Carbide MXene Research Articles

Vanadium Carbide MXene Florets Synthesized without HF and Modified with Nickel Disulfide for Enhanced Hydrogen Evolution Reaction

Vanadium Carbide MXene Florets Synthesized without HF and Modified with Nickel Disulfide for Enhanced Hydrogen Evolution Reaction

Passively generated Q-switched pulses fiber laser in 2µm wavelength using MXene Ti3C2Tx and Ti2CTx saturable absorber

Abstract In this paper, Q-switched Thulium-doped fiber lasers (TDFLs) operating near the 2 µm region were demonstrated, utilizing a newly developed Thulium doped fiber as the gain medium and titanium carbide MXene as the saturable absorber (SA). The Thulium-doped fiber with a composition of SiO2-GeO2-Al2O3-HfO2-Y2O3-Bi2O3, was produced from a preform prepared using the modified chemical vapor deposition (MCVD) process. Two variations of titanium carbide MXene-based SA, Ti3C2Tx and Ti2CTx, were tested and compared, both successfully generating Q-switched pulses. When Ti3C2Tx was used, the Q-switched pulse had a center wavelength of 1934.223 nm, a repetition rate of 55.39 kHz and a pulse width and 1.942 µs. For Ti2CTx, the generated Q-switched pulse has a center wavelength of 1932.229 nm, with a repetition rate of 77.28 kHz and a pulse width of 1.608 µs. The signal-to-noise ratio (SNR) values were 45.6 dB and 50.2 dB for Ti3C2Tx and Ti2CTx respectively. Based on the experimental results, both Ti3C2Tx and Ti2CTx show promise as SAs for generating Q-switched pulses in the 2 µm region within the TDFL cavity.

Spray-on electronic tattoos with MXene and liquid metal nanocomposites

Electronic tattoos present appealing forms of wearable devices operated directly on the skin. Although two-dimensional transition metal carbides (MXenes) are promising material choices, their films are susceptible to fracturing when subjected to tensile deformations. This study presents electronic tattoos comprising MXenes and liquid metal microcapsules fabricated by spray deposition onto the skin. The resulting nanocomposite has a low sheet resistance of approximately 2.2 Ω/sq. and can be repetitively deformed to 50 % strain. The enhanced deformability is attributed to the release of liquid metal from the microcapsules upon stretching, facilitating the repair of cracks in the nanocomposite layer. In addition, the nanocomposite conforms to the skin, sticks well, and moves with the body. It is also resistant to friction and sweat, making it suitable for various applications. A bifunctional electronic tattoo has been further developed, showcasing its capability to acquire biopotential signals and deliver electrical stimulation. Our study effectively improves the deformability of MXene-based nanocomposites for electronic tattoos, achieving seamless device integration in the body.

Preparation of amorphous Nd/Dy-based metal organic framework@MXene for solar driven selective photocatalytic and serving as sensor for fluorescence quenching detection, and biological activity

The development of a new Neodymium/Dysprosium metal–organic framework, referred to as Nd/Dy-BTC MOF, based on benzene-1,2,4-tricarboxylic acid, has been achieved through an in situ growth process on 2D transition metal carbides (MXene) surfaces. This synthesis was conducted via a solvothermal method utilizing a solvent mixture of water, ethanol, and dimethylformamide. The primary objective of this research is to investigate the framework’s efficacy as a photocatalyst for the degradation of anionic dye, as well as its potential for sensing certain explosives. The Nd/Dy-MOF@MXene has been characterized by various analysis techniques. The prepared Nd/Dy-MOF@MXene was utilized as catalyst in selective degradation of methyl orange dye. The study examined the influence of pH and catalyst concentration, revealing that the catalyst achieves peak efficiency of 93.55% when exposed to sunlight in an acidic medium. The reusability of the catalyst shows the highest efficient photocatalyst after four cycles of reusability. The detection of explosives, specifically 2,4,6-trinitrophenol, through photoluminescence techniques has been conducted, utilizing the Stern-Volmer equation to evaluate the quenching efficiency. The findings indicated remarkable efficiency and selectivity of Nd/Dy-MOF@MXene for 2,4,6-trinitrophenol, achieving a quenching efficiency of 91%. Furthermore, the reusability tests demonstrated that Nd/Dy-MOF@MXene exhibits outstanding recyclability, maintaining performance over five cycles. The antibacterial activity of Nd/Dy-MOF@MXene was investigated against Gram-positive and Gram-negative strains due to indication of medicine properties of Nd/Dy-MOF@MXene.

