Exploring the Influence of Critical Parameters for the Effective Synthesis of High-Quality 2D MXene

Laser-assisted exfoliation of Ti3C2Tx

As an emerging two-dimensional material, MXene has shown a wide range of applications, which has triggered the demand for efficient exfoliation of nanoflakes with large size and specific surface area. Here, we took advantage of the efficient photo-thermal conversion of Ti3C2Tx and employed 532 nm continuous wave laser irradiation to assist the traditional ultrasonic exfoliation, with no need for complex equipment and an expensive femtosecond or picosecond laser. This approach greatly improves the exfoliation efficiency, increases the size, uniformity and specific surface area of the Ti3C2Tx nanoflakes, and reduces energy consumption as well. The electrical conductivity of Ti3C2Tx film is also significantly enhanced (from 3135 to 7433 S m-1). It is demonstrated that the laser promotes the formation of Ti-OH and enhances the solubility of Ti3C2Tx in water, facilitating the exfoliation and preventing oxidation as a result.

Insights on updates in sodium alginate/MXenes composites as the designer matrix for various applications: A review

Advancements in two-dimensional materials, particularly MXenes, have spurred the development of innovative composites through their integration with natural polymers such as sodium alginate (SA). Mxenes exhibit a broad specific surface area, excellent electrical conductivity, and an abundance of surface terminations, which can be combined with SA to maximize the synergistic effect of the materials. This article provides a comprehensive review of state-of-the-art techniques in the fabrication of SA/MXene composites, analyzing the resulting structural and functional enhancements with a specific focus on advancing the design of these composites for practical applications. A detailed exploration of SA/MXene composites is provided, highlighting their utility in various sectors, such as wearable electronics, wastewater treatment, biomedical applications, and electromagnetic interference (EMI) shielding. The review identifies the unique advantages conferred by incorporating MXene in these composites, examines the current challenges, and proposes future research directions to understand and optimize these promising materials thoroughly. The remarkable properties of MXenes are emphasized as crucial for advancing the performance of SA-based composites, indicating significant potential for developing high-performance composite materials.

Molten salt synthesis of MXene-derived hierarchical titanate for effective strontium removal

The removal and recovery of radioactive Sr(II) from wastewater and seawater has been of great concern due to the negative environmental impacts of nuclear energy development and the potential risk of nuclear accidents. Herein, a facile molten salt synthesis strategy was developed to systematically investigated the reaction of different types of MXenes with nitrates. Among the products, K+ intercalated hierarchical titanate nanostructures (K-HTNs) obtained from the direct chemical transformation of multilayered Ti3C2Tx exhibited unique layered structures, good physicochemical properties, and outstanding adsorption performance for Sr(II). The maximum adsorption capacity of Sr(II) by K-HTNs reached 204 mg·g-1 at ambient temperature, and the good regeneration and reusability of the titanate was also demonstrated. K-HTNs showed preferential selectivity for Sr(II) in different environmental media containing competing ions, and the removal efficiency of Sr(II) in real seawater was as high as 93.3 %. The removal mechanism was elaborated to be the exchange of Sr2+ with K+/H+ in the interlayers of K-HTNs, and the adsorbed Sr(II) had a strong interaction with Ti-O- termination on the titanate surface. Benefiting from the merits of rapid and scalable synthesis and excellent adsorption performance, MXene-derived K-HTNs have broad application prospects for the purification of 90Sr-contaminated wastewater and seawater.

