Femtosecond excitation dynamics in gold nanospheres and nanorods

Femtosecond visible photoluminescence is detected from gold nanoparticles using time-resolved fluorescence upconversion spectroscopy. We directly compared this fast luminescence from gold nanospheres 25 nm with that obtained from nanorods 1540 nm, 1527 nm under vis 3.02 eV and UV4.65 eV excitation. A fast 50 fs decay was obtained for the nanoparticles and the emission was depolarized. Degenerate femtosecond pump-probe experiments in the low excitation intensity regime demonstrated much slower electron thermalization and/or equilibration dynamics on the time scale of a few hundred femtoseconds. These features strongly indicate a d-hole-conduction electron recombination process as the origin of this photoluminescence. A direct comparison of the fast emission spectra from nanorods and nanospheres is used to discuss the emission enhancement mechanism. These results suggest that the classical local field enhancement theory describes quantitatively well many of the emission features of nanorods with respect to those for nanospheres without invoking more complex models.

[1]  Louis E. Brus,et al.  Surface Enhanced Raman Spectroscopy of Individual Rhodamine 6G Molecules on Large Ag Nanocrystals , 1999 .

[2]  U. Kreibig,et al.  Optical Properties of Cluster–Matter: Influences of Interfaces , 1999 .

[3]  R. Ispasoiu,et al.  Large Optical Limiting from Novel Metal-Dendrimer Nanocomposite Materials , 2000 .

[4]  C. R. Chris Wang,et al.  Gold Nanorods: Electrochemical Synthesis and Optical Properties , 1997 .

[5]  Theodore Goodson,et al.  Relative enhancement of ultrafast emission in gold nanorods , 2002 .

[6]  A. Henglein,et al.  Electron-phonon coupling dynamics in very small (between 2 and 8 nm diameter) Au nanoparticles , 2000 .

[7]  Shen,et al.  Photoinduced luminescence from the noble metals and its enhancement on roughened surfaces. , 1986, Physical review. B, Condensed matter.

[8]  T. Goodson.  Time-resolved spectroscopy of organic dendrimers and branched chromophores. , 2005, Annual review of physical chemistry.

[9]  T. V. Shahbazyan,et al.  SIZE-DEPENDENT SURFACE PLASMON DYNAMICS IN METAL NANOPARTICLES , 1998 .

[10]  M. El-Sayed,et al.  Simulation of the Optical Absorption Spectra of Gold Nanorods as a Function of Their Aspect Ratio and the Effect of the Medium Dielectric Constant , 1999 .

[11]  T. Goodson,et al.  Femtosecond fluorescence dynamics and molecular interactions in a water-soluble nonlinear optical polymeric dye , 2000 .

[12]  J. Lakowicz,et al.  DNA hybridization assays using metal-enhanced fluorescence. , 2003, Biochemical and biophysical research communications.

[13]  G. Meister,et al.  New lifetime estimates for d-band holes at noble metal surfaces , 1999 .

[14]  Mostafa A. El-Sayed,et al.  Electron dynamics in gold and gold–silver alloy nanoparticles: The influence of a nonequilibrium electron distribution and the size dependence of the electron–phonon relaxation , 1999 .

[15]  M. Broyer,et al.  Ultrafast electron-electron scattering and energy exchanges in noble-metal nanoparticles , 2004 .

[16]  R. Rosei,et al.  Splitting of the interband absorption edge in Au , 1975 .

[17]  W. D. Bragg,et al.  PERCOLATION AND FRACTAL COMPOSITES: OPTICAL STUDIES , 2000 .

[18]  Thomas A. Klar,et al.  Plasmon emission in photoexcited gold nanoparticles , 2004 .

[19]  S. Lundqvist,et al.  Photoluminescence of noble metals , 1988 .

[20]  E. Coronado,et al.  The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment , 2003 .

[21]  Vallee,et al.  Size-dependent electron-electron interactions in metal nanoparticles , 2000, Physical review letters.

