Functionalized MXene composites for protection on metals in electric power

Metals used in electric power suffer from icing, wear, and corrosion problems, resulting in high energy consumption, economic losses, security risks, and increased CO2 emission. To address these problems, researchers have turned to two-dimensional (2D) transition metal carbide or nitride (MXene) materials, which possess strong near-infrared adsorption, photothermal conversion, shear ability, low friction coefficient, and impermeability. These properties make MXene a promising candidate for surface protection on metals in electric power, including anti-icing, anti-wear, and anti-corrosion applications. However, the comprehensively protective ability and the promising application of MXene in electric power have not yet been reported. In this review, recent progress in MXene-based composites for anti-icing, anti-wear, and anti-corrosion in electric power is summarized to understand the protective mechanisms and the promising applications. First, the chemical and structure of MXene are briefly introduced, followed by a summary of its intrinsic properties. Next, the latest research on deicing MXene composite coatings, anti-wear MXene-based composites and coatings, and anti-corrosive MXene coatings, along with the corresponding mechanisms, is discussed. Finally, the challenges and opportunities of MXene-based composites in electric power are highlighted. This review provides guidance for understanding the comprehensively protective abilities of MXene and rationally designing MXene-based materials used in electric power.

Photothermal composites for in-situ trace oil detection on ultra-clean surfaces

Oil is widely used as a lubricant in many industries. However, in the final product, oil is often considered a contaminant. In various production processes, such as semiconductor manufacturing, precision machining, and optical device fabrication, ultra-clean surfaces are crucial. Oil residues on these surfaces can adversely affect product performance and quality. Detecting and controlling oil residues enables enhancing product reliability and consistency. Previous lipid detection studies necessitate complex pre-processing, large instruments, or specialized manipulation and data reading capabilities. Existing methods for trace oil detection still cannot achieve on-site real-time monitoring. This study presents a photothermal conversion-based platform for trace oil adsorption and detection. Using polyester fiber membranes as the substrate, a composite material of chitosan and MXene was modified to remove trace oil on ultra-clean surfaces. Due to their inherent thermal conductivity and ability to trap heat inside, the oil molecules intensify the material's temperature rise under near-infrared excitation at 808 nm. By connecting a thermal imaging module to a smartphone, real-time detection of trace oil can be achieved.

Bridging the Thermal Divide: Nano-Architectonics and Interface Engineering Strategies for High-Performance 2D Material-Based Polymer Composites

Polymeric materials play a crucial role in thermal management because of their balanced mechanical and insulating properties. However, when combined with two-dimensional (2D) nanosheets, their low thermal conductivity is limited by interfacial thermal resistance (ITR). Although 2D nanosheets can improve the thermal performance of composites, aggregation and ITR are still major obstacles. This review analyzes the relationship between ITR and heat transfer efficiency at 2D nanosheet-polymer interfaces, examining factors like geometric mismatch, phonon scattering, and interphase bonding. It summarizes theoretical models and experimental methods for measuring ITR, focusing on interfacial modification strategies such as covalent functionalization and gradient nanostructuring, which enhance phonon coupling and filler dispersion to reduce ITR. Studies show that customized interfacial layers can lower ITR and boost composite thermal conductivity. The review also highlights challenges in scalable modification and optimization, and suggests future research should combine experiments and simulations to design high-performance 2D material-polymer composites with low ITR.

Ultrasensitive Room-Temperature NO2 Gas Sensor Based on MXene-Cu2O Composites

The development of real-time trace-level NO2 quantification platforms that can be operated at room temperature constitutes a critical advancement for occupational safety and public health monitoring systems. This study demonstrates a room-temperature NO2 sensor using MXene-Cu2O composites prepared via a hydrothermal method. Systematic evaluation of MXene-introduced effects identified the 0.84 wt % MXene-Cu2O composite as optimal, exhibiting 4-fold enhanced sensitivity and shorter response (55 s)/recovery (35 s) time compared to pure Cu2O. Additionally, the sensor exhibits a low detection limit (10 ppb), high selectivity, great reversibility, and long-term stability. The enhanced sensing performance originates from precisely engineered interfacial architectures between MXene and Cu2O, which effectively adjust the charge-transfer behavior through the conduction tunnel in the sensing material. Furthermore, oxygen vacancy engineering creates defect-mediated adsorption centers that promote selective NO2 chemisorption through charge polarization effects. This research offers a novel strategy for designing optimized structures to enhance the sensitivity of MOS-based materials for NO2 gas detection.

Challenges and future prospects of the 2D material-based composites for microwave absorption

The widespread use of electronic devices inevitably brings about the problem of electromagnetic pollution. As a result, it is important and urgent to develop efficient absorbing materials to alleviate increasing pollution issues. Recently, two-dimensional (2D) material-based microwave absorbers have attracted wide attention in microwave absorption due to their unique lamellar structure, large specific surface area, low density, good thermal and chemical stability. Through various modulation strategies such as structure configuration, pore/defect engineering, heteroatom doping and coupling of functional materials, 2D materials or 2D material-based composites exhibit excellent microwave absorption performance. In this review, the absorption mechanism is firstly introduced and then the latest progress in 2D material-based microwave absorbers is reviewed in depth. The challenges and future prospects for graphene, h-BN, and MXene-based microwave absorbers are discussed in the final part. This timely review aims to provide guidance or stimulation to develop advanced multifunctional 2D material-based microwave absorbers in this rapidly blossoming field.

Combined in- and out-of-plane chemical ordering in super-ordered MAX phases (s-MAX)

The challenge of synthesizing stable super-ordered MAX phases (s-MAX), with both in-plane and out-of-plane chemical ordering, lies in the combination of five different elements and the inherent order of them. A plethora of compositions is thus possible for these quinary phases, however finding the most promising ones and their suitable synthesis methods remains challenging. In this study, we address this issue by employing density functional theory (DFT) to investigate the phase stability of s-MAX phases with the general formulae M14M22M36Al3C9 (413 MAX) and M14M22M33Al3C6 (312 MAX). We identified 26 stable s-MAX phases, with in-plane order of M1 and M2 in the outer layer next to Al and out-of-plane order with M1 + M2 in the outer layer and M3 in the inner layers. An additional 14 s-MAX phases with partial disorder, i.e., M2 with in-plane order in the outer layer whereas disorder of M1 and M3 across outer and inner layers, were also found to be thermodynamically stable. Ideal super-ordered s-MAX is favoured over s-MAX with partial disorder when, among other things, the atomic size of M2 and M3 is larger than M1. These findings provide a framework for designing compositionally tuned s-MAX phases with enhanced functionality, contributing to the development of advanced materials and MXene precursors.

Defect-rich Co,N-doped Ti3C2Tx/C/poly (3,4-ethylenedioxy thiophene) molecularly imprinted sensor for ultrasensitive electrochemical detection of gatifloxacin

The molecular imprinting electrochemical sensors (MIECS) currently face issues such as low sensitivity and stability to be improved. This study innovatively combines ZIF-67/Ti3C2Tx, treated at high temperature, with molecular imprinting technology to construct a MIECS with excellent stability and high sensitivity. First, size-controllable ZIF-67 was grown in situ on Ti3C2Tx, and after high-temperature treatment, Co,N-Ti3C2Tx/C was obtained. This was combined with proton-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) to build the MIECS (Co,N-Ti3C2Tx/C/PEDOT/MIP/GCE). A series of structural characterization and electrochemical tests revealed that the synergistic effect of the abundant defect structures and the excellent proton conductivity of PEDOT significantly enhanced the electrochemical redox activity. The modified electrode demonstrated outstanding electrochemical performance, including an ultra-high electrochemical active surface area and selective recognition of gatifloxacin (GAT) through the imprinted cavities. Further investigation of the sensor's electrochemical detection performance for GAT showed that the fabricated sensor has high sensitivity, good stability, and excellent selectivity. Experimental results indicated that the sensor has a wide linear response range (0.005-50 μM), a low detection limit (2 nM), and test RSD values are all less than 5 % in honey, milk and lake water, and reliable recoveries were achieved in comparison with standard chromatographic methods. Highlight its potential for practical antibiotic monitoring applications.