Water-Triggered Self-Healing of Ti3C2Tx MXene Standalone Electrodes: Systematic Examination of Factors Affecting the Healing Process

MXenes, with their remarkable attributes, stand at the forefront of diverse applications. However, the challenge remains in sustaining their performance, especially concerning Ti3C2Tx MXene electrodes. Current self-healing techniques, although promising, often rely heavily on adjacent organic materials. This study illuminates a pioneering water-initiated self-healing mechanism tailored specifically for standalone MXene electrodes. Here, both water and select organic solvents seamlessly mend impaired regions. Comprehensive evaluations around solvent types, thermal conditions, and substrate nuances underline water's unmatched healing efficacy, attributed to its innate ability to forge enduring hydrogen bonds with MXenes. Optimal healing environments range from ambient conditions to a modest 50 °C. Notably, on substrates rich in hydroxyl groups, the healing efficiency remains consistently high. The proposed healing mechanism encompasses hydrogen bonding formation, capillary action-induced expansion of interlayer spacing, solvent lubrication, Gibbs free energy minimizing MXene nanosheet rearrangement, and solvent evaporation-triggered MXene layer recombination. MXenes' resilience is further showcased by their electrical revival from profound damages, culminating in the crafting of Joule-heated circuits and heaters.

Ba2-xHoxSr2-yNiyFe12O22 and its composite with MXene: synthesis, characterization and enhanced visible light mediated photocatalytic activity for colored dye and pesticide

The rapid recombination of charges of photogenerated electrons and holes severely limits single semiconductor photocatalytic applications. In this study, a simple and facile sol-gel approach was used to synthesize Ba2-xHoxSr2-yNiyFe12O22 (x = 0, 0.1 and y = 0, 0.5). The composite of holmium-nickel doped barium-strontium ferrite with MXene (Ba1.9Ho0.1Sr1.5Ni0.5Fe12O22@MXene) was synthesized by ultrasonication method. These synthesized samples were subsequently used to photodegrade rhodamine B (RhB) and pendimethalin under visible light illumination. The results of the experiments demonstrated that MXene, as a cocatalyst, considerably reduces the rate of recombination of charges and broadens absorption of visible light by providing increased surface functional groups to improve the photocatalytic activity of synthesized samples. MXene is thermally stable, have high electrical conductivity, have adjustable bandgap, and hydrophilic in nature. The optimized Ba1.9Ho0.1Sr1.5Ni0.5Fe12O22@MXene composite demonstrated an excellent photocatalytic rate by degrading 78.88% RhB and 75.59% pendimethalin in 140 minutes. Moreover, the scavenging experiment revealed that photogenerated electrons and holes were the primary active species involved in RhB and pendimethalin photodegradation, respectively. Ba1.9Ho0.1Sr1.5Ni0.5Fe12O22@MXene showed increased photocatalytic behavior because it has increased surface area which decreases rate of recombination of electron and hole pair, hence photocatalytic activity increases. It is observed that Ba1.9Ho0.1Sr1.5Ni0.5Fe12O22@MXene has potential application in photocatalytic degradation of harmful pollutants.

Can MXene be the Effective Nanomaterial Family for the Membrane and Adsorption Technologies to Reach a Sustainable Green World?

Environmental pollution has intensified and accelerated due to a steady increase in the number of industries, and exploring methods to remove hazardous contaminants, which can be typically divided into inorganic and organic compounds, have become inevitable. Therefore, the development of efficacious technology for the separation processes is of paramount importance to ensure the environmental remediation. Membrane and adsorption technologies garnered attention, especially with the use of novel and high performing nanomaterials, which provide a target-specific solution. Specifically, widespread use of MXene nanomaterials in membrane and adsorption technologies has emerged due to their intriguing characteristics, combined with outstanding separation performance. In this review, we demonstrated the intrinsic properties of the MXene family for several separation applications, namely, gas separation, solvent dehydration, dye removal, separation of oil-in-water emulsions, heavy metal ion removal, removal of radionuclides, desalination, and other prominent separation applications. We highlighted the recent advancements used to tune separation potential of the MXene family such as the manipulation of surface chemistry, delamination or intercalation methods, and fabrication of composite or nanocomposite materials. Moreover, we focused on the aspects of stability, fouling, regenerability, and swelling, which deserve special attention when the MXene family is implemented in membrane and adsorption-based separation applications.

