Dual Transient Bleaching of Au/PbS Hybrid Core/Shell Nanoparticles

Abstract

We examined the optical response of hybrid Au/PbS core/shell nanoparticles (NPs) using transient absorption spectroscopy. Finite-difference time-domain (FDTD) calculations and transient absorption measurements show that Au/PbS NPs have unique two extinction peaks: the peak at the longer wavelength (∼700 nm) is originated from the plasmon, and that at the shorter wavelength (550 nm) is from the local maximum of the refractive index of PbS. The transient absorption dynamics of Au/PbS NPs excited at 400 nm have clear oscillation behavior, which is assigned to the breathing mode of whole particle. We observed a weak excitation-wavelength dependence of the plasmon band. The time constant of electron–phonon coupling of Au/PbS NPs was obtained by changing the excitation intensity. We show that spectral properties of Au/PbS NPs are strongly altered by the hybrid formations, while their dynamics differ only minimally compared with those of Au NPs