Broadband Microwave Absorption of Nb2CTx Nanosheets by a One-Step Hydrothermal Method

As an emerging two-dimensional material, MXene holds great potential as a microwave-absorbing material due to its unique layered structure and flexibly tunable surface functional groups. Therefore, research on surface chemistry and interlayer engineering represents an effective strategy for optimizing the performance of MXene. In this work, we synthesized high-quality Nb2CTx nanosheets via a hydrothermal method. Detailed material characterization techniques have confirmed the synthesis of high-quality niobium-based nanosheets. The interlayer spacing, surface termination, and structural defects of the Nb2CTx nanosheets could be flexibly regulated by adjusting the duration of the hydrothermal etching process. This work reveals the etching time-dependent correlation of the electromagnetic parameters of Nb2CTx. It is noteworthy that the optimal impedance matching and microwave absorption performance were achieved after etching for 96 h, with a minimum reflection loss of -43.4 dB at an ultrathin thickness of 1.3 mm and an effective absorption bandwidth of 4.4 GHz at a thickness of 1.4 mm. This work presents a meaningful route to simultaneously adjust the nanoarchitecture and surface chemistry of MXene for advanced microwave absorption applications.

Strong MXene Induced Conductive Silk Fibers

Conductive silk fibers (CSFs) are attractive in the field of flexible wearable electronics and textiles, but it still exists a great challenge to simultaneously enhance the electrical conductivity and mechanical properties. Inspired by the core-sheath structure of Bombyx mori silks, a continuous strategy is demonstrated for the fabrication the strong MXene induced conductive silk fibers (MCSFs). The sericin sheath of silk fibers (SFs) is replaced by MXene/sodium alginate (MSA) layer, and the ultrathin sheath layer is tightly bridged with the core through strong interfacial interactions, including hydrogen bonds and electrostatic interactions. Therefore, the MCSFs show extraordinary tensile strength of 1037.9 MPa and outstanding electrical conductivity of 6400 S m-1, which exhibits obvious advantages compared with the previous reported silk fibers modified by other methods. In addition, the MCSFs also have a high toughness of 194.9 MJ m-3 and an ultra-sensitive gauge factor of 2269.3, resulting in their ability to monitor human pulse, body movements, and changes of ambient humidity in real time. The proposed bioinspired strategy for continuously fabricating ultra-strong and tough MCSFs provides an avenue for implementing functionalized silk fibers in next-generation wearable technologies, intelligent textiles, and human-machine interaction etc.

MXenes in healthcare: transformative applications and challenges in medical diagnostics and therapeutics

MXenes, a novel class of two-dimensional transition metal carbides, exhibit exceptional physicochemical properties that make them highly promising for biomedical applications. Their application has been explored in bioinstrumentation, tissue engineering, and infectious disease management. In bioinstrumentation, MXenes enhance the sensitivity and response time of wearable sensors, including piezoresistive, electrochemical, and electrophysiological sensors. They also function effectively as contrast agents in MRI and CT imaging for cancer diagnostics and therapy. In tissue engineering, MXenes contribute to both hard and soft tissue regeneration, playing a key role in neural, cardiac, skin and bone repair. Additionally, they offer innovative solutions in combating infectious and inflammatory diseases by facilitating antimicrobial surfaces and immune modulation. Despite their potential, several challenges hinder the clinical translation of MXene-based technologies. Issues related to synthesis, scalability, biocompatibility, and long-term safety must be addressed to ensure their practical implementation in medical applications. This review provides a comprehensive overview of MXenes in next-generation medical diagnostics, including the role they play in wearable sensors and imaging contrast agents. It further explores their applications in tissue engineering and infectious disease management, highlighting their antimicrobial and immunomodulatory properties. Finally, we discuss the key barriers to clinical translation and propose strategies for overcoming these limitations. This review aims to bridge current advancements with future opportunities for integration of MXenes in healthcare.

Mixed functionalization as a pathway to induce superconductivity in MXenes: vanadium and niobium carbide

The functionalization versatility of MXenes distinguishes them from other two-dimensional materials, enabling the design of numerous new materials with unique properties. By leveraging surface chemistry, functionalization allows for the manipulation of critical parameters such as the density of states and electron-phonon coupling, providing an excellent platform for exploring two-dimensional superconductivity. In this study, we investigate the impact of functionalization on vanadium carbide (V2C) MXene, which is intrinsically non-superconducting, by considering three different cases: (i) hydrogen adatoms, (ii) fluorine adatoms, and (iii) mixed functionalization with hydrogen and fluorine adatoms. We confirm the mechanical and dynamical stability of functionalized V2C using Born's stability criteria and phonon dispersion analyses. In all three cases, superconductivity emerges due to the presence of functional groups, which influence the electron-phonon interaction and electronic structure, leading to an enhanced electron-phonon coupling constant. The highest superconducting transition temperature is observed for mixed-functionalized V2C, attributed to the softening of the ZA phonon mode along with high-energy phonon modes induced by hydrogen. To further explore the potential of mixed functionalization in inducing superconductivity, we extend our approach to another non-superconducting MXene, Nb2C. The mixed-functionalized Nb2C exhibits a superconducting transition temperature of 9.2 K, which surpasses the reported values for Nb2CH2, Nb2CS2, and Nb2CBr2. These findings underscore the effectiveness of mixed functionalization in enabling superconductivity in MXenes, paving the way for future theoretical and experimental investigations.

2D-Supported Vertical MXenes for Ultrafast Filtering with Ultralow Inductance

Filtering supercapacitors (SCs) are promising for miniaturized power filter electronics due to their high capacitance and robust high-power performance. However, their adoption is limited by a poor low-frequency response in planar porous electrodes, causing mismatched operating frequencies and overheating risks. To address this, we develop MXene-based SCs using a novel vitamin C-assisted solution-thermal method to assemble Ti3C2Tx MXenes into 2D-supported vertical structures, enhancing the dynamic response for linear filtering. These SCs achieve an ultrafast frequency response of 13.8 kHz at a phase angle of -45°, with electric inductance 1/2000 that of commercial aluminum electrolytic capacitors (AECs). They exhibit high areal and volumetric capacitances and effectively smooth random AC waveforms into stable DC signals. Their practicality is demonstrated by replacing bulky AECs and parallel capacitors in a Bluetooth audio amplifier, delivering wireless audio playback without tone quality loss and highlighting their transformative potential for next-generation electronics.

Ion-Electron Interactions in 2D Nanomaterials-Based Artificial Synapses for Neuromorphic Applications

With the increasing limitations of conventional computing techniques, particularly the von Neumann bottleneck, the brain's seamless integration of memory and processing through synapses offers a valuable model for technological innovation. Inspired by biological synapse facilitating adaptive, low-power computation by modulating signal transmission via ionic conduction, iontronic synaptic devices have emerged as one of the most promising candidates for neuromorphic computing. Meanwhile, the atomic-scale thickness and tunable electronic properties of van der Waals two-dimensional (2D) materials enable the possibility of designing highly integrated, energy-efficient devices that closely replicate synaptic plasticity. This review comprehensively analyzes advancements in iontronic synaptic devices based on 2D materials, focusing on electron-ion interactions in both iontronic transistors and memristors. The challenges of material stability, scalability, and device integration are evaluated, along with potential solutions and future research directions. By highlighting these developments, this review offers insights into the potential of 2D materials in advancing neuromorphic systems.

