MXene Nanosheets Research Articles

An Electric‐Magnetic Dual‐Gradient Composite Film Comprising MXene, Hollow Fe3O4, and Bacterial Cellulose for High‐Performance EMI Shielding and Infrared Camouflage

AbstractIt is crucial to develop electromagnetic interference (EMI) shielding materials with high shielding efficiency (SE) and reduced reflection to mitigate the secondary pollution caused by electromagnetic waves (EMWs). Herein, a novel multilayer assembly strategy inspired by the structure of “Turkish dessert—Baklava” is proposed to introduce magnetic hollow Fe3O4 nanospheres (HFO) and conductive MXene nanosheets into a bacterial cellulose (BC) network. Through a layer‐by‐layer vacuum filtration approach, a composite BC/MXene/HFO film with a controllable electric‐magnetic dual‐gradient structure is achieved. The construction of electric‐magnetic dual gradients alleviates the impedance mismatch at the air‐film interface, resulting in reduced reflectivity toward EMWs, while the unique hollow structure of HFO facilitates the “absorption–reflection–reabsorption” process of EMWs. Consequently, the as‐prepared composite film (0.35 mm thickness) exhibits an extraordinary EMI SE of 67.6 dB and a reflection SE as low as 5.1 dB. Furthermore, it also demonstrates exceptional mechanical properties, efficient thermal management, and Joule heating capabilities, as well as remarkable passive and active infrared camouflage performances. This study offers an innovative approach to achieve less reflection and more absorption of EMWs, and expands the application scope of EMI shielding materials in precision electronics, aerospace, and military equipment fields.

Monolayer Interfacial Assembly toward Two‐Dimensional Mesoporous Heterostructure for Boosting Wave Absorption

AbstractMicrowave absorption materials play a key role in various fields, including military stealth, human safety protection, and so on. Construction of 2D mesoporous heterostructures is an attractive approach to enhance wave‐absorbing ability, while it is still a great challenge. Herein, 2D mesoporous carbon‐MXene‐carbon heterostructures (MCMCH) with channels parallel to surface are successfully prepared via a monolayer interfacial assembly strategy. Through the precise adjustment and polymerization, cylindrical micelles orderly monolayered assemble on both surfaces of 2D MXene nanosheets, resulting in 2D switch‐like polydopamine‐MXene‐polydopamine nanosheets, and 2D MCMCH are finally generated by further calcination. Due to the excellent dielectric polarization relaxation and conductive loss, MCMCH achieves the strongest reflection loss of −54.2 dB at a thickness of only 1.5 mm. The presence of mesochannels not only introduces air with a low permittivity for optimal impedance matching, but also further extends the attenuation path of the incident electromagnetic wave. The maximum radar cross‐section reduction of 26.9 dB m2 is achieved for the MCMCH compared to the perfect electric conductor. This work provides a reference for surface engineering based on 2D mesoporous heterostructures to enhance the microwave absorption performance.

Large stroke radially oriented MXene composite fiber tensile artificial muscles.

Actuation is normally dramatically enhanced by introducing so much yarn fiber twist that the fiber becomes fully coiled. In contrast, we found that usefully high muscle strokes and contractile work capacities can be obtained for non-twisted MXene (Ti3C2Tx) fibers comprising MXene nanosheets that are stacked in the fiber direction. The MXene fiber artificial muscles are called MFAMs. We obtained MFAMs that have high modulus in both the radial and axial directions by spinning a solution containing MXene nanosheets dispersed in an aqueous cellulose solution. We observed a highly reversible muscle contraction of 21.0% for a temperature increase from 25° to 125°C. The tensile actuation of MFAMs mainly results from reversible hydrogen bond orientation change during heating, which decreases intra-sheet spacing. The MFAMs exhibited fast, stable actuation to multiple temperature-generating stimuli, which increases their applications in smart textiles, robotic arms, and robotic grippers.

Prussian Blue Analogues "Dressed" in MXene Nanosheets Tightly for High Performance Lithium-Ion Batteries.

