Ti3AlC2 MAX and Ti3C2 MXene Quantum Sheets for Record-High Optical Nonlinearity

Ultrabroadband Optical Properties of 2D Titanium Carbide MXene

MXenes have rapidly ascended as a prominent class of two-dimensional (2D) materials, renowned for their distinctive optical and electrical properties. Despite extensive exploration of MXenes' optical properties, existing studies predominantly focus on the near-infrared (NIR) to the ultraviolet spectral range, leaving the mid-infrared (mid-IR) range relatively uncharted. In this study, we conducted a comprehensive characterization of the intrinsic optical properties of Ti3C2Tx MXene across an ultrabroadband spectral range, spanning from mid-IR (28 meV) to vacuum ultraviolet (VUV, 6.4 eV). For this purpose, Ti3C2Tx MXene films of varying thicknesses were coated on quartz substrates, resulting in two distinct categories: thin film samples with thicknesses below 50 nm and bulk-like samples with thicknesses exceeding 500 nm. Using spectroscopic ellipsometry, we analyzed the optical properties of films of various thicknesses and extracted detailed information on their dielectric functions. Our findings reveal resonances in the mid-IR to VUV range. Employing the Lorentz-Drude model to examine these resonances has uncovered the optical resistivity of MXene films and led to the identification of multiple plasmonic modes active in the visible to NIR range, as well as broad band-to-band transition-like resonances in the mid-IR range. This ultrabroadband optical versatility of Ti3C2Tx MXene is anticipated to bring about a wide range of thermal and optical applications.

Mechanochemical Pretreated Mn+1AXn (MAX) Phase to Synthesize 2D-Ti3C2Tx MXene Sheets for High-Performance Supercapacitors

Two-dimensional (2D) MXenes sheet-like micro-structures have attracted attention as an effective electrochemical energy storage material due to their efficient electrolyte/cation interfacial charge transports inside the 2D sheets which results in ultrahigh rate capability and high volumetric capacitance. In this article, Ti₃C₂T_x MXene is prepared by a combination of ball milling and chemical etching from Ti₃AlC₂ powder. The effects of ball milling and etching duration on the physiochemical properties are also explored, as well as the electrochemical performance of as-prepared Ti₃C₂ MXene. The electrochemical performances of 6 h mechanochemically treated and 12 h chemically etched MXene (BM-12H) exhibit an electric double layer capacitance behavior with an enhanced specific capacitance of 146.3 F g^-1 compared to 24 and 48 h treated samples. Moreover, 5000-cycle stability tested sample's (BM-12H) charge/discharge show increased specific capacitance due to the termination of the -OH group, intercalation of K⁺ ion and transformation to TiO₂/Ti₃C₂ hybrid structure in a 3 M KOH electrolyte. Interestingly, a symmetric supercapacitor (SSC) device fabricated in a 1 M LiPF₆ electrolyte in order to extend the voltage window up to 3 V shows a pseudocapacitance behavior due to Li on interaction/de-intercalation. In addition, the SSC shows an excellent energy and power density of 138.33 W h kg^-1 and 1500 W kg^-1, respectively. The ball milling pre-treated MXene exhibited an excellent performance and stability due to the increased interlayer distance between the MXene sheets and intercalation and deintercalation of Li⁺ ions.