Photon Factory Activity Report 2018 #36 (2019)

BL-27A/2017G545

Synthesis of Au stabilized Cu nanoparticles by gamma-ray irradiation reduction
methodFuminobu Hori1, Yuya Uchimura1, Shintaro Toda1, Toshiyuki Matsui1, Akihiro Iwase1, Noboru
Taguchi2, Shingo Tanaka2, Qiu Xu31) Osaka Prefecture University, Gakuen-cho1-1, Sakai, 599-8531 Osaka, Japan
2) National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka 563-8577, Japan
3) Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan1 Introduction
It is well known that metal nanoparticles (NPs) havesome specific properties, which are not appeared in bulk
materials such as catalytic activities, magnetic properties,electric conductivity and light absorption. In general, mostmetal nanoparticles are fabricated by chemical reduction
method. We have been trying to synthesize various kindsof metal nanoparticles in water solution by gamma-ray
irradiation reduction method. On the other hand, Copper
nanoparticles are key materials for various industrial fields,
because of its electrical and optical properties. Generally,
copper particles of microns have been synthesized usingchemical reduction methods. However, they are easy tooxidize and re-dissolved since their high surface activity,
so that it is difficult to fabricate copper particles below
nanometer size without surface oxidation. Previously, we
have successfully synthesized pure copper particles withan average size of about 20 nm diameter by gamma-ray
irradiation reduction method [1]. In this study, we been
trying to synthesize copper nanoparticles stabilized byaddition of gold in aqueous solution under gamma-ray
irradiation reduction field with various conditions. Thesenanoparticles were characterized by transmission electron
microscope (TEM), UV-vis, X-ray diffraction (XRD) and
X-ray Photoelectron Spectroscopy (XPS).
2 Experiment
Aqueous solutions of Cu2+ ion of copper complex((CH3COO)2Cu·H2O) with a cationic surfactant of sodium
dodecyl sulfate (SDS) and a radical scavenger of 8.5 and42.5 vol.% ethylene glycol (EG) were prepared. An
aqueous solution was poured into a polystyrene container
and was purged with argon gas for 10 minutes. After
degassing, they were irradiated with gamma-ray from 60Co
in a gamma irradiation facility at Kyoto University
Research Reactor Institute. Total dose of gamma-ray
irradiation was 20 kGy with the dose rate of 2.0 kGy/h.
After irradiation, gold complex (NaAuCl4·2H2O) wasadded into irradiated solutions in nitrogen atmosphere withthe concentration ratio of Cu:Au=1:1, 4:1 and 9:1. All ofthese solutions were examined by using an UV/vis
absorption spectrophotometer (Shimadzu UV-2550) in the
wavelength range of 200-800nm. Synthesized particles
were characterized by TEM on JEOL JEM-2000FX andXPS at KEK-PF BL-27A. The samples for TEM wereprepared by dispersing the all products on carbon films

Fig.1 XPS spectra of synthesized nanoparticles insolutions with different concentration ratio of Cu and Au.
with a molybdenum mesh by dropping the solutions andwere dried in vacuum. Also the samples for XPS wereprepared by dropping samples on germanium and dried invacuum.
3 Results and Discussion
Figure 1 shows XPS spectra of gamma-ray irradiation
reduced solutions including different concentration ratio ofAu and Cu. In this figure, a peak around 955 eV, which isoriginated from pure Cu metal, was found for Cu:Au=4:1
and 9:1 samples together with other peaks correspond tocopper oxyde. In case of Cu:Au=1:1 sample, however, noclear peak characteristic of pure Cu metal was appeared.
On the other hand, surface plasmon resonace (SPR) of Au(520 nm) was observed for all samples and weak peak ofCu SPR (560 nm) was confirmed. However, these 560 nm
and 520 nm peaks combined and becomes one broad peakwith increase of Cu concentration ratio. These results showthat added Au ions are reduced by reacting with Cu
nanoparticles but Cu nanoparticles can be retained morethan four times larger Cu concentration than that of Au ina solution.
References[1] T. Hori et al., Jap. J. Appl. Phys. 53 (2014) 05FC05.
*horif@mtr.osakafu-u.ac.jp