Transition Metal Carbonitrides Research Articles

Advances on MXene-Based Memristors for Neuromorphic Computing: A Review on Synthesis, Mechanisms, and Future Directions.

Neuromorphic computing seeks to replicate the capabilities of parallel processing, progressive learning, and inference while retaining low power consumption by drawing inspiration from the human brain. By further overcoming the constraints imposed by the traditional von Neumann architecture, this innovative approach has the potential to revolutionize modern computing systems. Memristors have emerged as a solution to implement neuromorphic computing in hardware, with research based on developing functional materials for resistive switching performance enhancement. Recently, two-dimensional MXenes, a family of transition metal carbides, nitrides, and carbonitrides, have begun to be integrated into these devices to achieve synaptic emulation. MXene-based memristors have already demonstrated diverse neuromorphic characteristics while enhancing the stability and reducing power consumption. The possibility of changing the physicochemical properties through modifications of the surface terminations, bandgap, interlayer spacing, and oxidation for each existing MXene makes them very promising. Here, recent advancements in MXene synthesis, device fabrication, and characterization of MXene-based neuromorphic artificial synapses are discussed. Then, we focus on understanding the resistive switching mechanisms and how they connect with theoretical and experimental data, along with the innovations made during the fabrication process. Additionally, we provide an in-depth review of the neuromorphic performance, making a connection with the resistive switching mechanism, along with a compendium of each relevant performance factor for nonvolatile and volatile applications. Finally, we state the remaining challenges in MXene-based devices for artificial synapses and the next steps that could be taken for future development.

Carrageenan-modified MXene nanocomposite-based all-printed flexible humidity sensor for healthcare application

Transition metal carbides and carbonitrides (MXene) have emerged as promising nanomaterials for humidity-sensitive applications due to their abundant hydrophilic active sites and chemically reactive surfaces. However, designing MXene-based flexible humidity sensors with rapid response rates, high sensitivity, and structural stability remains a formidable challenge. Herein, we propose an all-printed humidity sensor fabricated on a paper-based substrate with copper electrodes and carrageenan-modified MXene composite materials. The all-printed humidity sensor prepared in this work exhibited outstanding potential in humidity sensing, showcasing high sensitivity (2073.5 %) and rapid response/recovery times (4.6/5.8 s). Meanwhile, the humidity sensor exhibits outstanding structural stability (with capacitance fluctuation maintained within 8.5 % after 500 bending cycles) and remarkable cyclic stability. Based on its excellent sensing performance and stability, the CAMX-2 sensor can effectively monitor skin humidity, fingertip contact levels, and humidity changes during various exercise modes. Therefore, this work offers a viable strategy for achieving reliable humidity monitoring, showcasing significant potential in the fields of sensing devices and healthcare.

Effect of Ti3C2-MXene size on cell viability of human carcinoma cells

MXene nanoflakes, a new type of transition metal carbides, nitrides, and carbonitrides (named as MXene) have emerged as biocompatible transition metal structures, which illustrate desirable performance for various applications due to their unique physicochemical, and compositional virtues. MXenes are currently expanding their application from optical, chemical, electronic, and mechanical fields towards biomedical areas. In terms of biomedical applications, the biological toxicity of MXenes materials in different forms must be considered inevitably. In this paper, Ti3C2-MXene nanoflakes with different sizes have been prepared by means of wet etching method combined with powerful ultrasonication for exploring the effect in human breast carcinoma cells (MDA-MB-231 Cells) and human thyroid carcinoma cells (GLAG-66 Cells). Clinically representative MDA-MB-231 Cells and GLAG-66 Cells are selected as experimental subjects and their biotoxicities are characterized when exposed to Ti3C2-MXene nanoflakes with different sizes and concentrations. The results show that Ti3C2-MXene nanoflakes with sizes below 200 nm is almost non-toxic to MDA-MB-231 Cells and GLAG-66 Cells at low concentrations, and enhance their bioactivity and proliferation. When the nanoflake size is above 200 nm, Ti3C2-MXene has a significant inhibitory effect on the proliferation of the cells. This phenomenon may be due to the different roles of Ti3C2-MXene materials at different scales in cell proliferation as well as in complex physiological processes. This result is of great significance for material screening and design before biological experiments using Ti3C2-MXene.

