TY - JOUR T1 - Transition from nanoparticle to molecular behavior: a femtosecond transient absorption study of a size-selected 28 atom gold cluster JF - Chemical Physics Letters Y1 - 2002 A1 - Link, Stephan A1 - El-Sayed, Mostafa A A1 - Schaaff, T. G. A1 - Whetten, R. L. AB - The ultrafast electron dynamics of chemically prepared gold nanoclusters with a 28 atom gold core surrounded by 16 glutathione molecules were investigated. After excitation with femtosecond laser pulses these clusters show an induced transient absorption in the visible from 2.58 to 1.65 eV (480-750 nm) with a maximum around 2.07 eV (600 nm). The excited state relaxation shows a biexponential decay with a subpicosecond and a longer nanosecond decay time independent of the laser pump power. These results are different from those observed previously for larger gold nanoparticles, which suggests that the Au-28-glutathione system shows molecular properties. (C) 2002 Elsevier Science B.V. All rights reserved. VL - 356 SN - 0009-2614 N1 - Link, S El-Sayed, MA Schaaff, TG Whetten, RL M3 - 10.1016/s0009-2614(02)00306-8 ER - TY - JOUR T1 - Visible to infrared luminescence from a 28-atom gold cluster JF - Journal of Physical Chemistry B Y1 - 2002 A1 - Link, Stephan A1 - Beeby, A. A1 - FitzGerald, S. A1 - El-Sayed, Mostafa A A1 - Schaaff, T. G. A1 - Whetten, R. L. AB - The luminescence properties of chemically prepared gold nanoclusters, each composed of a 28-atom core and a glutathione (GSH) adsorbate layer consisting of 16 molecules, were investigated. These clusters show a distinct absorption onset at 1.3 eV corresponding to the opening of an electronic gap within the conduction band (HOMO-LUMO gap). Here we report on the radiative properties of these molecular-like Bald clusters. By using a combination of different detectors with sensitivities in the visible to the infrared (2.0-0.8 eV), a broad luminescence extending over this entire spectral range was observed. Our results further suggest that the luminescence can be separated into two bands with maxima around 1.5 and 1.15 eV indicating that radiative recombination between the ground state and two distinctively different excited states takes place. The: origin of the observed luminescence bands is discussed using a solid state as well as a molecular model for the electronic structure and relaxation of the clusters. The total quantum yield of the luminescence: as measured at ambient temperature was approximated to be about (3.5 +/- 1.0) x 10(-3). VL - 106 SN - 1520-6106 N1 - Link, S Beeby, A FitzGerald, S El-Sayed, MA Schaaff, TG Whetten, RL M3 - 10.1021/jp014259v ER -