While the tribological performance of carbide MXenes (Ti3C2Tx) has been widely reported, yet the role of the counterbody chemistry in governing the tribolayer evolution remains unexplored, which holds particularly true for carbonitrides. Here, we demonstrate that spray-deposited multilayer Ti3CNTx coatings exhibit a counterbody- and load-dependent tribological response under dry sliding (contact pressures up to 0.82 GPa). Against ceramic counterbodies, friction reduction of up to 76% and wear rates on the order of 10-6-10-5 mm3 N-1 m-1 range were verified, whereas metallic contacts promote distinct mechanochemical pathways. By combining complementary characterization of both wear tracks and counterbodies with density functional theory calculations, we establish a direct link between the interfacial adhesion, material transfer, and the resulting tribochemical evolution. Under low-load conditions, composite tribolayers composed of intact Ti3CNTx and limited oxide species enable an efficient shear accommodation and promote a stable transfer-layer formation. In this regard, Al2O3 stabilizes the transfer layer, Si3N4 exhibits a load-sensitive tribolayer degradation, and WC limits the tribochemical activation due to an efficient heat dissipation. Increasing the contact pressure favors amorphization and the formation of rutile TiO2 as well as iron oxides, leading to oxide-rich, load-bearing interfaces, particularly for chemically active counterbodies. DFT calculations reveal that intermediate adhesional strengths govern these responses by enabling a stable tribofilm formation while ensuring continuous material supply.

MXenes have gained considerable attention in solid lubrication due to their involved tribofilm formation offering low friction and extended durability at the same time. While the solid lubrication performance of carbide systems has been well explored, research on nitride MXenes remains considerably scarce. Therefore, we synthesized multilayer Ti2NTx from its parental Ti2AlN precursor. Coatings consisting of multilayer Ti2NTx were spray-coated onto AISI 304 steel substrates to assess their solid lubrication performance using linear reciprocating ball-on-disk tribometry varying normal loads (0.1-1.0 N) and durations (15-60 min). In case of Ti2NTx, the specific wear rates ranged between 5.09 and 6.79 & times;10(-8) mm(3)/(N & centerdot;mm) for 15 min testing and decreased to about 1.30 & times; 10(-8) mm(3)/(N & centerdot;mm) for extended durations (60 min and 1 N). In contrast, the Ti2AlN coating exhibited substantially higher friction (COF approximate to 0.55 for 0.4 N), while demonstrating lower wear rates of (2.84-3.17) & times; 10(-8) mm(3)/(N & centerdot;mm) for a test duration of 15 min. To understand the involved friction and wear mechanism as well as tribochemistry, the corresponding wear tracks were assessed by complementary materials characterization. While bare steel exhibited a high, noisy friction, characteristic for abrasion- and debris-dominated tribosystems, the Ti2AlN coatings showed similarly high friction under low loads, which is consistent with a formation of a rigid, oxide-rich tribofilm. In striking contrast, the Ti2NTx coatings rapidly run into a low and remarkably stable friction, insensitive to both load and sliding time, thus evidencing the development of a more continuous, easy-to-shear tribofilm. The results indicated that the lamellar structure of Ti2NTx lamellae and its chemistry promote a self-replenishing tribofilm, whereas the Ti2AlN coating and the steel reference remain governed by abrasive circulation of oxide/debris. Using simple, scalable spray-coating, this MAX-to-MXene route delivers durable, low-friction surfaces thus extending the concept of 2D solid lubrication to Ti2NTx, highlighting their potential for tribological applications.

