Mxene functionalized polymer composites: Synthesis and applications

Application Scopes of Miniaturized MXene-Functionalized Electrospun Nanofibers-Based Electrochemical Energy Devices

Exploring combinatorial materials, as well as rational device configuration design, are assumed to be the key strategies for deploying versatile electrochemical devices. MXene sheets have revealed a high hydrophilic surface with proper mechanical and electrical characteristics, rendering them supreme additive candidates to integrate in electrospun electrochemical power tools. The synergetic effects of MXene 2D layers with the nanofibrous networks can boost actuator responsive ability, battery capacity retention, fuel cell stability, sensor sensitivity, and supercapacitor areal capacitance. Their superior mechanical features can be endowed to the electrospun layers through the embedding of the MXene additive. In this review, the preparation and inherent features of the MXene configurations are briefly evaluated. The fabrication and overall performance of the MXene-loaded nanofibers applicable in electrochemical actuators, batteries, fuel cells, sensors, and supercapacitors are comprehensively figured out. Eventually, an outlook on the future development of MXene-based electrospun composites is presented. A substantial focus has been devoted to date to engineering conjugated MXene and electrospun fibrous frames. The potential performance of the MXene-decorated nanofibers presents a bright future of nanoengineering toward technological growth. Meanwhile, a balance between the pros and cons of the synthesized MXene composite layers is worthwhile to consider in the future.

MXenes-polymer nanocomposites for biomedical applications: fundamentals and future perspectives

The article discusses the promising synergy between MXenes and polymers in developing advanced nanocomposites with diverse applications in biomedicine domains. MXenes, possessing exceptional properties, are integrated into polymer matrices through various synthesis and fabrication methods. These nanocomposites find applications in drug delivery, imaging, diagnostics, and environmental remediation. They offer improved therapeutic efficacy and reduced side effects in drug delivery, enhanced sensitivity and specificity in imaging and diagnostics, and effectiveness in water purification and pollutant removal. The perspective also addresses challenges like biocompatibility and toxicity, while suggesting future research directions. In totality, it highlights the transformative potential of MXenes-polymer nanocomposites in addressing critical issues across various fields.

Progress and Perspective in harnessing MXene-carbon-based composites (0-3D): Synthesis, performance, and applications

MXene is recognized as a promising catalyst for versatile applications due to its abundant metal sites, physicochemical properties, and structural formation. This comprehensive review offers an in-depth analysis of the incorporation of carbon into MXene, resulting in the formation of MXene-carbon-based composites (MCCs). Pristine MXene exhibits numerous outstanding characteristics, such as its atomically thin 2D structure, hydrophilic surface nature, metallic electrical conductivity, and substantial specific surface area. The introduction of carbon guides the assembly of MCCs through electrostatic self-assembly, pairing positively charged carbon with negatively charged MXene. These interactions result in increased interlayer spacing, reduced ion/electron transport distances, and enhanced surface hydrophilicity. Subsequent sections delve into the synthesis methods for MCCs, focusing on MXene integrated with various carbon structures, including 0D, 1D, 2D, and 3D carbon. Comprehensive discussions explore the distinctive properties of MCCs and the unique advantages they offer in each application domain, emphasizing the contributions and advancements they bring to specific fields. Furthermore, this comprehensive review addresses the challenges encountered by MCCs across different applications. Through these analyses, the review promotes a deeper understanding of exceptional characteristics and potential applications of MCCs. Insights derived from this review can serve as guidance for future research and development efforts, promoting the widespread utilization of MCCs across a broad spectrum of disciplines and spurring future innovations.

MXene-Based Elastomer Mimetic Stretchable Sensors: Design, Properties, and Applications

Flexible sensors based on MXene-polymer composites are highly prospective for next-generation wearable electronics used in human-machine interfaces. One of the motivating factors behind the progress of flexible sensors is the steady arrival of new conductive materials. MXenes, a new family of 2D nanomaterials, have been drawing attention since the last decade due to their high electronic conductivity, processability, mechanical robustness and chemical tunability. In this review, we encompass the fabrication of MXene-based polymeric nanocomposites, their structure-property relationship, and applications in the flexible sensor domain. Moreover, our discussion is not only limited to sensor design, their mechanism, and various modes of sensing platform, but also their future perspective and market throughout the world. With our article, we intend to fortify the bond between flexible matrices and MXenes thus promoting the swift advancement of flexible MXene-sensors for wearable technologies.

