MXenes represent a promising class of 2D carbides, nitrides, and carbonitrides known for their high electrical conductivity, hydrophilicity, mechanical strength, and unique optoelectronic properties, which have led to numerous applications. However, their scalable synthesis in 1D morphology, such as nanotubes or scrolls, has not been demonstrated yet. This work presents a versatile and scalable method for manufacturing MXene scrolls, including Ti2CTx, Ti3C2Tx, Ti3CNTx, V2CTx, Nb2CTx, and Ta4C3Tx. We demonstrate a scalable and high-yield production up to 10 g of pure scrolls with precise control over their alignment and morphology. Properties of scrolls differ from 2D flakes; e.g., a freestanding film made of scrolled Nb2CTx presents 33 times increase in electrical conductivity and shows a superconducting state below 5.2 K. Films of MXene scrolls exhibit 3 times lower density and enhanced mass transport compared to flakes, resulting in an improved performance in supercapacitor electrodes and humidity sensors. The dispersion of the scrolls in water behaves like an electrorheological fluid. Aligning scrolls in an electric field allows for circuit switching between electrically insulating and conductive states. These scrolls can be assembled into vertically aligned MXene forests, fibers, and other architectures. The availability of 1D MXene scrolls offers exciting opportunities in many fields.

Fully stretchable organic light-emitting diodes (OLEDs), composed entirely of intrinsically stretchable materials, are essential for on-skin displays1-3. However, their low device efficiency has been a persistent barrier to practical applications for more than a decade4. Here we addressed this challenge by incorporating an intrinsically stretchable exciplex-assisted phosphorescent (ExciPh) layer. The elastomer-tolerant triplet-recycling mechanism mitigates exciton energy transfer limitations arising from the insulating elastomer matrix, yielding a light-emitting layer with more than 200% stretchability and an external quantum efficiency (EQE) of 21.7%. To translate this performance to fully stretchable devices, we integrated MXene-contact stretchable electrodes (MCSEs), which feature high mechanical robustness and tunable work function (WF), ensuring efficient hole and electron injection. These advances enable fully stretchable OLEDs with a record EQE of 17.0% and minimal luminescence loss under 60% strain. This approach to designing high-efficiency, mechanically compliant optoelectronics will enable the next-generation wearable and deformable displays.

MXenes are a rapidly expanding family of two-dimensional transition metal carbides and nitrides whose exceptional compositional, structural, and surface-chemical tunability has driven rapid growth across materials science, chemistry, physics, and engineering. This roadmap consolidates the current state of MXene research, spanning synthesis, processing, fundamental properties, computation, electrochemical energy storage, biomedical applications, electronics, optoelectronics, membranes, sensing, tribology, and extreme-environment technologies. By identifying key advances, persistent challenges, and emerging opportunities, the roadmap provides a forward-looking outlook for guiding MXenes from laboratory discovery toward transformative applications.

MXenes are well-known as highly biocompatible two-dimensional nanomaterials with a wide range of biomedical applications, including antibacterial strategies. However, the coexistence of high biocompatibility and reported strong antibacterial effects presents a fundamental contradiction that requires critical evaluation. In this study, we systematically investigated the antibacterial properties of pure Ti3C2T x , Nb2CT x , V2CT x , and Ti3CNT x MXene nanosheets of varying flake sizes using multiple in vitro assays and an in vivo wound model. High-resolution structural and chemical characterizations confirmed the use of high-quality, minimally oxidized MXene samples with well-defined surface terminations. Despite using multiple evaluation methods, including disk diffusion, broth microdilution, time-kill kinetics, ROS quantification, and electron microscopy, no significant antibacterial effects were observed at subtoxic concentrations. Furthermore, neither reactive oxygen species-mediated damage nor the hypothesized "nano-knife" mechanical disruption mechanism could be confirmed. This suggests that the previous observations of antibacterial properties resulted from incomplete removal of etching products or partial oxidation of MXene nanosheets. In contrast, we demonstrate that MXene-assisted photothermal therapy (PTT) under near-infrared laser irradiation offers highly effective and selective bacterial ablation. Ti3C2T x MXene exhibited strong photothermal performance, achieving complete bacterial killing in vitro and significant wound healing efficacy in an in vivo rat model. Targeted PTT using antibody-functionalized MXene nanosheets enabled the eradication of Escherichia coli while sparing nontarget bacteria. These findings suggest that while intrinsic antibacterial properties of pristine MXenes are limited, their biocompatibility and photothermal responsiveness make them promising platforms for next-generation, externally triggered antibacterial therapies.

