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Yury Gogotsi - One of the best experts on this subject based on the ideXlab platform.
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bulk and surface chemistry of the niobium max and MXene phases from multinuclear solid state nmr spectroscopy
Journal of the American Chemical Society, 2020Co-Authors: Yury Gogotsi, Kent J Griffith, Michael A Hope, Philip J Reeves, Mark Anayee, Clare P GreyAbstract:MXenes, derived from layered MAX phases, are a class of two-dimensional materials with emerging applications in energy storage, electronics, catalysis, and other fields due to their high surface areas, metallic conductivity, biocompatibility, and attractive optoelectronic properties. MXene properties are heavily influenced by their surface chemistry, but a detailed understanding of the surface functionalization is still lacking. Solid-state nuclear magnetic resonance (NMR) spectroscopy is sensitive to the interfacial chemistry, the phase purity including the presence of amorphous/nanocrystalline phases, and the electronic properties of the MXene and MAX phases. In this work, we systematically study the chemistry of Nb MAX and MXene phases, Nb2AlC, Nb4AlC3, Nb2CTx, and Nb4C3Tx, with their unique electronic and mechanical properties, using solid-state NMR spectroscopy to examine a variety of nuclei (1H, 13C, 19F, 27Al, and 93Nb) with a range of one- and two-dimensional correlation, wide-line, high-sensitivity, high-resolution, and/or relaxation-filtered experiments. Hydroxide and fluoride terminations are identified, found to be intimately mixed, and their chemical shifts are compared with other MXenes. This multinuclear NMR study demonstrates that diffraction alone is insufficient to characterize the phase composition of MAX and MXene samples as numerous amorphous or nanocrystalline phases are identified including NbC, AlO6 species, aluminum nitride or oxycarbide, AlF3·nH2O, Nb metal, and unreacted MAX phase. To the best of our knowledge, this is the first study to examine the transition-metal resonances directly in MXene samples, and the first 93Nb NMR of any MAX phase. The insights from this work are employed to enable the previously elusive assignment of the complex overlapping 47/49Ti NMR spectrum of Ti3AlC2. The results and methodology presented here provide fundamental insights on MAX and MXene phases and can be used to obtain a more complete picture of MAX and MXene chemistry, to prepare realistic structure models for computational screening, and to guide the analysis of property measurements.
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Tunable electrochromic behavior of titanium-based MXenes.
Nanoscale, 2020Co-Authors: Geetha Valurouthu, Kathleen Maleski, Narendra Kurra, Meikang Han, Kanit Hantanasirisakul, Asia Sarycheva, Yury GogotsiAbstract:Two-dimensional transition metal carbides, nitrides and carbonitrides, popular by the name MXenes, are a promising class of materials as they exhibit intriguing optical, optoelectronic and electrochemical properties. Taking advantage of their metallic conductivity and hydrophilicity, titanium carbide MXenes (Ti3C2Tx and others) are used to fabricate solution processable transparent conducting electrodes (TCEs) for the design of three-electrode electrochromic cells. However, the tunable electrochromic behavior of various titanium-based MXene compositions across the entire visible spectrum has not yet been demonstrated. Here, we investigate the intrinsic electrochromic properties of titanium-based MXenes, Ti3C2Tx, Ti3CNTx, Ti2CTx, and Ti1.6Nb0.4CTx, where individual MXenes serve as a transparent conducting, electrochromic, and plasmonic material layer. Plasmonic extinction bands for Ti3C2Tx, Ti2CTx and Ti1.6Nb0.4CTx are centered at 800, 550 and 480 nm, which are electrochemically tunable to 630, 470 and 410 nm, respectively, whereas Ti3CNTx shows a reversible change in transmittance in the wide visible range. Additionally, the switching rates of MXene electrodes with no additional transparent conductor electrodes are estimated and correlated with the respective electrical figure of merit values. This study demonstrates that MXene-based electrochromic cells are tunable in the entire visible spectrum and suggests the potential of the MXene family of materials in optoelectronic, plasmonic, and photonic applications, such as tunable visible optical filters and modulators, to name a few.