Improving the tribological performance of components and systems remains crucial to improve the resulting mechanical efficiency, durability, and sustainability. This study reports the development of composite coatings based on multilayer Ti3C2Tx (ML-Ti3C2Tx) and chemically modified polyketone (PKHEDA) for enhanced solid lubrication. In this regard, PKHEDA was synthesized via the Paal-Knorr reaction to improve MXenes' dispersion as well as coating's adhesion and chemical stability. Composite coatings with varying MXene-polymer ratios 1:3.3 (COM-1), 1:1.6 (COM-2), and 1:1 (COM-3) wt.-%, were spray-coated onto stainless-steel substrates and characterized using complementary materials characterization and tribo-testing. Our results demonstrate that PKHEDA effectively encapsulates ML-Ti3C2Tx, reducing its oxidation tendency and improving the overall coating integrity under mechanical stress. The tribological performance of the composite coatings was notably enhanced compared to pure Ti3C2Tx coatings and non-coated substrates, thus verifying a stable coefficient of friction and a reduction of the wear rate up to 87 %. The composite with a MXene-to-polymer ratio of 1:1.6 (COM-2) exhibited the best balance of load-bearing capacity, durability, and chemical resilience. These findings highlight the synergistic potential of ML-Ti3C2Tx/polyketone composites to develop high-performance, sustainable coatings for demanding tribological environments.

MXenes have emerged as promising solid lubricants due to their layered structure, tunable chemistry, and ability to form mechanically robust, wear-resistant tribo-films. However, most studies have focused on single-metal MXenes such as Ti3C2Tx, Ti3CNTx, or V2CTx, leaving multimetal MXenes largely unexplored. Here, we present a comprehensive tribological and mechanochemical evaluation of ordered double-transition metal Mo2TiC2Tx and Mo2Ti2C3Tx coatings under dry sliding in ambient conditions. Using nanoindentation mapping, X-ray photoelectron spectroscopy, Raman spectroscopy, and electron microscopy, we demonstrate that Mo2Ti2C3Tx tends to form dense, chemically stabilized, and mechanically robust tribo-layers thus maintaining a low and stable coefficient of friction (∼0.1) and wear rate (∼0.1 × 10-3 mm3/N·m) under a contact pressure of 0.55 GPa. These tribolayers exhibit improved mechanical properties (hardness ∼ 4.2 GPa; Young's modulus ∼ 103 GPa), along with increased carbide retention and reduced surface oxidation. In contrast, Mo2TiC2Tx coatings display a less favorable behavior, resulting in a higher COF (∼0.5), greater wear rate (∼1.3 × 10-3 mm3/N·m), and the formation of thinner, chemically degraded tribo-layers under comparable conditions. Mo2Ti2C3Tx exhibited the best tribological and mechanical performance under comparable conditions, clearly outperforming Ti3C2Tx, Ti3CNTx, and Mo2TiC2Tx. Our study introduces Mo-based MXenes as an emerging frontier in solid lubrication and the importance of MXene structure and composition in their tribo-layer evolution and stress accommodation mechanisms.

Intestinal disorders such as inflammatory bowel diseases (IBD) and gastrointestinal fistulae (GIFs) are marked by chronic inflammation, barrier dysfunction, and impaired repair, conditions insufficiently addressed by current treatments. Regenerative strategies able to restore epithelial integrity and support stromal and vascular remodeling are therefore highly needed. The stromal vascular fraction (SVF), a heterogeneous and autologous cell population from adipose tissue, offers angiogenic, immunomodulatory, and regenerative properties, while three-dimensional (3D) bioprinting enables its embedding in hydrogels to enhance survival and activity. MXenes (MX), a novel class of two-dimensional materials, can help to add further advantages through their bioactive, antioxidant, and pro-angiogenic features. In this contribution, we engineered 3D bioprinted constructs composed of SVF embedded in GelMA functionalized with MX. After confirming the biocompatibility of MX on multiple cell types, we demonstrated that SVF MX constructs notably promoted wound closure, endothelial tube formation, and epithelial proliferation, while maintaining stable, non-toxic ROS levels and demonstrating excellent cytocompatibility[GP1.1]. These findings highlight MX-enriched SVF constructs as an innovative platform for next-generation regenerative therapies, combining the autologous, low-immunogenic profile of SVF with the multifunctional properties of MX to address complex intestinal disorders.