Directional fabrication of an ultra-light and porous bacterial nanocellulose/MXene composite aerogel for efficient thermal management

Global warming has intensified extreme weather events, necessitating advanced thermal management systems to protect human health. Due to its unique properties of increasing phonon scattering at interlayer interfaces and wide spectral absorption, MXene has great potential in thermal management. However, the self-stacking tendency of MXene caused by hydrogen bonding and van der Waals force limits its further application. Herein, we have successfully fabricated an ultra-light (0.011 g cm-3) three-dimensional (3D) bacterial nanocellulose (BNC)/MXene aerogel (BM) through directional freezing. The BNC serves as scaffolds, offering a porous structure with ultra-low thermal conductivity (0.038 W m-1 K-1), high porosity (99.33 %), and excellent insulation (ΔT of 164 at 200 °C). Additionally, the BM aerogel shows remarkable photo-thermal conversion efficiency (98 % solar absorption, 0.25-2.5 μm), quick thermal response (88 °C in 10 s), and thermal stability (89 °C sustained after 120 min). These multifunctional properties make the BM aerogel a potential candidate for advanced thermal management in response to global climate challenges.

Interwoven MXene Sediment Architecture Empowers High-Performance Flexible Microwave Devices

Flexible microwave devices are critical in wearable electronic systems for wireless communication, where highly conductive materials are essential to ensure optimal electromagnetic performance. Titanium carbide (MXene), renowned for its excellent conductivity, lightweight, and easy fabrication, emerges as a promising alternative to conventional metal materials in wearable electronics. However, the technical limitation of MXene suspensions or sediments in fabricating high-performance microwave devices with low cost and scalable production present a huge challenge for their practical applications. Herein, an interwoven MXene sediment architecture is designed on natural cross-linked textiles, achieving high material yield and superior conductivity simultaneously. The architecture breaks up the planar conductive behavior of conventional stacked MXene films, facilitating multi-directional electron transport and pushing the conductivity of MXene sediment microwave devices up to 1.6 × 106 S m-1. The underlying mechanisms responsible for the improvement in conductivity are investigated using resistor network models and percolation theory. Moreover, the architecture demonstrates high performance in electromagnetic interference shielding, and supports high-quality and long-range wireless communications. This validation not only underscores the effectiveness of the interwoven MXene sediment architecture, but also establishes the MXene-based microwave devices as a transformative component for the next generation of high-performance flexible wireless communication technologies.

Interplay of Ultrafast Electron-Phonon and Electron-Electron Scattering in Ti3C2Tx MXenes: Ab Initio Quantum Dynamics

Nonthermal electrons are vital in solar energy and optoelectronics, yet their relaxation pathways are not fully understood. Ab initio quantum dynamics reveal that in Ti3C2O2 electron-phonon (e-ph) relaxation is faster than electron-electron (e-e) scattering due to strong coupling with the A1g phonon at 190 cm-1 and the presence of light C and O atoms. Nuclear quantum effects are minimal; vibrations influence e-e scattering only indirectly, and the A1g mode' zero-point energy is much lower than thermal energy at ambient conditions. Substituting O with heavier S in Ti3C2OS slows e-ph relaxation and enhances e-e scattering, making it a faster process. However, both channels proceed concurrently, challenging the e-e and e-ph time scale separation often used for metals. These results underscore the need for atomistic-level understanding of nonthermal electron dynamics, especially in light-element systems such as MXenes, and provide guidance for optimizing electronic relaxation in advanced optoelectronic materials and devices.

Defect Engineering for Flexible n-Type Mo2TiC2Tx o-MXene Thermoelectric Efficiency Enhancement

With the rapid advancement of wearable electronics, the demand for efficient portable power supplies has become increasingly urgent. Thermoelectric materials, which can directly convert heat, such as body heat, into electricity, offer a promising avenue for sustainable energy supplementation. However, achieving a high thermoelectric performance in flexible materials suitable for body heat harvesting remains a significant challenge. Here, we introduce a strategy for synergistically tuning surface oxygen defects and optimizing microstructures in low-dimensional semiconductor materials, resulting in flexible, ammoniated dual-transition metal carbide o-MXene N-Mo2TiC2Tx with enhanced properties. Theoretical and experimental analyses reveal that high-temperature ammoniation produces a low-oxygen-functionalized surface, reduces interlayer spacing, and minimizes defect density, thereby significantly increasing the electrical conductivity. Nitrogen atoms incorporated at the nanosheet terminals further increase the electron density near the Fermi level, resulting in an enhanced Seebeck coefficient. Consequently, N-Mo2TiC2Tx films treated at 900 K achieve an electrical conductivity of 1.03 × 104 S m-1, a Seebeck coefficient of -27.8 μV K-1, and a power factor of 7.99 μW m-1 K-2 at room temperature, nearly 1.2-fold higher than that of untreated materials, while retaining excellent flexibility. Moreover, a wearable thermoelectric generator constructed from these N-Mo2TiC2Tx films produces a voltage of 1.4 mV under a temperature gradient of approximately 12 K between human skin and ambient air, underscoring its excellent capacity for harvesting low-grade thermal energy. These findings establish a paradigm for the development of flexible, high-performance thermoelectric materials, paving the way for next-generation wearable and industrial energy applications.

Characterization of MXene-Based Materials by X-Ray Computed Tomography

MXenes are a class of 2D materials that have gained significant attention for their potential applications in energy storage, electromagnetic interference shielding, biomedicine, and (opto)electronics. Despite their broad range of applications, a detailed understanding of the internal architecture of MXene-based materials remains limited due to the lack of effective 3D imaging techniques. This work demonstrates the application of X-ray micro-computed tomography (micro-CT) to investigate various MXene systems, including nanocomposites, coated textiles, and aerogels. Micro-CT enables high-resolution, 3D visualization of the internal microstructure, MXene distribution, infiltration patterns, and defect formations, which significantly influence the material's performance. Moreover, the typical technical challenges and limitations encountered during sample preparation, scanning, and post-processing of micro-CT data are discussed. The information obtained from optical and electron microscopy is also compared with micro-CT, highlighting the unique advantages of micro-CT in providing comprehensive 3D imaging and quantitative data. This study highlights micro-CT as a powerful and nondestructive imaging tool for characterizing MXene-based materials, providing insights into material optimization and guidelines for developing future advanced applications.

Unperceivable Designs of Wearable Electronics

Wearable smart electronics are taking an increasing part of the consumer electronics market, with applications in advanced healthcare systems, entertainment, and Internet of Things. The advanced development of flexible, stretchable, and breathable electronic materials has paved the way to comfortable and long-term wearables. However, these devices can affect the wearer's appearance and draw attention during use, which may impact the wearer's confidence and social interactions, making them difficult to wear on a daily basis. Apart from comfort, one key condition for user acceptance is that these new technologies seamlessly integrate into our daily lives, remaining unperceivable to others. In this review, strategies to minimize the visual impact of wearable devices and make them more suitable for daily use are discussed. These new devices focus on being unperceivable when worn and comfortable enough that users almost forget their presence, reducing psychological discomfort while maintaining accuracy in signal collection. Materials selection is crucial for developing long-term and unperceivable wearable devices. Recent developments in these unperceivable electronic devices are also covered, including sensors, transistors, and displays, and mechanisms to achieve unperceivability are discussed. Finally, the potential applications are summarized and the remaining challenges and prospects are discussed.