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Oxidation-resistant titanium carbide MXene films
Journal of Materials Chemistry A, 2020Co-Authors: Yonghee Lee, Yury Gogotsi, Seon Joon Kim, Yong-jae Kim, Younghwan Lim, Yoonjeong Chae, Byeong-joo Lee, Young Tae Kim, Hee Han, Chi Won AhnAbstract:Two-dimensional transition metal carbides (MXenes) have attracted much attention due to their excellent electrical conductivity and outstanding performances in energy storage, telecommunication, and sensing applications. It is known that MXene flakes are readily oxidized in either humid air or aqueous environments. While the chemical instability of MXenes may limit their use in applications involving ambient environments and long-term operation, oxidation behaviour of MXene films has not been addressed. In this work, we demonstrate a hydrogen annealing method to increase the oxidation stability of Ti3C2 MXene in two different aspects: (1) dramatic improvement in the oxidation stability of pristine MXene films against harsh conditions (100% relative humidity, 70 °C), and (2) large recovery in the electrical conductivity of previously oxidized Ti3C2 MXene films. We also demonstrate an electric-field-induced heater capable of stable operation under highly oxidizing conditions, based on the oxidation-resistant MXene film. A total loss of heat generation ability was observed for the as-prepared MXene film, while the hydrogen-annealed one maintained its bright infrared radiation, under the highly oxidizing conditions. This work offers a solution to industrial applications of unprotected MXene films, securing their stable and long-term operation in humid conditions.
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an ultrafast conducting polymer MXene positive electrode with high volumetric capacitance for advanced asymmetric supercapacitors
Small, 2019Co-Authors: Ke Li, Xuehang Wang, Shuo Li, Patrick Urbankowski, Jianmin Li, Yuxi Xu, Yury GogotsiAbstract:: Pseudocapacitors or redox capacitors that synergize the merits of batteries and double-layer capacitors are among the most promising candidates for high-energy and high-power energy storage applications. 2D transition metal carbides (MXenes), an emerging family of pseudocapacitive materials with ultrahigh rate capability and volumetric capacitance, have attracted much interest in recent years. However, MXenes have only been used as negative electrodes as they are easily oxidized at positive (anodic) potential. To construct a high-performance MXene-based asymmetric device, a positive electrode with a compatible performance is highly desired. Herein, an ultrafast polyaniline@MXene cathode prepared by casting a homogenous polyaniline layer onto a 3D porous Ti3 C2 Tx MXene is reported, which enables the stable operation of MXene at positive potentials because of the enlarged work function after compositing with polyaniline, according to the first-principle calculations. The resulting flexible polyaniline@MXene positive electrode demonstrates a high volumetric capacitance of 1632 F cm-3 and an ultrahigh rate capability with 827 F cm-3 at 5000 mV s-1 , surpassing all reported positive electrodes. An asymmetric device is further fabricated with MXene as the anode and polyaniline@MXene as the cathode, which delivers a high energy density of 50.6 Wh L-1 and an ultrahigh power density of 127 kW L-1 .
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Introduction to 2D Transition Metal Carbides and Nitrides (MXenes)
2D Metal Carbides and Nitrides (MXenes), 2019Co-Authors: Babak Anasori, Yury GogotsiAbstract:Two-dimensional (2D) transition metal carbides and nitrides, known as MXenes, are a large family of 2D materials. Although the first MXene was discovered in 2011 without any prior prediction of their existence, the family has grown significantly, both from the chemistry and application perspectives. There are about thirty stoichiometric MXene compositions reported and many more are waiting to be discovered. MXenes reported to date are hydrophilic, typically with high metallic conductivity. MXenes have a variety of applications including energy generation and storage, electromagnetic interference shielding, water purification, catalysis, optoelectronics, gas- and biosensors, reinforcement for composites, and biomedical ones. This chapter gives an overview of MXenes and describes how each chapter of this book covers different properties and applications of MXenes.
Husam N Alshareef - One of the best experts on this subject based on the ideXlab platform.
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MXene hydrogels: fundamentals and applications.
Chemical Society reviews, 2020Co-Authors: Yizhou Zhang, Jehad K. El-demellawi, Qiu Jiang, Hanfeng Liang, Kanghyuck Lee, Xiaochen Dong, Husam N AlshareefAbstract:Hydrogels have recently garnered tremendous interest due to their potential application in soft electronics, human–machine interfaces, sensors, actuators, and flexible energy storage. Benefiting from their impressive combination of hydrophilicity, metallic conductivity, high aspect ratio morphology, and widely tuneable properties, when two-dimensional (2D) transition metal carbides/nitrides (MXenes) are incorporated into hydrogel systems, they offer exciting and versatile platforms for the design of MXene-based soft materials with tunable application-specific properties. The intriguing and, in some cases, unique properties of MXene hydrogels are governed by complex gel structures and gelation mechanisms, which require in-depth investigation and engineering at the nanoscale. On the other hand, the formulation of MXenes into hydrogels can significantly increase the stability of MXenes, which is often the limiting factor for many MXene-based applications. Moreover, through simple treatments, derivatives of MXene hydrogels, such as aerogels, can be obtained, further expanding their versatility. This tutorial review intends to show the enormous potential of MXene hydrogels in expanding the application range of both hydrogels and MXenes, as well as increasing the performance of MXene-based devices. We elucidate the existing structures of various MXene-containing hydrogel systems along with their gelation mechanisms and the interconnecting driving forces. We then discuss their distinctive properties stemming from the integration of MXenes into hydrogels, which have revealed an enhanced performance, compared to either MXenes or hydrogels alone, in many applications (energy storage/harvesting, biomedicine, catalysis, electromagnetic interference shielding, and sensing).