Constructed MXene matrix composites as sensing material and applications thereof: A review

Most studies on MXene matrix composites for sensor development have primarily focused on synthesis and application. Nevertheless, there is currently a lack of research on how the introduction of different materials affects the sensing properties of these composites. The rapid development of MXene has raised intriguing questions about improving sensor performance by combining MXene with other materials such as polymers, metals and inorganic non-metals. This review will concentrate on the construction of MXene-based composites and explore ways to enhance their sensor applications. Specifically, this review describes why the introduction of materials to the system brings the advantage of low concentration and high sensitivity assays, as well as the MXene-based frameworks that have been recently investigated. Lastly, in order to capture the current trend of MXene-based composites in sensor applications and identify promising research directions, this review will critically evaluate the potential applications of newly developed MXene systems.

Recent Advances in Photothermal Therapy at Near-Infrared-II Based on 2D MXenes

The use of photothermal therapy (PTT) with the near-infrared II region (NIR-II: 1000-1700 nm) is expected to be a powerful cancer treatment strategy. It retains the noninvasive nature and excellent temporal and spatial controllability of the traditional PTT, and offers significant advantages in terms of tissue penetration depth, background noise, and the maximum permissible exposure standards for skin. MXenes, transition-metal carbides, nitrides, and carbonitrides are emerging inorganic nanomaterials with natural biocompatibility, wide spectral absorption, and a high photothermal conversion efficiency. The PTT of MXenes in the NIR-II region not only provides a valuable reference for exploring photothermal agents that respond to NIR-II in 2D inorganic nanomaterials, but also be considered as a promising biomedical therapy. First, the synthesis methods of 2D MXenes are briefly summarized, and the laser light source, mechanism of photothermal conversion, and evaluation criteria of photothermal performance are introduced. Second, the latest progress of PTT based on 2D MXenes in NIR-II are reviewed, including titanium carbide (Ti3 C2 ), niobium carbide (Nb2 C), and molybdenum carbide (Mo2 C). Finally, the main problems in the PTT application of 2D MXenes to NIR-II and future research directions are discussed.

Significantly Enhanced Balance of Dielectric Properties of Polyvinylidene Difluoride Three-Phase Composites by Silver Deposited on K2Ni0.93Ti7.07O16 Hollandite Nanoparticles

Three-phase polymer composites are promising materials for creating electronic device components. The qualitative and quantitative composition of such composites has a significant effect on their functional, in particular dielectric properties. In this study, ceramic filler K2Ni0.93Ti7.07O16 (KNTO) with Ag coating as conductive additive (0.5, 1.0, 2.5 wt.%) was introduced into the polyvinylidene difluoride (PVDF) polymer matrix in amounts of 7.5, 15, 22.5, and 30 vol.%. to optimize the dielectric constant and dielectric loss tangent. The filler was characterized by X-ray phase analysis, Fourier-transform infrared spectroscopy and Scanning electron microscopy methods. The dielectric constant, dielectric loss tangent, and conductivity of three-phase composites KNTO@Ag-PVDF were studied in comparison with two-phase composites KNTO-PVDF in the frequency range from 102 Hz to 106 Hz. The dielectric constant values of composites containing 7.5, 15, 22.5, and 30 vol.% filler were 12, 13, 17.4, 19.2 for pure KNTO and 13, 19, 25, 31 for KNTO@Ag filler (2.5 wt.%) at frequency 10 kHz. The dielectric loss tangent ranged from 0.111 to 0.340 at a filler content of 7.5 to 30 vol.%. A significantly enhanced balance of dielectric properties of PVDF-based composites was found with K2Ni0.93Ti7.07O16 as ceramic filler for 1 wt.% of silver. Composites KNTO@Ag(1 wt.%)-PVDF can be applied as dielectrics for passive elements of flexible electronics.

Electrochemistry of Titanium Carbide MXenes in Supercapacitor

Novel electrode materials are always explored to achieve better performance of supercapacitors. Titanium carbide MXenes, Ti3 C2 Tx , are one of the very promising candidates for electrode materials in supercapacitors due to their unique structural and ion storage properties as 2D materials. Their large specific surface area, adjustable functionalized surface terminals, high electrical conductivities, hydrophilicity, and high Faradaic capacitance, also known widely but confusingly as pseudocapacitance, are highly desirable for making high-performance electrodes with increased dis-/charging rates and capacities. Herein, some selective electrochemical considerations of Ti3 C2 Tx MXenes for uses in supercapacitors are critically reviewed and assessed, aiming at a better fundamental understanding of the electrochemical basics and processes in Ti3 C2 Tx MXene-based electrode materials for supercapacitor applications.