Durable, cost-effective hydrogen evolution in acidic media requires electrocatalysts that can rival platinum in catalytic activity and stability. We report atomically engineered Ti3C2Tx@C2N heterostructure exploiting robust Ti-N interfacial bonding and electronic coupling to deliver platinum-like performance without noble metals. The hybrid catalyst exhibits ultralow overpotential of 42 mV at 10 mA cm-2 and Tafel slope of 36 mV dec-1, approaching commercial Pt/C benchmarks. More importantly, it maintains stable operation over 550 h at 100 mA cm-2 in corrosive acidic medium, far surpassing Pt/C. Structural analyses and density functional theory reveal that Ti & horbar;N interface optimizes hydrogen adsorption free energy and lowers the kinetic barrier for O & horbar;H bond cleavage, while the porous C2N scaffold enhances charge transport and active site accessibility. This synergistic structural and electronic design establishes a generalizable strategy for robust heterostructures, advancing scalable platinum-free electrocatalysts for next-generation proton exchange membrane electrolyzers and other energy conversion technologies.

The past decade has seen rapid growth in the number of experimentally realized two-dimensional (2D) materials with diverse chemical and physical properties. However, information on their crystal structure, synthesis routes, and measured or predicted properties remains scattered across thousands of publications. Here, we consolidate this fragmented knowledge by establishing X2DB─an open infrastructure that integrates experimental and computational data on 2D materials. Using extensive literature mining and direct community uploads, we identify 370 unique 2D materials that have been realized in monolayer or few-layer form and link them to their digital counterparts in computational databases, enabling consistent ab initio characterization of their properties across monolayer, bilayer, and bulk forms. We describe the structure and content of the database, highlight its support for community uploads, illustrate how it can be used to generate scientific insight, and introduce a hierarchical classification of the known set of 2D materials. Our work supports the integration and cross-fertilization of experimental and theoretical knowledge and contributes to data-driven and predictive synthesis of 2D materials.

The rapid growth of the 2D MXenes family is driven by the designer chemistry control of their composition and structures, including the transition metal and surface functional groups, non-metal X sublattice and atomic-layer configurations. This compositional diversity controls the chemical ordering, atomic-level defects and surface chemistry, ultimately shaping properties of the MXenes. In this Review, we discuss how variations in compositional diversity and atomic arrangement give rise to material properties that enable new applications and breakthroughs in technology. We review design strategies, including atomic vacancy control, intercalation engineering and surface functionalization, that fine-tune the composition–property relationships in MXenes. In addition, we present emerging areas of MXenes research, including advances in biomedicine, optoelectronics, environmental remediation and catalysis, communication and quantum technologies, space exploration and thermal management. The rapid growth of the 2D MXene family is driven by the designer chemistry control of their composition and structure. This Review discusses how compositional diversity, atomic arrangement, defects and surface chemistry govern properties, design strategies and emerging applications across technologies.

Surface groups are central to the properties of MXenes, yet their role in optical anisotropy remains largely unexplored. Here, we use a topochemical route to synthesize single crystals of stacked Ti3C2Cl2 and hybrid organic-inorganic MXenes (h-MXenes) with lateral sizes of 38-75 μm, rotational registry, and tunable interlayer spacing. Solid-state NMR spectroscopy shows that topochemical substitution generates mixed amido, imido, and hydride surface motifs, which modify the electronic structure of the Ti3C2 inorganic core. Imaging spectroscopic ellipsometry with micron-scale spatial resolution enables reconstruction of the complex dielectric tensor of individual multilayer crystals. Ti3C2Cl2 exhibits a type-II hyperbolicity above 930 nm, whereas h-MXenes do not display hyperbolicity within the measured 300-1700 nm window, instead showing reduced in-plane conductivity, suppressed out-of-plane light absorption, and a chain-length-dependent blue shift of a near-infrared absorption feature. These results demonstrate topochemical surface modification as a direct handle for engineering MXenes as surface-programmable optical media.

