Two-Dimensional\nTiVC Solid-Solution MXene as Surface-Enhanced\nRaman Scattering Substrate

Abstract

Two-dimensional\n(2D) MXenes are attractive candidates as surface-enhanced\nRaman scattering (SERS) substrates because of their metallic conductivity\nand abundant surface terminations. Herein, we report the facile synthesis\nof bimetallic solid-solution TiVC (MXene) and its application in SERS.\nThe few-layered MXene nanosheets with high crystallinity were successfully\nprepared using a one-step chemical etching method without ultrasonic\nand organic solvent intercalation steps. SERS activity of the as-prepared\nMXene was investigated by fabricating free-standing TiVC film as the\nsubstrate. A SERS enhancement factor of 10¹² and femtomolar-level\ndetection limit were confirmed using rhodamine 6G as a model dye with\n532 nm excitation. The fluorescent signal of the rhodamine 6G dye\nwas effectively quenched, making the SERS spectrum clearly distinguishable.\nFurthermore, we demonstrate that the TiVC-analyte system with ultrahigh\nsensitivity is dominated by the chemical mechanism (CM) based on the\nexperimental and simulation results. The abundant density of states\nnear the Fermi level of the TiVC and the strong interaction between\nthe TiVC and analyte promote the intermolecular charge transfer resonance\nin the TiVC–analyte complex, resulting in significant Raman\nenhancement. Additionally, several other probe molecules were used\nfor SERS detection to further verify CM-based selectivity enhancement\non the TiVC substrates. This work provides guidance for the facile\nsynthesis of 2D MXene and its application in ultrasensitive SERS detection.