Utilizing a pulsed laser deposition method, silver-copper (Ag–Cu) nanoparticles have been synthesized by irradiating the laser light of λ=248nm on Ag and Cu plates under the pressure below 1×104Pa. The peak absorption attributed to surface plasmon resonance (SPR) of the Ag–Cu nanoparticles appeared at 763nm, which was approximately 200nm higher wavelength than that of Ag nanoparticles. With increase in the annealing temperature from 300to548K, the peak absorption attributed to SPR of the Ag–Cu nanoparticles shifted continuously from 763to437nm. This fact proved that the peak absorption attributed to SPR can be tuned in the whole visible region by changing the annealing temperature only. Moreover, from the results of atomic force microscopy and grazing angle x-ray diffraction, the SPR wavelength tuning is conjectured due not to the change in the surface morphology of the Ag–Cu nanoparticles but to the increase in the electric conductivity of the nanoparticles induced by the precipitation of Cu atoms.

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