-like biochar with oxygen vacancies for efficient adsorption and degradation of emerging antivirals from water

In this research, a magnetic biochar derived from the Vicia ervilia plant and possessing graphene-like properties (BC-G/Fe3O4) was used along with the activator persulfate for the adsorption and degradation of emerging pollutants such as Remdesivir and Favipiravir. The morphology, specific surface area, graphitization degree, and surface chemistry properties of the composite were determined using various techniques. The results showed that the synthesized BC-G/Fe3O4 had a high SSA (506.556 m2/g), indicating its suitable adsorption properties for the removal of antiviral drugs. The impact of various factors on the adsorption-oxidation process, including pH, catalyst dosage, oxidant concentration, antiviral concentration, and temperature, was examined and optimized through the utilization of response surface methodology and central composite design. The highest removal percentage of Remdesivir (93 %) and Favipiravir (98 %) was achieved at an initial antiviral concentration of 125 mg/L, catalyst dosage of 7 mg for Remdesivir and 5 mg for Favipiravir, contact time of 120 min, and pH of 7. Through the implementation of radical scavenging experiments, a thorough understanding of the mechanisms involved in PMS activation and the degradation of Favipiravir and Remdesivir was attained. The findings of this study indicate that the BC-G/Fe3O4 catalyst possesses excellent biocompatibility, adsorption-degradation capabilities, and reusability. Consequently, it can be successfully employed to eliminate emerging pollutants from aquatic environments.

Investigation of the effect of electrodeposited Cu from graphite wrapped in polypyrrole film formed by chemical oxidation

The metallization of graphite substrates is currently confronted by negative issues including insufficient adhesion and inherent instability. In an effort to surmount these challenges, a layer of conductive polypyrrole (PPy) film on a graphite surface is formed through simple polymerization, followed by an electroplating copper layer. The graphite enveloped by the PPy film, subjected to cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analyses, demonstrates enhanced electrochemical activity and thus renders the more efficient electrodeposition of copper. Further investigation was conducted through orthogonal experiments to explore the optimal formulation of electroplating solutions containing popular additives including 3, 3′-dithiobis-1-propanesulfonic acid disodium salt (SPS), Janus Green B (JGB), and polyethylene glycol 8000 (PEG8000)., According to the optimal additive formulation, a dense copper layer with superior adhesion was electroplated on the graphite substrate employing PPy as an intermediate layer.

Molecular dynamics study of shale oil adsorption and diffusion behavior in reservoir nanopores: Impact of hydrocarbon composition and surface type

Understanding shale oil adsorption in reservoir nanopores is essential for efficient extraction. This study used MD simulations to analyze the adsorption and diffusion of two- and multi-component hydrocarbons (Aromatics, Alkanes, Resin) on various shale surfaces (Calcite, Montmorillonite, Quartzite, Organic) at 353 K and 25 MPa. Hydrocarbons formed a bilayer adsorption structure comprising a high-concentration adsorption layer (L1, 0.35–0.90 g/cm3) and a low concentration weak adsorption layer (L2), with adsorption density ranked as Resin > Aromatics > Alkanes. Reservoir surfaces were classified as ionic (e.g., calcite, montmorillonite) and non-ionic (e.g., quartz, graphite), and polar hydrocarbons exhibited higher adsorption densities and energies on ionic surfaces due to combined electrostatic and van der Waals interactions, while non-ionic surfaces showed smaller adsorption differences. For multicomponent hydrocarbons, adsorption layer densities followed the order: graphite > MMT-SiO > quartz > calcite > MMT-Na, with competitive adsorption observed. The polar component exhibited a greater adsorption advantage on the calcite, MMT-SiO side and graphite surfaces due to electrostatic interactions and π-π interactions, and a lesser advantage on the MMT-Na side and quartz surfaces. Hydrocarbon diffusivity was influenced by molecular mass and polarity and ordered as Alkanes > Aromatics ≫ Resin. Polar molecules had a weaker diffusion than nonpolar molecules at similar molecular masses. Among the multicomponent hydrocarbons, the self-diffusion coefficient (Self-D) of Resin increased, while that of lighter components decreased compared to two-component systems. These findings offer strategies for improving shale oil recovery by tailoring injection fluids to reservoir types, anionic surfactants or chelating agents may be used to reduce electrostatic interactions in carbonate and clay reservoirs, while nonionic surfactants may be more effective in quartz reservoirs.