Structural design and preparation of Ti3C2Tx MXene/polymer composites for absorption-dominated electromagnetic interference shielding

Electromagnetic interference (EMI) is a pervasive and harmful phenomenon in modern society that affects the functionality and reliability of electronic devices and poses a threat to human health. To address this issue, EMI-shielding materials with high absorption performance have attracted considerable attention. Among various candidates, two-dimensional MXenes are promising materials for EMI shielding due to their high conductivity and tunable surface chemistry. Moreover, by incorporating magnetic and conductive fillers into MXene/polymer composites, the EMI shielding performance can be further improved through structural design and impedance matching. Herein, we provide a comprehensive review of the recent progress in MXene/polymer composites for absorption-dominated EMI shielding applications. We summarize the fabrication methods and EMI shielding mechanisms of different composite structures, such as homogeneous, multilayer, segregated, porous, and hybrid structures. We also analyze the advantages and disadvantages of these structures in terms of EMI shielding effectiveness and the absorption ratio. Furthermore, we discuss the roles of magnetic and conductive fillers in modulating the electrical properties and EMI shielding performance of the composites. We also introduce the methods for evaluating the EMI shielding performance of the materials and emphasize the electromagnetic parameters and challenges. Finally, we provide insights and suggestions for the future development of MXene/polymer composites for EMI shielding applications.

Graphene composite paper synergized with micro/nanocellulose-fiber and silk fibroin for flexible strain sensor

The fabrication of uniform and strong graphene-based conductive paper is challenging due to easy aggregation and poor film formability of graphene. Herein, on the basis of good dispersing effect of nanocellulose, high content graphene (50 wt%) composite paper with micro/nanocellulose fibers and silk fibroin (SF) was manufactured via simple casting method. The synergistic effects of cellulose microfibers (CMFs), cellulose nanofibers (CNFs) and SF result in the paper with ideal combination of flexibility, electrical conductivity and mechanical strength, where CNFs, CMFs and SF act as dispersing and film forming for GNPs, dimensional stability, and interfacial binding agents, respectively. Extraordinarily, by adding SF, graphene nanosheets are tightly coated on the surface of CMFs. The composite paper shows a tensile strength of 49.29 MPa, surface resistance of 39.0-42.1 Ω and good joints bend sensing performance. Additionally, it is found that CMFs can hinder the micro-cracks from propagating during the cyclic elbow bending test. The graphene-based conductive paper is helpful for the development of smart clothing wearable biosensing devices.

Macroscale Superlubricity Induced by MXene/MoS2 Nanocomposites on Rough Steel Surfaces under High Contact Stresses

Toward the goal of achieving superlubricity, or near-zero friction, in industrially relevant material systems, solution-processed multilayer Ti₃C₂T_x-MoS₂ blends are spray-coated onto rough 52100-grade steel surfaces as a solid lubricant. The tribological performance was assessed in a ball-on-disk configuration in a unidirectional sliding mode. The test results indicate that Ti₃C₂T_x-MoS₂ nanocomposites led to superlubricious states, which has hitherto been unreported for both individual pristine materials, MoS₂ and Ti₃C₂T_x, under macroscale sliding conditions, indicating a synergistic mechanism enabling the superlative performance. The processing, structure, and property correlation were studied to understand the underlying phenomena. Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed the formation of an in situ robust tribolayer that was responsible for the performance at high contact pressures (>1.1 GPa) and sliding speeds (0.1 m/s). This report presents the lowest friction obtained by either MoS₂ or MXene or any combination of the two so far.

In Situ Growth of Ni-MOF Nanorods Array on Ti3C2Tx Nanosheets for Supercapacitive Electrodes

For the energy supply of smart and portable equipment, high performance supercapacitor electrode materials are drawing more and more concerns. Conductive Ni-MOF is a class of materials with higher conductivity compared with traditional MOFs, but it continues to lack stability. Specifically, MXene (Ti₃C₂T_x) has been employed as an electrochemical substrate for its high mechanical stability and abundant active sites, which can be combined with MOFs to improve its electrochemical performance. In this paper, a novel Ni-MOF nanorods array/Ti₃C₂T_x nanocomposite was prepared via a facile hydrothermal reaction, which makes good use of the advantages of conductive Ni-MOF and high strength Ti₃C₂T_x. The high density forest-like Ni-MOF array in situ grown on the surface of Ti₃C₂T_x can provide abundant active electrochemical sites and construct a pathway for effective ion transport. The formation of a "Ti-O···Ni" bond accomplished during an in situ growth reaction endows the strong interfacial interaction between Ni-MOF and Ti₃C₂T_x. As a result, the Ni-MOF/Ti₃C₂T_x nanocomposite can achieve a high specific capacitance of 497.6 F·g^-1 at 0.5 A·g^-1 and remain over 66% of the initial capacitance when the current density increases five times. In addition, the influence of the Ti₃C₂T_x concentration and reaction time on the morphology and performance of the resultant products were also investigated, leading to a good understanding of the formation process of the nanocomposite and the electrochemical mechanism for a supercapacitive reaction.