Enhanced Mechanical Properties and Sensing Performance of MXene-Based Dual-Crosslinked Hydrogel via EGCG Coating and Dynamic Covalent Bond

MXenes hold great promise for flexible sensors due to their outstanding electrical and mechanical properties. However, their practical application in aqueous environments is often compromised by oxidation susceptibility. Here, epigallocatechin gallate (EGCG), a naturally derived compound is introduced, as a protective coating for Ti₃C₂Tx MXene nanosheets. The catechol groups in EGCG form strong hydrogen bonds with MXene, significantly enhancing its oxidation resistance in aqueous environments for up to 40 days. By incorporating EGCG-coated MXene (MXene@EGCG) to form a dual-crosslinked hybrid network, a tough hydrogel with exceptional properties, including enhanced compressibility (>95%), high compressive strength (5.43 MPa), minimal residual strain (<1%), and rapid recovery within seconds is developed. Furthermore, the hydrogel exhibits superior sensing capabilities with a compressive gauge factor exceeding 10 and a stretch gauge factor of up to 3.72. This well-designed structure also endows it a low degree of hysteresis in compressive sensing. In vitro experiments confirm its great biocompatibility, desired self-adhesion properties, and practical utility as a sensing platform. This approach pioneers a versatile and transformative strategy for enhancing MXene stability and engineerability, unlocking new possibilities for fabricating high-performance hydrogel-based sensors capable of effectively sensing dynamic strains, which may find broad applications in the fields of multifunctional bioelectronics.

Induction of Chirality in MXene Nanosheets and Derived Quantum Dots: Chiral Mixed-Low-Dimensional Ti3C2Tx Biomaterials as Potential Agricultural Biostimulants for Enhancing Plant Tolerance to Different Abiotic Stresses

This work presents two advancements in the engineering design and bio-applications of emerging MXene nanosheets and derived quantum dots. First, a facile, versatile, and universal strategy is showcased for inducing the right- or left-handed chirality into the surface of titanium carbide-based MXene (Ti3C2Tx) to form stable mixed-low-dimensional chiral MXene biomaterials with enhanced aqueous colloidal dispersibility and debonding tolerance, mimicking the natural asymmetric bio-structure of most biomolecules and living organisms. In particular, Ti3C2Tx MXene nanosheets are functionalized with carboxyl-based terminals and bound feasibly with the D/L-cysteine amino acid ligands. The physicochemical characterizations of these 2D-0D/1D chiral MXene heterostructures suggest the inclusion of Ti3C2Tx nanosheets and different levels of self-derived MXene quantum dots and surface titanium-oxide nanoparticles, providing enhanced material stability and oxidative degradation resistance for tested months. Further, the interaction and molecular binding at cysteine-Ti3C2Tx/Ti-oxide interfaces, associated ion transport and ionic conductivity analysis, and charge re/distribution mechanisms are evaluated using density functional theory (DFT) calculations and electrochemical impedance spectroscopy (EIS) measurements. The second uniqueness of this study relies on the multifunctional application of optimal chiral MXenes as potential nano-biostimulants for enhancing plant tolerance to different abiotic conditions, including severe drought, salinity, or light stress. This surface tailoring enables high biocompatibility with the seed/seedling/plant of Arabidopsis thaliana alongside promoting multi-bioactivities for enhanced seed-to-seedling transition, seedling germination/maturation, plant-induced stomatal closure, and ROS production eliciting responses. Given that the induced chirality is a pivotal factor in many agro-stimulants and amino acid-containing fertilizers for enhanced interaction with plant cells/enzymes, boosting stress tolerance, nutrient uptake, and growth, these findings open up new avenues toward multiple applications of chiral MXene biomaterials as next-generation carbon-based nano-biostimulants in agriculture.

MXene-Regulated Indium-Based Metal-Organic Framework Material for Electrochemical Reduction of CO2 into Pure Formic Acid Aqueous Solution

Electrochemical CO2 reduction reaction provides a mild avenue for resource utilization of CO2. Metal-organic framework (MOF) materials are considered among the promising catalysts due to unique structural advantages. However, the catalytic performance of MOFs is hindered by poor conductivity, making it crucial to enhance the charge transfer for improved efficiency. Herein, a hybrid catalyst was constructed based on the In-based porphyrin framework (In-TCPP) and conducting MXene nanosheets for efficient CO2 conversion. As expected, MXene as a unique conductive support significantly improves the catalytic performance of the hybrid material, achieving a Faraday efficiency for HCOO- of 94.0% with a 2.2-fold increase in the practical current density. Furthermore, a pure formic acid solution with a concentration of ca. 0.22 M was prepared via execution in a solid-state electrolyte-mediated MEA (MEA-SSE) device. Theoretical calculations and in situ ATR-FTIR spectra reveal that the introduction of MXene not only endows the hybrid material with metallic properties to facilitate charge transfer but also modulates the electronic structure to optimize the adsorption of the key intermediate *OCHO. This work enlightens the rational design of MOF-based electrocatalysts via the regulation of MXene and demonstrates the promise of the MEA-SSE device for practical CO2 reduction applications.

MXene Surface Architectonics: Bridging Molecular Design to Multifunctional Applications

This review delves into the surface modification of MXenes, underscoring its pivotal role in improving their diverse physicochemical properties, including tailor MXenes' electrical conductivity, mechanical strength, and wettability. It outlines various surface modification strategies and principles, highlighting their contributions to performance enhancements across diverse applications, including energy storage and conversion, materials mechanics, electronic devices, biomedical sciences, environmental monitoring, and fire-resistant materials. While significant advancements have been made, the review also identifies challenges and future research directions, emphasizing the continued development of innovative materials, methods, and applications to further expand MXenes' utility and potential.

MXene-transition metal chalcogenide hybrid materials for supercapacitor applications

The rapid growth of technologies and miniaturization of electronic devices demand advanced the use of high-powered energy storage devices. The energy storage device are utilized in modern wearable electronics, stretchable screens, and electric vehicles. Due to their favorable electrochemical properties, nanomaterials have been used as electrodes for supercapacitors (SCs) with high power density, but they generally suffer from lower energy density than batteries. Compared to various nanomaterials, MXenes and transition metal chalcogenides (TMCs) have shown great potential for energy storage applications such as SCs. TMCs are gaining attention due to their stable electrochemical nature, adjustable surface activity, high electric conductivity, abundant chemically active sites, and stable cycling performance. However, the interlayer restacking and agglomeration of 2D materials limit their cycling performance. To overcome this, TMCs@MXene heterostructures have been developed, offering structurally stable electrodes with enhanced chemical active sites. In this review, we discuss recent advances in the development of different TMCs@MXene-based hybrids for the design of high performance SCs with improved specific capacitance, cycling life, energy density, and power density. The recent developments of this research field focusing on MXene-transition metal sulfides, MXene-transition metal selenides, and MXene-transition metal tellurides are elaborately discussed. Theoretical calculations carried out to understand the charge-storage mechanisms in these composites are reviewed. The importance of bimetallic TMCs and MXene heterostructure for enhanced energy storage is also highlighted.

Recent progress in the synthesis of nanostructured Ti3C2T x MXene for energy storage and wastewater treatment: a review

MXene-based functional 2D materials hold significant potential for addressing global challenges related to energy and water crises. Since their discovery in 2011, Ti3C2T x MXenes have demonstrated promising applications due to their unique physicochemical properties and distinctive morphology. Recent advancements have explored innovative strategies to enhance Ti3C2T x into multifunctional materials, enabling applications in gas sensing, electromagnetic interference shielding, supercapacitors, batteries, water purification, and membrane technologies. Unlike previous reviews that primarily focused on the synthesis, properties, and individual applications of MXenes, this work provides a fundamental discussion of their role in wastewater treatment, recent advancements in energy harvesting, and their broader implications. Additionally, this review offers a comparative analysis of MXene-based systems with other state-of-the-art materials, providing new insights into their future development and potential applications.