Study on Carbon Nanotubes of Pyrolysis Carbons P for In Situ Catalytic Formation on Expanded Graphite Surface

Study on Carbon Nanotubes of Pyrolysis Carbons P for In Situ Catalytic Formation on Expanded Graphite Surface

Polynorepinephrine and polydopamine-bacterial laccase coatings for phenolic amperometric biosensors

The successful fabrication of biosensors is greatly limited by the immobilization of their bioreceptor, thus we propose a facile and reproducible two-step method to modify graphite electrodes with a bacterial laccase, relying on a fast and controllable potentiostatic process to coat graphite surfaces with biomolecule-compatible thin films of polynorepinephrine (ePNE) and polydopamine (ePDA). Both polymers, synthesized with a similar thickness, were functionalized with bacterial laccase, displaying distinct electrochemical transducing behaviours at pH 5.0 and 7.0. ePNE layer enables adequate electron transfer of anionic and cationic species in acidic and neutral media, whereas transduction across ePDA strongly depends on pH and redox probe charge. ePNE stands out by improving the amperometric responses of the biosensing interface towards a phenolic acid (gallic acid) and a flavonoid (catechin), in respect to ePDA. The optimal graphite/ePNE/laccase interface outperforms biosensing interfaces based on fungal laccases at neutral pH, displaying detection sensitivities of 104 and 14.4 µA cm−2 mM−1for gallic acid and catechin, respectively. The fine synthetic control of the ePNE bio-inspired transduction layer and the use of an alkaliphilic bacterial laccase enabled the construction of an amperometric biosensing interface with extended pH range of polyphenols detection present in food products and agro-industrial waste.

Formation of highly stable interfacial nitrogen gas hydrate overlayers under ambient conditions

Surfaces (interfaces) dictate many physical and chemical properties of solid materials and adsorbates considerably affect these properties. Nitrogen molecules, which are the most abundant constituent in ambient air, are considered to be inert. Our study combining atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) revealed that nitrogen and water molecules can self-assemble into two-dimensional domains, forming ordered stripe structures on graphitic surfaces in both water and ambient air. The stripe structures of this study were composed of approximately 90 % and 10 % water and nitrogen molecules, respectively, and survived in ultra-high vacuum (UHV) conditions at temperatures up to approximately 350 K. Because pure water molecules completely desorb from graphitic surfaces in a UHV at temperatures lower than 200 K, our results indicate that the incorporation of nitrogen molecules substantially enhanced the stability of the crystalline water hydrogen bonding network on graphitic surfaces. Additional studies on interfacial gas hydrates can provide deeper insight into the mechanisms underlying formation of gas hydrates.

Effect of Cuso4 ⋅ 5H2O Concentration and Reaction Solution Temperature on the Uniformity of Cu Coating Prepared by Electroless Plating on Graphite Surface

AbstractCopper plating on graphite surfaces is employed as an effective strategy to enhance the wettability between Cu and graphite, which is otherwise inadequate. To achieve a uniformly coated Cu layer on graphite surfaces, this study utilized rotational electroless plating. Subsequently, the effects of CuSO4 ⋅ 5H2O concentrations (10, 15, 20, and 25 g/L) and reaction solution temperatures (30, 40, 50, and 60 °C) on the uniformity and density of the Cu coating on the graphite surface were investigated. The findings reveal that variations in the concentration of the CuSO4 ⋅ 5H2O have a limited impact on the uniformity and densification of the Cu coating. Specifically, as the concentration of CuSO4 ⋅ 5H2O increases from 10 g/L to 25 g/L, there is a slight decrease in the uniformity and integrity of the Cu coating, with the density of Cu‐coated graphite powder decreasing marginally from 3.646 g/cm3 to 6.642 g/cm3. In contrast, the temperature of the reaction solution has a significant effect on the uniformity and densification of the Cu coating. With an increase in the reaction solution temperature from 30 °C to 60 °C, there is a noticeable deterioration in the uniformity and integrity of the Cu coating, with a decrease in the density of Cu‐coated graphite powder from 3.653 g/cm3 to 6.620 g/cm3.