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MXenes for Plasmonic Photodetection.
Advanced materials (Deerfield Beach Fla.), 2019Co-Authors: Dhinesh Babu Velusamy, Jehad K. El-demellawi, Ahmed M. El-zohry, Andrea Giugni, Sergei Lopatin, Mohamed N. Hedhili, Ahmed E. Mansour, Enzo Di Fabrizio, Omar F. Mohammed, Husam N AlshareefAbstract:MXenes have recently shown impressive optical and plasmonic properties associated with their ultrathin-atomic-layer structure. However, their potential use in photonic and plasmonic devices has been only marginally explored. Photodetectors made of five different MXenes are fabricated, among which molybdenum carbide MXene (Mo2 CTx ) exhibits the best performance. Mo2 CTx MXene thin films deposited on paper substrates exhibit broad photoresponse in the range of 400-800 nm with high responsivity (up to 9 A W-1 ), detectivity (≈5 × 1011 Jones), and reliable photoswitching characteristics at a wavelength of 660 nm. Spatially resolved electron energy-loss spectroscopy and ultrafast femtosecond transient absorption spectroscopy of the MXene nanosheets reveal that the photoresponse of Mo2 CTx is strongly dependent on its surface plasmon-assisted hot carriers. Additionally, Mo2 CTx thin-film devices are shown to be relatively stable under ambient conditions, continuous illumination and mechanical stresses, illustrating their durable photodetection operation in the visible spectral range. Micro-Raman spectroscopy conducted on bare Mo2 CTx film and on gold electrodes allowing for surface-enhanced Raman scattering demonstrates surface chemistry and a specific low-frequency band that is related to the vibrational modes of the single nanosheets. The specific ability to detect and excite individual surface plasmon modes provides a viable platform for various MXene-based optoelectronic applications.
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MXetronics: Electronic and photonic applications of MXenes
Nano Energy, 2019Co-Authors: Hyunho Kim, Zhenwei Wang, Husam N AlshareefAbstract:MXenes, a large family of two-dimensional transition metal carbides and nitrides, have been attracting great interest since the discovery of Ti 3 C 2 T x in 2011. The unique combination of metallic conductivity and hydrophilicity in Ti 3 C 2 T x resulted in outstanding performances in electrochemical applications. The surface of MXene is highly chemically active after selective chemical etching of their precursor phases and always forms surface terminations such as hydroxyl, oxygen, or fluorine. Those surface functional groups not only affect their hydrophilic behavior and electrochemical properties such as ion adsorption and diffusion, but also affect their electronic structure, conductivity, work function, and hence their electronic properties. In this review, the emerging electronic and photonic applications of MXenes (henceforth referred to as MXetronics) are discussed. This is a fast-emerging field of MXene research with huge potential.
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all pseudocapacitive MXene ruo2 asymmetric supercapacitors
Advanced Energy Materials, 2018Co-Authors: Qiu Jiang, Mohamed Alhabeb, Yury Gogotsi, Narendra Kurra, Husam N AlshareefAbstract:© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2D transition metal carbides and nitrides, known as MXenes, are an emerging class of 2D materials with a wide spectrum of potential applications, in particular in electrochemical energy storage. The hydrophilicity of MXenes combined with their metallic conductivity and surface redox reactions is the key for high-rate pseudocapacitive energy storage in MXene electrodes. However, symmetric MXene supercapacitors have a limited voltage window of around 0.6 V due to possible oxidation at high anodic potentials. In this study, the fact that titanium carbide MXene (Ti3C2Tx) can operate at negative potentials in acidic electrolyte is exploited, to design an all-pseudocapacitive asymmetric device by combining it with a ruthenium oxide (RuO2) positive electrode. This asymmetric device operates at a voltage window of 1.5 V, which is about two times wider than the operating voltage window of symmetric MXene supercapacitors, and is the widest voltage window reported to date for MXene-based supercapacitors. The complementary working potential windows of MXene and RuO2, along with proton-induced pseudocapacitance, significantly enhance the device performance. As a result, the asymmetric devices can deliver an energy density of 37 µW h cm−2 at a power density of 40 mW cm−2, with 86% capacitance retention after 20 000 charge–discharge cycles. These results show that pseudocapacitive negative MXene electrodes can potentially replace carbon-based materials in asymmetric electrochemical capacitors, leading to an increased energy density.