Scalable ultrastrong MXene films with superior osteogenesis.

Titanium carbide MXene flakes have promising applications in aerospace, flexible electronic devices and biomedicine owing to their superior mechanical properties1 and electrical conductivity2 and good photothermal conversion3, biocompatibility4 and osteoinductivity5. It is highly desired yet very challenging to assemble MXene flakes into macroscopic high-performance materials in a scalable manner. Here we demonstrate a scalable strategy to fabricate high-performance MXene films by roll-to-roll-assisted blade coating (RBC) integrated with sequential bridging, providing good photothermal conversion and osteogenesis efficiency under near-infrared irradiation. MXene flakes were first bridged with silk sericin by hydrogen bonding and then assembled into macroscopic films using a continuous RBC process, followed by ionic bridging to freeze their aligned structure. The resultant large-scale MXene films with strong interlayer interactions are highly aligned and densified, exhibiting high tensile strength (755 MPa), toughness (17.4 MJ m-3) and electromagnetic interference (EMI) shielding capacity (78,000 dB cm2 g-1), as well as good ambient stability, photothermal conversion and bone regeneration performance. The proposed strategy not only paves a feasible way for realizing the practical applications of MXene in the fields of flexible EMI shielding materials and bone tissue engineering but also provides an avenue for the high-performance and scalable assembly of other two-dimensional flakes.

Evaluation of 2D Tantalum Carbide MXene for Room to Mid‐temperature Thermoelectric Applications

AbstractTantalum carbide MXene (Ta4C3Tx) were synthesized via HF etching of the Al intermediate layer from the parental tantalum aluminium carbide MAX phase (Ta4AlC3). The structural and vibrational studies confirm the formation of MXene from the MAX phase without disturbing the hexagonal crystal structure. The synthesized samples were analysed using XRD to understand the phase structure. In and out of plane vibrational properties were examined by Raman spectrometer. XPS confirms the successful HF etching of Al in MXene phase and all other elemental configurations. HR‐SEM and HR‐TEM revile the exfoliated layered structure of the MXene and hexagon diffraction pattern of the tantalum carbide MXene sample with increased d‐spacing. The TGA analysis demonstrated the thermal stability of the as‐synthesized post measured compounds. The synthesized tantalum carbide MXene shows stable thermoelectric properties over six thermal cycles. The temperature dependent transport properties were measured from 303 K to 803 K. Ta4C3Tx MXene shows a maximum Seebeck coefficient of 13.8 μV/K and a power factor of 1.88 μW/mK2 with the low lattice thermal conductivity of 5.42 W/mK at 803 K. In this present investigation, Tantalum carbide MXene demonstrated a decent thermoelectric property with high thermal cycling stability.

2D Titanium Carbide MXene and Single-Molecule Fluorescence: Distance-Dependent Nonradiative Energy Transfer and Leaflet-Resolved Dye Sensing in Lipid Bilayers.