Anti-cancer and visible-light-driven photocatalyst activities of graphene oxide nanosheets against A549 lung cancer cells and organic dyes

The use of graphene oxide (GO) nanosheets (NSs) in cancer cell treatment is a promising and innovative approach to eradicate lung cancer cells and to adsorb and photodegrade organic dyes in water. XRD results revealed that the produced GO NSs have a high crystallinity and a d-spacing value of 0.87 nm. The FTIR spectrum showed that several oxygen-containing functional groups were introduced at the graphite surface from the exfoliation process. The TGA curve result supported the synthesis of GO NSs from the characteristic weight loss behavior. The wrinkled and fold surface morphology of the synthesized GO NSs was confirmed using FE-SEM and TEM. Subsequently, the assessment of their in vitro anti-oxidant and hydroxyl radical scavenging characteristics revealed that the synthesized GO NSs possessed effective antioxidant properties. The viability of A549 lung cancer cells against GO NSs was found to decrease in a dose-dependent manner and their morphology and nuclear damages was assessed by AO/EB and DAPI staining assays. The increased oxidative stress resulted in greater apoptotic cell death, loss of nuclear integrity, and mitochondrial membrane damage against A549 lung cancer cells. The increasing caspase-3 and caspase-9 activation resulted in more apoptotic cell death and cell cycle arrest as determined by flow cytometry. Further, GO NSs demonstrated moderate photocatalytic activity under visible light irradiation, degrading methylene blue (MB) and bromothymol blue (BTB) dye molecules by 44 and 53.5 %, respectively, after 120 min irradiation. Finally, the present study demonstrated that GO NSs possess excellent anti-cancer and moderate photocatalyst activities.

Carbon Dots for Hydrogen Production. How Do They Work?

AbstractCarbon Dots (CDs) have gained significant attention for their fascinating optical properties, potential applications, and puzzling structural challenges. In the last decade, CDs have become the focal point in many photocatalysis studies, either as independent systems or combined with other established photocatalysts. CDs play a crucial role in enhancing the performance of heterostructures for overall water splitting, hydrogen (HER), and oxygen evolution reaction (OER). In these “Concepts,” we briefly explore the structure of CDs, highlighting their critical aspects, including their role within heterostructures, composition, the presence of fluorophores, and the interaction between the graphitic core and surface functional groups. We will also examine how these factors impact their photocatalytic properties, particularly in the context of future research on H₂ production.

Tuning the adhesion of diamond/copper interfaces through surface chemical modifications and reconstruction

Diamond and diamond-like carbon (DLC) coatings are well-known for their exceptional combination of tribological and mechanical properties, such as low friction coefficients and wear rates, together with high hardness and elastic modulus. A significant limitation in their employment concerns their spallation from the substrate; it is thus interesting to explore how DLCs adhesion can be tuned through chemical modifications of its surfaces. We employ ab initio simulations to study the effect of surface reconstruction and chemical species intercalation (B, P, O, F, N, S, H) on the adhesion of non-reconstructed and Pandey-reconstructed C(111)/Cu(111) interfaces. We found that the increment of graphitization at the diamond surface decreases the adhesion. Moreover, when a high degree of surface graphitization is present the best way to increase adhesion is to select atoms able to act as chemical bridges (e.g., B and N), compensating for the lack of interaction between the surfaces. Conversely, adhesion reduction of ∼100% can be achieved, regardless of the degree of surface graphitization, by intercalating an atomic species that does not bond with the countersurface and prevents the interaction between the slabs, i.e. F and S.

Environmental Influence on Stripe Formation at the Graphite-Water Interface.

Understanding characteristics of graphite-water interface is of scientific significance and practical importance. Ordered stripe structures have been observed at this interface, with their origins debated between condensed gas molecules and airborne hydrocarbons. Atomic force microscopy (AFM) studies have revealed variations in the morphology, formation and growth of these ordered structures. Here, we investigate the graphite-water interface under different environmental conditions using PeakForce Quantitative Nanomechanical (PF-QNM) AFM. Our findings reveal that stripe structures with 4 nm width and 0.5 nm periodicity, form and grow under wet laboratory conditions but not in pure inert gas or cleanroom environments. These stripes appear more readily when the graphite surface is immersed in water, with growth associated with gas nanodomains on the surface. This suggests that atmospheric contaminants migrate to the water-graphite interface, potentially facilitated by gas states. These findings underscore the impact of environmental conditions on graphitic materials, providing new insights into the mechanisms underlying stripe formation and growth.