MXene-Based Nanocomposites for Piezoelectric and Triboelectric Energy Harvesting Applications

Due to its superior advantages in terms of electronegativity, metallic conductivity, mechanical flexibility, customizable surface chemistry, etc., 2D MXenes for nanogenerators have demonstrated significant progress. In order to push scientific design strategies for the practical application of nanogenerators from the viewpoints of the basic aspect and recent advancements, this systematic review covers the most recent developments of MXenes for nanogenerators in its first section. In the second section, the importance of renewable energy and an introduction to nanogenerators, major classifications, and their working principles are discussed. At the end of this section, various materials used for energy harvesting and frequent combos of MXene with other active materials are described in detail together with the essential framework of nanogenerators. In the third, fourth, and fifth sections, the materials used for nanogenerators, MXene synthesis along with its properties, and MXene nanocomposites with polymeric materials are discussed in detail with the recent progress and challenges for their use in nanogenerator applications. In the sixth section, a thorough discussion of the design strategies and internal improvement mechanisms of MXenes and the composite materials for nanogenerators with 3D printing technologies are presented. Finally, we summarize the key points discussed throughout this review and discuss some thoughts on potential approaches for nanocomposite materials based on MXenes that could be used in nanogenerators for better performance.

Role of Oxygen in the Ti3AlC2 MAX Phase in the Oxide Formation and Conductivity of Ti3C2-Based MXene Nanosheets

Ti₃C₂T_x MXene, a two-dimensional transition metal carbide, has attracted substantial interest due to its unique physical properties and a wide range of potential applications. Although the properties of devices using MXene have been substantially enhanced in recent years, it is not fully understood how the oxygen concentration in Ti₃AlC₂ MAX affects oxide formation in Ti₃C₂-based MXene nanosheets and their fundamental properties. To this end, we compared two types of MAX phases: MAX with low oxygen content (LO-MAX) and MAX synthesized by a conventional process. Since the conventional MAX synthesis employs metal (Ti) as a primary material, it is referred to as metal-based MAX (MB-MAX) from here. The oxygen content of the LO-MAX was only 0.56 wt %, which was about 20% compared to that of MAX synthesized using conventional methods. We compared the properties of MXene nanosheets prepared from the LO-MAX with MXene nanosheets obtained from the MB-MAX. Microscopic and chemical analyses revealed smooth and wrinkle-free morphology and small amounts of oxygen in MXene nanosheets prepared from LO-MAX (LO-MXene). The LO-MXene nanosheet film exhibited an exceptionally high conductivity of 10,540 S/cm and an ultralow surface roughness of 1.7 nm, which originated from inhibited surface oxide formation. Moreover, the inhibition of oxide formation strengthened the function of -O or -OH groups on the surface of MXene, thereby facilitating strong hydrogen bonding to the polymer with hydroxyl groups. To clearly reveal these properties, we prepared a pressure sensor by coating these MXene nanosheets on nylon/polyester fibers. The fabricated sensor exhibited a high sensitivity of up to 85.6/kPa and excellent stretch stability and reliability. These results clearly revealed that lowering the oxygen content in MAX can make a decisive contribution to improving the fundamental properties of MXene nanosheets prepared therefrom.

Advances in Titanium Carbide (Ti3C2T x ) MXenes and Their Metal-Organic Framework (MOF)-Based Nanotextures for Solar Energy Applications: A Review