2D MXene Biomaterials for Catalytic Medical Applications.

In recent years, two-dimensional transition metal carbides, nitrides, and carbonitrides, termed as MXenes, have been widely applied in energy storage, photocatalysis and biomedicine owing to their unique physicochemical properties of large specific surface area, high electrical conductivity, excellent optical performance, good stability, etc. Moreover, due to their strong light absorption capacity in the first and second near-infrared bio-window, and their ability of being simply functionalized with multiple organic/inorganic materials, MXene biomaterials have shown great potential in the field of catalytic therapy. This review will summarize the common catalytic mechanism of MXene biomaterials and their latest applications in catalytic medicine such as tumor therapy, antibacterial and anti-inflammatory, and present the current challenges and opportunities in clinical translation for future development to promote the advancement of MXene biomaterials in the field of catalytic medicine.

2D MXene Biomaterials for Catalytic Medical Applications.

In recent years, two-dimensional transition metal carbides, nitrides, and carbonitrides, termed as MXenes, have been widely applied in energy storage, photocatalysis and biomedicine owing to their unique physicochemical properties of large specific surface area, high electrical conductivity, excellent optical performance, good stability, etc. Moreover, due to their strong light absorption capacity in the first and second near-infrared bio-window, and their ability of being simply functionalized with multiple organic/inorganic materials, MXene biomaterials have shown great potential in the field of catalytic therapy. This review will summarize the common catalytic mechanism of MXene biomaterials and their latest applications in catalytic medicine such as tumor therapy, antibacterial and anti-inflammatory, and present the current challenges and opportunities in clinical translation for future development to promote the advancement of MXene biomaterials in the field of catalytic medicine.

New stable transition metal carbonitrides: TM3C2N, TM3CN2, and TM4C3N

Transition metal carbonitrides have been widely applied in various fields due to their excellent physical and chemical properties. In the pursuit of identifying innovative and stable crystal structures among transition metal carbonitrides, we have employed first-principles calculations to investigate the substitution of transition metal elements (Cr, Hf, Mo, Nb, Ti, V, W, Zr) for Ta within three stable crystal structure types: Ta3C2N, Ta3CN2, and Ta4C3N. The thermal stability, dynamic stability, and mechanical stability of these twenty-four structures were systematically studied, and nine stable new crystal structures were finally identified. Our subsequent investigations have included assessments of their structural, electrical, and mechanical properties. Our findings in mechanical properties have revealed that five compounds, Nb3CN2, Hf4C3N, Nb4C3N, Ti4C3N, and Zr4C3N, exhibit hardness values of 20.3 GPa, 30.0 GPa, 22.4 GPa, 28.7 GPa, and 26.2 GPa, respectively. Furthermore, our electronic property assessments have indicated that these structures exhibit metallic characteristics.

Screening Conductive MXenes for Lithium Polysulfide Adsorption

AbstractMXenes are promising passive components that enable lithium‐sulfur batteries (LSBs) by effectively trapping lithium polysulfides (LiPSs) and facilitating surface‐mediated redox reactions. Despite numerous studies highlighting the potential of MXenes in LSBs, there are no systematic studies of MXenes’ composition influence on polysulfide adsorption, which is foundational to their applications in LSB. Here, a comprehensive investigation of LiPS adsorption on seven MXenes with varying chemistries (Ti2CTx, Ti3C2Tx, Ti3CNTx, Mo2TiC2Tx, V2CTx, Nb2CTx, and Nb4C3Tx), utilizing optical and analytical spectroscopic methods is performed. This work reports on the influence of polysulfide concentration, interaction time, and MXenes’ chemistry (transition metal layer, carbide and carbonitride inner layer, surface terminations and structure) on the amount of adsorbed LiPSs and the adsorption mechanism. These findings reveal the formation of insoluble thiosulfate and polythionate complex species on the surfaces of all tested MXenes. Furthermore, the selective adsorption of lithium and sulfur, and the extent of conversion of the adsorbed species on MXenes varied based on their chemistry. For instance, Ti2CTx exhibits a strong tendency to adsorb lithium ions, while Mo2TiC2Tx is effective in trapping sulfur by forming long‐chain polythionates. The latter demonstrates a significant conversion of intermediate polysulfides into low‐order species. This study offers valuable guidance for the informed selection of MXenes in various functional components benefiting the future development of high‐performance LSBs.