MXenes Functionalized with Macrocyclic Hosts: From Molecular Design to Applications

Two-dimensional (2D) MXene has aroused wide attention for its excellent physical and chemical properties. The interlayer engineering formed by layer-by-layer stacking of MXene nanosheets can be employed for molecular sieving and water purification by incorporating specific groups onto the exterior surface of MXene. Macrocyclic hosts exhibiting unique structural features and recognition ability can construct smart devices for external stimuli with reversible features between macrocycles and guests. On that basis, macrocyclic hosts can be anchored to MXene to provide numerous insights into their compositions and intercalation states. In this review, the MXene prepared based on macrocyclic hosts from molecular design to applications is highlighted. Various MXenes functionalized with macrocyclic hosts are empowered in functional membrane (including water purification, organic solvent nanofiltration, and electromagnetic shielding), photocatalysis, sensing, and adsorption (interactions with specific guest). Hopefully, this review can bring new inspiration to the design of multifunctional MXene-based materials and improving its practical applications.

2D MXene-Based Biosensing: A Review

MXene emerged as decent 2D material and has been exploited for numerous applications in the last decade. The remunerations of the ideal metallic conductivity, optical absorbance, mechanical stability, higher heterogeneous electron transfer rate, and good redox capability have made MXene a potential candidate for biosensing applications. The hydrophilic nature, biocompatibility, antifouling, and anti-toxicity properties have opened avenues for MXene to perform in vitro and in vivo analysis. In this review, the concept, operating principle, detailed mechanism, and characteristic properties are comprehensively assessed and compiled along with breakthroughs in MXene fabrication and conjugation strategies for the development of unique electrochemical and optical biosensors. Further, the current challenges are summarized and suggested future aspects. This review article is believed to shed some light on the development of MXene for biosensing and will open new opportunities for the future advanced translational application of MXene bioassays.

Investigation of improved optical and conductivity properties of poly(methyl methacrylate)–MXenes (PMMA–MXenes) nanocomposite thin films for optoelectronic applications

Polymer matrix composites composed of poly(methyl methacrylate) (PMMA) and MXenes (Ti3C2T x ) are synthesized using direct solution blending and casting techniques. MXenes are a new family of two-dimensional materials. Both optical and conductivity properties of the resulting PMMA-MXene nanocomposite thin films are studied as a function of MXene concentration, for the first time. The resulting thin films are in the micrometer range (8.10–8.80 µm) in thickness. As the concentration of MXenes increases, the PMMA embeds MXenes, causing structural disturbance but without any change in the crystal structure. The MXene thickness in single-layered structure is 15–20 nm. Optical investigations such as UV-Vis absorption, absorption coefficient, extinction coefficient, and band gap have been reported to study the light absorption of nanocomposites. Resistivity measurement associated with electrical conductivity is studied. The relationship between optical responses and electrical conductivity is discussed. When compared to pure PMMA (1 × 10−14 to 1 × 10−13 S m−1), nanocomposites have electrical conductivity that is more than 3,000 times higher. The nanocomposites containing 15 wt% MXenes had the highest conductivity of 1.35 × 10−3 S m−1. Both the conductivity improvement and tunable optical findings accelerate the route of integrating MXenes into polymers to create more promising multifunctional composites for optoelectronic applications such as conductive electrodes, thin film transistors, and logic circuits.

Applications of MXene-Containing Polypyrrole Nanocomposites in Electrochemical Energy Storage and Conversion

The atomically thick two-dimensional (2D) materials are at the forefront of revolutionary technologies for energy storage devices. Due to their fascinating physical and chemical features, these materials have gotten a lot of attention. They are particularly appealing for a wide range of applications, including electrochemical storage systems, due to their simplicity of property tuning. The MXene is a type of 2D material that is widely recognized for its exceptional electrochemical characteristics. The use of these materials in conjunction with conducting polymers, notably polypyrrole (PPy), has opened new possibilities for lightweight, flexible, and portable electrodes. Therefore, herein we report a comprehensive review of recent achievements in the production of MXene/PPy nanocomposites. The structural-property relationship of this class of nanocomposites was taken into consideration with an elaborate discussion of the various characterizations employed. As a result, this research gives a narrative explanation of how PPy interacts with distinct MXenes to produce desirable high-performance nanocomposites. The effects of MXene incorporation on the thermal, electrical, and electrochemical characteristics of the resultant nanocomposites were discussed. Finally, it is critically reviewed and presented as an advanced composite material in electrochemical storage devices, energy conversion, electrochemical sensors, and electromagnetic interference shielding.