MXenes, have been considered as a new generation anode material in lithium-ion batteries for lower lithium-ion diffusion barriers and superior conductivity. Unfortunately, their structures are prone to aggregation and stacking, hindering further shuttle of lithium ions and electrons, resulting in lower discharge capacity. Therefore, the introduction of interlayer spacers for the preparation of MXene-based hybrids has attracted much attention. Introducing Prubssian blue analogues (PBAs) as a new interlayer spacer to combine with MXene nanosheets can not only preserve the high conductivity of MXene and inhibit the volume expansion and structural degradation of the PBA component, but also inherit the characteristics of large specific surface area and high porosity of PBAs. By intelligent regulating the size of MXene sheets, Co-PBA@MXene hybrids with common sandwich-like structures and superior core-shell-like structures have been successfully obtained. Furthermore, Co@M(x:y) hybrids are prepared by intelligently adjusting the shell thickness of MXene through intelligently controlling of the mass ratio between Co-PBA and MXene. Among them, the Co@M(5:2) anode exhibits an excellent capacity (603mA h g-1 at 0.2 A g-1 after 100 cycles) and superior long-term cycling stability due to the protective and conductive properties provided by the MXene shell and multi-redox pairs and rich porosity from Co-PBA core.

In Situ Ag-Seeded Lamellar Ti3C2 Nanosheets: An Electroactive Interface for Noninvasive Diagnosis of Oral Carcinoma via Salivary TNF-α Sensing.

In the fast-paced quest for early cancer detection, noninvasive screening techniques have emerged as game-changers, offering simple and accessible avenues for precession diagnostics. In line with this, our study highlights the potential of silver nanoparticle-decorated titanium carbide MXene nanosheets (Ti3C2_AgNPs) as an electroactive interface for the noninvasive diagnosis of oral carcinoma based on the prevalence of the salivary biomarker, tumor necrosis factor-α (TNF-α). An in situ reduction was utilized to synthesize the Ti3C2_AgNPs nanohybrid, wherein Ti3C2 acts as the reducing agent, and the resulting nanohybrid was subjected to various characterization techniques to examine the optical, structural, and morphological attributes. The results revealed that spherical AgNPs formed on the surface of Ti3C2 MXene nanosheets by virtue of the low-valent Ti species present in Ti3C2, which facilitated the reduction of AgNO3 to AgNPs. Furthermore, the electrochemical characterization of the nanohybrid-modified screen-printed electrode (Ti3C2_AgNPs/SPE) indicated enhanced heterogeneous electron transfer kinetics. With these encouraging results, the Ti3C2_AgNPs nanohybrid was employed as an immobilization matrix for TNF-α antibodies and applied for electrochemical sensing. Analytical studies of the fabricated immunosensor, conducted by differential pulse voltammetry (DPV), exhibited a broader linear range (1 to 180 pg mL-1), a low limit of detection (0.97 pg mL-1), and high sensitivity (1.214 μA mL pg-1 cm-2) and specificity, even in artificial saliva, indicating its reliability for oral carcinoma diagnosis. Therefore, the Ti3C2_AgNP nanohybrid seems a promising candidate for the effective sensing of TNF-α and could also be explored for other biomarkers.

Synergistic Effects of Size-Confined MXene Nanosheets in Self-Powered Sustainable Smart Textiles for Environmental Remediation

Green renewable technologies have become a focus of energy research due to the adverse impacts of fossil fuels, greenhouse gases, climate change, global warming, and battery short life. A new generation of biomaterials with spontaneous piezoelectric properties is highly emerging for generating electricity from ubiquitous mechanical energy. Recent years, there has been a concerted effort to engineer robust 1D functional materials for nanogenerators, leveraging cellulose as the foundational material. This research work produced nanofiber composite of zinc oxide (ZnO) nanoparticles and MXene (Ti3C2) nanosheets incorporated into cellulose acetate (CA) polymer through electrospinning process forms the basis for ecofriendly highly durable smart textile fabrication. Formation of MXene nanosheets heterostructures significantly promoted the low conversion efficiency of conventional ZnO to highest output voltage of ⁓35V, and a short circuit current of ⁓3.34µA. Synergistic contribution of the piezo-enhanced photocatalytic activity of MXene/ZnO hetero-structured smart nanofibers offers greater environmental remediation of water resources from the contamination of methyl orange (MO) dye with a rate constant (k) of 66.14×10-3min-1. In addition, intelligent dual mechanistic membranes support sustainable operations (20000 cycles) with strong morphological and performance retention (⁓92%), showing good chemical and mechanical stability even under harsh operating conditions.

Extraction and incorporation of cellulose microfibers from textile wastes into MXene-enhanced PVA-borax hydrogel for multifunctional wearable sensors.