Electrochemical Nitrogen Reduction to Ammonia at Ambient Condition on the (111) Facets of Transition Metal Carbonitrides.

We conducted Density Functional Theory calculations to investigate a class of materials with the goal of enabling nitrogen activation and electrochemical ammonia production under ambient conditions. The source of protons at the anode could originate from either water splitting or H2, but our specific focus was on the cathode reaction, where nitrogen is reduced into ammonia. We examined the conventional associative mechanism, dissociative mechanism, and Mars-van Krevelen mechanism on the (111) facets of the NaCl-type structure found in early transition metal carbonitrides, including Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Sc, Y, and W. We explored the catalytic activity by calculating the free energy of all intermediates along the reaction pathway and constructing free energy diagrams to identify the steps that determine the reaction's feasibility. Additionally, we closely examined the potential for catalyst poisoning within the electrochemical environment, considering the bias required to drive the reaction. Furthermore, we assessed the likelihood of catalyst decomposition and the potential for catalyst regeneration among the most intriguing carbonitrides. Our findings revealed that the only carbonitride catalyst considered here exhibiting both activity and stability, capable of self-regeneration and nitrogen-to-ammonia activation, is NbCN with a low potential-determining step energy of 0.58 eV. This material can facilitate ammonia formation via a mixed associative-MvK mechanism. In contrast, other carbonitrides of this crystallographic orientation are likely to undergo decomposition, reverting to their parent metals under operational conditions.

Atom probe tomography investigation of sintered transition metal carbonitride - A Zr(C,N) study

Zirconium based nitrides, carbides and carbonitrides are highly technological compounds which received during the 1950s and 60s huge interest due to their combination of metal and refractory properties. The interest reiterated recently due to the need of compounds with high electrical conductivity, corrosion and oxidation resistance, and neutron transparency with the rise of mobility electrification and nuclear energy. Sintered Zr(C,N) is investigated with CHN elemental analysis combined with atom probe tomography (APT) to evaluate the composition and homogeneity of carbon and nitrogen from the bulk down to the nanometer scale. Results have shown a strong nitrogen loss and an enrichment in carbon which diffused from the graphite die and punch. Nevertheless, the composition is homogenous in the sample. Atom probe tomography suggests that the sintered alloy is sub-stoichiometric with carbon and nitrogen homogeneously distributed within the grain. The stoichiometry calculated corresponds to the estimation by Vegard’s law.

Charge-transfer-driven ultrasensitive SERS sensing in a two-dimensional titanium carbonitride MXene.

Two-dimensional (2D) MXenes stand out as promising platforms for surface-enhanced Raman scattering (SERS) sensing owing to their metallic feature, various compositions, high surface area, compatibility with functionalization, and ease of fabrication. In this work, we report a high-performance 2D titanium carbonitride (Ti3CN) MXene SERS substrate. We reveal that the abundant electronic density of states near the Fermi level of Ti3CN MXene boosts the efficiency of photo-induced charge transfer at the interface of Ti3CN/molecule, resulting in significant Raman enhancement. The SERS sensitivity of Ti3CN MXene is further promoted through a 2D morphology regulation and molecular enrichment strategies. Moreover, prohibited drugs are detectable on this substrate, presenting the potential of trace-amount analysis on Ti3CN MXene. This work provides a deep insight of the SERS mechanisms of Ti3CN MXene and broadens the practical application of transition metal carbonitride MXene SERS substrates.

Exploring transformative and multifunctional potential of MXenes in 2D materials for next-generation technology