Multifunctional Ti3C2Tx-alginate foams for energy harvesting and fire warning

Foams that combine seemingly opposite properties, such as high thermal insulation and electrical conductivity, are highly sought after for modern-day advanced applications. However, achieving a balance of these properties necessitates careful tuning of material compositions. Here, we prepared ice-templated Ti3C2Tx-alginate composite foams and investigated the role of Ti3C2Tx MXene in triboelectric energy production, thermal insulation, and flame retardancy. Our results show that adding 5 wt% Ti3C2Tx enhances the triboelectric output of 6 mm thick foams (380 V, 7.7 μA, 43 mW m-2) by 110%. Despite incorporating electrically conducting Ti3C2Tx, these macroporous composite foams have a thermal conductivity of only 62 mW m-1 K-1, while they also show flame-retardant properties, exhibiting self-extinguishing behavior. Finally, we demonstrate these composite foams for constructing smart fire alarm systems as they respond to small changes in electrical resistance induced by fire. Our findings prove that Ti3C2Tx is a versatile filler for biopolymer foams, introducing complementary functionalities that can be exploited in energy and safety applications.

Ion desolvation for boosting the charge storage performance in Ti3C2 MXene electrode

Clarifying the relationship between ion desolvation, ion-electrode interactions, and charge storage capacity during ion intercalation in host electrode materials is crucial for advancing fast and efficient energy storage systems. However, the absence of direct evidence for ion desolvation and lack of detailed understanding of the interactions between surface terminations and intercalated cations (Li ions)/solvents hinder the exploration of their effects on energy storage mechanisms. In this paper, we study the intercalation of Li ions from a non-aqueous electrolyte in two-dimensional metal carbides Ti3C2 MXenes with different surface chemistries: HF-Ti3C2 (F-, OH- and O-terminated) and MS-Ti3C2 (O- and Cl-terminated) MXenes. We are able to visualize the full ion desolvation and solvents-ions co-intercalation in the interlayers of MS-MXene and HF-MXene, respectively at the atomic scale. The combination of several techniques and characterization tools reveal that the complete ion desolvation in Cl- and O-terminated MS-Ti3C2 MXenes is associated with the formation of a dense solid electrolyte interface layer, resulting in improved charge storage capacity. The O-rich surface terminations of MS-MXenes are found to be responsible for the efficient Li ions storage. These findings shed lights on identifying the critical role of non-electrostatic ion-electrode interactions and ion desolvation in designing high-performance energy storage devices.

D-Orbital-Modulated Ruthenium Embedded within Functionalized Hollow MXene Networks for Enhanced Hydrazine-Assisted Hydrogen Production

Electrochemical green hydrogen production via water splitting is an attractive and sustainable pathway; however, the sluggish kinetics of anodic oxygen evolution reaction is still a critical challenge. In this study, an effective electrocatalyst engineering approach is demonstrated by preparing an innovative hybrid of ruthenium d-orbitals-regulated nanoclusters embedding within functionalized hollow Ti3C2 MXene networks (Ru0.91Ni0.09-N/O-Ti3C2) to promote the hydrazine-assisted hydrogen production. A specific charge redistribution is revealed, locally concentrating at interfaces derived from stable Ru(Ni)-N/O-Ti coordination and d-p orbital hybridization. The charge transfer effect from Ni to Ru within Ru0.91Ni0.09 structure and Ru0.91Ni0.09 to N/O-Ti3C2 tailors electronic features of Ru sites to enable reasonable adsorption/desorption toward reactant intermediates. The Ru0.91Ni0.09-N/O-Ti3C2 requires an overpotential of only 29.3 mV for cathodic hydrogen evolution and a low potential of -29.9 mV for anodic hydrazine oxidation to reach 10 mA cm-2, showing excellent stability. The hydrazine-assisted hydrogen production system based on Ru0.91Ni0.09-N/O-Ti3C2 electrodes delivers small cell voltages of 0.02 V at 10 mA cm-2 and 0.92 V at industrial current level of 1.0 A cm-2. This work may open a new electrocatalysis strategy from lab scale to industry for robust and efficient green hydrogen production.

Epitope-Imprinted Field-Effect Transistors Overcome Debye Length Limitations for Label-Free Protein Detection

Graphene-based field-effect transistor (GFET) biosensors face limitations in detecting charged analytes due to ionic screening (Debye screening effect). This limitation restricts their ability to detect charged target analytes in situ in physiological solutions. To overcome this challenge, we present a non-destructive van der Waals (vdW) integration of an epitope molecular-imprinted membrane (EMIM) with a GFET biosensor. This innovative vdW-heterostructured biosensor, termed the EMIM-Chip, features a 3.3 ± 1.7 nm thin EMIM dielectric layer self-assembled on the graphene surface. The EMIM layer, featuring specifically imprinted cavities, replaces antibodies and effectively mitigates ionic screening. This innovation enables rapid in situ detection of Alzheimer's disease (AD) biomarker Aβ proteins (50 aM-5 pM) in purified samples and patient plasma/urine within minutes. Notably, these sensors retain their functionality even after 30 days of environmental storage, positioning our approach as a promising foundation for future medical tool development.

Multifunctional Sensitive Positive Friction Layer of TPU/MXene/STO Composited Film for Triboelectric Nanogenerator

Triboelectric nanogenerators (TENGs) are ideal candidates for flexible wearable electronics due to their simple structure, high output voltage, and sensitivity. However, the output of the flexible TENG for wearable electronics still needs further improvement. This study fabricated a positive triboelectric layer with fillers to improve the output equipped with a dense, irregular surface structure by using electrospinning. The effect of the composite filler consisting of conductive MXene nanosheets and ferroelectric strontium titanate nanoparticles was investigated by adjusting their ratio. Compared to pure thermoplastic polyurethane (TPU), the voltage and current of the TMS-based (TPU/MXene/STO) TENG increased by 7 and 34 times. Furthermore, the fabricated TENG has been successfully applied in flexible sensing. It can detect the curvature of different object grips and various breathing conditions, making it promising for intelligent sensing and health monitoring applications. This study successfully developed a low-cost, high-performance, and highly sensitive TENG, which shows significant potential in smart wearable devices.

MXene/Doxorubicin Complex-Loaded Supramolecular Hydrogels for Near Infrared-Triggered Synergistic Cancer Therapy

Photothermal therapy (PTT) has attracted great interest due to the high spatial precision and reduced general toxicity compared to conventional cancer therapies. However, PTT often faces challenges such as incomplete tumor eradication and collateral damage to healthy tissues. Here, we report an injectable MXene-doxorubicin (MD) complex-loaded supramolecular hydrogel (MDGel) for dual synergistic cancer therapy of near-infrared (NIR) PTT and chemotherapy. MDGel is prepared by the host-guest interaction between gelatin-cyclodextrin (GE-CD) and hyaluronic acid-adamantane (HA-AD), facilitating the efficient dispersion of MD complexes in the hydrogel. NIR irradiation triggers the PTT and the release of doxorubicin with increasing temperature. In vitro therapeutic effect is confirmed by achieving nearly 80% cancer cell death via the synergistic effect, compared to the single-modality treatment. In vivo tumor inhibition (68.9% volume reduction) is further validated in skin cancer-bearing model mice with no substantial negative side effect. With its prolonged retention, NIR light-controlled release, and localized therapeutic effect, the MDGel system would provide a notable paradigm as a versatile platform for dual synergistic cancer therapy.