Conductive hydrogel has drawn great concern in wearable sensors, human-machine interfaces, artificial intelligence (AI), health monitoring, et al. But it still remains challenge to develop hydrogel through facile and sustainable methods. In this work, a conductive, flexible, bendable, and self-healing hydrogel (PBCM) composed of polyvinyl alcohol (PVA), borax, cellulose microfibers (CMFs), and MXene nanosheet was fabricated by a simple and efficient strategy. The carboxylated CMFs were extracted from waste ramie fibers via a one-pot ammonium persulfate oxidation method. The crystallinity and tensile strength were increased 70 % and 4 times due to the addition of CMFs and MXene compared to the pristine PVA-borax hydrogel. The incorporation of MXene nanosheets acts as multifunctional cross-linkers and energy transfer platform, promoting the electrical conductivity, stretchability, and bendability of hydrogel remarkably. The PBCM-2 hydrogel exhibited the maximum electrical conductivity of 0.81 S/cm. Additionally, the dynamic borate ester linkage imparts self-healing ability to the hydrogel. The resulting PBCM hydrogel demonstrated excellent resistance to fire and pH response properties. Moreover, it showed sensitivity in monitoring various human physiological movements, including finger, wrist, elbow, knee bending, and drinking water, indicating its potential for wearable sensing applications like health care and sports training.

Selective captivation of DOX via topotactic surface enrichment with hydrated sodium ions on engineered MXene nanosheets

Effective adsorption doxorubicin drug from aqueous system was achieved by utilizing a surface functionalized, two-dimensional transition metal carbide (MXene). Synthesis of impurity-free parent phase, subsequent etching and alkalization produced surface...

Porphyrin-graphdiyne analogue modified MXene nanosheets for highly efficient, stable and long-term antibacterials

Porphyrin-graphdiyne analogue modified MXene nanosheets for highly efficient, stable and long-term antibacterials

MXene-driven augmentation of hole-selective self-assembled monolayer interfaces for efficient and stable p-i-n perovskite solar cells

MXene nanosheets enhance electrical properties of SAM-based HTLs in perovskite solar cells to achieve 23.25% efficiency with reduced trap states and negligible hysteresis.

Unlocking the Potential of Polydopamine-Mediated Hybrid MXene and hBN 2D Nanosheets for Improved Thermal Energy Storage and Management

Unlocking the Potential of Polydopamine-Mediated Hybrid MXene and hBN 2D Nanosheets for Improved Thermal Energy Storage and Management

Thermoelectric Modulation of Neat Ti3C2Tx MXenes by Finely Regulating the Stacking of Nanosheets

Emerging two-dimensional MXenes have been extensively studied in a wide range of fields thanks to their superior electrical and hydrophilic attributes as well as excellent chemical stability and mechanical flexibility. Among them, the ultrahigh electrical conductivity (σ) and tunable band structures of benchmark Ti3C2Tx MXene demonstrate its good potential as thermoelectric (TE) materials. However, both the large variation of σ reported in the literature and the intrinsically low Seebeck coefficient (S) hinder the practical applications. Herein, this study has for the first time systematically investigated the TE properties of neat Ti3C2Tx films, which are finely modulated by exploiting different dispersing solvents, controlling nanosheet sizes and constructing composites. First, deionized water is found to be superior for obtaining closely packed MXene sheets relative to other polar solvents. Second, a simultaneous increase in both S and σ is realized via elevating centrifugal speed on MXene aqueous suspensions to obtain small-sized nanosheets, thus yielding an ultrahigh power factor up to ~ 156μWm-1K-2. Third, S is significantly enhanced yet accompanied by a reduction in σ when constructing MXene-based nanocomposites, the latter of which is originated from the damage to the intimate stackings of MXene nanosheets. Together, a correlation between the TE properties of neat Ti3C2Tx films and the stacking of nanosheets is elucidated, which would stimulate further exploration of MXene TEs.

Fabrication of Polydopamine‐Coated High‐Entropy MXene Nanosheets for Targeted Photothermal Anticancer Therapy

AbstractTransition metal carbides, nitrides, and carbonitrides (MXenes) have emerged as a promising class of 2D materials that can be used for various applications. Recently, a new form of high‐entropy MXenes has been reported, which contains an increased number of elemental species that can increase the configurational entropy and reduce the Gibbs free energy. The unique structure and composition lead to a range of intriguing and tunable characteristics. Herein, the fabrication of high‐entropy MXene TiVNbMoC3Tx (T = surface terminations) with a layer of polydopamine is reported, followed by immobilization of a phthalocyanine‐based fluorophore for imaging and the peptide sequence QRHKPREGGGSC for targeting the epidermal growth factor receptor (EGFR) overexpressed in cancer cells. The resulting nanocomposite exhibits high biocompatibility and superior photothermal property. Upon laser irradiation at 808 nm, the light‐to‐heat conversion efficiency is up to 56.1%, which is significantly higher than that of conventional 2D materials. In vitro studies show that these nanosheets could be internalized selectively into EGFR‐positive cancer cells and effectively eliminate these cells mainly through photothermal‐induced apoptosis. Using 4T1 tumor‐bearing mice as an animal model, the nanosheets could accumulate at the tumor and effectively eradicate the tumor upon laser irradiation without causing noticeable adverse effects to the mice.