Abstract The performance of concentrated solar power (CSP) plants is greatly limited by corrosion and degradation at the interfaces between materials and their environments, particularly under high-temperature molten salt conditions. While advanced alloys and conventional coatings are considered good alternatives to increase their service life, the reliability of future generations of this technology remains uncertain. In this regard, MAX phases and MXenes should not be considered as inherently superior replacements but rather as tunable systems that offer alternative approaches to interface design, oxidation control, and degradation mitigation. In this perspective, we envision reinterpreting MAX phases as a chemically expandable and defect-sensitive platform, in which integrating compositional variations, structural hierarchies, and transformation pathways into MXenes will enable the development of a promising corrosion mitigation strategy. Therefore, we propose that MXenes should be considered as dynamically evolving surfaces, with their termination chemistry, defect topology, and interactions with the environment playing critical roles in their long-term performance. To address the current challenges, we recommend an integrated multiscale approach that combines advanced in situ characterization techniques, atomistic simulations, thermodynamic modeling, and machine learning. This approach will help to establish predictive relationships among structure, defects, and performance, leading to more durable, multifunctional interfaces.

Polyurethane (PU) coatings used in mechanically demanding infrastructure applications but remain susceptible to wear, frictional damage, and environmental degradation. In this contribution, low loadings of non-functionalized Ti3C2Tx were incorporated into a commercial two-component PU paint to evaluate their influence on the tribological, mechanical, and time-dependent electrochemical response. MXene contents of 0.25 - 1.0 wt.-% were dispersed in the PU formulation and spray-coated onto AISI 304 stainless-steel substrates. Under controlled dry reciprocating sliding, the MXene-containing coatings exhibited a smoother running-in response and reduced wear relative to neat PU. MX-1.0 provided the highest wear resistance, with reductions of approximately 79.0 and 85.4% at 400 and 800 mN, respectively. Spatially resolved nanoindentation mapping showed that the MXene incorporation modifies the local mechanical response within the wear tracks. MX-0.25 exhibited the most homogeneous mechanical response and the highest scratch critical loads, whereas MX-1.0 achieved the greatest resistance to material removal despite a more heterogeneous local mechanical response. These results indicate that the as-deposited mechanical properties alone do not fully determine the wear behavior, which also depends on the evolution of the sliding interface and the resulting tribolayer regions. Electrochemical impedance spectroscopy showed composition- and immersion-time-dependent changes in impedance and phase angle. These results indicate that Ti3C2Tx modifies the electrochemical response of the PU coatings during saline immersion, without demonstrating a uniform improvement in barrier performance. Overall, the study provides laboratory-scale evidence of the potential of non-functionalized Ti3C2Tx as an additive for commercial PU coatings intended for mechanically demanding applications, while further application-specific testing is required to assess long-term durability under high-traffic service conditions.

The development and optimization of concentrated solar power plants (CSP) plants, which are considered promising sources of renewable and clean energy, have attracted significant attention. Recently, efforts to improve the efficiency of these plants have focused on increasing their operational temperature. However, this approach presents challenges, particularly regarding the corrosion of metallic components due to the higher temperatures of the molten salts used for energy storage. One potential solution to enhance the thermophysical properties of molten salts and mitigate corrosion is the incorporation of nanomaterials as additives. To This study investigates the effect of multilayer TisC2Tx MXenes at concentrations of 0.5, 1, 2, and 3 wt.-% on the thermal properties of nanofluids consisting of solar salt, thus aiming at enhancing the thermophysical performance for high-temperature thermal energy storage applications. This pioneering research explores how the concentration of MXene affects the specific heat capacity (Cp), melting temperature (Tm), and decomposition temperature (Td) of the nanofluids. Our results verified that adding MXenes to solar salt helps to enhance its thermal properties, particularly the decomposition temperature (Td) to 609.8 degrees C (compared to 586.2 degrees C for pure solar salt) and specific heat capacity (Cp), enabling better heat storage. These enhancements are attributed to structural and chemical effects induced by multilayer TisCaTx, as supported by experimental analyses (TGA, DSC, SEM, Raman spectroscopy, and XRD) and computational simulations. This demonstrates the potential of TisC2Tx for advancing high-temperature thermal energy storage systems in CSP plants.