Tough MXene-Cellulose Nanofibril Ionotronic Dual-Network Hydrogel Films for Stable Zinc Anodes

Developing ionotronic interface layers for zinc anodes with superior mechanical integrity is one of the efficient strategies to suppress the growth of zinc dendrites in favor of the cycling stability of aqueous zinc-ion batteries (AZIBs). Herein, we assembled robust 2D MXene-based hydrogel films cross-linked by 1D cellulose nanofibril (CNF) dual networks, acting as interface layers to stabilize Zn anodes. The MXene-CNF hydrogel films integrated multifunctionalities, including a high in-plane toughness of 18.39 MJ m-3, high in-plane/out-of-plane elastic modulus of 0.85 and 3.65 GPa, mixed electronic/ionic (ionotronic) conductivity of 1.53 S cm-1 and 0.52 mS cm-1, and high zincophilicity with a high binding energy (1.33 eV) and low migration energy barrier (0.24 eV) for Zn2+. These integrated multifunctionalities, endowed with coupled multifield effects, including strong stress confinement and uniform ionic/electronic field distributions on Zn anodes, effectively suppressed dendrite growth, as proven by experiments and simulations. An example of the MXene-CNF|Zn showed a reduced nucleation overpotential of 19 mV, an extended cycling life of over 2700 h in Zn||Zn cells, and a high capacity of 323 mAh g-1 in Zn||MnO2 cells, compared with bare Zn. This work offers an approach for exploring mechanically robust 1D/2D ionotronic hydrogel interface layers to stabilize the Zn anodes of AZIBs.

MXene synthesis in a semi-continuous 3D-printed PVDF flow reactor

Two-dimensional transition metal carbides, nitrides and carbonitrides known as MXenes represent a promising class of functional materials for electrochemical energy storage, catalysis, electromagnetic shielding, and optoelectronics. Typical synthesis methods require highly concentrated acids and HF-containing or HF-forming chemicals, under batch conditions. Environmentally friendly, safe, efficient, and scalable synthesis methods for MXenes have been identified as the number one research challenge for MXene research over the next decade. Here we use flow chemistry to present a semi-continuous synthesis of Ti3C2T z in a custom 3D-printed reactor. The synthesis is safer and is the first step towards scalable methods, yielding fully etched MXenes with better removal of Al from the starting MAX phase compared to the equivalent batch procedure.

Anode Materials for Proton Batteries: Progress and Prospects

A proton battery is considered as a promising energy storage solution with the merits of fast kinetics, high safety, low cost, and environmental benignity. The realization of these merits depends on the exploration of the appropriate and high-performance electrode materials. Although many anode materials of proton batteries have been reported, a dedicated summary of the progress, challenges, and prospects of anode materials for proton batteries has not been reported. Through discussions on the proton storage mechanisms, advantages and limitations of various anode materials, optimization strategies to boost their proton storage capability, and their potential applications, this review seeks to provide a comprehensive theoretical foundation and practical guidance for future research and development of proton battery technology. First, the preparation methods and proton storage mechanism of anode materials have been discussed. Then, the limitations and optimization strategies have been summarized. After that, the next section elaborately focuses on the proton storage performance of different types of anode materials. Finally, the challenges and prospects of anode materials for proton batteries have been proposed. This review aims to provide insight into the efficient design and optimization of anode materials for practical applications of proton batteries.

Few-Layered MXene Modulating In Situ Growth of Carbon Nanotubes for Enhanced Microwave Absorption

MXene is widely used in the fields of microwave absorption and electromagnetic shielding to balance electromagnetic pollution with the development of communication technologies and human health, due to its excellent surface functional groups and tunable electronic properties. Although pure multilayered MXene has an excellent accordion-like structure, the weak dielectric loss and lack of magnetic loss result in poor microwave absorption performance. Here, we propose a strategy for the catalytic growth of CNTs by the electrophoretic deposition of adsorbed metal ions, leading to the successful preparation of Ni-MWCNTs/Ti3C2Tx composites with a "layer-by-layer" structure, achieved through in situ regulated growth of CNTs. By introducing dielectric-magnetic synergy to improve the impedance matching conditions, and by regulating the diameter of the CNTs to alter the electromagnetic parameters of Ni-MWCNTs/Ti3C2Tx, the 2-Ni-MWCNTs/Ti3C2Tx composite achieves the best reflection loss (RL) value of -44.08 dB and an effective absorption bandwidth of 1.52 GHz at only 2.49 mm thickness. This unique layered structure and the regulation strategy provide new opportunities for the development of few-layered MXene composites.

Surface Functionalization of Ti3C2Tx MXenes in Epoxy Nanocomposites: Enhancing Conductivity, EMI Shielding, Thermal Conductivity, and Mechanical Strength

MXenes have gained significant attention as multifunctional fillers in MXene-polymer nanocomposites. However, their inherently hydrophilic surfaces pose challenges in compatibility with hydrophobic polymers such as epoxy, potentially limiting composite performance. In this study, high-crystalline Ti3C2Tx MXenes were functionalized with alkylated 3,4-dihydroxy-l-phenylalanine ligands, transforming the hydrophilic MXene flakes into a more hydrophobic form, thus significantly enhancing compatibility with the epoxy matrix. This surface functionalization enabled uniform dispersion and supported the formation of a percolation network within the epoxy matrix at a low filler loading of just 0.12 vol %. Consequently, the functionalized MXene-epoxy nanocomposites exhibited remarkable performance, including an electrical conductivity of 8200 S m-1, outstanding electromagnetic interference (EMI) shielding effectiveness (SE) of 100 dB at 110 GHz (61 dB at 8.2 GHz), improved thermal conductivity of 1.37 W m-1 K-1, and a 300% increase in tensile toughness (271 KJ m-3). These properties substantially outperformed those of their nonfunctionalized counterparts and surpassed previously reported MXene-polymer nanocomposites. This study underscores the critical role of surface functionalization in unlocking the full potential of two-dimensional (2D) MXenes in polymer composites, providing a pathway to advanced multifunctional nanocomposite materials.

Microfluidic Spun Self-Healable Janus-Core Composite Microfibers as Smart Fiber Actuators

Smart fiber actuators with self-sensing and intelligent actuation can perceive environmental changes and respond with real-time movements. Herein, Janus-core composite microfibers (JCCMFs), consisting of a Janus NIR-driven active-passive core and a self-healable hydrogel shell, are fabricated through a microfluidic process. The resulting JCCMFs can perform rapid NIR-driven bending within 6 s and achieve fast self-healing within 5 min. The fast self-healing improves durability and enables straightforward assembly into biomimetic actuators without the need for additional adhesive. Furthermore, the JCCMFs also possess potential piezoresistive abilities, enabling applications as hybrid smart actuators and exhibiting excellent performance in touch sensitivity and microtexture recognition .

MXenes and MXene-based composites for biomedical applications

MXenes, a novel class of two-dimensional materials, have recently emerged as promising candidates for biomedical applications due to their specific structural features and exceptional physicochemical and biological properties. These materials, characterized by unique structural features and superior conductivity, have applications in tissue engineering, cancer detection and therapy, sensing, imaging, drug delivery, wound treatment, antimicrobial therapy, and medical implantation. Additionally, MXene-based composites, incorporating polymers, metals, carbon nanomaterials, and metal oxides, offer enhanced electroactive and mechanical properties, making them highly suitable for engineering electroactive organs such as the heart, skeletal muscle, and nerves. However, several challenges, including biocompatibility, functional stability, and scalable synthesis methods, remain critical for advancing their clinical use. This review comprehensively overviews MXenes and MXene-based composites, their synthesis, properties, and broad biomedical applications. Furthermore, it highlights the latest progress, ongoing challenges, and future perspectives, aiming to inspire innovative approaches to harnessing these versatile materials for next-generation medical solutions.