Understanding the structure-property relationships in layered transition-metal carbides or nitrides, known as MXenes, is of critical importance for their rational design, synthesis, and application. However, the vast chemical and structural diversity of MXenes, stemming from their wide range of M and X elements, surface terminations, and different atomic coordination environments, makes it challenging to clearly understand these structure- property relationships. In this work, we perform first-principles density functional theory (DFT) calculations and molecular dynamics (MD) simulations to comprehensively investigate the stability and a variety of physical properties of MXenes with different coordination environments. Using Ti- and Mo-based carbide MXenes as model systems, energetic calculations reveal that Ti-based MXenes are most stable in octahedral coordination, whereas Mo-based MXenes preferentially adopt prismatic coordination. This fundamental difference in preferred atomic coordination gives rise to markedly distinct properties between these two systems as a function of the fraction of octahedral and prismatic sites. For instance, the in-plane stiffness of Ti-based MXenes increases as octahedral coordination becomes dominant, but it decreases in the Mo-based MXenes under the same conditions. Additional stability analyses based on mechanical, lattice-dynamical, and temperature-dependent thermodynamic properties demonstrate that many metastable MXenes not only satisfy the strict stability criteria but can also undergo phase transitions among different structures and even become stabilized at elevated temperatures. Although surface terminations, such as F and O atoms, do not alter the energetic ordering or the overall stiffness trends among stable and metastable MXenes, they influence other material properties. For instance, O termination can induce semiconducting behavior in both stable and metastable Ti2CO2 MXenes. This study significantly advances the fundamental understanding of structure-property relationships in MXenes and provides valuable guidance for developing coordination-based design principles to precisely engineer MXenes with improved properties.

Neurotechnologies capable of both modulating and recording neural activity are critical for investigating neural function and disease. Optoelectronic probes incorporating micro-light-emitting diodes (μLEDs) and transparent microelectrodes enable colocalized optogenetic stimulation and electrophysiological recordings with high spatiotemporal resolution but often suffer from stimulation artifacts. In this work, we present a thin, flexible, and conformal neural interface integrating blue μLEDs (460 nm) with transparent Ti3C2Tx MXene micro-electrocorticography (μECoG) electrodes for simultaneous, crosstalk-free optical stimulation and electrical recordings. Transparent Ti3C2Tx μECoG electrodes show an optical transmittance of 54.9 ± 0.9% at 460 nm and an impedance modulus of 291.9 ± 99.9 kΩ at 1 kHz. The μLEDs provide up to 86.1 ± 14.7 mW mm-2 with minimal tissue heating and negligible optical distortion through transparent Ti3C2Tx channels. We systematically investigate the mechanisms of the stimulation artifacts and present a methodological framework that is generalizable across multimodal neural interface materials and geometries. With this framework, we demonstrate that the Ti3C2Tx electrodes are minimally susceptible to photoelectric artifacts and that the remaining electromagnetic interference artifacts are minimized using transient μLED drive pulse shaping, ultimately achieving artifact-free, colocalized functionality. The novel multimodal interface is validated in an acute mouse model, establishing it as a powerful platform that enables bidirectional, crosstalk-free interrogation of neural circuits with high spatiotemporal precision.

MXenes are among the most extensively studied materials nowadays due to their functional versatility stemming from their tunable chemical and physical properties. MXenes have been predominantly synthesized by selective wet-chemical etching of parent MAX phases, followed by Li+ intercalation and subsequent delamination. This study demonstrates the substitution of Li+ with Na+ in the preparation of Ti-based MXenes for biomedical and biocatalytic applications, where biologically active Li+ is undesirable. Here, a MILD (Minimally Intensive Layer Delamination) synthesis method of Ti3C2T x and Ti3CNT x is modified by replacing LiF with nontoxic and cost-effective NaF. The produced samples had flake sizes and surface chemistries comparable to those of LiF-MILD samples. The electrical conductivity of Ti3C2T x films made from those flakes exceeded 5500 S/cm. Multiple acid mixtures were investigated, with 12 M HCl producing stable MXene colloids after 48 h of etching without sonication, yielding flakes significantly larger than those obtained using 9 M HCl. The Ti3C2T x flakes exhibited a conventional 2D morphology, while Ti3CNT x scrolled, forming cylindrical nanostructures. With the proper adjustments to the etching conditions, the proposed approach may apply to the synthesis of other Ti-based MXenes.