MXenes, a rapidly growing family of two-dimensional (2D) transition metal carbides, nitrides, or carbonitrides (Mn+1XnTx, where M is a transition metal, X is carbon, nitrogen, or both, and T represents surface functional groups), have captured the scientific community's interest due to their exceptional physicochemical properties and diverse technological applications. This comprehensive review explores the latest breakthroughs in MXene synthesis and characterisation, emphasising their multifaceted applications in energy storage, catalysis, sensing, and other cutting-edge domains. This review examines the most widely used MXene synthesis strategies, including selective etching and delamination, and highlight recent advancements in controlling surface terminations, composition, and morphology. The influence of these synthetic parameters on MXene properties is discussed in detail. Characterisation techniques, ranging from spectroscopic methods to electron microscopy, are essential for elucidating MXenes' structure-property relationships. Research into energy storage leverages MXenes' high electrical conductivity, large surface area, and chemical tunability. This has led to significant progress in the field. This paper presents research efforts focused on optimising MXenes for both battery and supercapacitor applications. Additionally, the catalytic prowess of MXenes, particularly in electrocatalysis and photocatalysis, is explored, emphasising their role in green energy technologies and environmental remediation. MXenes' remarkable sensitivity and selectivity make them promising candidates for sensing various gases, biomolecules, and ions, offering exciting possibilities in healthcare and environmental monitoring. Importantly, this review underscores the need for continued optimisation of MXene synthesis protocols to achieve large-scale production, enhanced stability, and precise control over properties across various fields.

Recent Progress in MXene‐Based Electrochemical Actuators and Capacitors

A new family of two‐dimensional (2D) transition metal carbides, carbonitrides, and nitrides (MXenes) has attracted increasing attention owing to their electrical, chemical, and physical properties. Together with various attractive properties of the MXenes, they also exhibit electrochemical induced deformation (i.e., expansion/contraction) via ion intercalation/de‐intercalation in/from MXene layers. In this respect, MXenes offer the possibility of application as the electrode of electrochemical actuators (ECAs). While the MXene‐based ECAs are still in their infancy stage, researchers have made great effort to achieve high‐performance MXene‐based electrochemical capacitors (ECs). As the name suggests, both ECAs and ECs shared common traits in which their operations are based on electrochemical processes. This review provides the recent progress in the MXene‐based ECAs in parallel with that in the MXene‐based ECs to gain insights from the relatively mature developments in EC applications. Finally, based on the findings from previous studies on both electrochemical applications, perspectives on future MXene‐based ECAs in terms of electrode, electrolyte, and cell configuration are provided.

Are (100) facets of transition metal carbonitrides suitable as electrocatalysts for nitrogen reduction to ammonia at ambient conditions?

Sustainable and energy-efficient ammonia production requires facile nitrogen reduction for hydrogen preservation and inorganic fertilizers. A nitrogen reduction apparatus with optimal stability, selectivity, and activity for ambient temperatures and pressure is needed to catalyze ammonia synthesis. This paper describes the investigation of using transition metal carbonitrides as catalyst to reduce molecular nitrogen electrochemically to NH3 at room temperature and atmospheric pressure. Density functional theory calculations determine the competition among associative, dissociative, and Mars-van Krevelen mechanisms where in most cases the Mars-van Krevelen is a more favorable reaction pathway. VCN and NbCN are the best candidates for ammonia production via the Mars-van Krevelen mechanism at low onset potentials of −0.52 V and −0.53 V vs reversible hydrogen electrode on the (100) facets. These carbonitrides are predicted to favor nitrogen reduction reaction rather than hydrogen evolution reaction.

BRIEF OVERVIEW OF METHODS FOR PRODUCING TiSiCN COATINGS AND THE METHOD OF REACTIVE PLASMA SPRAYING

Modern materials science sets itself the task of developing new materials with multifunctional coatings. Materials with such coatings are widely used in various fields of technology: construction and energy, microelectronics, aviation and others. The main reason for the emergence and development of technology for applying multifunctional protective coatings is the desire to increase the durability of parts and assemblies of various machine mechanisms. Wear-resistant hard coatings based on transition metal nitrides and carbonitrides are widely used to extend the life of forging and extrusion dies and high-speed machining tools. Over the past two decades, the widespread use of these coatings has stimulated and supported the development of new processes and materials in an attempt to further improve their properties. Among these coatings, the higher hardness, excellent oxidation resistance and high thermal stability of coatings such as TiSiN and TiSiCN make them the most promising candidates for demanding tribological applications. In addition, TiSiCN coating is a promising material used in marine environments due to its excellent anti-wear and corrosion resistance, as well as high hardness and low friction coefficient. These combinations of properties make TiSiCN coatings potential candidates for protective layers in the automotive and petroleum industries.The article briefly examines the possibilities of producing TiSiCN coatings using different deposition methods to control the properties of the resulting films and the features of the reactive plasma spraying method. The work describes the most common methods and technologies for producing carbonitride coatings currently used. The latest developments and current trends in the field of plasma spray coating technologies are reviewed, taking into account important innovations for industrial coatings. New conclusions that were obtained as a result of fundamental and applied research in physics or chemistry are based on them. The article provides a comparative review of the characteristics of obtaining wear-resistant TiSiCN coatings and the features of using reactive plasma spraying to obtain wear-resistant coatings. Based on an analysis of the literature, it can be argued that the further development of reactive plasma technology is associated with the development of a new resource-saving method for the formation of composite coatings with increased corrosion and tribological characteristics, which corresponds to the development trends of world science.

