Dynamics of laser excited colloidal gold nanoparticles functionalized with cysteine derivatives

•The ultrafast dynamics of AuNPs were investigated using femtosecond laser pulses.•The “hot” electrons dynamics shows two components: fast (1 ps) and slow (300 ps).•We studied the transient absorption behavior of the S-ligands functionalized AuNPs.•The relaxation times varied with increasing the ligand fraction.

The ultrafast dynamics of Au colloidal nanoparticles excited with femtosecond laser pulses is investigated experimentally. The transient absorption signal presents a bleaching of the surface plasmon band and a transient absorption at the wings of the band. The kinetics of the “hot” electrons in Au nanoparticles show a fast component of around 1 ps and a slower one of approximately 300 ps. Additionally, we found that the time of the ground state population recovery of Au nanoparticles depends on the pump wavelength. Furthermore, the interaction of Au nanoparticles with cysteine and cystine is studied at different pump wavelengths. The increase of the ligand concentration produces a variation of the relaxation times, as well as a delay of the time zero kinetics due to the adsorption of the ligands to the Au surface.

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