Ag Nanoparticle Films for Color Applications
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Ag Nanoparticle Films for Color Applications Satoru Hashimoto1, Teruyoshi O. Hirano2, Osamu Okitsu3, Mizue Ebisawa4, Takayasu Suzuki5 and Shuichi Maeda5 1 Hyoukaken Co., Ltd., 1-8-4-905 Sakumacyou, Chiyoda-ku, Tokyo, Japan. 2 Hirano Consulting Engineer Office, 1-17-7 Nishi-Shinbashi, Mitano-ku, Tokyo, Japan. 3 GGK 1-17-7 Nishi-Shinbashi, Co.,Ltd., Minato-ku, Tokyo, Japan. 4 Tokyo Metropolitan Industrial Technology Research Institute, 3-13-10 Nishigaoka, Kita-ku, Tokyo, Japan. 5 Optical and Imaging Science & Technology, Tokai University, 4-1-1, Kitakaname, Hiratsukashi, Kanagawa, Japan ABSTRACT The focus of this present work is concerned with a novel and facile method for obtaining colored Ag nanoparticle films using a sulfide as a coloring agent. The Ag nanoparticle films change their colors depending on the dipping time in a solution of a sulfide and the dipping time is at most on the second time scale. The color of the films, initially sliver (shiny white), changes to shiny yellow, red, and blue. Our scanning electron microscopy studies indicate that the color of the Ag nanoparticle films depend on the particle size of the Ag nanoparticle films. INTRODUCTION It is well known that Ag nanoparticles absorb visible light of various wavelengths due to surface plasmon resonance and the wavelength depends on particle size, particle shape, and local refractive index [1]. It is also known that colloidal Ag nanoparticles which have spherical morphology can be converted into larger ones which have prismatic morphology by photoinduced method as shown in figure 1 [2]. The light-irradiation process results in Ag nanoparticle colloids which have a variety of colors depending on the irradiation time. However, this irradiation process in the colloid system requires many hours for the conversion of Ag nanoparticles.
V isible light
７０ ｈ 20 nm
Figure 1 Schematic diagram of showing the conversion from small spherical Ag nanoparticles to large prismatic ones by photoinduced method in a colloid system.
Recently, we have discovered a novel and facile method for preparing colored Ag nanoparticle films. In our method, the target for color change is not Ag nanoparticle colloids but Ag nanoparticle films. Specifically Ag nanoparticle films made by sliver mirror reaction are colored by dipping them in a solution of a sulfide. To the best of our knowledge, this is the first time to control the colors of Ag nanoparticle films by using chemicals. It is of great scientific interest to elucidate the mechanism of the color change of our Ag nanoparticle films. Therefore, in this paper, these Ag nanoparticle films have been characterized in terms of their particle size, surface chemical compositions and optical properties by experimental techniques, including scanning electron microscopy, X-ray photoelectron spectroscopy, and visible reflection spectra. EXPERIMENT Ag nanoparticle films before coloration were made by sliver mirror reaction. Synthetic procedure has been described in detail elsewhere [3]. The coloration of the Ag nanoparticle films