Two-dimensional (2D) MXenes, such as Ti₃C₂Tₓ, are promising materials due to their high specific surface area, excellent electrical conductivity, and mechanical robustness. However, their applicability is limited by their tendency to restack and agglomerate as well as their poor oxidation resistance in oxygen-rich or -OH-containing environments, thus notably downgrading their structural, chemical, and electrical characteristics. In this study, the oxidative stability of multi-layer (ML) Ti₃C₂Tₓ (obtained via a two-step chemical functionalization strategy) was evaluated by thermal analysis. First, ML-Ti₃C₂Tₓ was decorated with primary amine groups using N1-(3-Trimethoxysilylpropyl)diethylenetriamine (TMSPDETA) with a standard silanization method and subsequently functionalized with aliphatic polyketones via the Paal-Knorr reaction. The functionalized ML-Ti₃C₂Tₓ were characterized by Raman spectroscopy, electron microscopy, and elemental analysis, while the thermo-oxidative stability was validated by thermogravimetric analysis coupled with infrared spectroscopy of the evolved gases. The polyketone-modified Ti₃C₂Tₓ displayed an increased onset temperature for oxidation (Tonset increased from 371 to 408 °C), while keeping the structural integrity of ML-Ti₃C₂Tₓ. Our results demonstrate that polymer grafting not only preserves the layered morphology of ML-Ti₃C₂Tₓ but also enhances its chemical stability, offering a scalable approach for improving the performance of MXenes in high-temperature and oxidative environments.

The integration of two-dimensional covalent organic frameworks (2D COFs) as thin films on transparent conductive substrates remains a major challenge due to limited control over crystallization, thickness, and film continuity. Herein, we report a surface-initiated solvothermal polymerization strategy for the controlled synthesis of ultrathin TpBpy covalent organic framework (COF) films on indium tin oxide (ITO) substrates. The approach combines self-assembled monolayer (SAM) functionalization with a grafting step to confine nucleation and enable directional growth at the solid-liquid interface. The resulting films exhibit homogeneous coverage, controlled thickness (similar to 20 nm). A comprehensive characterization by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray reflectivity (XRR), wide-angle X-ray scattering (WAXS) and X-ray photoelectron spectroscopy (XPS) confirms the structural integrity and compositional uniformity of the films. Nanomechanical AFM analysis revealed that the TpBpy COF films possess good mechanical robustness (similar to 1 GPa). Conductive-AFM and electrochemical impedance spectroscopy (EIS) demonstrated the semiconducting nature of the films, as well as capacitive behavior. Time-resolved studies elucidate a fiber-to-film morphological transition, consistent with a self-assembly mechanism driven by pi-pi stacking and hydrogen bonding. These findings elucidate the growth pathway and highlight the importance of surface engineering and reaction time in achieving uniform, defect-free COF films. This work provides a versatile route for the fabrication of high-quality COF thin films on transparent conductive substrates, advancing their integration into optoelectronic and electrochemical devices.

MXene coatings have shown excellent wear-resistance and durability under solid lubrication due to tribochemically induced tribo-films. While their structure and morphology are partially explored, no knowledge about the tribo-layers' mechanical properties is available. Therefore, our study combines systematic mechanical (nano-indentation) and tribological testing (ball-on-disk tribometry) with advanced materials characterization to shed light on the interplay between chemistry, structure and mechanical properties of the tribolayer formed under different loads and the resulting tribological performance. For a normal load of 100 mN, the tribolayer induced a 56% friction reduction while maintaining a remarkable mechanical integrity, with an average friction coefficient of about 0.22 and a wear rate of about 4.5 x 10-5 mm3/N & sdot;m. When increasing the load to 400 mN, the formed tribolayer became densified and structurally reorganized, accompanied with tribo-oxidation, resulting in notable increase of hardness and Young's modulus (over 80%) compared with the as-deposited coating. The observed structural changes affected friction and wear, as the enhanced mechanical properties improved the tribolayer's ability to withstand higher mechanical stresses, thus improving friction and wear under more severe conditions. Our findings lay the fundamental base for a deeper understanding of the relationship between microstructure, chemistry, and mechanical properties of the formed tribolayers and their tribological response thus positioning Ti3C2Tx coatings as promising solutions for demanding tribological applications requiring wear resistance and durability.

