Fig. 5. Plasmon excitation boosts interfacial charge transfer in AuNR@TiO₂ heterostructures.

(A) Efficiencies of charge injection at different excitation wavelengths obtained from NIR transient absorption spectroscopy excited at 1.15 μm (blue bars), determine the sum of direct and indirect charge transfer pathways by monitoring free carrier absorption in the TiO₂ conduction band. Efficiencies of total (direct + indirect) charge transfer, (green bars) calculated from the changes in slopes of pump fluence–dependent electron-phonon relaxation times τ_e–ph using a visible probe at the LSPR maximum. The widths of the blue and green bars reflect the spectral width of the excitation, and the error bars are the fit uncertainties. The spectrally resolved efficiencies of the isolated direct charge transfer pathway (gray bars) obtained through quantifying CID as a function of single-particle resonance maxima λ_max. The CID efficiencies are binned with a width of 20 nm, and the error bars are the SD of the single-particle data. (B) CID dependence on scattering λ_max. Gray points are CID values from Fig. 2E, while the green line is the predicted wavelength dependence of CID according to the Persson model. Inset: Illustration of adsorbate-induced resonance state formation at the Au-TiO₂ interface according to the Persson model.