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All Pseudocapacitive MXene‐RuO2 Asymmetric Supercapacitors
Advanced Energy Materials, 2018Co-Authors: Qiu Jiang, Mohamed Alhabeb, Yury Gogotsi, Narendra Kurra, Husam N AlshareefAbstract:© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2D transition metal carbides and nitrides, known as MXenes, are an emerging class of 2D materials with a wide spectrum of potential applications, in particular in electrochemical energy storage. The hydrophilicity of MXenes combined with their metallic conductivity and surface redox reactions is the key for high-rate pseudocapacitive energy storage in MXene electrodes. However, symmetric MXene supercapacitors have a limited voltage window of around 0.6 V due to possible oxidation at high anodic potentials. In this study, the fact that titanium carbide MXene (Ti3C2Tx) can operate at negative potentials in acidic electrolyte is exploited, to design an all-pseudocapacitive asymmetric device by combining it with a ruthenium oxide (RuO2) positive electrode. This asymmetric device operates at a voltage window of 1.5 V, which is about two times wider than the operating voltage window of symmetric MXene supercapacitors, and is the widest voltage window reported to date for MXene-based supercapacitors. The complementary working potential windows of MXene and RuO2, along with proton-induced pseudocapacitance, significantly enhance the device performance. As a result, the asymmetric devices can deliver an energy density of 37 µW h cm−2 at a power density of 40 mW cm−2, with 86% capacitance retention after 20 000 charge–discharge cycles. These results show that pseudocapacitive negative MXene electrodes can potentially replace carbon-based materials in asymmetric electrochemical capacitors, leading to an increased energy density.
Kent J Griffith - One of the best experts on this subject based on the ideXlab platform.
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bulk and surface chemistry of the niobium max and MXene phases from multinuclear solid state nmr spectroscopy
Journal of the American Chemical Society, 2020Co-Authors: Yury Gogotsi, Kent J Griffith, Michael A Hope, Philip J Reeves, Mark Anayee, Clare P GreyAbstract:MXenes, derived from layered MAX phases, are a class of two-dimensional materials with emerging applications in energy storage, electronics, catalysis, and other fields due to their high surface areas, metallic conductivity, biocompatibility, and attractive optoelectronic properties. MXene properties are heavily influenced by their surface chemistry, but a detailed understanding of the surface functionalization is still lacking. Solid-state nuclear magnetic resonance (NMR) spectroscopy is sensitive to the interfacial chemistry, the phase purity including the presence of amorphous/nanocrystalline phases, and the electronic properties of the MXene and MAX phases. In this work, we systematically study the chemistry of Nb MAX and MXene phases, Nb2AlC, Nb4AlC3, Nb2CTx, and Nb4C3Tx, with their unique electronic and mechanical properties, using solid-state NMR spectroscopy to examine a variety of nuclei (1H, 13C, 19F, 27Al, and 93Nb) with a range of one- and two-dimensional correlation, wide-line, high-sensitivity, high-resolution, and/or relaxation-filtered experiments. Hydroxide and fluoride terminations are identified, found to be intimately mixed, and their chemical shifts are compared with other MXenes. This multinuclear NMR study demonstrates that diffraction alone is insufficient to characterize the phase composition of MAX and MXene samples as numerous amorphous or nanocrystalline phases are identified including NbC, AlO6 species, aluminum nitride or oxycarbide, AlF3·nH2O, Nb metal, and unreacted MAX phase. To the best of our knowledge, this is the first study to examine the transition-metal resonances directly in MXene samples, and the first 93Nb NMR of any MAX phase. The insights from this work are employed to enable the previously elusive assignment of the complex overlapping 47/49Ti NMR spectrum of Ti3AlC2. The results and methodology presented here provide fundamental insights on MAX and MXene phases and can be used to obtain a more complete picture of MAX and MXene chemistry, to prepare realistic structure models for computational screening, and to guide the analysis of property measurements.