Simply prepared α-Ni(OH)2-based electrode for efficient electrocatalysis of EOR and OER

As one of the most efficient Ni phases towards ethanol oxidation reaction (EOR), α-Ni(OH)2 is aimed to be simply prepared. Various α-Ni(OH)2-rich deposits are obtained chronoamperometrically from NiCl2 solution onto a pristine graphite surface at different potentials. After careful optimization, the optimum values deposition potential and time are found to be -0.9 V and 150 s, respectively. At longer deposition times, the predominant component of the deposits is the β-Ni(OH)2 phase. The optimum electrode, Ni(OH)2/G(opt), exhibits remarkable EOR catalytic activity with an ethanol oxidation peak current of 325.35 mA/cm2. Moreover, Ni(OH)2/G(opt) demonstrates noteworthy activity and durability for oxygen evolution reaction (OER) in 1 M NaOH. Whereas the overpotential at current density of 10 mA/cm2 (ηt=0) is 0.37 V; however, after 24 h it slightly increases to (ηt=24h) 0.39 V. These values imply significant outcomes for our novel and straightforward preparation method for creating highly efficient electrocatalysts for both EOR and OER using time- and cost-effective materials.

“Stick–slip” fluctuations in local electrical conductivity maps on graphite surfaces: A revisit

Electrical conductivity images of graphite surfaces are routinely obtained using scanning probe microscopy. Although the acquired conductivity maps often display a trigonal pattern with smooth variations, a “stick–slip” type of fluctuation has also been reported, where the local conductivity inversely correlates with the friction force during probe scanning. In this work, we revisit the lattice-resolved variations in local conductivity on graphite surfaces and reveal a new series of behaviors. Unlike previous observations, we demonstrate that local conductivity can exhibit in-phase, out-of-phase, or mixed-mode correlations with “stick–slip” lateral force signals. These behaviors are attributed to the cross-talk effect between interface contact conductivity and lateral force, induced by the inhomogeneous conductivity of the tip apex. This mechanism is experimentally validated, showing that local conductivity variations can switch within a single scan due to spontaneous changes in the conductivity of the tip. Our findings enhance the understanding of lattice-resolved electrical conductivity data on graphite surfaces and suggest a novel approach to amplify small lateral forces using inhomogeneous probe tips.

Cobalt-catalyzed carbonization from polyacrylonitrile for preparing nitrogen-containing ordered mesoporous carbon CMK-1 electrode with high electric double-layer capacitance

Ordered mesoporous carbon CMK-1 was prepared via carbonization at a relatively low temperature (the first step) followed by partial graphitization (the second step of carbonization at higher temperature) inside the ordered mesopores of cobalt-loaded mesoporous silica MCM-48 using polyacrylonitrile (PAN) as a carbon/nitrogen source. This first step of the carbonization is called “infusibilization”, and the resultant material is denoted as PANinf. In an advanced temperature-programmed desorption analysis of the PANinf/MCM-48 composite, the temperature of the observed HCN signal indicated that carbonization was reduced from 550 to 450 °C by a Co catalyst. The amount of typical N2 formation associated with the selective removal of pyridinic N species, resulting in the graphitic surface formation, also increased at a relatively high temperature (approximately 1000 °C) with the aid of the Co catalyst. The CMK-1 prepared through cobalt-catalyzed carbonization exhibited a higher electric double-layer capacitance with an Et4N+BF4–/propylene carbonate electrolyte, and higher electrical conductivity than CMK-1 prepared without a catalyst. This also implied the progress of graphitization within the carbonaceous wall. These results suggest that the edge planes of the graphitic domains in CMK-1 are predominantly exposed on the surfaces of the carbonaceous walls, resulting in an increase in the number of adsorptive sites for the electrolyte during capacitance measurements.

Supramolecular Anchoring of Fe(III) Molecular Redox Catalysts into Graphitic Surfaces Via CH-π and π-π Interactions for CO2 Electroreduction.

Photoelectrochemical devices require solid anodes and cathodes for the easy assembling of the whole cell and thus redox catalysts need to be deposited on the electrodes. Typical catalyst deposition involves drop casting, spin coating, doctor blading or related techniques to generate modified electrodes where the active catalyst in contact with the electrolyte is only a very small fraction of the deposited mass. We have developed a methodology where the redox catalyst is deposited at the electrode based on supramolecular interactions, namely CH-π and π-π between the catalyst and the surface. This generates a very well-defined catalysts-surface structure and electroactivity, together with a very large catalytic response. This approach represents a new anchoring strategy that can be applied to catalytic redox reactions in heterogeneous phase and compared to traditional methods involves about 4-5 orders of magnitude less mass deposition to achieve comparable activity and with very well-behaved electroactivity and stability.