High-Entropy 1T-Phase Quantum Sheets of Transition-Metal Disulfides

Quantum sheets of transition-metal dichalcogenides (TMDs) are promising nanomaterials owing to the combination of both 2D nanosheets and quantum dots with distinctive properties. However, the quantum sheets usually possess semiconducting behavior associated with 2H phase, it remains challenging to produce 1T-phase quantum sheets due to the easy sliding of the basal plane susceptible to the small lateral sizes. Here, an efficient high-entropy strategy is developed to produce 1T-phase quantum sheets of transition-metal disulfides based on controllable introduction of multiple metal atoms with large size differences to retard the sliding of basal plane. The key is the topological conversion of in-plane ordered carbide laminates (i-MAX) compatible with multiple atoms to high-entropy transition-metal disulfides with high strains and 1T phase, which facilely triggers the fracture into 1T-phase quantum sheets with average size of 4.5 nm and thickness of 0.7 nm during the exfoliation process. Thus, the 1T-phase disulfide quantum sheets show high electrocatalytic activities for lithium polysulfides, achieving a good rate performance of 744 mAh g-1 at 5 C and a long cycle stability in lithium-sulfur batteries.

In Situ Formation of Ripplocations in Hybrid Organic-Inorganic MXenes

Inorganic-organic hybrid MXenes (h-MXenes) are a family of 2D transition metal carbides and nitrides functionalized with alkylimido and alkylamido surface groups. Using cryogenic and room temperature scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS), it is shown that ripplocations, a form of a fundamental defect in 2D and layered structures, are abundant in this family of materials. Furthermore, detailed studies of electron probe sample interactions, focusing on structural deformations caused by the electron beam are presented. The findings indicate that at cryogenic temperatures (≈100 K) and below a specific dose threshold, the structure of h-MXenes remains largely intact. However, exceeding this threshold leads to electron beam-induced deformation through ripplocations. Interestingly, the deformation behavior, required dose, and resultant structure are highly dependent on temperature. At 100 K, it is demonstrated that the electron beam can induce ripplocations in situ with a high degree of precision.

Stiff and self-healing hydrogels by polymer entanglements in co-planar nanoconfinement

Many biological tissues are mechanically strong and stiff but can still heal from damage. By contrast, synthetic hydrogels have not shown comparable combinations of properties, as current stiffening approaches inevitably suppress the required chain/bond dynamics for self-healing. Here we show a stiff and self-healing hydrogel with a modulus of 50 MPa and tensile strength up to 4.2 MPa by polymer entanglements in co-planar nanoconfinement. This is realized by polymerizing a highly concentrated monomer solution within a scaffold of fully delaminated synthetic hectorite nanosheets, shear oriented into a macroscopic monodomain. The resultant physical gels show self-healing efficiency up to 100% despite the high modulus, and high adhesion shear strength on a broad range of substrates. This nanoconfinement approach allows the incorporation of novel functionalities by embedding colloidal materials such as MXenes and can be generalized to other polymers and solvents to fabricate stiff and self-healing gels for soft robotics, additive manufacturing and biomedical applications.

Anion Vacancies Coupling with Heterostructures Enable Advanced Aerogel Cathode for Ultrafast Aqueous Zinc-Ion Storage

As a potential cathode material, manganese-based sulfide has recently attracted increasing interest due to its many advantages in aqueous zinc-ion storage. Unfortunately, some challenges such as sluggish kinetics, unstable structure, and controversial phase transition mechanism during the energy storage process hinder its practical application. Herein, inspired by density functional theory (DFT) calculations, a novel 3D sulfur vacancy-rich and heterostructured MnS/MXene aerogel is designed, and used as a cathode for aqueous Zn-ion batteries/hybrid capacitors (ZIBs/ZICs) for the first time. Thanks to the synergistic modification strategy of sulfur vacancies and heterostructures, the as-constructed MnS/MXene//Zn ZIBs exhibit significantly enhanced electrochemical properties, especially outstanding rate capability and cyclic stability. More encouragingly, the as-assembled MnS/MXene//porous carbon (PC) ZICs exhibit an ultrahigh energy density, a high power density, and a splendid cycling lifespan. Most notably, systematic kinetic analyses, ex situ characterizations, and DFT calculations illustrate that MnS/MXene first irreversibly converts into MnOx@ZnMnO3/MXene, and then undergoes a reversible conversion from MnOx@ZnMnO3/MXene to MnOOH@ZnMn2O4/MXene, accompanied by the co-insertion/extraction of H+ and Zn2+. The synergistic modification strategy of sulfur vacancies and heterostructures and the thorough mechanistic study proposed in this work offer valuable guidance for designing and exploiting high-performance cathodes in aqueous zinc-based energy storage devices.

Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions

Atomic site catalysts (ASCs) have recently gained prominence for their potential in the electrochemical hydrogen evolution reaction (HER) due to their exceptional activity, selectivity, and stability. ASCs with individual atoms dispersed on a support material, offer expanded surface areas and increased mass efficiency. This is because each atom in these catalysts serves as an active site, which enhances their catalytic activity. This review is focused on providing a detailed analysis of ASCs in the context of the HER. It will delve into their properties, types, and performance to provide a comprehensive understanding of their role in electrochemical HER processes. The introduction part underscores HER's significance in transitioning to sustainable energy sources and emphasizes the need for innovative catalysts like ASCs. The fundamentals of the HER section emphasizes the importance of understanding the HER and highlights the key role that catalysts play in HER. The review also explores the properties of ASCs with a specific emphasis on their atomic structure and categorizes the types based on their composition and structure. Within each category of ASCs, the review discusses their potential as catalysts for the HER. The performance section focuses on a thorough evaluation of ASCs in terms of their activity, selectivity, and stability in HER. The performance section assesses ASCs in terms of activity, selectivity, and stability, delving into reaction mechanisms via experimental and theoretical approaches, including density functional theory (DFT) studies. The review concludes by addressing ASC-related challenges in HER and proposing future research directions, aiming to inspire further innovation in sustainable catalysts for electrochemical HER.

MXenes in healthcare: synthesis, fundamentals and applications

Since their discovery over a decade ago, MXenes have transformed the field of "materials for healthcare", stimulating growing interest in their healthcare-related applications. These developments have also driven significant advancements in MXenes' synthesis. This review systematically examines the synthesis of MXenes and their applications in sensing and biomedical fields, underscoring their pivotal role in addressing critical challenges in modern healthcare. We describe the experimental synthesis of MXenes by combining appropriate laboratory modules with the mechanistic principles underlying each synthesis step. In addition, we provide extensive details on the experimental parameters, critical considerations, and essential instructions for successful laboratory synthesis. Various healthcare applications including sensing, biomedical imaging, synergistic therapies, regenerative medicine, and wearable devices have been explored. We further highlight the emerging trends of MXenes, viz., their role as nanovehicles for drug delivery, vectors for gene therapy, and tools for immune profiling. By identifying the important parameters that define the utility of MXenes in biomedical applications, this review outlines strategies to regulate their biomedical profile, thereby serving as a valuable guide to design MXenes with application-specific properties. The final section integrates experimental research with theoretical studies to provide a comprehensive understanding of the field. It examines the role of emerging technologies, such as artificial intelligence (AI) and machine learning (ML), in accelerating material discovery, structure-property optimization, and automation. Complemented by detailed supplementary information on synthesis, stability, biocompatibility, environmental impact, and theoretical insights, this review offers a profound knowledge base for understanding this diverse family of 2D materials. Finally, we compared the potential of MXenes with that of other 2D materials to underscore the existing challenges and prioritize interdisciplinary collaboration. By synthesizing key studies from its discovery to current trends (especially from 2018 onward), this review provides a cohesive assessment of MXene synthesis with theoretical foundations and their prospects in the healthcare sector.