Ti3C2Tx MXene Polymer Composites for Anticorrosion: An Overview and Perspective

As the most studied two-dimensional (2D) material from the MXene family, Ti₃C₂T_x has constantly gained interest from academia and industry. Ti₃C₂T_x MXene has the highest electrical conductivity (up to 24,000 S cm^-1) and one of the highest stiffness values with a Young's modulus of ∼ 334 GPa among water-dispersible conductive 2D materials. The negative surface charge of MXene helps to disperse it well in aqueous and other polar solvents. This solubility across a wide range of solvents, excellent interface interaction, tunable surface functionality, and stability with other organic/polymeric materials combined with the layered structure of Ti₃C₂T_x MXene make it a promising material for anticorrosion coatings. While there are many reviews on Ti₃C₂T_x MXene polymer composites for catalysis, flexible electronics, and energy storage, to our knowledge, no review has been published yet on MXenes' anticorrosion applications. In this brief report, we summarize the current progress and the development of Ti₃C₂T_x polymer composites for anticorrosion. We also provide an outlook and discussion on possible ways to improve the exploitation of Ti₃C₂T_x polymer composites as anticorrosive materials. Finally, we provide a perspective beyond Ti₃C₂T_x MXene composition for the development of future anticorrosion coatings.

The physio-chemical properties and applications of 2D nanomaterials in agricultural and environmental sustainability

Global hunger and nutritional deficiency demand the advancement of existing and conventional approaches to food production. The application of nanoenabled strategies in agriculture has opened up new avenues for enhancing crop yield and productivity. Recently, two-dimensional (2D) nanomaterials (NMs) have manifested new possibilities for increasing food production and nutrition. Graphene nanosheets, the 2D form of graphene has been exemplary in enhancing the loading capacity of agro-active ingredients, their target-specific delivery, bioavailability, and controlled release with slow degradation, resulting in the increased shelf-life/active time of the agro-active components. Also, the development of novel formulations/composites of MXenes and Transition Metal Dichalcogenides (TMDs) can foster plant growth, metabolism, crop production, protection and improvement of soil quality. Additionally, the 2D NM-based biosensors can monitor the nutrient levels and other parameters affecting agronomical traits in plants. This review provides an insight into the details of 2D NM synthesis and functionalization methods. Notably, the review highlights the broad-range of 2D NM applications and their suitability in the development of nanotechnology-based agriformulations. The 2D NM-based derivatives have shown immense potential in enhancing the pedologic parameters, crop productivity, pest-protection and nutritional value. Thus, assisting in achieving food and environmental sustainability goals.

MXene-Chitosan Composites and Their Biomedical Potentials

Today, MXenes with fascinating electronic, thermal, optical, and mechanical features have been broadly studied for biomedical applications, such as drug/gene delivery, photothermal/photodynamic therapy, antimicrobials/antivirals, sensing, tissue engineering, and regenerative medicine. In this context, various MXene-polymer composites have been designed to improve the characteristics such as physiological stability, sustained/controlled release behaviors, biodegradability, biocompatibility, selectivity/sensitivity, and functionality. Chitosan with advantages of ease of modification, biodegradability, antibacterial activities, non-toxicity, and biocompatibility can be considered as attractive materials for designing hybridized composites together with MXenes. These hybrid composites ought to be further explored for biomedical applications because of their unique properties such as high photothermal conversion efficiency, improved stability, selectivity/sensitivity, stimuli-responsiveness behaviors, and superior antibacterial features. These unique structural, functional, and biological attributes indicate that MXene-chitosan composites are attractive alternatives in biomedical engineering. However, several crucial aspects regarding the surface functionalization/modification, hybridization, nanotoxicological analyses, long-term biosafety assessments, biocompatibility, in vitro/in vivo evaluations, identification of optimization conditions, implementation of environmentally-benign synthesis techniques, and clinical translation studies are still need to be examined by researchers. Although very limited studies have revealed the great potentials of MXene-chitosan hybrids in biomedicine, the next steps should be toward the extensive research and detailed analyses in optimizing their properties and improving their functionality with a clinical and industrial outlook. Herein, recent developments in the use of MXene-chitosan composites with biomedical potentials are deliberated, with a focus on important challenges and future perspectives. In view of the fascinating properties and multifunctionality of MXene-chitosan composites, these hybrid materials can open significant new opportunities in the future for bio- and nano-medicine arena.