Clare P Grey - One of the best experts on this subject based on the ideXlab platform.
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bulk and surface chemistry of the niobium max and MXene phases from multinuclear solid state nmr spectroscopy
Journal of the American Chemical Society, 2020Co-Authors: Yury Gogotsi, Kent J Griffith, Michael A Hope, Philip J Reeves, Mark Anayee, Clare P GreyAbstract:MXenes, derived from layered MAX phases, are a class of two-dimensional materials with emerging applications in energy storage, electronics, catalysis, and other fields due to their high surface areas, metallic conductivity, biocompatibility, and attractive optoelectronic properties. MXene properties are heavily influenced by their surface chemistry, but a detailed understanding of the surface functionalization is still lacking. Solid-state nuclear magnetic resonance (NMR) spectroscopy is sensitive to the interfacial chemistry, the phase purity including the presence of amorphous/nanocrystalline phases, and the electronic properties of the MXene and MAX phases. In this work, we systematically study the chemistry of Nb MAX and MXene phases, Nb2AlC, Nb4AlC3, Nb2CTx, and Nb4C3Tx, with their unique electronic and mechanical properties, using solid-state NMR spectroscopy to examine a variety of nuclei (1H, 13C, 19F, 27Al, and 93Nb) with a range of one- and two-dimensional correlation, wide-line, high-sensitivity, high-resolution, and/or relaxation-filtered experiments. Hydroxide and fluoride terminations are identified, found to be intimately mixed, and their chemical shifts are compared with other MXenes. This multinuclear NMR study demonstrates that diffraction alone is insufficient to characterize the phase composition of MAX and MXene samples as numerous amorphous or nanocrystalline phases are identified including NbC, AlO6 species, aluminum nitride or oxycarbide, AlF3·nH2O, Nb metal, and unreacted MAX phase. To the best of our knowledge, this is the first study to examine the transition-metal resonances directly in MXene samples, and the first 93Nb NMR of any MAX phase. The insights from this work are employed to enable the previously elusive assignment of the complex overlapping 47/49Ti NMR spectrum of Ti3AlC2. The results and methodology presented here provide fundamental insights on MAX and MXene phases and can be used to obtain a more complete picture of MAX and MXene chemistry, to prepare realistic structure models for computational screening, and to guide the analysis of property measurements.
Babak Anasori - One of the best experts on this subject based on the ideXlab platform.
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synthesis and electrochemical properties of 2d molybdenum vanadium carbides solid solution MXenes
Journal of Materials Chemistry, 2020Co-Authors: David Pinto, Babak Anasori, Kanit Hantanasirisakul, Hemesh Avireddy, Christopher E Shuck, Grayson Deysher, J R Morante, William PorzioAbstract:MXenes have demonstrated high performance as negative electrodes in supercapacitors with aqueous electrolytes due to their high redox capacitance. However, oxidation limits their use under positive potential, requiring asymmetric devices with positive electrodes made of other materials which are usually less capacitive compared to MXenes and therefore limit the device performances. Here, we report the synthesis of two-dimensional molybdenum vanadium carbides (MoxV4−xC3), previously unexplored double transition metal MXenes, by selective etching of aluminum from MoxV4−xAlC3 MAX phase precursors. Unlike the ordered double transition metal MXenes reported previously, MoxV4−xC3 exhibits a Mo–V solid solution in the transition metal layers. We have synthesized and characterized four different compositions of MoxV4−xC3 with x = 1, 1.5, 2, and 2.7. We showed that by changing the Mo : V ratio, the surface terminations (O : F ratio), and electrical and electrochemical properties of the resulting MXenes can be tuned. The Mo2.7V1.3C3 composition showed a remarkable volumetric capacitance (up to 860 F cm−3) and high electrical conductivity (830 S cm−1) at room temperature. Moreover, these solid solution MXenes have demonstrated the ability to operate in a wider range of positive potentials compared to other MXenes. Following this discovery, we coupled a Mo2.7V1.3C3 positive electrode with a well-studied Ti3C2 MXene negative electrode to create an all-MXene supercapacitor, as a proof of concept.