Tuning MXene Properties through Cu Intercalation: Coupled Guest/Host Redox and Pseudocapacitance.

MXenes are 2D transition metal carbides, nitrides, and/or carbonitrides that can be intercalated with cations through chemical or electrochemical pathways. While the insertion of alkali and alkaline earth cations into Ti3C2Tx MXenes is well studied, understanding of the intercalation of redox-active transition metal ions into MXenes and its impact on their electronic and electrochemical properties is lacking. In this work, we investigate the intercalation of Cu ions into Ti3C2Tx MXene and its effect on its electronic and electrochemical properties. Using X-ray absorption spectroscopy (XAS) and ab initio molecular dynamics (AIMD), we observe an unusual phenomenon whereby Cu2+ ions undergo partial reduction upon intercalation from the solution into the MXene. Furthermore, using in situ XAS, we reveal changes in the oxidation states of intercalated Cu ions and Ti atoms during charging. We show that the pseudocapacitive response of Cu-MXene originates from the redox of both the Cu intercalant and Ti3C2Tx host. Despite highly reducing potentials, Cu ions inside the MXene show an excellent stability against full reduction upon charging. Our findings demonstrate how electronic coupling between Cu ions and Ti3C2Tx modifies electrochemical and electronic properties of the latter, providing the framework for the rational design and utilization of transition metal intercalants for tuning the properties of MXenes for various electrochemical systems.

Nano-Innovations in Cancer Therapy: The Unparalleled Potential of MXene Conjugates.

MXenes are two-dimensional transition metal carbides, nitrides, and carbonitrides that have become important materials in nanotechnology because of their remarkable mechanical, electrical, and thermal characteristics. This review emphasizes how crucial MXene conjugates are for several biomedical applications, especially in the field of cancer. These two-dimensional (2D) nanoconjugates with photothermal, chemotherapeutic, and photodynamic activities have demonstrated promise for highly effective and noninvasive anticancer therapy. MXene conjugates, with their distinctive optical capabilities, have been employed for bioimaging and biosensing, and their excellent light-to-heat conversion efficiency makes them perfect biocompatible and notably proficient nanoscale agents for photothermal applications. The synthesis and characterization of MXenes provide a framework for an in-depth understanding of various fabrication techniques and their importance in the customized formation of MXene conjugates. The following sections explore MXene-based conjugates for nanotheranostics and demonstrate their enormous potential for biomedical applications. Nanoconjugates, such as polymers, metals, graphene, hydrogels, biomimetics, quantum dots, and radio conjugates, exhibit unique properties that can be used for various therapeutic and diagnostic applications in the field of cancer nanotheranostics. An additional layer of understanding into the safety concerns of MXene nanoconjugates is provided by detailing their toxicity viewpoints. Furthermore, the review concludes by addressing the opportunities and challenges in the clinical translation of MXene-based nanoconjugates, emphasizing their potential in real-world medical practices.

Tuning the Microenvironment of Water Confined in Ti3C2Tx MXene by Cation Intercalation.

