High energy XPS analysis of Ag-diacetylene hybrid nano-particles
related to plasmon damping
Hideki Yoshikawa1), Hidetoshi Oikawa2), Mihai A. Vlaicu1), Masahiro Kimura3), Shigeo Tanuma4),
Akito Masuhara2), Hitoshi Kasai2), Hachiro Nakanishi2)
1)

Harima office, National Institute for Materials Science (NIMS), BL15 SPring-8, 1-1-1 Kouto, Sayo,Hyogo 679-5198, Japan2)
Institute of multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira,Aoba, Sendai, Miyagi 980-8577, Japan3)
SPring-8 Service Co. 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan4)
National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki, 305-004,Japan
It is well-known that electric field enrichment by the surface plasmon excitation on a metal
is useful to enhance nonlinear optical properties. Nanometer-sized metal particle is the most suitablematerial to realize nonlinear optical properties owing to its large surface area and quantum
confinement effect. Masuhara et al. succeed to synthesize core-shell type hybridized nanocrystals
using the co-reprecipitation procedure [1]. They used acetylene monomer which were composed of
1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD), and covered Ag nano particles. They found that thesurface plasmon in this hybridized Ag/diacetylene nanoparticles was damped by the polymerizationof diacetylene after ultra violet (UV) light irradiation. Our motivation to analyze hybridized nanocrystal is to reveal the origin of plasmon damping mechanism for Ag/diacetylene nano crystals andrealize the long-life hybrid nanocrystal with intense surface plasmon.
In this work, we have focused attention on the core Ag structure before/after polymerizationof diacetylene. For this, we have measured high energy XPS spectra of this nanocrystal to evaluate
the electronic structure of hybrid nano crystal, especially core Ag particles on which surface
plasmon exists. High energy XPS experiment was done at the BL15XU beamline of SPring-8.
Photon energy was set to be 4750 eV. Figure 1 shows the valence band XPS spectra of core Ag ofhybrid nano crystals before/after UV irradiation. In Fig.1, it can be concluded that we observed nodifference between valence band XPS spectra of Ag core covered with monomer-diacetylene andAg core covered with polydiacetylene. However, there is difference between hybrid nano crystal
and Ag metal. These data indicated as follows: " 4d band narrowing", "5s band enrichment","broadening of Fermi edge", "Fermi edge shift to higher binding energy".
Combination of high energy XPS analysis
with the L3MM Auger XANES analysis at Ag L3edge revealed that there were no change ofelectronic structure of overall Ag core before/after
UV irradiation and "4d band narrowing" and otherphenomena mentioned above come from thecluster size effect of Ag cluster. These cluster size
effect is visible under the condition that cluster issmaller than 4 nm. Muvlaney [2] showed
theoretically that the surface plasmon on thesesmall clusters is easily damped owing to theshrinking space of the surface plasmon. We canconclude that plasmon damping of Ag/diacetylene
Binding Energy (eV)nano crystals is caused by the instability of surface
plasmon on tiny cluster smaller than 4nm.
Figure 1 Valence band XPS spectra of core Agof hybrid nano crystals before/after UV[1] Masuhara et al. Jpn. J. Appl. Phys. 40 (2001)
irradiation. Valence band spectrum of Ag
L1129-L1131.
metal is also indicated as a reference. X-ray[2] P. Mulvaney: Langmuir, 12, 788 (1996).
energy was 4750 eV.
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Ag nano particle in polyDA
Ag nano particle in DA
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