Despite their growing popularity, many fundamental properties and applications of MXene materials remain underexplored. Here, the nonradiative energy transfer properties of 2D titanium carbide MXene are investigatedand their application in single-molecule biosensing is explored for the first time. DNA origami positioners are used for single dye placement immobilized by a specific chemistry based on glycine-MXene interactions, allowing precise control of their orientation on the surface. Each DNA origami structure carries a single dye molecule at predetermined heights. Single-molecule fluorescence confocal microscopy reveals that energy transfer of an organic emitter (ATTO 542) on transparent thin films made of spincast Ti3C2Tx flakes follows a cubic distance dependence, where 50% of energy transfer efficiency is reached at 2.7nm (d0). MXenes are applied as short-distance spectroscopic nanorulers, determining z distances of dye-labeled supported lipid bilayers fused on MXene's hydrophilic surface. Hydration layer (2.1nm) and lipid bilayer thickness (4.5nm) values that agree with the literature are obtained. These results highlight titanium carbide MXenes as promising substrates for single-molecule biosensing of ultrathin assemblies, owing to their sensitivity near the interface, a distance regime that is typically inaccessible to other energy transfer tools.

Ultrafast Synthesis of MXenes in Minutes via Low-Temperature Molten Salt Etching.

Developing green and efficient preparation strategies is a persistent pursuit in the field of 2D transition metal nitrides and/or carbides (MXenes). Traditional etching methods, such as HF-based or high-temperature Lewis-acid-molten-salt etching route, require harsher etching conditions and exhibit lower preparation efficiency with limited scalability, severely constraining their commercial production and practical application. Here, an ultrafast low-temperature molten salt (LTMS) etching method is presented for the large-scale synthesis of diverse MXenes within minutes by employing NH4HF2 as the etchant. The increased thermal motion and improved diffusion of molten NH4HF2 molecules significantly expedite the etching process of MAX phases, thus achieving the preparation of Ti3C2Tx MXene in just 5minutes. The universality of the LTMS method renders it a valuable approach for the rapid synthesis of various MXenes, including V4C3Tx, Nb4C3Tx, Mo2TiC2Tx, and Mo2CTx. The LTMS method is easy to scale up and can yield more than 100g Ti3C2Tx in a single reaction. The obtained LTMS-MXene exhibits excellent electrochemical performance for supercapacitors, evidently proving the effectiveness of the LTMS method. This work provides an ultrafast, universal, and scalable LTMS etching method for the large-scale commercial production of MXenes.

Sensitive Electrochemical Determination of Quercetin in Fruit Juice Using an Aluminum Hydroxide Oxide–Titanium Carbide MXene Composite

A hybrid material composed of aluminum hydroxide oxide (AlOOH) and titanium carbide (Ti3C2) nanosheets was synthesized and used for electrochemical sensing of quercetin. The Ti3C2 nanosheets were synthesized using a selective etching technique, followed by the hydrothermal growth of AlOOH on the nanosheet surfaces. Cyclic voltammetry and differential pulse voltammetry were performed to evaluate the electrochemical properties of the AlOOH@Ti3C2 nanocomposites. Under optimal conditions, the AlOOH@Ti3C2 modified electrode exhibited wide linearity and high sensitivity. The practicality of the sensor was verified through an interference study and real sample analysis. Additionally, the sensing platform exhibited outstanding operational and storage stability.

MXene Electrodes for All Strain-Free Solid-State Batteries.

All-solid-state batteries with nonflammable inorganic solid electrolytes are the key to addressing the safety issues of lithium-ion batteries with flammable organic liquid electrolytes. However, conventional electrode materials suffer from substantial volume changes during Li+ (de)intercalation, leading to mechanical failure of interfaces between electrode materials and solid electrolytes and then severe performance degradation. In this study, we report strain-free charge storage via the interfaces between transition metal carbides (MXenes) and solid electrolytes, where MXene shows negligible structural changes during Li+ (de)intercalation. Operando scanning electron transmission microscopy with electron energy-loss spectroscopy reveals the pillar effect of trapped Li+ in the interlayer spaces of MXene to achieve the strain-free features. An all strain-free solid-state battery, which consists of a strain-free Ti3C2Tx negative electrode and a strain-free disordered rocksalt Li8/7Ti2/7V4/7O2 positive electrode, demonstrates long-term stable operation while preserving the interfacial contact between electrode materials and solid electrolytes.