Ultrathin transparent photonic films that are simultaneously robust, cytocompatible, and actively antimicrobial remain rare. Here, the critical physical properties of freestanding micrometer-thick films composed of layered cellulose nanofibers intercalated with Ti3C2Tx MXene nanosheets (CNF-MXene) are established. Correlated co-alignment of MXene flakes with near-perfect in-plane order is achieved in the cellulose nanofiber matrix by vacuum-assisted filtration. The Herman's orientation parameter of MXene nanosheets reaches up to 0.94, approaching the theoretical limit of 1.0 for perfect orientational order. Flow-assisted alignment and nanofiber-mediated confinement are proposed to suppress MXene restacking and lock the unique film architecture into a stable scaffold. This highly ordered structure yields a significant increase in mechanical strength and elastic modulus. Moreover, co-alignment of individual flakes at ultralow volume fractions (below 1%) creates accessible, photothermally active surface sites within optically clear films. As a result, these ultrathin CNF-MXene membranes combine near-infrared-activated photothermal antimicrobial behavior and molecular adsorption of organic dye as a proxy for accessibility, highlighting a distinctive multifunctional platform for active bio-based films with strong potential for wound-healing applications and long-term functionality preservation.

Niobium‐based MXenes exhibitefficient near‐infrared (NIR) absorption but remain underexplored for in vivo cancer therapy. In this study, we investigated Nb 4 C 3 T x MXene as an NIR‐II photothermal therapy (PTT) sensitizer for melanoma. Both in vitro and in vivo experiments were performed using Nb 4 C 3 T x in combination with pulsed 1064 nm laser irradiation. Tumor growth, histological changes, and spatial localization of MXene were assessed to evaluate therapeutic efficacy and safety. Nb 4 C 3 T x significantly enhanced tumor suppression under pulsed NIR‐II irradiation, inducing extensive destruction of melanoma cells while sparing surrounding tissue. Histological analysis revealed macrophage‐mediated uptake and clearance of MXene, with no evidence of persistent accumulation in tumor remnants or visceral organs. Pulsed laser irradiation provided precise and rapid heating, improving treatment accuracy and minimizing collateral damage. However, complete tumor eradication was not achieved, likely owing to limited light penetration in bulky tumors and the nontargeted distribution of pristine MXene. Our study demonstrates the feasibility and safety of Nb 4 C 3 T x MXene‐assisted PTT in vivo, providing the first experimental evidence of its therapeutic potential in melanoma treatment. These findings establish Nb 4 C 3 T x as a promising platform for pulsed laser–mediated PTT, while highlighting the need for targeted functionalization and treatment optimization to achieve selective tumor ablation.

MXenes, an emerging class of two-dimensional van der Waals materials, have become the focus of research, demonstrating exceptional potential in electrochemical, biochemical and electronic applications. This chapter provides a brief overview of MXenes, covering their fundamental characteristics, synthesis methods and current challenges, with particular attention on synthesis methods.

MXenes are two-dimensional carbides and nitrides that are relatively simple to manufacture. Even when very thin and flexible, their films can replace metals in many devices, such as electromagnetic shields and antennas, offering excellent performance. The lack of models for predicting their nanostructure-dependent homogenized electromagnetic properties hinders the design and optimization of such devices. Classical linear homogenization models, related to the Maxwell-Garnett approach, are useful for relatively low inclusion volume fractions and the dipolar field approximates the inclusion field well. Neither of these assumptions holds well for MXenes, which can be treated as layers of high-aspect-ratio conducting flakes. A numerical linear homogenization model and an analytical model useful for understanding the effects of the MXene nanostructure on the effective dielectric constant are presented. Numerical estimates are obtained using integral equations for the induced charges on the surfaces of MXene flakes. Parametric studies over varying aspect ratios, inter-flake spacing, and stacking configuration reveal that interleaved stacking can yield higher dielectric enhancement. The effective permittivity increases significantly with increasing aspect ratios in a linear fashion. The findings are consistent with experimental reports of high permittivity in MXene-based composites and offer design insights for engineering high-dielectric constant nanomaterials for electromagnetic interference shielding and communication applications.

