title: Optical properties and electronic energy relaxation of metallic Au144(SR)60 nanoclusters.
abstract: Electronic energy relaxation of Au144(SR)60(q) ligand-protected nanoclusters, where SR = SC6H13 and q = -1, 0, +1, and +2, was examined using femtosecond time-resolved transient absorption spectroscopy. The observed differential transient spectra contained three distinct components: (1) transient bleaches at 525 and 600 nm, (2) broad visible excited-state absorption (ESA), and (3) stimulated emission (SE) at 670 nm. The bleach recovery kinetics depended upon the excitation pulse energy and were thus attributed to electron-phonon coupling typical of metallic nanostructures. The prominent bleach at 525 nm was assigned to a core-localized plasmon resonance (CLPR). ESA decay kinetics were oxidation-state dependent and could be described using a metal-sphere charging model. The dynamics, emission energy, and intensity of the SE peak exhibited dielectric-dependent responses indicative of Superatom charge transfer states. On the basis of these data, the Au144(SR)60 system is the smallest-known nanocluster to exhibit quantifiable electron dynamics and optical properties characteristic of metals.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.
authors.forename: Chongyue
authors.initials: C
authors.lastname: Yi
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Tofanelli
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ackerson
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Knappenberger
mesh_terms: D004583:Electrons; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry*; D050607:Organogold Compounds / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D050607:Organogold Compounds