Bismuth Sulfide Nanorod/Vanadium Carbide MXene as Nitrogen Dioxide Gas Sensor Operating at Room Temperature under Ultraviolet-Assisted Recovery

Bismuth Sulfide Nanorod/Vanadium Carbide MXene as Nitrogen Dioxide Gas Sensor Operating at Room Temperature under Ultraviolet-Assisted Recovery

Acidic "Water-in-Salt" Electrolyte Enables a High-Energy Symmetric Supercapacitor Based on Titanium Carbide MXene.

Titanium carbide MXene, Ti3C2Tx, exhibits ultrahigh capacitance in acidic electrolytes at negative potentials yet poor stability at positive potentials, resulting in low-energy densities for Ti3C2Tx-based symmetric supercapacitors. Utilizing "water-in-salt" electrolytes has successfully expanded the stable operation potential window of MXenes. However, this advancement comes at the cost of sacrificing their high capacitance in acidic electrolytes. In this work, we report an acidic "water-in-salt" (AWIS) electrolyte composed of sulfuric acid and saturated lithium halide, which effectively doubled the energy density of the Ti3C2Tx-based symmetric supercapacitor compared to those with bare acidic electrolytes. Specifically, the AWIS electrolyte successfully expanded the voltage window of the symmetric device to 1.1 V. A high specific capacitance of 112.34 F g-1 (at 10 mV s-1) was obtained due to the presence of proton redox. As a result, the symmetric device achieved a high-energy density of 19.1 Wh kg-1 and a high capacitance retention of 96.3% after 10,000 cycles. This work demonstrates the importance of designing stable and redox-active electrolytes for high-energy MXene-based symmetric supercapacitors.

DFT based investigations on inherent CO2 adsorption and direct dissociation capability of Ti2C and Nb2C mxenes

Transition metal carbide MXenes, specifically Ti2C and Nb2C, have been investigated for their ability to efficiently adsorb and dissociate CO2 using First Principles Calculations based on Density Functional Theory (FPS-DFT). Pure Ti2C and Nb2C sheets were studied with the adsorption of 1 to 4 CO2 molecules, and the results were analyzed for each case. For 4 CO2 molecules adsorbed on Ti2C and Nb2C sheets, the weight percentage (wt%) ratio was found to be 21.39% and 14.33%, respectively. The Density of States (DOS) analysis revealed that, upon CO2 adsorption, the CO2 molecule dissociates into CO and O atoms on the MXene surface. The CO molecule showed no significant hybridization with the host sheet atoms, whereas the O atom exhibited strong hybridization with the MXene surface. Transition State (TS) profiles illustrated the dissociation steps on both Ti2C and Nb2C surfaces. Phonon calculations confirmed the dynamic stability of both pure and CO2 adsorbed MXenes. Molecular Dynamics (MD) simulations conducted at 900 K indicated uniform temperature and Mean Square displacement (MSD) profiles, suggesting the stability of both pure and CO2 adsorbed MXenes at elevated temperatures, as well as uniform CO2 adsorption behavior. The adsorption energies for Ti2C and Nb2C sheets were calculated to be in the range of -1.89 to -2.77eV, suggesting that the adsorption process is favorable, spontaneous, and predominantly involves chemisorption. These findings indicate that Ti2C and Nb2C MXenes, in their intrinsic forms, are promising candidates for CO2 adsorption and dissociation technologies.

Tuning Nanochannel Microenvironments of a Thermoresponsive MXene Membrane for Mixed Molecule Gradient Separation.