Competitive Electrochemical Apta-Assay Based on cDNA-Ferrocene and MXenes for Staphylococcus aureus Surface Protein A Detection.

Staphylococcus aureus (S. aureus) represents one of the most frequent worldwide causes of morbidity and mortality due to an infectious agent. It is a part of the infamous ESKAPE group, which is highly connected with increased rates of healthcare-associated infections and antimicrobial resistance. S. aureus can cause a large variety of diseases. Protein A (PrA) is a cell-wall-anchored protein of S. aureus with multiple key roles in colonization and pathogenesis and can be considered as a marker of S. aureus. The development of aptasensors, having an aptamer as a specific biorecognition element, increases selectivity, especially when working with complex matrices. The association with state-of-the-art materials, such as MXenes, can further improve the analytical performance. A competitive aptasensor configuration based on a ferrocene (Fc)-labeled cDNA hybridized (cDNA-Fc S13) on a specific aptamer (APT) for PrA in the presence of MXene nanosheets was designed for the indirect detection of S. aureus. The aptasensor displayed a linear range of 10-125 nM, an LOD of 3.33 nM, and a response time under 40 min. This configuration has been tested in real samples from volunteers diagnosed with S. aureus infections with satisfactory results, enabling the perspective to develop decentralized devices for the rapid detection of bacterial strains.

A Review on MXene/Nanocellulose Composites: Toward Wearable Multifunctional Electromagnetic Interference Shielding Application.

With the rapid development of mobile communication technology and wearable electronic devices, the electromagnetic radiation generated by high-frequency information exchange inevitably threatens human health, so high-performance wearable electromagnetic interference (EMI) shielding materials are urgently needed. The 2D nanomaterial MXene exhibits superior EMI shielding performance owing to its high conductivity, however, its mechanical properties are limited due to the high porosity between MXene nanosheets. In recent years, it has been reported that by introducing natural nanocellulose as an organic framework, the EMI shielding and mechanical properties of MXene/nanocellulose composites can be synergically improved, which are expected to be widely used in wearable multifunctional shielding devices. In this review, the electromagnetic wave (EMW) attenuation mechanism of EMI shielding materials is briefly introduced, and the latest progress of MXene/nanocellulose composites in wearable multifunctional EMI shielding applications is comprehensively reviewed, wherein the advantages and disadvantages of different preparation methods and various types of composites are summarized. Finally, the challenges and perspectives are discussed, regarding the performance improvement, the performance control mechanism, and the large-scale production of MXene/nanocellulose composites. This review can provide guidance on the design of flexible MXene/nanocellulose composites for multifunctional electromagnetic protection applications in the future intelligent wearable field.

Drying Controlled Synthesis of Catalytic Metal Nanocrystals Within 2D‐Material Nanoconfinements

AbstractThe synthesis of low‐dimensional metal nanocrystals with precise atom‐to‐nanoscale structure control is crucial for modulating their physicochemical properties. Traditional synthetic routes encounter challenges due to isotropic metallic bonding, which leads to limited control over metal nanostructures. Herein, a versatile approach is developed using various 2D material (2DM) nanoconfinements to produce a wide range of metal nanocrystals with controllable morphologies. Utilizing graphene oxide (GO) and Ti3C2Tx MXene nanosheets, thin multilayer films are assembled through vacuum filtration and are crosslinked with tetraammineplatinum(II) nitrate (TPtN), followed by in situ thermal reduction. By controlling the concentration of TPtN solution, precise loadings of platinum (Pt) are attained while preserving the nanoconfinement integrity. Two water removal techniques, air‐drying and freeze‐drying, are investigated to assess their impacts on resultant morphologies of Pt nanocrystals. Transmission electron microscopy and molecular dynamics simulations demonstrate high‐aspect‐ratio Pt nanosheets on MXene substrates and few‐atom Pt nanoclusters on GO substrates. A decrease in size distribution is observed upon the use of freeze‐drying. In the semihydrogenation reaction of phenylacetylene, freeze‐dried Pt–MXene heterostructures achieve a high turnover frequency of 2.93 s−1. This comprehensive study highlights the potential of utilizing 2DM nanoconfinement to synthesize metal nanostructures for catalysts and beyond.

