Fig. 2: Concept of the broadband impulsive vibrational spectroscopy (IVS) experiment with plasmonic MXenes.

a The scheme of the pump-probe IVS used to measure the SP-vibrational coupling and vibrations of Ti₃C₂T_x. The pump pulse generates excited electrons, and then the dynamics of electrons and lattices were monitored by the probe pulse. b Absorption spectra of plasmonic MXenes: Ti₃C₂T_x (red line) and Mo₂CT_x (green line) films. c The pump-probe data detected at 900 nm show photoinduced differential transmission as a function of the time delay. The inset shows a 2D map of the photoinduced differential transmission. d Fitting results from a differential transmission signal consisting of relaxation and oscillating components, which are equivalent to the vibration mode frequency. e The vibrational spectrum was obtained from the fast Fourier transform (FFT) of differential transmission data after subtraction of the relaxation process.