Drawing inspiration from dynamic biological ion channels, researchers have developed various artificial membranes featuring responsive nanochannels. Typically, these membranes modify mass transport behaviors by manipulating the responsive layer on the inner surfaces of the intrinsic layer. In this study, we build two-dimensional lamellar membranes composed of titanium carbide MXene and poly(N-isopropylacrylamide), endowed with dual-level regulatable nanochannels, achieved through adjustments of nanochannel microenvironments. The size of these two-dimensional nanochannels can be altered by both the thermoresponsive polymer layer and the intrinsic MXene layer that could undergo spontaneous oxidation. The multilevel regulation strategy substantially enhances the molecular selectivity of MXene separation membranes, which is further applied for precise gradient separation toward multiple molecules. This advancement showcases the versatility and transformative capabilities of responsive nanochannel technology, setting the stage for innovative developments in diverse fields.

Metal-organic framework (MOF) integrated Ti3C2 MXene composites for CO2 reduction and hydrogen production applications: a review on recent advances and future perspectives.

Titanium carbide (Ti3C2) MXenes due to their structural and optical characteristics rapidly emerged as the preferred material, particularly in catalysis and energy applications. On the other hand, because of its enormous surface/volume ratio and porosity, Metal-organic Frameworks (MOFs) show promise in several areas, including catalysis, delivery, and storage. The potential to increase the applicability of these magic compounds might be achieved by taking advantage of the inherent flexibility in design and synthesis, and optical characteristics of MXenes. Thus, coupling MOF with Ti3C2 MXenes to construct hybrid composites is considered promising in a variety of applications, including energy conversion and storage. This paper presents a systematic discussion of current developments in Ti3C2 MXenes/MOF composites for photocatalytic reduction of CO2, and production of hydrogen through water splitting. Initially, the overview and characteristics of MXenes and MOFs are independently discussed and then a detailed investigation of efficiency enhancement is examined. Different strategies such as engineering aspects, construction of binary and ternary composites and their efficiency enhancement mechanism are deliberated. Finally, different strategies to explore further in various other applications are suggested. Although Ti3C2 MXenes/MOF composites have not yet been thoroughly investigated, they are potential photocatalysts for the production of solar fuel and ought to be looked into further for a range of applications.

Two-dimensional vanadium carbide (V2C) MXene derived heterostructures for high-performance lithium storage

Li3VO4 is notable for its high theoretical capacity and favorable lithium-ion insertion potential, making it a promising candidate for lithium storage applications. However, its practical use is limited by low electronic conductivity, which results in reduced electrochemical performance and significant resistance polarization during lithium storage. Herein, we developed a Li3VO4/V2CTx heterostructure using a MXene-derived approach, where Li3VO4 is anchored onto a conductive V2CTx MXene substrate. Theoretical calculations suggest that the heterostructure exhibits enhanced lithium adsorption capabilities compared to V2CTx, indicating improved interactions with lithium ions. The synthesized Li3VO4/V2CTx heterostructure demonstrates excellent rate performance and cycling stability. Additionally, a lithium-ion capacitor utilizing this heterostructure as the anode and activated carbon as the cathode achieves impressive power density and energy density. This study underscores the potential of this heterostructure as a high-performance anode material and offers valuable insights for the design of other advanced electrode materials.

Measuring the Surface Energy of Nanosheets by Emulsion Inversion.

Solution-processed nanomaterials can be assembled by a range of interfacial techniques, including as stabilizers in Pickering emulsions. Two-dimensional (2D) materials present a promising route toward nanosheet-stabilized emulsions for functional segregated networks, while also facilitating surface energy studies. Here, we demonstrate emulsions stabilized by the 2D materials including the transition metal carbide MXene, titanium carbide (Ti3C2T x ), and develop an approach for in situ measurement of nanosheet surface energy based on emulsion inversion. This approach is applied to determine the influence of pH and nanosheet size on surface energy for MXene, graphene oxide, pristine graphene, and molybdenum disulfide. The surface energy values of hydrophilic Ti3C2T x and graphene oxide decrease significantly upon protonation of usually dissociated functional groups, facilitating emulsion stabilization. Similarly, pristine graphene and molybdenum disulfide increase in surface energy when their surface functional groups are deprotonated under basic conditions. In addition, the surface energies of these pristine materials are correlated with nanosheet size, which allows for the calculation of the basal plane and edge surface energies of pristine nanosheets. This understanding of surface energies and control of emulsion inversion will allow design of emulsion-templated structures and surface energy studies of a wide range of solution-processable nanomaterials.