Oxidation‐Driven Enhancement of Intrinsic Properties in MXene Electrodes for High‐Performance Flexible Energy Storage

AbstractMXenes, a novel class of 2D materials, exhibit great potential for energy storage due to their unique layered structure and excellent electrical conductivity. However, improving the intrinsic electrochemical storage capacity of MXenes remains a significant challenge, often requiring the incorporation of other Faradaic materials. Oxidation, in particular, poses a key issue that impacts the capacity of MXene devices. In this study, controlled oxidation is employed to create nanoscale holes within MXene, transforming them into holey MXene (H‐MXene) nanosheets. These porous structures shorten ion transport distances and increase ion transport pathways, thereby significantly enhancing the electrochemical storage capacity of MXenes. The resulting H‐MXene micro‐supercapacitors (MSCs) demonstrate exceptional performance, achieving an aerial capacitance 2.5 times that of unmodified MXene electrodes, along with excellent cycling stability, retaining 91.7% of their capacitance after 10 000 cycles. Additionally, a flexible integrated system combining energy storage and sensing functionalities is developed, showcasing its scalability in self‐powered sensing applications. The incorporation of self‐healing polyurethane (PU) enables the device to retain 90% of its storage capacity after undergoing self‐healing. This study presents a novel approach for developing high‐performance MXene‐based energy storage devices and provides valuable insights into efficient ion transport and storage in 2D materials.

Fabrication of Porous MXene/Cellulose Nanofibers Composite Membrane for Maximum Osmotic Energy Harvesting.

Two-dimensional (2D) nanofluidic channels are emerging as potential candidates for harnessing osmotic energy from salinity gradients. However, conventional 2D nanofluidic membranes suffer from high transport resistance and low ion selectivity, leading to inefficient transport dynamics and limiting energy conversion performance. In this study, we present a novel composite membrane consisting of porous MXene (PMXene) nanosheets featuring etched nanopores, in conjunction with cellulose nanofibers (CNF), yielding enhancement in ion flux and ion selectivity. A mild H2O2 oxidant is employed to etch and perforate the MXene sheets to create a robust network of cation transportation nanochannels that effectively reduces the energy barrier for cation transport. Additionally, CNF with a unique nanosize and high charge density further enhances the charge density and mechanical stability of the nanofluidic system. Under neutral pH and room temperature, the PMXene/CNF membrane demonstrates a maximum output power density of 0.95 W·m-2 at a 50-fold KCl gradient. Notably, this represents a 43% improvement over the performance of the pristine MXene/CNF membrane. Moreover, 36 nanofluidic devices connected in series are demonstrated to achieve a stable voltage output of 5.27 V and power a calculator successfully. This work holds great promise for achieving sustainable energy harvesting with efficient osmotic energy conversion utilization.

Heterostructured Co-NiSe2 Nanorods on MXene Nanosheets as Synergistic Electrode Material for Supercapacitor

Heterostructured Co-NiSe₂ Nanorods on MXene Nanosheets as Synergistic Electrode Material for Supercapacitor

Mesoporous MXene nanosheets/CNF composite aerogels for electromagnetic wave absorption and multifunctional response

To acquire excellent wave-absorbing materials with broadened applications, transition metal carbides (Ti3C2Tx, MXene) have been the research focus. However, the high conductivity of MXene limits its electromagnetic wave (EMW) absorption capability; meanwhile, the inferior mechanical properties of MXene-based aerogels severely restrict their applications. Here, porous MXene (PMXene) nanosheets were prepared by hydrogen peroxide etching, which was then physically and chemically crosslinked with cellulose nanofibres (CNF) to successfully prepare PMXene/CNF composite wave-absorbing aerogels with excellent mechanical properties. PMXene/CNF aerogel achieved a minimum reflection loss (RLmin) of − 72.27 dB and an effective absorption bandwidth (EAB) of 5 GHz at a thickness of 1.63 mm without any magnetic component. The aerogels exhibited excellent environmental stability at a density of 12.5 mg/cm3, including fatigue resistance (100 compression cycles, 0.075 energy loss efficiency) and low-temperature resistance. Refining the mechanical properties exploits the aerogel’s potential for motion monitoring and electronic skin applications. In addition, the aerogels integrate properties such as water–oil separation, photothermal conversion, and thermal insulation (thermal conductivity of 0.045 W/(m-K)). Therefore, multifunctional PMXene/CNF aerogels have a broad potential for future application in the defence industry, electronic devices, and smart wearable fields.