MXenes have attracted attention due to their high specific surface area, excellent electrical conductivity, and considerable mechanical properties. Multilayer Ti3C2Tx faces challenges related to restacking and agglomeration as well as its limited oxidation/degradation resistance in oxygen-containing environments. In this study, multilayer Ti3C2Tx is chemically functionalized by silanization with trimethoxy(octyl)silane while varying the dispersion approach. The impact of four sonication approaches on the success of silanization of Ti3C2Tx by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, is studied. Regardless of the approach, all procedures successfully silanize Ti3C2Tx, demonstrating the robustness of each individual procedure. Moreover, the various sonication approaches do not affect the samples' morphology. The two-step sonication approach (method B) that consists of dispersing Ti3C2Tx first in isopropanol for 20 min using bath-sonication and then dispersing them for 30 min in isopropanol/toluene/trimethoxy(octyl)silane using bath sonication notably reduces the amount of amorphous carbon in Ti3C2Tx, indicating an enhanced structural quality due to the reduced amount of defective carbon. The silanized Ti3C2Tx obtained using method B shows an enhanced oxidation stability, a greater hydrophobicity, and an improved stability in apolar solvents compared to pristine Ti3C2Tx.

MXenes have attracted attention due to their high specific surface area, excellent electrical conductivity, and considerable mechanical properties. Multilayer Ti 3 C 2 T x faces challenges related to restacking and agglomeration as well as its limited oxidation/degradation resistance in oxygen‐containing environments. In this study, multilayer Ti 3 C 2 T x is chemically functionalized by silanization with trimethoxy(octyl)silane while varying the dispersion approach. The impact of four sonication approaches on the success of silanization of Ti 3 C 2 T x by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy, is studied. Regardless of the approach, all procedures successfully silanize Ti 3 C 2 T x , demonstrating the robustness of each individual procedure. Moreover, the various sonication approaches do not affect the samples’ morphology. The two‐step sonication approach (method B) that consists of dispersing Ti 3 C 2 T x first in isopropanol for 20 min using bath‐sonication and then dispersing them for 30 min in isopropanol/toluene/trimethoxy(octyl)silane using bath sonication notably reduces the amount of amorphous carbon in Ti 3 C 2 T x , indicating an enhanced structural quality due to the reduced amount of defective carbon. The silanized Ti 3 C 2 T x obtained using method B shows an enhanced oxidation stability, a greater hydrophobicity, and an improved stability in apolar solvents compared to pristine Ti 3 C 2 T x .

The convergence of nanotechnology and tissue engineering has paved the way for innovative cancer treatments that leverage the unique light absorption properties of nanomaterials. Indeed, photothermal therapy (PTT) and photodynamic therapy (PDT) utilize nanomaterials to convert near-infrared light into therapeutic energy for cancer treatment. This study focuses on the application of poly(lactic-co-glycolic acid) (PLGA) scaffolds, enhanced by graphene oxide, Ti3C2Tx MXene, and TiS2 transition metal dichalcogenides for PDT and PTT treatments evaluated within 3D-bioprinted breast cancers. Our scaffolds were designed to exploit the photothermal conversion efficiency and capability to generate reactive oxygen species (ROS) to compare the specific features of each 2D material. We demonstrated a reduction in tumor viability under scaffold irradiation, along with the exploration of biological responses to damage such as autophagy and pyroptosis, verifying that these scaffolds can differentially induce these processes depending on the light responsiveness of each material. The integration of these materials within 3D-printed scaffolds does not only enhance the therapeutic efficacy of PTT and PDT, but also offers a precise method to control the cellular environment after therapy, i.e. tissue regeneration and antibacterial effects, providing insights into the potential for these technologies to be adapted for personalized medicine for breast cancer treatment and reconstruction.