A Novel Method for Determining the Threshold Plating Current in Li-Ion Batteries via Electrical Measurements

Lithium-ion (Li-ion) batteries play a vital role in our daily lives by powering essentials like smartphones, electric vehicles, and energy storage systems. One of the main factors that lead to accelerated aging of Li-ion batteries is the lithium plating effect. An improved understanding of lithium plating holds the potential to extend lifespan, enhance performance, and reduce cost of lithium-ion batteries. Lithium plating occurs while charging in low temperatures or with high currents, as lithium-ions accumulate on the anode.Lithium plating can be separated into two parts, a reversible and an irreversible part. During relaxation, when the battery sits idle, or while discharging, reversible plating is stripped from the anode. Typically, when plating is stripped, a voltage plateau can be observed. In contrast, irreversible plating consists of lithium deposits that cannot be stripped during discharge, therefore causing a loss of capacity.In this work, we present a novel non-destructive method for determining a cell's threshold plating current using only electrical measurements. The method is validated using commercial 3.2Ah Panasonic NCR18650B cells at varying low temperatures and charging currents. The designed method requires the use of two identical cells, a reference and a test cell. After completely discharging both batteries at room temperature to reach 0% depth of discharge (DOD), the same plating tests at low temperatures are conducted on both cells. Once the cells are fully charged with a constant current of 0.5C, the reference cell experiences relaxation for 10 minutes. Simultaneously, a sine wave current is applied to the test cell, leading to small charging and discharging cycles. During the positive half-wave of the sine, plating occurs and during the negative half-wave reversible plating is stripped again. As plating only occurs, once the threshold plating current is exceeded, the sine amplitude must be greater than this threshold. It is important to note that, the charging current consists of intercalation current and plating current.Intercalation is the insertion of Li-ion into the layered structure of graphite during charging. As charging progresses, the surface concentration of intercalated lithium increases, but simultaneously, the number of vacancies for lithium intercalation at the graphite surface decreases. When the anode potential falls below 0V, thermodynamically allowing lithium plating, the intercalation current decreases and the plating current increases. With continued charging, the plating current continues to increase, while the intercalation current gradually diminishes.We assume that only the part of the sine exceeding this threshold is responsible for the lithium plating, while the portion below this threshold contributes to intercalation. In contrast, the negative half-wave is completely responsible for stripping. After 10 minutes, both cells are discharged with a low current while the remaining reversible plating is stripped. From the voltage and current measurements during discharge, we can compute how much reversible plating was stripped during the sine phase and during the discharge. To determine the plating current, the plated charge amount dQ on the positive sine half-wave is calculated by the difference between the stripped charge amount on the sine negative half-wave and the difference between the stripped charge amount of the reference cell and the test cell (c.f. attached figure). With the known plated charge amount dQ, the sine is integrated to find the threshold plating current.To validate the precision of this method, we subject an additional cell to charging at the same low temperature as the other cells. The charging involved varying currents from 0.04C to 0.4C in 10 steps, with a 1.5-hour interval between each step for the cell to cool down. To determine the threshold plating current, a differential voltage analysis (DVA) was conducted at each step, thus identifying the lowest current where a voltage plateau occurred, as the threshold plating current. Further refinement involves smaller steps to achieve a more accurate plating current. We assume this result is the true threshold plating current. Comparing with our novel method, in the worst case we achieve an error of less than 100mA. To ensure the reliability and reproducibility of this method across varying cells, additional plating tests, involving various cell chemistry types, are planned. Figure 1

Upcycling of Graphite Anodes via Tailored Solvent Treatment

To achieve a truly closed-loop direct recycling process for lithium-ion batteries, all component materials must be recovered. To date, direct recycling method development has primarily focused on the high-value transition-metal cathode materials, while the inherently lower-value graphite has been challenging to recover in a cost-effective manner. However, end-of-life graphite contains a unique engineered value due to the presence of the solid electrolyte interphase (SEI). Growth of the SEI during the cell’s active lifetime stabilizes the electronically reactive graphite surface through an irreversible consumption of Li, and thus necessitates both excess lithiation of the cathode and a costly and time-intensive formation procedure during manufacturing. An optimized pre-formed SEI that capitalizes on existing SEI components from end-of-life batteries has the potential to significantly reduce cathode lithiation requirements and eliminate the critical bottleneck of formation cycling during cell remanufacturing. Further, retaining Li at the anode obviates the need for a separate Li leaching and recovery step, improving the overall efficiency of the direct recycling line. In this work, we present a novel approach to “upcycling” spent graphite through use of tailored chemical treatment to remove adverse (i.e., highly resistive and/or poorly passivating) SEI species while retaining beneficially passivating components. We have explored a rational set of solvents spanning a range of polarity, proticity, and molecular size to evaluate structure-property-performance relationships between applied solvent(s), removed and remaining SEI species, and electrochemical response of the resulting graphite product. Further, we have developed and optimized a robust and holistic analysis procedure that couples symmetric-cell electrochemical testing, multi-modal materials characterization, and advanced electrochemical modeling. These analysis results inform a set of correlative metrics for graphite performance relative to both solvent properties and upcycled SEI composition. We demonstrate effective tunability in the residual SEI composition by varying solvent identity and concentration, and report on several promising solvent systems that achieve comparable performance to pristine graphite. Figure 1

