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Electronic and optical characterization of 2D Ti<sub>2</sub>C and Nb<sub>2</sub>C (MXene) thin films
摘要： Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes) are emerging as a new class of 2D materials, with extensive opportunities for property tailoring due to the numerous possibilities for varying chemistries and surface terminations. Here, Ti2AlC and Nb2AlC MAX phase epitaxial thin films were deposited on sapphire substrates by physical vapor deposition. The films were then etched in LiF/HCl solutions, yielding Li-intercalated, 2D Ti2CTz and Nb2CTz films, whose terminations, transport and optical properties were characterized. The former exhibits metallic conductivity, with weak localization below 50 K. In contrast, the Nb-based film exhibits an increase in resistivity with decreasing temperature from RT down to 40 K consistent with variable range hopping transport. The optical properties of both films were determined from spectroscopic ellipsometry in the 0.75 to 3.50 eV range. The results for Ti2AlTz films confirm the metallic behavior. In contrast, no evidence of metallic behavior is observed for the Nb2CTz film. The present work therefore demonstrates that one fruitful approach to alter the electronic and optical properties of MXenes is to change the nature of the transition metal.
关键词： transition metal carbide,thin films,MXene,transport properties
更新于2025-09-19 17:15:36
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Transition Metal Carbide Core/Shell Nanoparticles by Ultra-Short Laser Ablation in Liquid
摘要： Transition metal carbide nanoparticles are a class of technological interesting materials with a wide range of applications. Among metal carbides, tantalum carbides have good compatibility with the biological environment while molybdenum carbides are used as catalyst in electrochemical reactions. Laser ablation of bulk transition metal targets in some liquids is here reported and laser ablation in organic solvents is used as simple synthetic strategy for the production of carbide nanostructures. Herein, the nanoparticles produced by ultra-short laser ablation of tantalum and molybdenum in water, acetone, ethanol and toluene have been characterized by TEM, XRD and XPS analysis. The combined effect of metal and solvent chemical and physical properties on the composition of the nanomaterials obtained has been pointed out. In particular, the different reactivity of Ta and Mo with respect to oxidizing species determines the composition of particles obtained in water, on the other hand the organic solvents decomposition allows to obtain transition metal carbide (TMC) nanoparticles. The observed carbonaceous shell formed on TMC allows to protect the particle’s carbidic core and to improve and tailor the applications of these nanomaterials.
关键词： ultrashort laser ablation in liquid,transition metal carbide,core/shell nanostructures,solvent degradation
更新于2025-09-19 17:13:59
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Two-dimensional transition metal carbide and nitride (MXene) derived quantum dots (QDs): synthesis, properties, applications and prospects
摘要： The progress of two-dimensional (2D) MXene-derived QDs (MQDs) is in the early stages, but the materials have aroused great interest due to their high electrical conductivity, abundant active catalytic sites, easily tunable structure, satisfactory dispersibility, remarkable optical properties, good biocompatibility, manifold functionalizations, and so on. However, up to now, there is still no review paper on MQDs. Herein, the research advances of MQDs, including their synthetic routes (top-down and bottom-up methods), properties (structural, electronic, optical and magnetic properties), functionalizations (surface modifications, heteroatom doping and the construction of composites) and applications (sensing, biomedical, catalysis, energy storage and optoelectronic devices etc.), are critically highlighted, and the future prospects and challenges of MQDs are discussed. This review will serve as a one-stop point for comprehending the most advanced developments of MQDs, and will hopefully enlighten researchers to employ MQDs for satisfying the growing requirements of the diverse applications.
关键词： transition metal carbide,MXene,prospects,properties,nitride,Two-dimensional,applications,synthesis,quantum dots
更新于2025-09-19 17:13:59
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Facile Synthesis of Uniform Metal Carbide Nanoparticles from MOFs by Laser Metallurgy
摘要： We report the fast and efficient conversion of metal-organic frameworks (MOFs) to phase pure transition metal carbide (TMC) nanoparticles with uniform size using laser as the energy source, consuming only 6-Watt power. Nanoparticles of HfC, ZrC, TiC, V8C7, α-MoC, Cr3C2 and FeCx with homogeneous sizes (varied between 6 and 20 nm) were successfully produced, among which HfC and ZrC nanoparticles were obtained, for the first time, with sizes less than 10 nm and in pure phase. This method was operated directly in air, in stark contrast to traditional furnace heating and laser spray methods, where protective atmosphere are required. The use of MOFs allowed us to precisely tune the composition of TMC nanoparticles by dialing in the right type and desirable amounts of organic linkers. FeCx nanoparticles doped with various percentages of nitrogen atoms were synthesized for Fischer-Tropsch reaction without any pretreatment or activation. Extremely high iron time of yield (FTY) values were observed, 415 μmol gFe -1 s-1 and 550 μmol gFe -1 s-1 (with addition of K), in a 40 h test without any decay in performance. High olefin to paraffin ratio was achieved for C2 to C11 products, where the ratio for C3 was higher than 10.
关键词： laser,nano,transition metal carbide,metal-organic framework,Fischer-Tropsch synthesis
更新于2025-09-12 10:27:22