C. D, Karki B, Samatha K, Kim AA, Park M, Pant B. Advancements in MXene-Polymer Nanocomposites in Energy Storage and Biomedical Applications

MXenes are 2D ceramic materials, especially carbides, nitrides, and carbonitrides derived from their parent ‘MAX’ phases by the etching out of ‘A’ and are famous due to their conducting, hydrophilic, biocompatible, and tunable properties. However, they are hardly stable in the outer environment, have low biodegradability, and have difficulty in drug release, etc., which are overcome by MXene/Polymer nanocomposites. The MXenes terminations on MXene transferred to the polymer after composite formation makes it more functional. With this, there is an increment in photothermal conversion efficiency for cancer therapy, higher antibacterial activity, biosensors, selectivity, bone regeneration, etc. The hydrophilic surfaces become conducting in the metallic range after the composite formation. MXenes can effectively be mixed with other materials like ceramics, metals, and polymers in the form of nanocomposites to get improved properties suitable for advanced applications. In this paper, we review different properties like electrical and mechanical, including capacitances, dielectric losses, etc., of nanocomposites more than those like Ti₃C₂T_x/polymer, Ti₃C₂/UHMWPE, MXene/PVA-KOH, Ti₃C₂T_x/PVA, etc. along with their applications mainly in energy storing and biomedical fields. Further, we have tried to enlist the MXene-based nanocomposites and compare them with conducting polymers and other nanocomposites. The performance under the NIR absorption seems more effective. The MXene-based nanocomposites are more significant in most cases than other nanocomposites for the antimicrobial agent, anticancer activity, drug delivery, bio-imaging, biosensors, micro-supercapacitors, etc. The limitations of the nanocomposites, along with possible solutions, are mentioned.

Graphene-based TiO2 composites for photocatalysis & environmental remediation: synthesis and progress

Photoactive nanomaterials constitute an emerging field in nanotechnology, finding an extensive array of applications spanning diverse areas, including electronics and photovoltaic devices, solar fuel cells, wastewater treatment, etc. Titanium dioxide (TiO₂), in its thin-film form, has been exhaustively surveyed as potential photocatalysts for environmental remediation owing to its innocuousness, stability, and photocatalytic characteristics when subjected to ultraviolet (UV) irradiation. However, TiO₂ has some shortcomings associated with a large bandgap value of around 3.2 eV, making it less efficient in the visible spectral range. TiO₂ is often consolidated with various carbon nanomaterials to overcome this limitation and enhance its efficiency. Graphene, a 2-dimensional allotrope of carbon with a bandgap tuned between 0 and 0.25 eV, exhibits unique properties, making it an attractive candidate to augment the photoactivity of semiconductor (SC) oxides. Encapsulating graphene oxide onto TiO₂ nanospheres demonstrates intensified photocatalytic properties and exceptional recyclability for the degeneration of certain dyes, including Rhodamine B. This review encompasses various techniques to synthesize graphene-based TiO₂ photoactive composites, emphasizing graphene capsulized hollow titania nanospheres, nanofibers, core/shell, and reduced graphene oxide-TiO₂-based nanocomposites. It also consolidates the application of the aforestated nanocomposites for the disintegration of various synthetic dyes, proving efficacious for water decontamination and degradation of chemicals and pharmaceuticals. Furthermore, graphene-based TiO₂ nanocomposites used as lithium (Li)-ion batteries manifesting substantial electrochemical performance and solar fuel cells for energy production are discussed here.

MXenes-A New Class of Two-Dimensional Materials: Structure, Properties and Potential Applications

A new class of two-dimensional nanomaterials, MXenes, which are carbides/nitrides/carbonitrides of transition and refractory metals, has been critically analyzed. Since the synthesis of the first family member in 2011 by Yury Gogotsi and colleagues, MXenes have quickly become attractive for a variety of research fields due to their exceptional properties. Despite the fact that this new family of 2D materials was discovered only about ten years ago, the number of scientific publications related to MXene almost doubles every year. Thus, in 2021 alone, more than 2000 papers are expected to be published, which indicates the relevance and prospects of MXenes. The current paper critically analyzes the structural features, properties, and methods of synthesis of MXenes based on recent available research data. We demonstrate the recent trends of MXene applications in various fields, such as environmental pollution removal and water desalination, energy storage and harvesting, quantum dots, sensors, electrodes, and optical devices. We focus on the most important medical applications: photo-thermal cancer therapy, diagnostics, and antibacterial treatment. The first results on obtaining and studying the structure of high-entropy MXenes are also presented.