4D-STEM and Eels Analysis of Complex C-Based Sensor Architectures

Transforming high-carbon precursors into open-porous carbon foams and coatings via thermal processes is gaining attention as a sustainable method for various applications, including catalysis, energy utilization, and sensing [1]. In this research, we adopt a one-step laser patterning approach to selectively pyrolyze doctor-bladed ink coatings on flexible PET substrates, thereby producing highly porous, intricately designed CO2 sensor structures with a thickness of about 50 µm. Our ink formulation includes glucose as a pore-forming agent and adenine as a nitrogen source to enhance sensing capabilities. Laser processing in an oxygen-rich setting results in flexible, highly porous sensor heterostructures characterized by distinct areas enriched with nitrogen and oxygen functionalities. The laser intensity’s attenuation with depth leads to the development of a distinctly porous graphitic surface layer (serving as the electrical transducer layer) and a denser nitrogen-enriched lower sensor layer, linked by a narrow transitional region [2]. To understand the formation and functionality of these sensors, we conducted an in-depth TEM analysis of cross-sections of the complete device, prepared through ultramicrotomy cross-sectioning. STEM-EELS elemental distribution maps distinctly show the chemical composition differences between the upper and lower layers of the sensor. Principal component analysis was utilized to separate the complex sensor structures into their constituent crystalline and amorphous carbon and nitrogen-containing phases. 4D-STEM analysis exposed the arrangement of the crystalline graphitic phase and the orientation of graphite basal planes adjacent to the pores of the open-porous sensor. Analyzing these structural parameters is essential for understanding the electrical performance of the sensor, as depicted in Figure 1 [3]. Figure 1: A (top)) SEM micrograph of sensor embedded in epoxy, (bottom) depth-dependent thermal laser intensity attenuation; B (left)) HA ADF-STEM micrograph showing different sensor layers, (middle) STEM-EELS nitrogen distribution map, (right) PCA bond analysis, C) HRTEM images of sensor from transducer (top) and sensor (bottom) layers with SAED image of respective ROIs (inset); D) 4D-STEM analysis depicting misalignment angle between graphitic carbon basal plane normal relative to the pore surface normalReferences[1] M. Hepp, et al. npj Flexible Electronics 6, 1-9 (2022)[2] H. Wang, et al. Advanced Functional Materials 32, 2207406 (2022)[3] C. Ophus, et al. Microscopy and Microanalysis 28, 390-403 (2022) Acknowledgements: We acknowledge use of the DFG-funded Micro-and Nanoanalytics Facility (MNaF) at the University of Siegen (INST 221/131-1). Figure 1

Laser surface structuring of diamond-like carbon films for tribology

The paper overviews experimental findings of the direct laser processing and surface microstructuring (texturing) of various diamond-like carbon films (a-C:H, ta-C, DLN, metal-doped DLN), aimed at improvements of their tribological and nanotribological properties. The nanosecond UV and femtosecond IR/visible pulsed lasers were applied in microprocessing of the films, focusing on high precision surface structuring with fs-laser pulses. The studies were concentrated on the following tasks: (i) surface graphitization in laser microstructuring of the films under different irradiation conditions, (ii) lubricated friction performance of DLN films micropatterned with UV ns and visible fs pulsed lasers, and (iii) nanoscale friction of laser-structured DLN and metal-doped DLN films examined with contact-mode atomic force microscopy. The important findings of our studies are related to fabrication of highly-precise microgroove/microcrater patterns on DLN films and improvements of frictional properties of the laser-structured films at the macro, micro and nanoscale. The surface microstructures improved the film properties under oil-lubricated sliding in dependence on their geometrical parameters (size, depth, period) and ambient temperature. The nanoscale friction behavior of laser-structured films was shown to be controlled by the surface graphitization, nanoscale roughness, capillary forces and wear of AFM tips during friction force imaging.