Introducing new materials with low cost and superior solar harvesting efficiency requires urgent attention to solve energy and environmental challenges. Titanium carbide (Ti₃C₂T _x ) MXene, a 2D layered material, is a promising solution to solve the issues of existing materials due to their promising conductivity with low cost to function as a cocatalyst/support. On the other hand, metal-organic frameworks (MOFs) are emerging materials due to their high surface area and semiconducting characteristics. Therefore, coupling them would be promising to form composites with higher solar harvesting efficiency. Thus, the main objective of this work to disclose recent development in Ti₃C₂T _x -based MOF nanocomposites for energy conversion applications to produce renewable fuels. MOFs can generate photoinduced electron/hole pairs, followed by transfer of electrons to MXenes through Schottky junctions for photoredox reactions. Currently, the principles, fundamentals, and mechanism of photocatalytic systems with construction of Schottky junctions are critically discussed. Then the basics of MOFs are discussed thoroughly in terms of their physical properties, morphologies, optical properties, and derivatives. The synthesis of Ti₃C₂T _x MXenes and their composites with the formation of surface functionals is systematically illustrated. Next, critical discussions are conducted on design considerations and strategies to engineer the morphology of Ti₃C₂T _x MXenes and MOFs. The interfacial/heterojunction modification strategies of Ti₃C₂T _x MXenes and MOFs are then deeply discussed to understand the roles of both materials. Following that, the applications of MXene-mediated MOF nanotextures in view of CO₂ reduction and water splitting for solar fuel production are critically analyzed. Finally, the challenges and a perspective toward the future research of MXene-based MOF composites are disclosed.

Advances of MXenes; Perspectives on Biomedical Research

The last decade witnessed the emergence of a new family of 2D transition metal carbides and nitrides named MXenes, which quickly gained momentum due to their exceptional electrical, mechanical, optical, and tunable functionalities. These outstanding properties also rendered them attractive materials for biomedical and biosensing applications, including drug delivery systems, antimicrobial applications, tissue engineering, sensor probes, auxiliary agents for photothermal therapy and hyperthermia applications, etc. The hydrophilic nature of MXenes with rich surface functional groups is advantageous for biomedical applications over hydrophobic nanoparticles that may require complicated surface modifications. As an emerging 2D material with numerous phases and endless possible combinations with other 2D materials, 1D materials, nanoparticles, macromolecules, polymers, etc., MXenes opened a vast terra incognita for diverse biomedical applications. Recently, MXene research picked up the pace and resulted in a flood of literature reports with significant advancements in the biomedical field. In this context, this review will discuss the recent advancements, design principles, and working mechanisms of some interesting MXene-based biomedical applications. It also includes major progress, as well as key challenges of various types of MXenes and functional MXenes in conjugation with drug molecules, metallic nanoparticles, polymeric substrates, and other macromolecules. Finally, the future possibilities and challenges of this magnificent material are discussed in detail.

Synthesis, Characterization, Photocatalysis, and Antibacterial Study of WO3, MXene and WO3/MXene Nanocomposite

Tungsten oxide (WO₃), MXene, and an WO₃/MXene nanocomposite were synthesized to study their photocatalytic and biological applications. Tungsten oxide was synthesized by an easy and cost-effective hydrothermal method, and its composite with MXene was prepared through the sonication method. The synthesized tungsten oxide, MXene, and its composite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), energy-dispersive X-ray analysis (EDX), and Brunauer–Emmett–Teller (BET) for their structural, morphological, spectral, elemental and surface area analysis, respectively. The crystallite size of WO₃ calculated from XRD was ~10 nm, the particle size of WO₃ was 130 nm, and the average thickness of MXene layers was 175 nm, which was calculated from FESEM. The photocatalytic activity of as-synthesized samples was carried out for the degradation of methylene blue under solar radiation, MXene, the WO₃/MXene composite, and WO₃ exhibited 54%, 89%, and 99% photocatalytic degradation, respectively. WO₃ showed maximal degradation ability; by adding WO₃ to MXene, the degradation ability of MXene was enhanced. Studies on antibacterial activity demonstrated that these samples are good antibacterial agents against positive strains, and their antibacterial activity against negative strains depends upon their concentration. Against positive strains, the WO₃/MXene composite’s inhibition zone was at 7 mm, while it became 9 mm upon increasing the concentration. This study proves that WO₃, MXene, and the WO₃/MXene nanocomposite could be used in biological and environmental applications.