MXene/Carbon Nanotube Hybrids: Synthesis, Structures, Properties, and Applications

Since the successful preparation of few-layer transition metal carbides from three-dimensional MAX phases in 2011, MXenes (known as a family of layered transition metal carbides, nitrides, and carbonitrides) have been intensively studied. Though MXenes have been adopted as active materials in many applications, issues including aggregation and restacking are likely to hamper their potential applications. In order to address these prevailing challenges, the concept of MXene/carbon nanotube (CNT) hybrids was proposed initially in 2015, where CNTs were incorporated as the spacers and conductive additives. Ever since, MXene/CNT hybrids with different architectures have been synthesized by a number of methods and applied in numerous fields. Herein, after the discussion about general synthesis approaches, architectures, and properties of the hybrids, this Review summarized the recent advances in the application of MXene/CNT hybrids in energy storage devices, sensors, electrocatalysis, electromagnetic interference shielding, and water treatment, in which the function of individual components was clarified. In the end, the current research trend in this field were discussed and several technical issues were highlighted along with some suggestions on future research directions.

Exploring the Effects of MXene on Nonisothermal Crystallization and Melting Behavior of β-Nucleated Isotactic Polypropylene

In this study, one of the commonly used MXene (Ti3C2Tx) and β nucleated isotactic polypropylene (β-iPP)/MXene composites of different compositions were fabricated. The effects of MXene on non-isothermal crystallization and polymorphic behavior of β-iPP/MXene composites were comparatively studied. The non-isothermal crystallization kinetics indicates that for all samples, the lower cooling rates promote composites to crystallize at higher temperatures. When MXene and β-Nucleating agent (β-NA) are added separately, the crystallization temperature of composites shifts towards higher temperatures at all cooling rates. When MXene and β-NA are added simultaneously, the composite shows different cooling rate dependence, and the effects of improving crystallization temperatures is more obvious under rapid cooling. The activation energy of four samples iPP, iPP/MXene, iPP/β-NA, and iPP/MXene/β-NA were -167.5, -185.5, -233.8, and -218.1 kJ/mol respectively, which agree with the variation tendency of crystallization temperatures. The polymorphic behavior analysis obtained from Differential Scanning calorimetry (DSC) is affected by two factors: the ability to form β-crystals and the thermal stability of β-crystals. Because β-crystals tend to recrystallize to α-crystals below a critical temperature, to eliminate the effect of β-α recrystallization, the melting curves at end temperatures Tend = 50 °C and Tend = 100 °C are comparatively studied. The results show that more thermally unstable β-crystals would participate in β-α recrystallization with higher cooling rates. Moreover, thermal stability of β-crystals is improved by adding MXene. To further verify these findings, samples of three different thermal conditions were synthesized and analyzed by DSC, X-Ray Diffraction (XRD), and Polarized Light Optical Microscopy (PLOM), and the results were consistent with the above findings. New understandings of synthesizing β-iPP/MXene composites with adjustable morphologies and polymorphic behavior were proposed.

Properties of S-Functionalized Nitrogen-Based MXene (Ti2NS2) as a Hosting Material for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have received extensive attention due to their high theoretical specific capacity and theoretical energy density. However, their commercialization is hindered by the shuttle effect caused by the dissolution of lithium polysulfide. To solve this problem, a method is proposed to improve the performance of Li-S batteries using Ti₂N(Ti₂NS₂) with S-functional groups as the sulfur cathode host material. The calculation results show that due to the mutual attraction between Li and S atoms, Ti₂NS₂ has the moderate adsorption energies for Li₂S_x species, which is more advantageous than Ti₂NO₂ and can effectively inhibit the shuttle effect. Therefore, Ti₂NS₂ is a potential cathode host material, which is helpful to improve the performance of Li-S batteries. This work provides a reference for the design of high-performance sulfur cathode materials.

Recent Advances in MXene/Polyaniline-Based Composites for Electrochemical Devices and Electromagnetic Interference Shielding Applications

Due to serious global warming and environmental issues, the demand for clean and sustainable energy storage devices is significantly increased. Often accompanied by rapid growth of portable electronic vehicles and devices, massive electromagnetic wave pollution becomes unavoidable. To mitigate the above two issues, this mini-review summaries preparation methods and recent developments of MXene/polyaniline-based composites for their applications in electrochemical devices and electromagnetic interference shielding. Based on excellent synergistic effects between single compounds and designed hierarchical structures, MXene/polyaniline-based composites usually exhibit enhanced physical and chemical properties, showing great potentials in sustainable electrochemical properties and electromagnetic wave protections for human health as well as normal operation of precise electronic devices.

