Enhanced Photothermal Effects and Excited-State Dynamics of Plasmonic Size-Controlled Gold–Silver–Gold Core–Shell–Shell Nanoparticles

The synthesis, characterization, and excited-state dynamics of colloidal gold–silver–gold core–shell–shell nanoparticles are reported. These plasmonic nanoparticles are spherical in shape with uniform shells. The plasmonic extinction peak wavelengths can be controlled over the visible and near-infrared regions by varying the thicknesses of the gold and silver shells. These unique spectroscopic properties make these nanoparticles potential candidates for biologically relevant applications including photothermal cancer therapy and biosensing. The ratio of the gold shell thickness to the overall particle size shows a linear dependence with the position of the plasmon extinction peak wavelength. Temperature measurements after laser irradiation show that the colloidal core–shell–shell nanoparticles have a higher photothermal effect compared to spherical gold nanoparticles and gold nanorods. Transient absorption measurements determine that the phonon–phonon scattering lifetime is considerably faster in the core–shell–shell nanoparticles than in the gold nanospheres and gold nanorods, which contributes to the higher photothermal efficiencies. In addition, the synthesis of extended core–shell architectures with controllable core and shell dimensions of alternating gold/silver shells is reported for advanced plasmonic engineering.