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Introduction to 2D Transition Metal Carbides and Nitrides (MXenes)
2D Metal Carbides and Nitrides (MXenes), 2019Co-Authors: Babak Anasori, Yury GogotsiAbstract:Two-dimensional (2D) transition metal carbides and nitrides, known as MXenes, are a large family of 2D materials. Although the first MXene was discovered in 2011 without any prior prediction of their existence, the family has grown significantly, both from the chemistry and application perspectives. There are about thirty stoichiometric MXene compositions reported and many more are waiting to be discovered. MXenes reported to date are hydrophilic, typically with high metallic conductivity. MXenes have a variety of applications including energy generation and storage, electromagnetic interference shielding, water purification, catalysis, optoelectronics, gas- and biosensors, reinforcement for composites, and biomedical ones. This chapter gives an overview of MXenes and describes how each chapter of this book covers different properties and applications of MXenes.
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Control of MXenes' electronic properties through termination and intercalation.
Nature communications, 2019Co-Authors: James L. Hart, Babak Anasori, Yury Gogotsi, Kanit Hantanasirisakul, Andrew C. Lang, David Pinto, Yevheniy Pivak, J. Tijn Van Omme, Steven J. May, Mitra L. TaheriAbstract:MXenes are an emerging family of highly-conductive 2D materials which have demonstrated state-of-the-art performance in electromagnetic interference shielding, chemical sensing, and energy storage. To further improve performance, there is a need to increase MXenes’ electronic conductivity. Tailoring the MXene surface chemistry could achieve this goal, as density functional theory predicts that surface terminations strongly influence MXenes' Fermi level density of states and thereby MXenes’ electronic conductivity. Here, we directly correlate MXene surface de-functionalization with increased electronic conductivity through in situ vacuum annealing, electrical biasing, and spectroscopic analysis within the transmission electron microscope. Furthermore, we show that intercalation can induce transitions between metallic and semiconductor-like transport (transitions from a positive to negative temperature-dependence of resistance) through inter-flake effects. These findings lay the groundwork for intercalation- and termination-engineered MXenes, which promise improved electronic conductivity and could lead to the realization of semiconducting, magnetic, and topologically insulating MXenes. Two-dimensional transition metal carbides and nitrides (MXenes) have emerged as highly conductive and stable materials, of promise for electronic applications. Here, the authors use in situ electric biasing and transmission electron microscopy to investigate the effect of surface termination and intercalation on electronic properties.
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self assembly of transition metal oxide nanostructures on MXene nanosheets for fast and stable lithium storage
Advanced Materials, 2018Co-Authors: Yitao Liu, Babak Anasori, Yury Gogotsi, Qizhen Zhu, Peng Zhang, Ning Sun, Huan LiuAbstract:Recently, a new class of 2D materials, i.e., transition metal carbides, nitrides, and carbonitrides known as MXenes, is unveiled with more than 20 types reported one after another. Since they are flexible and conductive, MXenes are expected to compete with graphene and other 2D materials in many applications. Here, a general route is reported to simple self-assembly of transition metal oxide (TMO) nanostructures, including TiO2 nanorods and SnO2 nanowires, on MXene (Ti3 C2 ) nanosheets through van der Waals interactions. The MXene nanosheets, acting as the underlying substrate, not only enable reversible electron and ion transport at the interface but also prevent the TMO nanostructures from aggregation during lithiation/delithiation. The TMO nanostructures, in turn, serve as the spacer to prevent the MXene nanosheets from restacking, thus preserving the active areas from being lost. More importantly, they can contribute extraordinary electrochemical properties, offering short lithium diffusion pathways and additional active sites. The resulting TiO2 /MXene and SnO2 /MXene heterostructures exhibit superior high-rate performance, making them promising high-power and high-energy anode materials for lithium-ion batteries.
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saturable absorption in 2d ti c MXene thin films for passive photonic diodes
Advanced Materials, 2018Co-Authors: Yongchang Dong, Vadym N. Mochalin, Babak Anasori, Yury Gogotsi, Kathleen Maleski, Sergii Chertopalov, Sriparna Bhattacharya, Apparao M Rao, Ramakrishna PodilaAbstract:MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti3 CNTx (Tx represents functional groups such as OH and F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber-based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti3 C2 Tx thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties. Using the open aperture Z-scan method, it is found that the SA behavior in Ti3 C2 Tx MXene arises from plasmon-induced increase in the ground state absorption at photon energies above the threshold for free carrier oscillations. The saturation fluence and modulation depth of Ti3 C2 Tx MXene is observed to be dependent on the film thickness. Unlike other 2D materials, Ti3 C2 Tx is found to show higher threshold for light-induced damage with up to 50% increase in nonlinear transmittance. Lastly, building on the SA behavior of Ti3 C2 Tx MXenes, a Ti3 C2 Tx MXene-based photonic diode that breaks time-reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated.