Application of MXenes in Perovskite Solar Cells: A Short Review

Application of MXene materials in perovskite solar cells (PSCs) has attracted considerable attention owing to their supreme electrical conductivity, excellent carrier mobility, adjustable surface functional groups, excellent transparency and superior mechanical properties. This article reviews the progress made so far in using Ti3C2Tx MXene materials in the building blocks of perovskite solar cells such as electrodes, hole transport layer (HTL), electron transport layer (ETL) and perovskite photoactive layer. Moreover, we provide an outlook on the exciting opportunities this recently developed field offers, and the challenges faced in effectively incorporating MXene materials in the building blocks of PSCs for better operational stability and enhanced performance.

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.

Preparation, Properties, and Microbial Impact of Tungsten (VI) Oxide and Zinc (II) Oxide Nanoparticles Enriched Polyethylene Sebacate Nanocomposites

Nanoparticles of tungsten oxide (WO₃) and zinc oxide (ZnO) enriched polyethylene sebacate (PES) nanocomposites were prepared through the coprecipitation process and condensation polymerization reaction. The obtained nano-sized particles of WO₃ and ZnO, PES, and nanocomposites (WO₃-PES NC and ZnO-PES NC) were investigated. The average molecular weight of the cured PES was measured by employing the gel permeation chromatography (GPC) technique. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) spectra assured the formation of the polymeric nanocomposites.WO₃ and ZnO nanoparticles supposed a condensed porous spherical phase found implanted in the polymer structure, as detected by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. These nano-scale systems achieved an electrical activity based on the conductive nanoparticles embedded matrix as a result of the ion-ion interactions. The microbial influence of the nanocomposites was examined against pathogenic bacteria; Pseudomonas aeruginosa,Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, and Fungi; Aspergillus niger, and Candidaalbicans. Results exhibited that these nanocomposites have antimicrobial effects from moderate to slightly high on bacteria and high on fungi which was confirmed by a clear zone of inhibition. This study contributes to the design of reasonable composites to be under evaluation for their catalytic effect.

Mechanotribological Aspects of MXene-Reinforced Nanocomposites

MXenes are recently discovered 2D nanomaterial with superior mechanical, thermal, and tribological properties, being commonly employed in a wide variety of critical research areas, ranging from cancer therapy to energy and environmental applications. Due to their special properties, such as mechanoceramic nature with excellent mechanical performance, thermal stability and rich surface properties, MXenes have tremendous potential as advanced composite structures, especially those based on polymers due to a great affinity between macromolecules and the terminating groups of 2D MXenes. MXenes have been extensively explored in metal matrix nanocomposites as well as in solid- or liquid-based lubrication systems owing to the 2D structure and antifriction characteristics. The purpose of the this paper is to provide a comprehensive insight into the material, mechanical, and tribological properties of the MXene nanolayers with discussions on the recent advancements attained from MXene-reinforced nanocomposites starting with the synthesis, fabrication techniques, intricacies of the underlying physics and mechanisms, and finally focusing on the progress in computational studies. This analysis of MXene-based composites will stimulate an emerging field with innumerable opportunities and ample potentials to produce newfangled materials and structures with targeted properties.

Adipose tissue-derived mesenchymal stem cells and chitosan/poly (vinyl alcohol) nanofibrous scaffolds for cartilage tissue engineering

Osteoarthritis (OA) has been defined as a chronic inflammatory joint disease characterized by progressive articular cartilage degeneration. Recently growing interest in regenerative medicine, using cell therapy and tissue engineering, where cellular components in combination with engineered scaffolds and bioactive materials were used to induce functional tissue regeneration. In the present study, nanofibrous scaffold based on chitosan (CS)/poly (vinyl alcohol) (PVA) were used to develop biologically functionalized biomaterial to mimic the extracellular matrix, allowing the human adipose tissue derived mesenchymal stem cells (ADSCs) to proliferate and differentiate to chondrogenic cells. The morphology of the nanofibrous mat was examined using field emission scanning electron microscope (FE/SEM). The characteristic functional groups and the nature of the chemical bonds between atoms were evaluated using Fourier transform infrared spectroscopy (FTIR) spectrum. Characterization of the seeded cells was morphologically evaluated by scanning electron microscopy and by flow cytometry for the expression of the stem cell surface markers. The differentiation potential was verified after chondrogenic induction by analyzing the expression of chondrogenic marker genes using real-time (RT PCR). Current study suggest significant potential for the use of ADSCs with the nanofibrous scaffolds in improving the osteoarthritis pathology.