A “gas–liquid–solid” triphasic selective etching strategy is developed, producing MXenes with uniform halogen surface terminations and enhanced electrical conductivity.

The widespread use of antibiotics has raised concerns about their residues in dairy products, meat, fish, and poultry, which can pose risks to human health and lead to substantial economic losses. Therefore, the rapid, sensitive, and cost-effective detection of low concentrations of various antibiotics in food samples is critical. This work reports on the fabrication of MXene fibers by coating commercial nylon yarns with Ti3C2, Ti3C1.75N0.25, and Ti3C1.5N0.5 MXenes and their use as electrodes in an impedimetric electronic tongue (e-tongue). The MXene-modified fiber-based e-tongue was employed in the detection of trace amounts of cloxacillin benzathine, tetracycline hydrochloride, and streptomycin sulfate. By treating the collected electrical resistance data, the system could differentiate the antibiotics and detect their presence in real milk samples at concentrations as low as 10 nM. The use of low-cost MXene-modified nylon fibers as electrodes, which can be fabricated through rapid and straightforward methods, enhances the scalability and practicability of the e-tongue system. This approach represents a promising and robust alternative for the sensitive detection of diverse antibiotic residues in food matrices.

Titanium carbide MXene (Ti₃C₂Tₓ) is an emerging metallic material with promise for (opto)electronics and thermal management. Yet how photoexcitation—particularly via photogenerated thermal energy—modifies its charge carrier dynamics remains poorly understood. By combining time-resolved terahertz spectroscopy and transient reflectance measurements, we reveal a long-lived, photo-induced suppression of conductivity, which we attribute to efficient lattice heating and slow heat dissipation in Ti₃C₂Tx. A systematic variation of pump photon energy reveals that this ‘negative’ photoconductivity can equivalently be induced by lattice temperature increases, indicating a thermal origin. Repetition-rate-dependent transient reflectance measurements further show residual heat persisting over 100 ns, substantially longer than in conventional metals. Our work presents a unified understanding of photothermal effects in Ti₃C₂Tₓ and their influence on non-equilibrium charge transport, underscoring its potential for photothermal electronics and light-to-thermal energy storage applications. The authors report long-lived pump-induced conductivity suppression in metallic Ti3C2 MXenes using ultrafast terahertz and reflectance spectroscopy. The effect is attributed to strong photothermal heating and slow heat dissipation.

MXene-based electrodes have emerged as promising materials for electro-ionic soft actuators, yet their performance remains largely limited to the extensively studied Ti3C2Tx composition. Here, we introduce Ti3CNTx MXene as a chemically engineered alternative and reveal how nitrogen incorporation fundamentally enhances ion kinetics and actuation behavior. When integrated with PEDOT:PSS (PP), the Ti3CNTx-PP composite electrode demonstrated markedly superior electrochemical performance, achieving an areal capacitance of 562 mF cm⁻²—significantly higher than Ti3C2Tx-PP (204 mF cm⁻²) and pristine PP (159 mF cm⁻²). This enhancement originates from the higher electronegativity of Ti–N bonding, which increases redox-active sites, enlarges interlayer spacing, and accelerates ion diffusion within the MXene framework. Under a low driving voltage of 1 V at 0.1 Hz, the Ti3CNTx-PP actuator exhibited a peak-to-peak displacement of 14.5 mm, outperforming Ti3C2Tx-PP (8.05 mm) and pristine PP (5.5 mm). Frequency- and voltage-dependent actuation tests further confirmed the dominance of Ti3CNTx across all conditions, highlighting its fast ion transport and stronger charge-induced deformation. These findings establish nitrogen-rich Ti3CNTx as a high-efficiency MXene for low-voltage soft actuation and demonstrate electronegativity-driven composition engineering as a powerful strategy for advancing soft robotics, artificial muscles, and next-generation electro-active devices.