[22]  M. El-Sayed,et al.  Shape and size dependence of radiative, non-radiative and photothermal properties of gold nanocrystals , 2000 .

[23]  Lukas Novotny,et al.  Continuum generation from single gold nanostructures through near-field mediated intraband transitions , 2003 .

[24]  M. El-Sayed,et al.  Laser-Induced Shape Changes of Colloidal Gold Nanorods Using Femtosecond and Nanosecond Laser Pulses , 2000 .

[25]  D. L. Jeanmaire,et al.  Surface raman spectroelectrochemistry: Part I. Heterocyclic, aromatic, and aliphatic amines adsorbed on the anodized silver electrode , 1977 .

[26]  A. Mooradian,et al.  Photoluminescence of Metals , 1969 .

[27]  R. W. Christy,et al.  Optical Constants of the Noble Metals , 1972 .

[28]  R. Twieg,et al.  Ultrafast Exciton Dynamics in a Branched Molecule Investigated by Time-Resolved Fluorescence, Transient Absorption, and Three-Pulse Photon Echo Peak Shift Measurements† , 2004 .

[29]  C. Mirkin,et al.  Scanometric DNA array detection with nanoparticle probes. , 2000, Science.

[30]  M. El-Sayed,et al.  The `lightning' gold nanorods: fluorescence enhancement of over a million compared to the gold metal , 2000 .

[31]  P. Corkum,et al.  The use of intense-field ionization in time-resolved measurements , 1996 .

[32]  T. Goodson,et al.  Optical properties and applications of dendrimer–metal nanocomposites , 2004 .

[33]  Gyoujin Cho,et al.  Femtosecond Emission Studies on Gold Nanoparticles , 2002 .

[34]  T. Goodson.  Optical excitations in organic dendrimers investigated by time-resolved and nonlinear optical spectroscopy. , 2005, Accounts of chemical research.

[35]  James P. Gordon,et al.  Radiation Damping in Surface-Enhanced Raman Scattering , 1982 .

[36]  R. Ispasoiu,et al.  Ultrafast time-resolved photoluminescence from novel metal–dendrimer nanocomposites , 2001 .

[37]  Yongli Gao,et al.  FEMTOSECOND PHOTOEMISSION STUDY OF ULTRAFAST ELECTRON DYNAMICS IN SINGLE-CRYSTAL AU(111) FILMS , 1998 .

[38]  M. Brereton.  Classical Electrodynamics (2nd edn) , 1976 .

[39]  C. Mirkin,et al.  Nanoparticles with Raman spectroscopic fingerprints for DNA and RNA detection. , 2002, Science.

[40]  T. V. Shahbazyan,et al.  Surface collective excitations in ultrafast pump-probe spectroscopy of metal nanoparticles , 2000 .

[41]  Yaochun Shen,et al.  SURFACE-ENHANCED SECOND-HARMONIC GENERATION AND RAMAN SCATTERING , 1983 .

[42]  R. Twieg,et al.  Electronic interactions in a branched chromophore investigated by nonlinear optical and time-resolved spectroscopy. , 2004, The Journal of chemical physics.

[43]  A. Goncharenko,et al.  Local-field enhancement of spontaneous decay in nanosystems: some estimations for dielectric particles , 2004 .

[44]  Sun,et al.  Femtosecond-tunable measurement of electron thermalization in gold. , 1994, Physical review. B, Condensed matter.

[45]  Jess P. Wilcoxon,et al.  Photoluminescence from nanosize gold clusters , 1998 .

[46]  Paul Mulvaney,et al.  Drastic reduction of plasmon damping in gold nanorods. , 2002 .

[47]  H. Petek,et al.  The role of Auger decay in hot electron excitation in copper , 2000 .

[48]  J. Lakowicz.  Principles of fluorescence spectroscopy , 1983 .

[49]  Franz R. Aussenegg,et al.  Enhanced dye fluorescence over silver island films: analysis of the distance dependence , 1993 .