2D metal carbides and nitrides (MXenes) for sensors and biosensors

MXenes are layered two-dimensional (2D) materials discovered in 2011 (Ti₃C₂X) and are otherwise called 2D transition metal carbides, carbonitrides, and nitrides. These 2D layered materials have been in the limelight for a decade due to their interesting properties such as large surface area, high ion transport, biocompatibility, and low diffusion barrier. Therefore, MXenes are widely preferred by researchers for applications in electronics, sensing, biosensing, electrocatalysis, super-capacitors and fuel cells. There are a number of methods available for the bulk synthesis of MXene-based nanomaterials. In addition, the possibility of structural modification as required and its outstanding surface chemistry offer a fascinating interface for the development of novel biosensors. In this review, we specifically discuss important MXene synthesis routes. Moreover, critical parameters such as surface functionalization that can dictate the mechanical, electronic, magnetic, and optical properties of MXenes are also discussed. Following this, methods available for the surface functionalization and modification strategies of MXenes are also discussed. Furthermore, the emergence of gas, electrochemical, and optical biosensors based on MXenes since its first report is discussed in detail. Finally, future directions of MXenes biosensors for critical applications are discussed.

MXene: Evolutions in Chemical Synthesis and Recent Advances in Applications

Two-dimensional materials have secured a novel area of research in material science after the emergence of graphene. Now, a new family of 2D material-MXene is gradually growing and making itsmark in this field of study. MXenes since 2011 have been synthesized and experimented on in several ways.The HF treatment although successful poses some serious problems that gradually propelled the ideas of new synthesis methods. This review of the literature covers the major breakthroughs of MXene from the year of its discovery to recent endeavors, highlighting how the synthesis mechanisms have been developed over the years and also the importance of good characterization of data. Results and properties of this class of materials arealso briefly discussed alongwith recent advance in applications.

Emerging 2D Nanomaterials for Biomedical Applications

Two-dimensional (2D) nanomaterials are an emerging class of biomaterials with remarkable potential for biomedical applications. The planar topography of these nanomaterials confers unique physical, chemical, electronic and optical properties, making them attractive candidates for therapeutic delivery, biosensing, bioimaging, regenerative medicine, and additive manufacturing strategies. The high surface-to-volume ratio of 2D nanomaterials promotes enhanced interactions with biomolecules and cells. A range of 2D nanomaterials, including transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), layered silicates (nanoclays), 2D metal carbides and nitrides (MXenes), metal-organic framework (MOFs), covalent organic frameworks (COFs) and polymer nanosheets have been investigated for their potential in biomedical applications. Here, we will critically evaluate recent advances of 2D nanomaterial strategies in biomedical engineering and discuss emerging approaches and current limitations associated with these nanomaterials. Due to their unique physical, chemical, and biological properties, this new class of nanomaterials has the potential to become a platform technology in regenerative medicine and other biomedical applications.

Investigation and Optimization of Mxene Functionalized Mesoporous Titania Films as Efficient Photoelectrodes

Three-dimensional mesoporous TiO2 scaffolds of anatase phase possess inherent eximious optical behavior that is beneficial for photoelectrodes used for solar energy conversion applications. In this regard; substantial efforts have been devoted to maximizing the UV and/or visible light absorption efficiency; and suppressing the annihilation of photogenerated charged species; in pristine mesoporous TiO2 structures for improved solar illumination conversion efficiency. This study provides fundamental insights into the use of Mxene functionalized mesoporous TiO2 as a photoelectrode. This novel combination of Mxene functionalized TiO2 electrodes with and without TiCl4 treatment was successfully optimized to intensify the process of photon absorption; charge segregation and photocurrent; resulting in superior photoelectrode performance. The photocurrent measurements of the prepared photoelectrodes were significantly enhanced with increased contents of Mxene due to improved absorption efficiency within the visible region; as verified by UV-Vis absorption spectroscopy. The anatase phase of TiO2 was significantly augmented due to increased contents of Mxene and postdeposition heat treatments; as evidenced by structural analysis. Consequently; an appreciable coverage of well-developed grains on the FTO surface was observed in SEM images. As such; these newly fabricated conductive mesoporous TiO2 photoelectrodes are potential candidates for photoinduced energy conversion and storage applications.