Pulsed Electrochemical Exfoliation for an HF-Free Sustainable MXene Synthesis

MXenes are a 2D materials (2DM) class with high industrialization potential, owing to their superb properties and compositional variety. However, ensuring high etching efficiency in the synthesis process without involving toxic, hazardous or non-sustainable chemicals are challenging. In this work, an upscalable electrochemical MXene synthesis is presented. This novel protocol uses a non-toxic and sustainable sodium tetrafluoroborate/hydrochloric acid (NaBF4/HCl) electrolyte and increases etching efficiency by applying cathodic pulsing via pulse voltammetry. Hydrogen bubble formation restores electrochemical activity, and effectively supports 2D-sheet removal, allowing continuous etching at higher yields in situ. In detail, yields of up to 60% electrochemical MXene (EC-MXene) with no byproducts from a single exfoliation cycle are achieved. EC-MXene had an excellent quality with high purity as assessed using chemical mapping by scanning electron microscopy with energy dispersive electron spectroscopy (SEM/EDX) and surface termination analysis performed with X-ray photoelectron spectroscopy (XPS) and, for the first time, with low energy ion scattering (LEIS). Further properties of EC-MXenes such as dimensions and adhesion energy of single flakes, vibrational peaks, and interlayer spacing are provided by atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy (Raman), and transmission electron microscopy (TEM) respectively. Pulsed electrochemical synthesis is key to surface reactivation at the electrodes' interface, which results in improved exfoliation and quality of EC-MXenes. This paves the way for scaling up and green industrialization of MXenes.

Super-elastic, hydrophobic composite aerogels for triboelectric nanogenerators

Progress toward the advancement of environmentally friendly energy harvesting devices is critical for eco-environmental protection. There is an urgent need for developing energy harvesting devices from biobased materials. However, it is still a challenge to utilize biobased cellulose nanofiber (CNF) aerogels in triboelectric nanogenerators (TENGs) due to their poor mechanical properties, hydrophilicity, and weak polarization capability. Here, we demonstrate a facile strategy to fabricate a super-elastic, hydrophobic CNF/MXene composite aerogel for TENGs through fluorosilane crosslinking and a directional freeze-dried assembled structure. This aerogel can withstand up to 80% compressive strain, rebound to 95.33% of its original height, and exhibit hydrophobicity (water contact angle = 137.65°). In addition, the induction of MXene and the silane coupling agent endows the aerogel with enhanced electronegativity and charge density. These properties enable the CNF/MXene aerogel to harvest energy with an output voltage of 100 V and a short-circuit charge density of ∼900 nC cm-3, while maintaining stability for 1000 cycles. This aerogel holds great application potential in the field of self-powered sensing and raindrop energy harvesting.

Synthesis of Ti4Au3C3 and its derivative trilayer goldene through chemical exfoliation

Achieving large two-dimensional (2D) sheets of any metal is challenging due to their tendency to coalescence or cluster into 3D shapes. Recently, single-atom-thick gold sheets, termed goldene, was reported. Here, we ask if goldene can be extended to include multiple layers. The answer is yes, and trilayer goldene is the magic number, for reasons of electronegativity. Experiments are made to synthesize the atomically laminated phase Ti4Au3C3 through substitutional intercalation of Si layers in Ti4SiC3 for Au. Density functional theory calculations suggest that it is energetically favorable to insert three layers of Au into Ti4SiC3, compared to inserting a monolayer, a bilayer, or more than three layers. Isolated trilayer goldene sheets, ~100 nanometers wide and 6.7 angstroms thick, were obtained by chemically etching the Ti4C3 layers from Ti4Au3C3 templates. Furthermore, trilayer goldene is found in both hcp and fcc forms, where the hcp is ~50 milli-electron volts per atom more stable at room temperature from ab initio molecular dynamic simulations.

Biocomposites of 2D layered materials

Molecular composites, such as bone and nacre, are everywhere in nature and play crucial roles, ranging from self-defense to carbon sequestration. Extensive research has been conducted on constructing inorganic layered materials at an atomic level inspired by natural composites. These layered materials exfoliated to 2D crystals are an emerging family of nanomaterials with extraordinary properties. These biocomposites are great for modulating electron, photon, and phonon transport in nanoelectronics and photonic devices but are challenging to translate into bulk materials. Combining 2D crystals with biomolecules enables various 2D nanocomposites with novel characteristics. This review has provided an overview of the latest biocomposites, including their structure, composition, and characterization. Layered biocomposites have the potential to improve the performance of many devices. For example, biocomposites use macromolecules to control the organization of 2D crystals, allowing for new capabilities such as flexible electronics and energy storage. Other applications of 2D biocomposites include biomedical imaging, tissue engineering, chemical and biological sensing, gas and liquid filtration, and soft robotics. However, some fundamental questions need to be answered, such as self-assembly and kinetically limited states of organic-inorganic phases in soft matter physics.

Bright yellow fluorescent N-doped Ti3C2 MXene quantum dots as an "on/off/on" nanoprobe for selective As3+ ion detection

Ti3C2 MXene quantum dots (MQDs) are considered to be an emerging nanomaterial in recent times, but the majority of MQDs exhibit limited emission properties in the blue-light region. Longer-wavelength emissive quantum dots are highly desirable in terms of various biological aspects including deep tissue penetration, superior signal-to-noise ratio, reduced radiation damage, etc. In this study, bright yellow fluorescent nitrogen-doped MQDs (N-MQDs) were successfully prepared using a one-pot hydrothermal method. The synthesized N-MQDs showed maximum emission at 570 nm upon excitation at a wavelength of 420 nm, with an optimum fluorescence quantum yield of 13.8%. Interestingly, the emission of the N-MQDs was significantly quenched upon the addition of As3+ ions. A mechanistic investigation revealed that static quenching was involved in the decrease in the fluorescence via the formation of a non-fluorescent complex due to the interaction of the functional groups of the N-MQDs and As3+. The quenched fluorescence was surprisingly recovered upon treatment of the complex with 2-amino-6-methoxybenzothiazole (MBTZ). The strong interaction of MBTZ with As3+ led to the detachment of the quencher from the N-MQDs, resulting in fluorescence recovery. The re-appearance of the functional groups of the N-MQDs after the addition of MBTZ was confirmed via spectroscopic study. Thus, the fluorescence "on/off/on" phenomenon of the N-MQDs nanoprobe was utilised for the instantaneous detection of As3+ and MBTZ. The limit of detection values were calculated to be 30 nM and 0.44 μM with a good linearity for As3+ and MBTZ, respectively. In addition, a solid sensor has been fabricated to recognize As3+ in wastewater, revealing its potential for on-site application in the near future.

Efficient spatial self-phase modulation in the near-infrared and visible regimes of transition metal carbonitride Ti3CN

Transition metal carbides, nitrides, and carbonitrides (MXenes) have attracted great interest in all-optical modulation applications due to their excellent nonlinear optical properties. Herein, we investigated the spatial self-phase modulation (SSPM) of Ti3CN flake suspension at wavelengths ranging from 405 to 1064 nm. Broadband third-order nonlinear optical susceptibility χ(3) values of Ti3CN were found to be ∼10-9 e.s.u. (5.35 × 10-9 e.s.u. at 532 nm), which was 3 to 5 times greater than those of transition metal dichalcogenides. In particular, Ti3CN exhibited a faster nonlinear optical response time (0.36 s) in the near-infrared region than that in the visible regime (0.4 to 0.53 s), with the response time increasing with wavelength in the visible regime. Our study reveals that Ti3CN can serve as a potential candidate for applications in nonlinear optical devices, especially for near-infrared all-optical devices.