V2CTx MXene for sustainable wastewater treatment: Inspired by the exoskeletons of nature’s microscopic architects

The polyvinylidene fluoride (PVDF) membrane is prepared and its wetting properties are tuned through polyvinyl alcohol (PVA) coating. Subsequently, a layer of Vanadium Carbide MXene (V2CTx) is derived from etching the Aluminium layer from Vanadium Aluminium Carbide (V2AlC) MAX phase. The V2CTx MXene is deposited onto the PVA-coated PVDF through vacuum deposition. This incorporation ensures that the V2CTx is deeply rooted within the substrate bolstering its separation capabilities with an underwater superoleophobic and in-air superhydrophilic surface. The bi-functional membrane serves as an essential experimental validation for the application of V2CTx MXene in treating oily wastewater. It efficiently separates oil and water while aiding in aqueous-oil demulsification, providing an innovative solution for wastewater treatment. Additionally, this membrane demonstrates effective adsorption of organic contaminants due to the presence of V2CTx MXene, further enhancing its remediation capabilities. Therefore, this work introduces a pioneering approach utilizing V2CTx MXene in treating oily wastewater.

Tunable magnetism in nitride MXenes: consequences of atomic layer stacking.

We have performed density functional theory (DFT) based calculations to investigate the effects of stacking patterns on the electronic and magnetic properties of several nitride MXenes. MXenes, a relatively new addition to the family of two-dimensional materials, have exhibited fascinating properties in several occasions, primarily due to their compositional flexibility. However, compared to carbide MXenes, nitride MXenes are much less explored. Moreover, the structural aspects of MXenes and the tunability they may offer have not been explored until recently. In this work, we have combined these two less-explored aspects to examine the structure-property relationships in the field of magnetism. We find that in the family of M2NT2 (M = Sc, Ti, V, Cr, Mn; T = O, F) MXenes, the stacking of transition metal planes has a substantial effect on the ground state and finite temperature magnetic properties. We also find that the electronic ground states can be tuned by changing the stacking pattern in these compounds, making the materials appropriate for applications as magnetic devices. Through a detailed analysis, we have connected the unconventional stacking pattern-driven tunability of these compounds with regard to electronic and magnetic properties to the local symmetry, inhomogeneity (or lack of it) of structural parameters, and electronic structures.

Facile synthesis of Eu3+-doped niobium carbide MXene quantum dots for parallel detection of hypoxanthine and fluoxetine via fluorescence quenching and enhancement mechanisms.

Ahydrothermal synthetic method is established to produce blue fluorescent Eu3+-doped niobium carbide MXene quantum dots (Eu3+-Nb2C MQDs). The synthesized Eu3+-Nb2C MQDs demonstrated a quantum yield of 20.61% and a maximum emission intensity at 405nm. The as-prepared Eu3+-Nb2C MQDs acted as a sensor for the rapid and sensitive detection of hypoxanthine through fluorescence quenching, and of fluoxetine through fluorescence enhancement mechanisms. The emission peak of Eu3+-Nb2C MQDs at 405nm exhibited a linear response for hypoxanthine and fluoxetine in the ranges of 0.5-25µM and 0.125-2.5µM, with detection limits of 15.0 and 3.7nM, respectively. The newly developed probe was effectively used for the selective detection of hypoxanthine and fluoxetine in biofluids and pharmaceutical samples. Remarkably, theEu3+-Nb2C MQDs exhibited minimal cytotoxicity towards A549 lung cancer cells and showed great potential as imaging agent for imaging of Saccharomyces cerevisiae cells.