Efficient photocatalytic degradation of hazardous pollutants by homemade kitchen blender novel technique via 2D-material of few-layer MXene nanosheets

To attain elevated class MXene (Ti₃C₂Tx) through a homemade kitchen blender method, high shear mechanical exfoliation is highly required for the efficient delimitations of MXene nanosheets from bulk MAX (Ti₃AlC₂). We examine large-scale industrial productions of the MXene nanosheets, where combing the predicted 2D materials using a blender is a first-time novel approach with the delaminating solvent as a dimethyl sulfoxide (DMSO). And also manually created layered MXene systems (handmade) delaminating MXene sheets (MX-H) was furthermore employed for environmental dye-degradations applications. The materials characterizations was done for both the bulk MAX, MX-H and the MX-B. Additionally, the surface morphological studies like scanning electron microscopy (SEM) were investigated for both MX-H and MX-B as-prepared samples. SEM images indicated the high shear blander technique formations highly expanded/delaminated MXene (Ti₃C₂Tx) nanosheets compared to MX-H samples. FTIR technique is employed to identify -OH, C-H, C-O stretching vibrations for both materials. Raman spectroscopy analysis of MX-H and MX-B revealed 484.80 cm^-1 Raman shift assigned to E1g phonon mode of (Ti, C, O). The ultraviolet UV visible absorption spectra explored pure and catalyst added Methylene Blue (MB) dye stock solution using annular type photoreactor with visible light source of 300 W. The comparatives of MAX, MX-H and MX-B samples was investigated as photocatalytic activity, The blender made (MX-B) sample revealed 98% of efficiency.

Effects of MXene on Nonisothermal Crystallization Kinetics of Isotactic Polypropylene

MXenes, a family of two-dimensional transition-metal carbides/nitrides, have attracted great attention and shown promising application in polymer composites. In this study, a typical MXene Ti3C2T x was prepared by selective etching. The structure and morphology of Ti3C2T x were studied by X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy, and the results proved that Ti3C2T x was successively fabricated. Then, Ti3C2T x /isotactic polypropylene composites with different Ti3C2T x dosages were fabricated, and the nonisothermal crystallization kinetics and melting behavior of the composites were investigated. The results indicated that when a small amount of Ti3C2T x was added, the crystallization parameters including the crystallization peak temperature and the crystallization rate increased, suggesting that crystallization was promoted. When the weight percentage of Ti3C2T x exceeded 1%, the crystallization parameters showed a reverse trend, suggesting that crystallization was hindered. The activation energy of composites with 0, 0.25, 0.5, and 1 wt % Ti3C2T x were calculated to be -164.5, -196.5, -193.8, and -147.95 kJ/mol, respectively, revealing that the crystallization of composites is concentration-dependent. The impact of Ti3C2T x dosage on the crystalline structure of the composites was studied using XRD. The related mechanism was proposed.

Recent advances in MXene-based force sensors: a mini-review

As an emerging two-dimensional (2D) material, MXene has excellent conductivity and abundant surface functional groups. Its unique layered structure, large surface area, and prominent hydrophilicity show remarkable performances, which allow abundant possibilities to work as the sensing element alone or combined with other auxiliary materials. As a senior member of MXenes, Ti₃C₂T_x has shown great potential in the development of force sensors. The research development of force sensors based on Ti₃C₂T_x MXene is reviewed in this paper, presenting the advanced development of force sensors in various forms and summaring their current preparation strategies and characteristics. In addition, the corresponding challenges and prospects of the MXene-based sensors are also discussed for future research.

As an emerging two-dimensional (2D) material, MXene has excellent conductivity and abundant surface functional groups.