The local microenvironment has recently been found to play a major role in the electrocatalytic activity of nanomaterials. Modulating the microenvironment by adding alkali metal cations into the electrolyte can be used to either suppress hydrogen or oxygen evolution, thereby extending the electrochemical window of energy storage systems, or to tune the selectivity of electrocatalysts. MXenes are a large family of two-dimensional transition metal carbides, nitrides, and carbonitrides that have shown potential for use in electrochemical energy storage applications. Due to their negatively charged surfaces, MXenes can accommodate cations and water molecules between the layers. Nevertheless, the nature of the aqueous microenvironment in the MXene interlayer space is poorly understood. Here, we apply Fourier transform infrared spectroscopy (FTIR) to probe the hydrogen bonding of intercalated water in Ti3C2Tx as a function of intercalated cation and relative humidity. Substantial changes in the FTIR spectra after cation exchange demonstrate that the hydrogen bonding of water molecules confined between the MXene layers is strongly cation-dependent. Furthermore, the IR absorbance of the confined water correlates with resistivity estimated by 4-point probe measurements and interlayer distance calculated from XRD patterns. This work demonstrates that cation intercalation strongly modulates the confined microenvironment, which can be used to tune the activity or selectivity of electrochemical reactions in the interlayer space of MXenes in the future.

A Critical Review of Two-Dimensional Nanomaterial MXenes and their Applications in Water Treatment

: Environmental pollution has accelerated and intensified because of the acceleration of industrialization, therefore fabricating excellent materials to remove hazardous pollutants has become inevitable. MXenes as emerging transition metal nitrides, carbides, or carbonitrides with high conductivity, hydrophilicity, excellent structural stability, and versatile surface chemistry, become ideal candidates for water treatment. This review summarizes recent advances in the synthesis and applications of MXenes as adsorbents, photocatalysts, and separation membranes for water purification. Extensive information related to the synthesis and applications of MXenes for water treatment and their associated patents were collected. This review has given a comprehensive survey of the recently reported 2D nanomaterial (NM) MXenes which are used in various water treatment applications. The effects of structure control, surface modification and composite of MXene on the adsorption performance of MXene and the formation of effective heterojunction, photocatalysts separation membrane were discussed in detail. The existing problems in the water treatment applications of MXene were summarized and analyzed. The overview also features discussions on the computational attempts, biocompatibility, and environmental impact in the exploration of MXenes for applications of water treatment, highlighting the challenges and opportunities of these advanced 2D NMs. The prospects of designing MXene based water treatment materials with excellent performance were put forward.

Titanium carbide MXene/silver nanostars composite as SERS substrate for thiram pesticide detection

Two-dimensional transition metal carbonitrides, Ti3C2Tx MXene nanosheets, have drawn much attention due to their unique optical properties. These materials have huge potential to be employed as surface-enhanced Raman scattering (SERS) substrates. Herein, to combine the benefits of metal nanoparticles and MXene as SERS substrates, we prepared composite SERS films with different volume ratios composed of Ti3C2Tx MXene with silver nanostars (AgNs) as a promising SERS substrate for detection of pesticides. These SERS films were prepared via a drop-casting technique. The SERS activities of the MXene/AgNs composites were evaluated through detection of the thiram pesticide. MXene/AgNs exhibited the highest SERS intensity compared to MXene or AgNs substrate alone. Sampling from 20 different areas and samples of the substrate gave very consistent SERS signals. The MXene/AgNs substrate shows good stability for 1 month when stored in a small transparent container with silica gel. The MXene/AgNs SERS substrate exhibits excellent sensitivity able to detect thiram concentrations as low as 10−8 M which also having low a relative standard deviation (RSD) value for reproducibility and stability over a significant period.

Recent advances in the role of MXene based hybrid architectures as electrocatalysts for water splitting.

The development of non-noble metal based and cost-effective electrocatalysts for water splitting has attracted significant attention due to their potential in production of clean and green hydrogen fuel. Discovered in 2011, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have demonstrated promising performance as electro catalysts in the water splitting process due to their high electrical conductivity, very large surface area and abundant catalytic active sites. However, their-long term stability and recyclability are limited due to restacking and agglomeration of MXene flakes. This problem can be solved by combining MXene with other materials to create their hybrid architectures which have demonstrated higher electrocatalytic performance than pristine MXenes. Electrolysis of water encompasses two half-cell reactions, hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode. Firstly, this concise review explains the mechanism of water splitting. Then it provides an overview of the recent advances about applications of MXenes and their hybrid architectures as HER, OER and bifunctional electrocatalysts for overall water splitting. Finally, the recent challenges and potential outlook in the field have been presented. This concise review may provide further understanding about the role of MXene-based hybrid architectures to develop efficient electrocatalysts for water splitting.