2D MXene nanosheets have gained increasing attention in tribology due to their excellent wear resistance and solid lubrication capabilities. While carbide-based MXenes have been extensively studied, the tribological performance of carbonitride MXenes, especially under dry conditions, has yet to be assessed. Therefore, we studied the mechanical and tribological performance of multilayer Ti3CNT x coatings, revealing their load-dependent tribochemical response. Using linear-reciprocating ball-on-disk tribometry combined with advanced structural and surface characterization, we demonstrate that Ti3CNT x coatings provide excellent friction reduction and wear resistance at low loads due to the formation of compact, aligned, and protective tribofilms. Under higher loads, however, the coatings undergo a transition to severe wear dominated by the formation of rutile TiO2, a behavior not previously observed in carbide-based MXenes (anatase TiO2). Our findings highlight the critical role of X-site chemistry (C, N, or CN) in governing tribo-oxidation pathways and tribolayer stability, underscoring the influence of carbonitride composition on the long-term performance of MXene coatings in solid lubrication applications, which are essential for aerospace applications, electrical contacts, or dry-running bearings.

This study investigates the possibility of modifying lubricating greases by 2D graphene oxide (GO) and lithium iron phosphate (LiFePO4) to enhance their tribological performance. GO's layered structure plays a crucial role in reducing friction by facilitating easy sliding between rubbing surfaces, making it an effective solid lubricant. The impact of these additives on friction reduction, wear resistance, and the tribolayer formation ability is evaluated by ball-on-disc tribometry with an emphasis on durability and sustainability. Comparative results reveal that unmodified greases exhibit a high susceptibility to wear, including oxide formation and severe plastic deformation. In contrast, greases with GO show a notable reduction in friction, while the addition of LiFePO4 contributes to the formation of a continuous protective layer that substantially reduces abrasive wear. The combination of GO and LiFePO4 results in a homogeneous, durable tribofilm that effectively protects surfaces against severe wear providing long-term friction stability. Although lab-scale LiFePO4 is used, the findings suggest a great potential for extending the useful life of recycled LiFePO4 from lithium-ion batteries, similar to commercial LiFePO4 thus confirming significant improvements in the grease performance but also highlighting the potential to advance toward more sustainable solutions in industrial applications and electric vehicles.

Black phosphorus (BP), a rather new 2D material, features excellent electronic, optical, and tribological properties, but its potential for solid lubrication is completely unexplored. Therefore, our paper aims at experimentally evaluating the solid lubrication performance of 2D black phosphorus (BP) in dependence of the coating thickness by performing tribological tests under ball-on-disc linear-reciprocating sliding in dry conditions. BP was spray-coated onto bearing steel discs, while the effect of the thickness was evaluated by fabricating two BP coatings, BP-thin and BP-thick. Our results demonstrate that BP coatings reduced friction compared to uncoated reference samples. However, only thicker BP coatings are capable to induce a stable, long-lasting four-fold friction reduction, which was mainly traced back to the formation of a stable tribofilm in the contact zone. Therefore, our study proves the potential of BP for solid lubrication purposes with the overall aim to kick-start and boost more research endeavours in this newly emerging field.

Under vacuum conditions, MoS2 is an excellent 2D solid lubricant with remarkable tribological properties. However, its beneficial performance rapidly deteriorates when wear occurs. Within this context, MXene nano-sheets provide a potential alternative to MoS2 due to their superior wear resistance verified under ambient conditions. However, their vacuum performance is completely unexplored. Therefore, this paper aims at scrutinizing the frictional and wear performance of multi-layer Ti3C2Tx and Ti3C2Tx/MoS2 hybrid coatings used as solid lubricants under vacuum by reciprocating sliding tests using a pin-on-disc vacuum tribometer having MoS2 coatings as reference. To understand the involved friction and wear mechanisms as well as to elucidate the involved tribolayer formation, the wear tracks were analysed post-mortem by scanning electron microscopy and X-ray photoelectron spectroscopy. Our results evidenced that multi-layer Ti3C2Tx are not a suitable solid lubricant under vacuum conditions (friction higher than MoS2 coatings). In contrast, MXene/MoS2 hybrid coatings outperformed the pure MoS2 coatings thus displaying the best tribological performance, experiencing low friction for the entire test duration and reduced wear. Therefore, MXene/MoS2 hybrid coatings proved immense potential as anti-friction and wear resistance coatings for future work and prospective space applications.