Modulating nonequilibrium electron–phonon interactions and energy relaxation in MXenes by surface-anchored Mo3S7 nanoclusters

Abstract

Abstract Electron–phonon (e–ph) interactions govern photoinduced nonequilibrium dynamics of MXenes, determining hot-carrier relaxation and parasitic heat accumulation. However, strategies to deliberately modulate these interactions through chemical control, together with mechanistic understanding, remain underexplored. Here, we demonstrate the effective modulation of nonequilibrium e–ph interactions in Ti 3 C 2 T x MXene via surface-anchored Mo 3 S 7 nanoclusters, which introduce a rapid energy harvesting pathway competing with intrinsic e–ph relaxation. Using mild ligand substitution, Mo 3 S 7 nanoclusters are densely and homogenously anchored onto Ti 3 C 2 T x via coordination bonding between Mo centers and O-terminations. Femtosecond transient absorption and optical-pump terahertz-probe spectroscopy reveal an ultrafast, sub-100 fs nonthermal electron and/or energy extraction, with efficiency increasing from ~28.6 % at 1.55 eV to ~38.2 % at 3.88 eV. This excitation-energy-dependent enhancement is enabled by improved energetic alignment between hot electrons in Ti 3 C 2 T x and the conduction-band manifold of Mo 3 S 7 . The competitive depletion of nonthermal electrons suppresses coherent A 1g phonon excitation, reducing effective e–ph interactions. Our study offers a viable strategy for modulating e–ph interactions in MXenes, advancing hot carrier relaxation and thermal management in next-generation optoelectronic devices.